Patent Publication Number: US-8979786-B2

Title: Autoretroperfusion devices and systems

Description:
PRIORITY 
     The present application is related to, and claims the priority benefit of, and is a U.S. §371 national stage entry of, International Patent Application Serial No. PCT/US2008/087863, filed Dec. 19, 2008, the contents of which are hereby incorporated by reference in their entirety into this disclosure. 
     BACKGROUND 
     While direct surgical and percutaneous revascularization through procedures such as a percutaneous transluminal coronary angioplasty (“PTCA”) or coronary artery bypass grafting (“CABG”) remain the mainstay of treatment for angina and coronary artery disease (“CAD”), there are many cardiac conditions that are not amendable to such conventional revascularization therapies. Because of this, much effort has been made to find alternative methods of revascularization for ischemic cardiac patients who are not candidates for revascularization by conventional techniques. Such patients are generally identified as “no-option” patients because there is no conventional therapeutic option available to treat their condition. 
     Currently, there are multiple specific conditions for which conventional revascularization techniques are known to be ineffective as a treatment. Two specific examples of such cardiac conditions include, without limitation, diffuse CAD and refractory angina. Furthermore, a percentage of all patients diagnosed with symptomatic CAD are not suitable for CABG or PTCA. In addition and for various reasons discussed below, diabetic patients—especially those with type 2 diabetes—exhibit an increased risk for having CAD that is not effectively treated by conventional revascularization techniques. 
     There is currently little data available on the prevalence and prognosis of patients with symptomatic CAD that is not amendable to revascularization through conventional methods. However, one study indicated that out of five hundred (500) patients with symptomatic CAD who were considering direct myocardial revascularization and angiogenesis, almost twelve percent (12%) were not suitable for CABG or PTCA for various reasons. Furthermore, in general, patients with atherosclerotic involvement of the distal coronary arteries have high mortality and morbidity. For example, a study conducted on patients indicated that, one (1) year after being diagnosed with atherosclerotic involvement of the distal coronary arteries, 39.2% of such patients had had a cardiac-related death, 37.2% had had an acute myocardial infarction, and 5.8% had developed congestive heart failure. Overall, 82.2% of the patients with atherosclerotic involvement of distal coronary arteries had developed or experienced a significant cardiac event within one (1) year. 
     A. Diffuse CAD and Refractory Angina 
     CAD is typically not focal (i.e. limited to one point or a small region of the coronary artery), but rather diffused over a large length of the entire vessel, which is termed “diffuse CAD.” Several studies indicate that patients with a diffusely diseased coronary artery for whom standard CABG techniques cannot be successfully performed constitute about 0.8% to about 25.1% of all patients diagnosed with CAD. Furthermore, it is believed that diffuse CAD is much more common than conventionally diagnosed because it is often difficult to detect by an angiogram due to the two-dimensional views. 
     Practitioners have realized that the quality of a patient&#39;s distal coronary arteries is one of the critical factors related to a successful outcome of a surgical revascularization. As previously indicated, there is considerable evidence that CABG for vessels having diffuse CAD results in a relatively poor outcome. In fact, studies have indicated that diffuse CAD is a strong independent predictor of death after a CABG procedure. Further, as previously noted conventional revascularization techniques have also proven ineffective on a subgroup of patients with medically refractory angina. In line with the aforementioned reasoning, this is likely because patients with medically refractory angina have small or diffusely diseased distal vessels that are not amenable to conventional revascularization therapies. Accordingly, patients exhibiting diffuse CAD or medically refractory angina are often considered no-option patients and not offered bypass surgery, PCTA, or other conventional procedures. 
     B. Diabetes as a Risk Factor 
     Diabetes is an important risk factor for the development of CAD, diffuse or asymptomatic, and it has been estimated that approximately seventy-five percent (75%) of the deaths in diabetic patients are likely attributed to CAD. It is estimated that 16 million Americans have diabetes, with only 10 million being diagnosed. Patients with diabetes develop CAD at an accelerated rate and have a higher incidence of heart failure, myocardial infarction, and cardiac death than non-diabetics. 
     According to recent projections, the prevalence of diabetes in the United States is predicted to be about ten percent (10%) of the population by 2025. Further, the increasing prevalence of obesity and sedentary lifestyles throughout developed countries around the world is expected to drive the worldwide number of individuals with diabetes to more than 330 million by the year 2025. As may be expected, the burden of cardiovascular disease and premature mortality that is associated with diabetes will also substantially increase, reflecting in not only an increased amount of individuals with CAD, but an increased number of younger adults and adolescents with type 2 diabetes who are at a two- to four-fold higher risk of experiencing a cardiovascular-related death as compared to non-diabetics. 
     In addition to developing CAD at an accelerated rate, CAD in diabetic patients is typically detected in an advanced stage, as opposed to when the disease is premature and symptomatic. Consequently, when diabetic patients are finally diagnosed with CAD they commonly exhibit more extensive coronary atherosclerosis and their epicardial vessels are less amendable to interventional treatment, as compared to the non-diabetic population. Moreover, as compared with non-diabetic patients, diabetic patients have lower ejection fractions in general and therefore have an increased chance of suffering from silent myocardial infarctions. 
     C. No-Option Patients 
     Some studies have shown that two-thirds (⅔rds) of the patients who were not offered bypass surgery, because of diffuse CAD or otherwise, either died or had a non-fatal myocardial infarction within twelve (12) months. Furthermore, patients diagnosed with diffuse CAD ran a two-fold increased risk of in-hospital death or major morbidity, and their survival rate at two (2) years was worse than those patients who exhibited non-diffuse CAD or other complicating conditions. As previously indicated, the majority of these patients are considered no-option patients and are frequently denied bypass surgery as it is believed that CABG would result in a poor outcome. 
     Due to the increasing numbers of no-option patients and a trend in cardiac surgery towards more aggressive coronary interventions, a growing percentage of patients with diffuse CAD and other no-option indications are being approved for coronary bypass surgery because, in effect, there are no other meaningful treatment or therapeutic options. Some effects of this trend are that the practice of coronary bypass surgery has undergone significant changes due to the aggressive use of coronary stents and the clinical profiles of patients referred for CABG are declining. As such, performing effective and successful coronary bypass surgeries is becoming much more challenging. Bypass grafting diffusely diseased vessels typically requires the use of innovative operations such as on-lay patches, endarterectomies and more than one graft for a single vessel. Patients with “full metal jackets” (or multiple stents) are typically not referred to cardiac surgeons and often end up as no-option patients despite the attempts of using these innovative surgeries. 
     In recent decades, the spectrum of patients referred for CABG are older and are afflicted with other morbidities such as hypertension, diabetes mellitus, cerebral and peripheral vascular disease, renal dysfunction, and chronic pulmonary disease. In addition, many patients referred for CABG have advanced diffuse CAD and have previously undergone at least one catheter-based intervention or surgical revascularization procedure that either failed or was not effective. Because of this, the patient&#39;s vessels may no longer be graftable and complete revascularization using conventional CABG may not be feasible. An incomplete myocardial revascularization procedure has been shown to adversely affect short-term and long-term outcomes after coronary surgery. 
     Due in part to some of the aforementioned reasons, reoperative CABG surgery is now commonplace, accounting for over twenty percent (20%) of cases in some clinics. It is well established that mortality for reoperative CABG operations is significantly higher than primary operations. As such, the risk profile of reoperative patients is significantly increased and such patients are subjected to an increased risk of both in-hospital and long-term adverse outcomes. 
     Further, clinicians have also turned to unconventional therapies to treat non-option patients. For example, coronary endarterectomy (“CE”) has been used as an adjunct to CABG in a select group of patients with diffuse CAD in order to afford complete revascularization. However, while CE was first described in 1957 as a method of treating CAD without using cardiopulmonary bypass and CABG, this procedure has been associated with high postoperative morbidity and mortality rates and has been afforded much scrutiny. Nevertheless, CE is the only therapeutic option available for many no-option patients with diffuse CAD. 
     Similarly, because conventional therapies have proven ineffective or are unavailable to high risk patients, perioperative transmyocardial revascularization (“TMR”) has been indicated for patients suffering from medically refractory angina. TMR has proven effective for most patients suffering from refractory angina; the mortality rate after TMR in patients with stable angina ranges between about one to twenty percent (1-20%). Furthermore, in one study, TMR resulted in a higher preoperatively mortality rate in patients with unstable angina than those with stable angina (27% versus 1%). Some even report an operative mortality rate as low as twelve percent (12%). Patients who experience angina and who cannot be weaned from intravenous nitroglycerin and heparin have a significantly higher operative mortality rate (16-27% versus 1-3%). Based on these findings, the clinical practice has been to avoid taking such patients to the operating room for TMR if at all possible. The success of TMR is thought to be due to improved regional blood flow to ischemic myocardium, but the precise mechanisms of its effects remain unclear. 
     BRIEF SUMMARY 
     Disclosed herein are the devices, systems and methods for providing controlling blood perfusion pressure and/or providing retroperfusion to at least one ischemic tissue in a minimally invasive manner. At least some of the disclosed embodiments enable an anastomosis to be formed between a vein and an artery without the use of sutures and through a non-invasive procedure. In addition, various disclosed embodiments provide a cannula device comprising a Y-configuration for bifurcating the arterial flow between an anastomosis and the underlying artery. Examples of the devices, systems and methods described herein can further provide simultaneous autoretroperfusion therapy to more than one area of an ischemic tissue. 
     In at least one embodiment of a catheter for controlling blood perfusion pressure, the catheter comprises an elongated body having a proximal open end, a distal open end, at least one lumen extending between the proximal open end and the distal open end, and a cannula having a hollow interior. In this at least one embodiment, the hollow interior of the cannula is in fluid communication with at least one of the at least one lumens of the elongated body, and the cannula extends from the elongated body such that an angle is formed therebetween. The elongated body of the catheter may be configured for placement within an arterial vessel or any other vessel of interest. The hollow interior of the cannula may further comprise a first diameter and the at least one lumen of the elongated body may further comprise a second diameter. In at least one example, the first diameter of the hollow interior of the cannula is less than the second diameter of the at least one lumen of the elongated body. However, it will be understood that the hollow interior of the cannula may comprise any diameter and, in at least one embodiment, the hollow interior of the cannula is between about 2.7 millimeters to about 4 millimeters in diameter. 
     The cannula of the catheter may also be moveable between a substantially extended configuration and a substantially collapsed configuration. Here, the substantially extended configuration may comprise any angle between about 15° and about 90° and the substantially collapsed configuration may comprise any angle that is less than about 15°. In at least one example of the cannula, the cannula is biased towards the substantially extended configuration. 
     The catheter described herein may further comprise an expandable balloon coupled with the elongated body of the catheter in a position adjacent to where the cannula extends from the elongated body. The expandable balloon may comprise any configuration and, in at least one embodiment, is configured to prevent fluid leakage through an arterial opening when the expandable balloon is in a substantially inflated configuration and the elongated body of the catheter is positioned within an arterial vessel such that the cannula extends through the arterial opening. In this at least one embodiment, the catheter may also comprise a balloon port and a secondary lumen. Here, the balloon port may be in fluid communication with the expandable balloon through a secondary lumen of the catheter. The balloon port may be configured for subcutaneous implantation on a patient or otherwise. 
     In a yet another example of the catheter described herein, the catheter may comprise an elongated body for placement within a vessel and having a proximal end, a distal end. In addition, the catheter may comprise at least one lumen extending between the proximal end and the distal end of the elongated body. Here, the distal end of the catheter may be configured to receive a fluid flowing through the vessel and the proximal end of the catheter may be configured to allow the fluid received by the distal end of the elongated body to flow from the at least one lumen of the catheter therethrough. In addition, the catheter may comprise a cannula extending from the elongated body such that an angle is formed between the cannula and the elongated body. The cannula may comprise a hollow interior that is in fluid communication with the at least one of the at least one lumens of the elongated body and be configured to route a portion of the fluid received by the distal end of the elongated body outside of the vessel. In at least one embodiment of the catheter, the vessel that the elongated body is configured for placement in comprises an artery. 
     Systems are also disclosed herein for controlling blood perfusion pressure within a vein. In at least one embodiment, a system may comprise a first catheter for placement within an arterial vessel, a second catheter for placement within a venous vessel and a connector. The distal end of the second catheter may further comprise at least one sensor capable of monitoring a condition within a venous vessel. In at least one embodiment of this system, the first catheter may comprise embodiments of the catheter previously described herein. Further, the second catheter may comprise a proximal end, a distal end, and at least one lumen extending between the proximal end and the distal end. In this at least one embodiment, the connector is coupled with the cannula of the first catheter and the proximal end of the second catheter. In addition, embodiments of the connector may comprise a means for measuring data associated with the fluid flowing from the first catheter to the second catheter through the connector. In certain embodiments, the fluid of the system comprises arterial blood. In this manner, the system described herein can form an anastomosis between an arterial vessel and a venous vessel such that arterial blood can flow therethrough. 
     Additionally, in at least some embodiments, the second catheter may comprise an expandable balloon coupled with the exterior of the distal end of the second catheter. The at least one lumen of the second catheter of the system may further comprise at least one primary lumen and at least one secondary lumen. Here, for example, the expandable balloon may be in fluid communication with the at least one secondary lumen of the second catheter. Additionally, the system may further comprise a balloon port in fluid communication with the expandable balloon of the second catheter through the at least one secondary lumen. 
     In yet another at least one embodiment of the system, the system may further comprise a stenosis positioned within the at least one primary lumen of the second catheter. In this manner, the stenosis can affect the pressure of the fluid flowing through the primary lumen of the catheter. In at least one embodiment, the stenosis may comprise an expandable balloon. In such an embodiment, the at least one lumen of the second catheter may also further comprise a tertiary lumen in fluid communication with the expandable balloon positioned within the primary lumen of the second catheter. Still further, the system may comprise a balloon port in fluid communication with the expandable balloon positioned within the primary lumen of the second catheter through the tertiary lumen of the second catheter. 
     In yet another at least one embodiment, the second catheter of the system may further comprise an expandable balloon coupled therewith. Where the system comprises a first expandable balloon coupled with the primary lumen of the second catheter and a second expandable balloon coupled with the second catheter, the first and second expandable balloons of the second catheter may be capable of being inflated and deflated independently of each other through respective balloon ports coupled therewith. Accordingly, a clinician can independently control each expandable balloon coupled with the second catheter. 
     The systems described herein may further comprise a first graft coupled with the proximal end of the second catheter and the connector such that the at least one lumen of the second catheter is in fluid communication with the at least one lumen of the first catheter. In this manner, the first graft may be used to form a portion of the anastomosis formed between the arterial vessel and the venous vessel. Alternatively, a second graft may also be coupled with the cannula of the first catheter and the connector such that the at least one lumen of the second catheter is in fluid communication with the at least one lumen of the first catheter. In yet another at least one embodiment, the system may comprise both a first graft and a second graft, wherein the first graft is coupled with the cannula of the first catheter and the connector, and the second graft is coupled with the cannula of the first catheter and the connector such that the at least one lumen of the second catheter is in fluid communication with the at least one lumen of the first catheter. 
     As previously described, the controller of the system may comprise a means for measuring data associated with fluid flowing therethrough and/or may simply be capable of measuring data associated with fluid flowing therethrough. In addition, the system may further comprise a remote module either in direct or wireless communication with the controller and/or the means for measuring data. In at least some embodiments, the remote module may be capable of receiving the data measured by the connector, either through wired transmission, wireless communication (for example and without limitation through telemetry, radio waves, or wireless internet), or other transmission means known in the art. Here, the means for measuring data and/or the controller may be capable of transmitting the data collected to the remote module either through wired transmission, wireless communication, or other transmission means known in the art. 
     Other examples of the controller of the system described herein may further comprise a means for regulating blood flow and/or may simply be capable of regulating blood flow. In such examples, the remote module may be capable of adjusting the means for regulating blood flow either wirelessly, through wired transmission, or otherwise. As such, the remote module may be able to communicate with the controller, either wirelessly or otherwise, such that it can adjust the controller to regulate the blood flow flowing therethrough pursuant to a set of instructions. 
     The system described herein may further comprise at least one guidewire having a proximal end and a distal end. In at least one embodiment, the at least one guidewire is capable of being slidably inserted within the at least one lumen of the second catheter. Furthermore, the distal end of the at least one guidewire further comprises a plurality of electrodes disposed thereon. In certain embodiments, the plurality of electrodes may comprise a combination of excitation and detection electrodes for use in determining the cross-sectional area of a vessel. 
     In other embodiments, the system described herein may further comprise a third catheter for placement within a venous vessel adjacent to the second catheter described above. The third catheter may comprise a proximal end, a distal end, and at least one lumen extending between the proximal end and the distal end. Furthermore, in certain embodiments, the third catheter may be configured identically to the embodiments of the second catheter described above. In addition to the third catheter, at least one embodiment of the system may further comprise a Y-connector configured for placement within the venous vessel. The Y-connector may comprise an open proximal end, a distal end having at least two branches, and a lumen extending between the open proximal end and bifurcating between the at least two branches of the distal end, the open proximal end of the Y-connector coupled with the connector, one of the at least two branches of the distal end coupled with the proximal end of the second catheter, and one of the at least two branches of the distal end coupled with the proximal end of the third catheter such that the at least one lumen of the second catheter and the at least one lumen of the third catheter are in fluid communication with the at least one lumen of the first catheter. 
     In at least one method for arterializing a vein, the method comprises the steps of: providing the system described above; introducing the distal end of the first catheter into an artery through an arterial opening such that a first amount of arterial blood flows through the at least one lumen of the elongated body of the first catheter, the cannula extends through the arterial opening, and a second amount of arterial blood flows through the cannula of the first catheter; introducing the distal end of the second catheter into a vein to be arterialized; and forming an anastomosis between the artery and the vein by coupling the connector with the cannula of the first catheter and the proximal end of the second catheter. The method may also further comprise the step of decreasing the pressure of the amount of arterial blood flowing through the cannula of the first catheter prior to allowing the amount of arterial blood to flow into the vein to be arterialized through the distal end of the second catheter. Furthermore, the step of introducing the distal end of the first catheter into an artery further comprises the steps of: providing an introducer having a proximal end, a sharp distal end and a hollow interior extending between the proximal end and the sharp distal end, the first catheter slidably disposed in the substantially collapsed configuration within the hollow interior of the introducer; puncturing the artery with the sharp distal end of the introducer to create an arterial opening; advancing the sharp distal end of the introducer through the arterial opening and into the lumen of the artery; withdrawing the sharp distal end of the introducer through the arterial opening such that the elongated body of the first catheter remains within the lumen of the artery; retaining the cannula of the first catheter within the hollow interior of the introducer; and withdrawing the sharp distal end of the introducer such that the cannula is released from the hollow interior of the introducer in the substantially extended configuration and extends through the arterial opening. In yet another at least one embodiment, the step of introducing the distal end of the first catheter into an artery further comprises the step of inflating the first expandable balloon to anchor the elongated body of the first catheter within the artery and prevent leakage through the arterial opening. 
     In yet another embodiment of the method described herein, the step of introducing the distal end of the second catheter into a vein to be arterialized further comprises the steps of: providing a delivery catheter and a guidewire, the delivery catheter comprising a proximal end, a distal end, and a hollow interior extending between the distal end and the proximal end and capable of slidably receiving at least the second catheter and the guidewire therein, and the guidewire comprising a proximal end and a distal end; introducing the delivery catheter into the lumen of the vein; advancing the distal end of the delivery catheter to or near a targeted location within the lumen of the vein; introducing the guidewire into the hollow interior of the delivery catheter; advancing the distal end of the guidewire into the lumen of the vein through the distal end of the delivery catheter; and advancing the distal end of the second catheter into the lumen of the vein and to a location at or near the targeted location by threading the distal end second catheter over the guidewire. In addition, the method may further comprise the step of inflating the expandable balloon to anchor the distal end of the second catheter within the lumen of the vein at or near the targeted location and/or the step of measuring the cross-sectional area of the lumen of the vein in the targeted location. 
     The method described herein may further comprise additional steps directed towards decreasing the pressure of the arterial blood flowing through the cannula of the first catheter. In at least one embodiment, the step of decreasing the pressure of the amount of arterial blood flowing through the cannula of the first catheter prior to allowing the arterial blood to flow into the vein to be arterialized through the distal end of the second catheter comprises positioning a stenosis within the at least one lumen of the second catheter to partially occlude the same. In at least one embodiment, the stenosis comprises an expandable balloon. In yet another at least one embodiment, the stenosis comprises a resorbable stenosis. Furthermore, in at least one embodiment of the method, the at least one lumen of the first catheter of the system may comprise a first diameter and the hollow interior of the cannula of the first catheter of the system comprises a second diameter, wherein the second diameter is less than the first diameter such that a difference in pressure is achieved between the arterial blood flowing through the elongated body of the first catheter and the arterial blood flowing through the hollow interior of the cannula. In other embodiments of the method described herein, the controller of the system may comprise a means for regulating blood flow and the step of decreasing the pressure of the amount of arterial blood flowing through the cannula of the first catheter prior to allowing the arterial blood to flow into the vein to be arterialized through the distal end of the second catheter may comprise adjusting the means for regulating blood flow. 
     Methods for simultaneously arterializing at least two venous branches are also described, with at least one embodiment of the method comprising the steps of: providing at least one embodiment of the system described above; introducing the distal end of the first catheter into an artery such that a first amount of arterial blood flows through the elongated body of the first catheter and a second amount of arterial blood can flow through the cannula of the first catheter; introducing the distal end of the second catheter into a first venous branch of a vein to be arterialized; introducing the distal end of the third catheter into a second venous branch of the vein to be arterialized; introducing the distal end of the Y-connector into the vein; and forming an anastomosis between the artery and the vein by coupling the connector with the cannula of the first catheter and the proximal end of the Y-connector. Further, the method may further comprise the step of decreasing the pressure of the amount of arterial blood flowing through the cannula of the first catheter prior to allowing the amount of arterial blood to flow into the first venous branch through the distal end of the second catheter or into the second venous branch through the distal end of the third catheter. In addition, at least one embodiment of the method may comprise the step of introducing the distal end of the first catheter into an artery further comprises the steps of: providing an introducer having a proximal end, a sharp distal end and a hollow interior extending between the proximal end and the sharp distal end, the first catheter slidably disposed in the substantially collapsed configuration within the hollow interior of the introducer; puncturing the artery with the sharp distal end of the introducer to create an arterial opening; advancing the sharp distal end of the introducer through the arterial opening and into the lumen of the artery; withdrawing the sharp distal end of the introducer through the arterial opening such that the elongated body of the first catheter remains within the lumen of the artery; retaining the cannula of the first catheter within the hollow interior of the introducer; and withdrawing the sharp distal end of the introducer such that the cannula is released from the hollow interior of the introducer in the substantially extended configuration and extends through the arterial opening. 
     Furthermore, in yet another at least one embodiment, the method for simultaneously arterializing at least two venous branches may further comprise the steps of introducing the distal end of the second catheter into a first venous branch of a vein to be arterialized and introducing the distal end of the third catheter into a second venous branch of the vein to be arterialized further comprise the steps of: providing a delivery catheter, a first guidewire, and a second guidewire, the delivery catheter comprising a proximal end, a distal end, and a hollow interior extending between the distal end and the proximal end and capable of slidably receiving at least the second catheter and the guidewire therein, and the first and second guidewires each comprising a proximal end and a distal end; introducing the distal end of the delivery catheter into the lumen of the vein; advancing the distal end of the delivery catheter to or near a targeted location within the lumen of the vein; introducing the first guidewire into the delivery catheter; advancing the distal end of the first guidewire through the distal end of the delivery catheter to a targeted location within the first venous branch of the vein; advancing the distal end of the second catheter over the first guidewire and through the hollow interior of the delivery catheter; advancing the distal end of the second catheter through the distal end of the delivery catheter to the targeted location within the first venous branch of the vein; introducing the second guidewire into the delivery catheter; advancing the distal end of the second guidewire through the distal end of the delivery catheter to a targeted location within the second venous branch of the vein; advancing the distal end of the third catheter through the hollow interior of the delivery catheter over the second guidewire; and advancing the distal end of the third catheter through the distal end of the delivery catheter to the targeted location within the second venous branch of the vein. In yet another embodiment of the methods described herein, the first catheter of the system further comprises an expandable balloon coupled with the elongated body in a location adjacent to the cannula, and wherein the step of introducing the distal end of the first catheter into an artery further comprises the step of inflating the first expandable balloon to anchor the elongated body of the first catheter within the artery and to prevent leakage through the arterial opening. In addition, the second catheter of the system may further comprise a first expandable balloon coupled with the exterior of the distal end of the second catheter and the third catheter of the system further comprises a second expandable balloon coupled with the exterior of the distal end of the third catheter, and further comprising the steps of: inflating the first expandable balloon to anchor the distal end of the second catheter at the targeted location within the first venous branch of the vein; inflating the second expandable balloon to anchor the distal end of the third catheter at the targeted location within the second venous branch of the vein; and withdrawing the first and second guidewires and the delivery catheter from the vein. In yet another embodiment of the method, the method may further comprise the steps of: measuring the cross-sectional area of the first venous branch of the vein; and measuring the cross-sectional area of the second venous branch of the vein. Embodiments of the method may additionally comprise the step of sizing the first and second expandable balloons respectfully based on the measurements of the first and second venous branches. Still further, in at least one embodiment of the method, the step of decreasing the pressure of the amount of the amount of arterial blood flowing through the cannula of the first catheter prior to allowing the amount of arterial blood to flow into the first venous branch through the distal end of the second catheter or into the second venous branch through the distal end of the third catheter comprises the steps of: positioning a first stenosis within the at least one lumen of the second catheter to partially occlude the same; and positioning a second stenosis within the at least one lumen of the third catheter to partially occlude the same. In yet another at least one embodiment of the method, the controller of the system further comprises a means for regulating blood flow and wherein the step of decreasing the pressure of the amount of the amount of arterial blood flowing through the cannula of the first catheter prior to allowing the amount of arterial blood to flow into the first venous branch through the distal end of the second catheter or into the second venous branch through the distal end of the third catheter comprises adjusting the means for regulating blood flow. 
     Kits are also described herein for performing a medical procedure. In at least one embodiments, such kits may comprise a first catheter for placement within an arterial vessel, the first catheter comprising an elongated body having a proximal open end, a distal open end, at least one lumen extending between the proximal open end and the distal open end, and a cannula having a hollow interior that is in fluid communication with at least one of the at least one lumens of the elongated body, and the cannula extends from the elongated body such that an angle is formed therebetween; a second catheter for placement within a venous vessel, the second catheter having a proximal end, a distal end, and at least one lumen extending between the proximal end and the distal end; a connector coupled with the cannula of the first catheter and the proximal end of the second catheter, the connector comprising a means for measuring data associated with fluid flowing therethrough; an introducer for delivering the first catheter into the arterial vessel, the introducer having a proximal end, a sharp distal end and a hollow interior, the hollow interior capable of slidably receiving the first catheter therein; at least one guidewire; and a delivery catheter for delivering at least the second catheter into the venous vessel, the delivery catheter comprising a proximal end, a distal end, and a hollow interior capable of slidably receiving the at least one guidewire and the second catheter therein. Such a kit may also comprise a third catheter for placement within the venous vessel, the third catheter having a proximal end, a distal end, and at least one lumen extending between the proximal end and the distal end; and a Y-connector configured for placement within the venous vessel and having an open proximal end, a distal end having at least two branches, and a lumen extending between the open proximal end and bifurcating between the at least two branches of the distal end, one of the at least two branches of the distal end coupled with the proximal end of the second catheter, and one of the at least two branches of the distal end coupled with the proximal end of the third catheter. Furthermore, a kit as described herein my further comprise at least one graft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a catheter for placement within an arterial vessel and that may be used to deliver retroperfusion therapy. 
         FIG. 2A  shows a side view of the catheter of  FIG. 1  in a collapsed position. 
         FIG. 2B  shows a side view of the catheter of  FIG. 1  in an extended position. 
         FIG. 3  shows a side view of an autoretroperfusion system positioned to deliver retroperfusion therapy to a heart. 
         FIGS. 4A and 4B  show perspective views of the distal end of a venous catheter used in the autoretroperfusion system of  FIG. 3 . 
         FIG. 5  shows the components of an autoretroperfusion system that can be used to deliver retroperfusion therapy to ischemic tissue. 
         FIG. 6  shows a view of the base and diaphragmatic surface of a heart with the distal ends of two components of the autoretroperfusion system of  FIG. 5  positioned therein such that the autoretroperfusion system can deliver simultaneous selective autoretroperfusion therapy thereto. 
         FIG. 7  shows a flow chart of a method for delivering autoretroperfusion therapy. 
         FIG. 8A  shows a side view of the catheter of  FIG. 1  in a collapsed position within an introducer. 
         FIG. 8B , shows a side view of the catheter of  FIG. 1  being introduced via an introducer into an arterial vessel. 
         FIGS. 8C and 8D  show side views of the introducer of  FIG. 8A  being removed from an arterial vessel, thereby deploying the projection cannula of the catheter of  FIG. 1 . 
         FIG. 8E  shows a side view of the catheter of  FIG. 1  anchored within an arterial vessel through the use of an expandable balloon. 
         FIG. 9  shows a schematic view of the autoretroperfusion system of  FIG. 5  as applied to a heart. 
         FIG. 10  shows a schematic view of the autoretroperfusion system of  FIG. 5  as applied to a heart. 
         FIG. 11  shows a schematic view of a step of the method of  FIG. 7  as the method is applied to a heart. 
         FIG. 12  shows a flow chart of a method for delivering simultaneously selective autoretroperfusion therapy. 
         FIG. 13  shows a schematic view of a step of the method of  FIG. 12  as the method is applied to a heart. 
         FIG. 14  shows a schematic view of a step of the method of  FIG. 12  as the method is applied to a heart. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated by those of skill in the art that the following detailed description of the disclosed embodiments is merely exemplary in nature and is not intended to limit the scope of the appended claims. The embodiments discussed herein include devices, systems, and methods useful for providing selective autoretroperfusion to the venous system and simultaneously achieving the controlled arterialization of the venous system. The devices, systems and methods disclosed herein can be used to safely and selectively arterialize venous vessels in order to decrease the stress thereon and prevent rupture of the same. Accordingly, through the use of the devices, systems and methods disclosed herein, long-term autoretroperfusion of oxygenated blood through the coronary venous system can be achieved, thereby providing a continuous supply of oxygen-rich blood to an ischemic area of a tissue or organ. While the devices, systems and methods disclosed herein are described in connection with a heart, it will be understood that such devices, systems and methods are not limited in their application solely to the heart and the same may be used in connection with any ischemic tissue and/or organ in need of an oxygen-rich blood supply. 
     Now referring to  FIG. 1 , a side view of a catheter  10  is shown. The catheter  10  is configured to be placed within an arterial vessel and comprises a flexible, elongated tube having a proximal end  12 , a distal end  14  and at least one lumen  15  extending between the proximal end  12  and the distal end  14 . The dimensions of the catheter  10  may vary depending on the particulars of a specific patient or with respect to the artery to be cannulated. For example and without limitation, where the catheter  10  is used to in a system for autoretroperfusion of the coronary sinus, the catheter  10  may comprise a diameter of about 2.7 millimeters to about 4 millimeters (about 8 Fr to about 12 Fr). Furthermore, the at least one lumen  15  of the catheter  10  comprises a sufficient diameter such that blood can flow therethrough. In addition, the catheter  10  may be comprised of any appropriate material, including without limitation, polyurethane or silicone rubber. Furthermore, the catheter  10  may be coated with heparin or any other suitable anti-coagulant such that the catheter  10  may be placed within a vessel for an extended period of time without inhibiting blood flow due to coagulation. 
     The distal end  14  of the catheter  10  is configured to allow arterial blood to flow therethrough and into the at least one lumen  15  of the catheter  10 . Similarly, the proximal end  12  of the catheter  10  is configured to allow blood within the at least one lumen  15  to flow out of the catheter  10 . Accordingly, when the catheter  10  is positioned within an arterial vessel, the oxygenated blood is allowed to flow into the catheter  10  through the distal end  14  of the catheter  10 , through the at least one lumen  15 , and out of the catheter  10  through the proximal end  12  of the catheter  10 . In this manner, placement of the catheter  10  within a vessel does not inhibit the flow of blood through the vessel or significantly affect the pressure of the blood flow within the vessel. 
     As shown in  FIG. 1 , the catheter  10  further comprises a projection cannula  16  that extends from the proximal end  12  of the catheter  10  and forms a Y-shaped configuration therewith. The projection cannula  16  comprises a flexible tube of material that is appropriate for insertion within a vessel and placement within an opening in a vessel wall. Furthermore, the projection cannula  16  comprises at least one lumen  18 , a proximal end  20 , and a distal end  22 . The distal end  22  of the projection cannula  16  is coupled with the body of the catheter  10  and configured to allow the lumen  18  of the projection cannula  16  to communicate with at least one of the at least one lumens  15  of the catheter  10 . Accordingly, when blood flows through the at least one lumen of the catheter  10 , a portion of the blood flow enters the lumen  18  of the projection cannula  16  through the distal end  22  thereof and flows out through the proximal end  20  of the projection cannula  16 . In this manner, the catheter  10  is capable of bifurcating the flow of blood through the vessel in which it is inserted and routing some of that blood flow out of the vessel and to another location. 
     This bifurcation can be exploited to modify the pressure of the blood flowing through the projection cannula  16  and/or through the proximal end  12  of the catheter  10  by manipulating the dimensions of the projection cannula  16  and the body of the catheter  10 . For example, and without limitation, if the diameter of the projection cannula  16  is less than the diameter of the at least one lumen  15  of the catheter  10 , the majority of the blood will flow through the proximal end  12  of the catheter  10  and the pressure of the remaining blood that flows through the smaller projection cannula  16  will necessarily be reduced. Predictably, the smaller the diameter of the lumen  18  of the projection cannula  16 , the greater the pressure drop that can be achieved in the blood flowing through the lumen  18  of the projection cannula  16 . Accordingly, with respect to the catheter&#39;s  10  application to autoretroperfusion therapies, the projection cannula  16  can be used to re-route blood flow from an artery to a vein while simultaneously achieving the necessary pressure drop in the re-routed blood between the arterial system and unarterialized venous system. Moreover, the catheter  10  is capable of maintaining substantially normal blood flow through the artery in which it is housed as the arterial blood not re-routed through the projection cannula  16  is allowed to flow through the open proximal end  12  of the catheter  10  and back into the artery in the normal antegrade fashion. 
     Due to the configuration of the projection cannula  16  and the material of which it is comprised, the projection cannula  16  is capable of hingedly moving relative to the body of the catheter  10  between a collapsed position and an extended position. Now referring to  FIGS. 2A and 2B , the projection cannula  16  is shown in the collapsed position ( FIG. 2A ) and in the extended position ( FIG. 2B ). When the projection cannula  16  is in the collapsed position, the projection cannula  16  is positioned substantially parallel with the body of the catheter  10 . Alternatively, when the projection cannula  16  is in the extended position, the projection cannula  16  is positioned such that the projection cannula  16  forms an angle θ with the proximal end  12  of the catheter  10 . The value of angle θ may be selected depending on the desired application of the catheter  10 . For example, in at least one embodiment, the angle θ may comprise any value ranging between about 15° and about 90°. In another example, the angle θ may comprise about 45° when the projection cannula  16  is in the extended position. 
     The projection cannula  16  is biased such that, when it is not subject to a downward force, the projection cannula  16  rests in the expanded position. Conversely, when a downward force is applied to the projection cannula  16  by way of an introducer or otherwise, the projection cannula  16  moves into and remains in the collapsed position until the downward force is removed. In this manner, the projection cannula  16  may be introduced into a vessel in the collapsed position through the use of an introducer or shaft and thereafter move into the expanded position when the catheter  10  is properly positioned within the vessel and the introducer or shaft is removed. 
     Optionally, as shown in  FIG. 1 , the catheter  10  may further comprise an expandable balloon  58  coupled with an intermediary portion of the external surface of the catheter  10  such that the expandable balloon  58  encases the catheter  10  and the distal end  22  of the projection cannula  18 . The expandable balloon  58  may be any expandable balloon  58  that is appropriate for insertion within a vessel and may comprise any material suitable for this function, including without limitation, polyethylene, latex, polyestherurethane, polyurethane, sylastic, silicone rubber, or combinations thereof. In operation, the expandable balloon  58  can be used to anchor the catheter  10  in a desired position within a vessel wall and prevent leakage from the opening in the vessel wall through which the projection cannula  16  traverses. 
     The expandable balloon  58  is capable of being controlled by a clinician such that it can inflate and/or deflate to the proper size. The sizing of the expandable balloon  58  will differ between patients and applications. The expandable balloon  58  may be in fluid communication with a balloon inflation port  62  through a secondary lumen  60  within the lumen  18  of the projection cannula  16 . Alternatively, the expandable balloon  58  may be in fluid communication with the balloon inflation port  62  through a tube or other means that is positioned within the lumen  18  of the projection cannula  16  as shown in  FIG. 1 . The balloon port  62  may be positioned subcutaneously or otherwise such that a clinician can easily access the balloon port  62  when the catheter  10  is positioned within a vessel. In this manner the balloon port  62  can be accessed by a clinician, subcutaneously, percutaneously or otherwise, and used to inflate or deflate the expandable balloon  58  with no or minimal invasion to the patient. 
     Now referring to  FIG. 3 , an autoretroperfusion system  100  is shown positioned to allow arterial blood to irrigate the coronary sinus of a heart  101 . With respect to the heart  101 , the autoretroperfusion system  100  may be used for treatment of myocardial infarctions by injecting arterial blood into the coronary sinus in synchronism with the patient&#39;s heartbeat. Furthermore, the autoretroperfusion system  100  is capable of controlling the pressure of the arterial blood flow as it enters the venous vessel such that when the arterial blood flow is first introduced into the venous system, the pressure of the re-routed arterial blood flow is reduced to protect the thinner venous vessels. In this manner, the venous system is allowed to gradually arterialize. Further, after the selected venous vessel has sufficiently arterialized, the autoretroperfusion system  100  is capable of reducing or ceasing its influence on the pressure of the re-routed arterial blood flow such that the standard arterial blood flow pressure is thereafter allowed to flow into the arterialized venous vessel. 
     Autoretroperfusion system  100  comprises the catheter  10 , a second catheter  150 , and a connector  170 . The catheter  10  is for placement within an arterial vessel and is configured as previously described in connection with  FIGS. 1-2B . The second catheter  150  is configured for placement within the venous system. The connector  170  is configured to form an anastomosis between the catheter  10  and the second catheter  150  and further functions to monitor various data points on the blood flow flowing therethrough. In addition, in at least one embodiment, the connector  170  is capable of controlling the pressure of arterial blood flowing therethrough. 
     The second catheter  150  is configured for placement within a venous vessel wall  114  and comprises a flexible tube having a proximal end  152 , a distal end  154  and at least one lumen  156  extending between the proximal end  152  and the distal end  154 . Both the proximal end  152  and the distal end  154  of the second catheter  150  are open and in communication with the at least one lumen  156  of the second catheter  150 , thereby allowing blood to flow into the at least one lumen  156  through the proximal end  152  and out of the distal end  154  back into the venous vessel  114 . The second catheter  150  may be any catheter known in the art that is capable of intravascular insertion and advancement through the venous system and may comprise any appropriate material, including without limitation, polyurethane or silicone rubber. In at least one embodiment, the second catheter  150  is configured to receive a guidewire  510  (see  FIGS. 4A and 4B ) through the at least one lumen  156  to facilitate the intravascular delivery of the distal end  154  of the second catheter  150  into the desired location of the venous vessel  114 . Furthermore, similar to the catheter  10 , the second catheter  150  may be coated with heparin or any other suitable anti-coagulant prior to insertion in order to facilitate the extended placement of the second catheter  150  within the venous vessel  114 . Accordingly, the autoretroperfusion system  100  may be used to deliver chronic retroperfusion treatment to an ischemic area of a body. 
       FIGS. 4A and 4B  show side views of the distal end  154  of the second catheter  150  positioned within the venous vessel wall  114 . As shown in  FIG. 4A , the distal end  154  of the second catheter  150  may further comprise an expandable balloon  158  coupled with the external surface of the second catheter  150 . In operation, the expandable balloon  158  can be used to anchor the distal end  154  of the second catheter  150  in the desired location within the venous vessel wall  114 . The expandable balloon  158  may be any expandable balloon that is appropriate for insertion within a vessel and can be formed of any material suitable for this function, including without limitation, polyethylene, latex, polyestherurethane, polyurethane, sylastic, silicone rubber, or combinations thereof. 
     The expandable balloon  158  is capable of being controlled by a clinician such that it can inflate and/or deflate to the proper size. The sizing of the expandable balloon  158  will differ between patients and applications and it is often important to determine the proper sizing of the expandable balloon  158  to ensure the distal end  154  of the second catheter  150  is securely anchored within the desired location of the vessel wall  114 . The accurate size of the expandable balloon  158  can be determined through any technique known in the art, including without limitation, by measuring the compliance of the expandable balloon  158  ex vivo or in vivo. In addition, the distal end  154  of the second catheter  150  may further comprise a plurality of electrodes that are capable of accurately measuring the cross-sectional area of the vessel of interest as is known in the art. For example, the plurality of electrodes may comprise a combination of excitation and detection electrodes as described in detail in the currently pending U.S. patent application Ser. No. 11/891,981 entitled System and Method for Measuring Cross-Sectional Areas and Pressure Gradients in Luminal Organs, and filed on Aug. 14, 2007, which is hereby incorporated by reference in its entirety. In at least one embodiment, such electrodes may comprise impedance and conductance electrodes and may be used in connection with ports for the suction of fluid from the vessel and/or the infusion of fluid therein. 
     The expandable balloon  158  may be in fluid communication with a secondary lumen  160  disposed within the at least one lumen  156  of the second catheter  150 . In this example, the secondary lumen  160  is coupled with a balloon port  162  that extends from the proximal end  152  of the second catheter  150  (see  FIG. 3 ). Accordingly, when the autoretroperfusion system  100  is positioned within a patient, the balloon port  162  can be easily accessed by a clinician, subcutaneously, percutaneously or otherwise, and used to inflate or deflate the expandable balloon  158  with no or minimal invasion to the patient. 
     As shown in  FIGS. 4A and 4B , the distal end  154  of the second catheter  150  may further comprise at least one sensor  166  coupled therewith. In at least one embodiment, the at least one sensor  166  is disposed on the distal end  154  of the second catheter  150  distally of the expandable balloon  158 ; however, it will be understood that the at least one sensor  166  may be disposed in any location on the distal end  154  of the second catheter  150 . 
     The at least one sensor  166  may be used for monitoring purposes and, for example, may be capable of periodically or continuously monitoring the pressure of the blood flow flowing through the at least one lumen  156  of the first catheter  150  or the venous vessel  14  in which the second catheter  150  is inserted. Additionally, one of the at least one sensors  166  may be used to monitor the pH or the concentrations of carbon dioxide, lactate, or cardiac enzymes within the blood. Furthermore, the at least one sensor  166  is capable of wirelessly communicating the information it has gathered to a remote module through the use of telemetry technology, the interne, or other wireless means, such that the information can be easily accessed by a clinician on a real-time basis or otherwise. 
     Now referring back to  FIG. 3 , the autoretroperfusion system  100  further comprises a connector  170 . The connector  170  comprises any connector or quick connector known in the medical arts that is capable of forming an anastomosis between an artery and a vein such that oxygenated blood from the arterial system can flow into the venous system. For example, the connector  170  may comprise an annular connector that is capable of coupling with the proximal end  20  of the projection cannula  16  of the catheter  10  and with the proximal end  152  of the second catheter  150  such that arterial blood can flow continuously from the at least one lumen  15  of the catheter  10  to the at least one lumen  156  of the second catheter  150 . The connector  170  may be formed of any suitable material known in the art including, but not limited to, silicon rubber, poly(tetrafluoroethene), and/or polyurethane. 
     The connector  170  of the autoretroperfusion system  100  may comprise a pressure/flow regulator unit that is capable of measuring the flow rate of the blood moving therethrough, the pressure of the blood moving therethrough, and/or other data regarding the blood flowing through the anastomosis. The connector  170  may also be capable of transmitting such gathered data to a remote module  180  through a lead placed intravascularly or, in the alternative, through telemetry or another wireless means. The remote module  180  may comprise any device capable of receiving the data collected by the connector  170  and displaying the same. For example, and without limitation, the remote module  180  may comprise any display device known in the art or a computer, a microprocessor, hand-held computing device or other processing means. 
     Additionally, the connector  170  may further comprise a means for regulating the blood flow through the anastomosis. One of the main challenges of successfully delivering retroperfusion therapies is that the arterial blood pressure must be reduced prior to being introduced into a vein due to the thinner and more fragile anatomy of venous walls. Indeed, subjecting a non-arterialized venous vessel to the high pressures of arterial blood flow typically results in rupture of the venous vessel. Accordingly, with retroperfusion therapies, it is critical to ensure that the pressure of the arterial blood flow is at least initially controlled such that the venous vessel can arterialize prior to being subjected to the unregulated pressure of the arterial blood flow. 
     In at least one embodiment the connector  170  may comprise an external compression device to facilitate the control of the flow rate of the blood moving through the anastomosis. Alternatively, other means that are known in the art may be employed to regulate the blood flow and pressure of the blood flowing through the anastomosis formed by the connector  170 . In at least one embodiment, the means for regulating the blood flow through the anastomosis formed by the connector  170  is capable of regulating the pressure and/or flow velocity of the blood flowing through the anastomosis. For example, the means for regulating blood flow can be adjusted to ensure that about a 50 mg Hg pressure drop occurs in the blood flow between the arterial vessel and the venous vessel. 
     The connector  170  is capable of not only transmitting data to the remote module  180 , but also receiving commands from the remote module  180  and adjusting the means for regulating blood flow pursuant to such commands. Accordingly, when the autoretroperfusion system  100  is positioned within a patient for retroperfusion therapy, a clinician can use the remote module  180  to view the blood flow data collected by the connector  170  and non-invasively adjust the connector  170  to achieve the desired pressure and/or flow through the anastomosis. Such remote control of the connector  170  is particularly useful as a clinician may incrementally decrease the connector&#39;s  170  regulation of the blood flow without surgical intervention during the venous arterialization process and/or after the venous vessel arterializes. 
     Further, where the remote module  180  comprises a computer or other processing means, the remote module  180  is also capable of being programmed to automatically analyze the data received from the connector  170  and, based on the results thereof, suggest how to adjust the means of regulating the blood flow of the connector  170  and/or automatically adjust the means of regulating the blood flow of the connector  170  to achieve the optimal result. For example, and without limitation, when the autoretroperfusion system  100  is implanted into a patient and the anastomosis is first performed, the remote module  180  can automatically adjust the means for regulating the blood flow of the connector  170  based on the initial blood flow data received by the remote module  180 . In this manner, the desired pressure drop between the arterial system and the venous system is immediately achieved and the risk of venous rupture is significantly reduced. 
     Alternatively, where the connector  170  of the autoretroperfusion system  100  does not comprise a means for regulating blood flow, the gradual arterialization of the venous vessel can be achieved through other techniques known in the art. For example, in at least one embodiment, the autoretroperfusion system  100  further comprises a coil designed to at least partially occlude the vein of interest. In this manner, the pressure is allowed to build in front of the portion of the vein at least partially occluded by the coil and the vein gradually arterializes. In this at least one embodiment, the coil may comprise a metallic memory coil (made of nitinol, stainless steel or other acceptable materials that are radioopaque) and is covered with polytetrafluorethylene, polyethylene terephthalate, polyurethane or any other protective covering available in the medical arts. 
     Additionally, gradual arterialization can be performed by the second catheter  150 . In this embodiment of autoretroperfusion system  100 , the at least one lumen  156  of the second catheter  150  is designed to provide an optimal stenosis geometry to facilitate the desired pressure drop as the arterial blood flows therethrough and into the venous system. For example, and without limitation, the at least one lumen  156  may further comprise an internal balloon or resorbable stenosis as disclosed in International Patent Application No. PCT/US2006/029223, entitled “Devices and Methods for Controlling Blood Perfusion Pressure Using a Retrograde Cannula,” filed Jul. 28, 2006, which is hereby incorporated by reference herein. 
     In at least one embodiment, the stenosis comprises an internal expandable balloon (not shown) positioned within the lumen  156  of the second catheter  150 . In this at least one embodiment, the internal expandable balloon can be used to provide a pressure drop between the arterial and venous systems as is required to achieve the gradual arterialization of the target vein. The internal expandable balloon and the external expandable balloon  158  of the second catheter  150  may be positioned concentrically or, alternatively, the internal expandable balloon and the expandable balloon  158  may be coupled with distinct portions of the second catheter  150 . 
     The internal expandable balloon may comprise any material suitable in the medical arts, including, without limitation, polyethylene, latex, polyestherurethane, polyurethane, sylastic, silicone rubber, or combinations thereof. Further, the internal expandable balloon may be in fluid communication with a tertiary lumen (not shown) disposed within the at least one lumen  156  of the second catheter  150 . In this embodiment, the tertiary lumen is also in fluid communication with an internal balloon port that extends from the proximal end  152  of the second catheter  150 . Accordingly, the internal balloon port can be easily accessed by a clinician, subcutaneously, percutaneously or otherwise, and the internal balloon port can be used to inflate or deflate the internal expandable balloon with minimal or no discomfort to the patient when the system  100  is in operation. Alternatively, the internal expandable balloon may be in fluid communication with the at least one lumen  156  of the second catheter  150 . In this example, the arterial blood flow through the at least one lumen  156  functions to inflate and deflate the internal expandable balloon in conjunction with the systolic and diastolic components of a heart beat. 
     The internal expandable balloon may be sized to a specific configuration in order to achieve the desired stenosis. In one embodiment, the size of the desired stenosis may be obtained by measuring the pressure at the tip of the distal end  156  of the second catheter  150  with the at least one sensor  166  while the internal expandable balloon is being inflated. Once the desired intermediate pressure is obtained, the internal expandable balloon volume may then be finalized and the vein is thereafter allowed to arterialize at the modified pressure for a defined period of time. At the end of the defined period (typically about 2-3 weeks), the internal expandable balloon may be removed from the at least one lumen  156  of the second catheter  150 . 
     Insertion and/or removal of the internal expandable balloon from the system  100  may be achieved through the internal balloon port and the related tertiary lumen of the second catheter  150 . For example, if the internal expandable balloon is no longer necessary to control the pressure on the venous system because the arterialization of the vein is substantially complete, the internal expandable balloon can be deflated through use of internal balloon port and withdrawn from the system  100  through the tertiary lumen and the internal balloon port. 
     Other embodiments of the system  100  may comprise other suitable means for providing a stenosis within the at least one lumen  156  of the second catheter  150  such that a pressure drop is achieved in blood flowing therethrough. For example, while a stenosis can be imposed by inflation of the internal expandable balloon, it may also be imposed through positioning a resorbable material within the at least one lumen  156  of the second catheter  150 . The resorbable stenosis may be comprised of a variety of materials including, for example and without limitation, magnesium alloy and polyols such as mannitol, sorbitol and maltitol. The degradation rate of the resulting resorbable stenosis will be dependent, at least in part, upon on what type of material(s) is selected to make-up the resorbable stenosis and the same may be manipulated to achieve the desired effect. 
     In addition to the aforementioned components of the autoretroperfusion system  100 , the autoretroperfusion system  100  may further include a first graft  185  and a second graft  190  as shown in  FIG. 3 . In this embodiment, the first graft  185  is coupled with the proximal end  20  of the projection cannula  16  (that extends through the exterior arterial wall  116 ) and the connector  170 . Further, the second graft  190  is coupled with the proximal end  152  of the second catheter  150  (positioned within the venous vessel wall  114 ) and the connector  170 . Accordingly, in this at least one embodiment, the second graft  190  is capable of traversing the venous vessel wall  114  in such a manner that the anastomosis is sealed and no blood flow is allowed to leak from the anastomosed vein  114 . 
     In this manner, the first and second grafts  185 ,  190  facilitate the formation of an elongated anastomosis between the venous and arterial vessels  114 ,  116  and thereby relieve any pressure that may be applied to the two vessels  114 ,  116  due to the anastomosis formed therebetween. For example and without limitation, in at least one embodiment the combined length of the grafts  185 ,  190  and the connector  170  is about 6 centimeters. However, it will be understood that the grafts  185 ,  190  may comprise any length(s) so long as the dimensions allow for an anastomosis to form between the applicable vessels and a fully developed blood flow is achieved from the artery to the venous vessel of interest. 
     Alternatively, the autoretroperfusion system  100  may only comprise the second graft  190  in addition to the catheter  10 , the second catheter  150  and the connector  170 . In this embodiment, the connector  170  is coupled with the proximal end  20  of the projection cannula  16  and the second graft  190 . Furthermore, the second graft  190  is further coupled with the proximal end  152  of the second catheter  150  such that the second graft  190  traverses an opening within the venous vessel wall  114  (see  FIG. 5 ). 
     The grafts  185 ,  190  may comprise any biocompatible, non-resorbable material having the necessary strength to support the surrounding tissue and withstand the pressure asserted by the blood flow therethrough. Furthermore, the grafts  185 ,  190  must exhibit the necessary flexibility to form an anastomosis between the vein and the artery within which the catheter  10  and the second catheter  150  are respectively housed. For example, and without limitation, the grafts  185 ,  190  may comprise any conventional implant including synthetic and natural prosthesis, grafts, and the like. The grafts  185 ,  190  may also comprise a variety of suitable materials, including those conventionally used in anastomosis procedures, including, without limitation, natural and synthetic materials such as heterologous tissue, homologous tissue, polymeric materials, Dacron, fluoropolymers, and polyurethanes. For example, and without limitation, the first and second grafts  185 ,  190  may comprise a material such as GORE-TEX (polytetraflouroethylene). The grafts  185 ,  190  may be coated with heparin or any other suitable anti-coagulant. Accordingly, the first graft  185  and the second graft  190  may be placed within a vessel or have blood flow therethrough for an extended period of time without inhibiting blood flow due to coagulation. 
     In at least one embodiment of the autoretroperfusion system  100 , the components of the system  100  are available in a package. Here, the package may also contain at least one sterile syringe containing the fluid to be injected into the balloon port  62  to inflate the expandable balloon  58  of the catheter  10  and/or the balloon port  162  to inflate the expandable balloon  158  of the second catheter  150 . Furthermore, the package may also contain devices to facilitate delivery of the autoretroperfusion system  100  such as venous and arterial access devices, a delivery catheter, a guidewire and/or mandrel, an introducer to maintain the catheter  10  in the collapsed position during delivery and, in those embodiments where a coil is used to arterialize the vein of interest, a pusher bar as is known in the art. 
     The guidewire facilitates the delivery of the autoretroperfusion system  100  into a vessel by providing support to the components thereof. The guidewire may comprise any guidewire known in the art. Furthermore, the distal end of the guidewire may comprise a plurality of impedance electrodes that are capable of taking measurements of the size and vessel in which the guidewire is inserted through the use of impedance technology. Additionally, in at least one embodiment, the impedance electrodes may be further capable of communicating such measurements to the remote module  180  through telemetry or other wireless means in a manner similar to the at least one sensor  166  of the distal end  154  of the second catheter  150 . In at least one embodiment, the distal end of the guidewire may comprise two tetrapolar sets of impedance electrodes disposed on its distal-most tip. 
     Based on the information gathered by the impedance electrodes, a clinician can obtain accurate measurements of a selective region of a vessel. In this manner, the expandable balloon  158  coupled with the distal end  154  of the second catheter  150  may be properly sized and the amount of fluid or gas needed to inflate the expandable balloon  158  can be determined prior to introducing the second catheter  150  into the vein of interest. For example, a clinician can use the plurality of impedance electrodes on the guidewire to obtain measurements of the size and shape of the sub-branches of the coronary sinus. Details regarding the specifications and use of the impedance electrodes are described in detail in the currently pending U.S. patent application Ser. No. 10/782,149 entitled “System and Method for Measuring Cross-Sectional Areas and Pressure Gradients in Luminal Organs,” and filed on Feb. 19, 2004, which is hereby incorporated by reference herein in its entirety. 
     Now referring to  FIG. 5 , components of a simultaneous selective autoretroperfusion system  300  are shown. The simultaneous selective autoretroperfusion system  300  (the “SSA system  300 ”) are configured identically to the autoretroperfusion system  100  except that the SSA system  300  further comprises a third catheter  350  and a Y connector  320 , both configured for placement within the venous vessel wall  114 . Specifically, the SSA system  300  comprises the catheter  10 , the second catheter  150 , the third catheter  350 , the connector  170 , and the Y connector  320 . It will be understood that the SSA system  300  can also further comprise the first graft  185  and/or the second graft  190 , and the remote module  180  as described in connection with autoretroperfusion system  100 . 
     The third catheter  350  is configured for placement within the venous vessel wall  114  adjacent to the second catheter  150 . The third catheter  350  is configured identically to the second catheter  150  and comprises a flexible tube having a proximal end  352 , a distal end  354  and at least one lumen  356  extending between the proximal end  352  and the distal end  354 . Both the proximal end  352  and the distal end  354  of the third catheter  350  are open and in communication with the at least one lumen  356  of the third catheter  350 , thereby allowing blood to flow into the at least one lumen  356  through the proximal end  352  and out of the distal end  354  back into the venous vessel  114 . 
     The third catheter  350  may be any catheter known in the art that is capable of intravascular insertion and advancement through the venous system. The third catheter  350  may comprise any appropriate material, including without limitation, polyurethane or silicone rubber. In at least one embodiment, the third catheter  350  is configured to receive a guidewire  310  (see  FIGS. 5 and 6 ) through the at least one lumen  356  in order to facilitate the intravascular delivery of the distal end  354  of the third catheter  350  into the desired location of the venous vessel  114 . Furthermore, the third catheter  350  is coated with heparin or any other suitable anti-coagulant prior to insertion in order to facilitate the extended placement of the third catheter  350  within the venous vessel  114 . 
     As shown in  FIG. 5 , the distal end  354  of the third catheter  350  further comprises an expandable balloon  358  coupled with the external surface of the third catheter  350 . In operation, the expandable balloon  358  can be used to anchor the distal end  354  of the third catheter  350  in the desired location within the venous vessel wall  114 . The expandable balloon  358  may be any expandable balloon that is appropriate for insertion within a vessel and can be formed of any material suitable for this function, including without limitation, polyethylene, latex, polyestherurethane, polyurethane, sylastic, silicone rubber, or combinations thereof. 
     Similar to the expandable balloon  158  of the second catheter  150 , the expandable balloon  358  is capable of being controlled by a clinician such that it can inflate and/or deflate to the proper size. The appropriate size of the expandable balloon  358  can be determined through any technique known in the art, including without limitation, by measuring the compliance of the expandable balloon  358  ex vivo or in vivo. Furthermore, when the guidewire  310  is used to facilitate the delivery of the distal end  354  of the third catheter  350  into the desired location within the venous vessel wall  114 , the electrodes on the distal end of the guidewire  310  may be used to accurately measure the cross-sectional area of the venous vessel  114  such that the expandable balloon  358  can be precisely sized prior to insertion into the vein  114 . 
     In this at least one embodiment, the expandable balloon  358  is in fluid communication with a secondary lumen  360  disposed within the at least one lumen  356  of the third catheter  350 . In this example, the secondary lumen  360  is coupled with a balloon port  362  that extends from the proximal end  352  of the third catheter  350 . Accordingly, when the SSA system  300  is positioned within a patient, the balloon port  362  can be easily accessed by a clinician, subcutaneously, percutaneously or otherwise, and used to inflate or deflate the expandable balloon  358  with no or minimal invasion to the patient. 
     Similar to the second catheter  150 , the distal end  354  of the third catheter  350  may further comprise at least one sensor  366  coupled therewith. The at least one sensor  366  may be configured identically to the at least one sensor  166  of the second catheter  150  and, accordingly, the at least one sensor  366  may be used to monitor the pressure of blood flow through the at least one lumen  356  of the third catheter  350  or the venous vessel  114  or to monitor the pH or the concentrations of carbon dioxide, lactate, or cardiac enzymes within the blood. Furthermore, the at least one sensor  366  is capable of communicating the data it gathers to the remote module  180  through the use of a wireless technology such that a clinician can easily access the gathered information on a real-time basis or otherwise. In at least one embodiment, the at least one sensor  366  is disposed on the distal end  354  of the third catheter  350  distally of the expandable balloon  358 ; however, it will be understood that the at least one sensor  366  may be disposed in any location on the distal end  354  of the third catheter  350 . 
     The Y connector  320  of the SSA system  300  comprises flexible material and has a proximal end  322 , a distal end  324  and at least one lumen  326  extending between the proximal and distal ends  322 ,  324 . The proximal end  322  of the Y connector  322  is open and configured to be securely coupled with the graft  190 . The distal end  324  of the Y connector  322  comprises two open ends which extend from the body of the Y connector  322  in a substantially Y-shaped configuration. The two open ends of the distal end  324  of the Y connector  322  thereby divide the at least one lumen  326  into two separate channels and thus the blood flowing through the at least one lumen  326  is yet again bifurcated. 
     The proximal end  152  of the second catheter  150  is coupled with one of the two open ends of the distal end  324  of the Y connector  322 , thereby receiving a portion of the blood flow that flows through the at least one lumen  326  of the Y-connector. Similarly, the proximal end  352  of the third catheter  350  is coupled with the other open end of the distal end  324  of the Y connector  322  and, thus, the third catheter receives a portion of the blood flow that flows through the at least one lumen  326  of the Y-connector. In this manner, the SSA system  300  can be used to simultaneously retroperfuse more than one ischemic area of the body. 
     In application, the second catheter  150  and the third catheter  350  are positioned adjacent to each other within the venous vessel wall  114  as shown in  FIG. 5 . Furthermore, the distal ends  154 ,  354  of the second and third catheters  150 ,  350 , respectively, may be placed within different veins such that the arterial blood is delivered to selective portions of ischemic tissue. For example, as shown in  FIG. 6 , in at least one embodiment the SSA system  300  can be applied to a heart  314  to provide an arterial blood supply to two separate coronary veins, or sub-branches, simultaneously. In this at least one embodiment, the distal ends  154 ,  354  of the second and third catheters  150 ,  350  are both advanced through the coronary sinus  370 . As the diameter of the coronary sinus  370  ranges from about 10 to about 20 millimeters, cannulating the coronary sinus  370  with both the second and third catheters  150 ,  350  does not occlude the normal antegrade flow of the blood therethrough. Upon reaching the veins or sub-branches of interest, the distal ends  154 ,  354  of the second and third catheters  150 ,  350  are each independently positioned within the veins of interest. In the example shown in  FIG. 6 , the second catheter  150  is positioned within the interventricular vein  374  and the distal end  354  of the third catheter  350  is positioned within the middle cardiac vein  376 . As with autoretroperfusion system  100 , the expandable balloons  158 ,  358  are inflated through balloon ports  162 ,  362 , respectively (shown in  FIG. 5 ), such that the distal ends  154 ,  354  of the second and third catheters  150 ,  350  are securely anchored in the desired location within the veins of interest. In this manner, the SSA system  300  can deliver controlled arterial blood flow to, and thus arterialize, two areas of the heart  314  simultaneously. 
     In at least one embodiment of the SSA system  300 , the components of the system  300  are available in a package. Here, the package may also contain sterile syringes with the fluids to be injected into the balloon ports  162 ,  362  to inflate the expandable balloons  158 ,  358 , respectively. Furthermore, the package may also contain devices to facilitate delivery of the SSA system  300  such as arterial and venous access devices, a delivery catheter, at least two guidewires (configured as described in connection with the delivery of autoretroperfusion system  100 ), an introducer to maintain the catheter  10  in the collapsed position during delivery and, in those embodiments where a coil is used to arterialize the vein of interest, a pusher bar as is known in the art. 
     Now referring to  FIG. 7 , a flow chart of a method  400  for performing automatic retroperfusion using the system  100  is shown. While the method  400  is described herein in connection with treating a heart through catheterization of the coronary sinus, it will be understood that the method  400  may be used to perform autoretroperfusion on any organ or tissue in need of retroperfusion treatment. 
     Method  400 , and the embodiments thereof, can be performed under local anesthesia and do not require any arterial sutures. Further, once implanted, the system  100  can deliver chronic treatment to the patient as the system  100  is capable of remaining within a patient&#39;s vascular system for an extended period of time. In this manner, the system  100  and method  400  can be used to treat no-option patients and greatly enhance their quality of life. 
     As shown in  FIG. 7 , in one approach to the method  400 , at step  402  an artery  502  of interest is percutaneously punctured under local anesthesia with a conventional artery access device or as otherwise known in the art. For example and without limitation, in at least one embodiment, an 18 gauge needle is inserted into the femoral or subclavian artery. At step  404 , the catheter  10  housed in a collapsed position within an introducer  504  (see  FIG. 8A ) is inserted into the artery  502  of interest. After the distal end  14  of the catheter  10  is positioned in the desired location within the artery  502 , the introducer  504  is proximally withdrawn from the artery  502  as shown in  FIG. 8B , leaving the catheter  10  positioned therein. 
     In at least one embodiment, the projection cannula  16  is configured such that when the introducer  504  is withdrawn in a proximal direction, the proximal end  12  of the catheter  10  is released from the introducer  504  before the proximal end  20  of the projection cannula  16  is released from the introducer  504 . In this manner, the proximal end  12  of the catheter  10  is delivered within the interior of the arterial wall  502 , while the projection cannula  16  remains housed within the interior of the introducer  504  as shown in  FIG. 8C . Furthermore, because the introducer  504  no longer applies downward pressure to the projection cannula  16  relative to the proximal end  12  of the catheter  10 , the projection cannula  16  is allowed to shift from the collapsed position to the expanded position and therefore extends in a direction that is not parallel with the artery  502  or the body of the catheter  10 . In this manner, as shown in  FIGS. 8C and 8D , the proximal end  20  of the projection cannula  16  is directed through the opening formed in the arterial wall  502  by the introducer  504 . 
     Accordingly, when the catheter  10  is positioned within the artery  502 , the antegrade blood arterial blood flow is allowed to continue through the artery  502  through the proximal end  12  of the catheter  10 , while only a portion of the arterial blood is rerouted through the projection cannula  16  and into the veins  506  of interest. In this manner, the normal blood flow through the artery  502  is not inhibited by operation of the autoretroperfusion system  100 . Furthermore, in addition to bifurcating the blood flowing through the artery  502 , the projection cannula  16  traversing the arterial wall  502  further functions to anchor the catheter  10  in the desired position within the artery  502 . 
     In the embodiment where the catheter  10  further comprises the expandable balloon  58  (see  FIG. 1 ), step  404  may further comprise inflating the expandable balloon  58  to the desired size by injecting fluid into the balloon port  62 . In this manner, the expandable balloon  58  functions to further anchor the catheter  10  in the desired location within the artery  502  and seal the opening in the artery  502  through which the projection cannula  16  projects (see  FIG. 8E ). 
     At step  406 , a vein  506  of interest is percutaneously punctured under local anesthesia with a conventional venous access device or as otherwise known in the art. For example and without limitation, in at least one embodiment, an 18 gauge needle is inserted into the femoral or subclavian vein. At step  408 , a delivery catheter  508  is inserted into and advanced through the vein  506  to catheterize the coronary sinus ostium. A guidewire  510  is then inserted at step  410  into the delivery catheter  510  and advanced into the lumen of the vein  506  through the distal end of the delivery catheter  510 . Furthermore, the guidewire  510  is advanced into the region of interest by use of x-ray (i.e. fluoroscopy), direct vision, transesophageal echocardiogram, or other suitable means or visualization techniques. 
       FIGS. 9 and 10  show schematic views of the method  400  as applied to a heart  500 . Specifically, in this at least one embodiment, at steps  402  and  404  the artery  502 , which in  FIG. 9  comprises the subclavian artery, is punctured and the catheter  10  is inserted and positioned therein. Further, at step  406  the vein  506 , which in  FIG. 9  comprises the subclavian vein, is punctured and at step  408  the delivery catheter  508  is advanced through the superior vena cava  518  and into the coronary ostium of the coronary sinus  520 . As shown in  FIG. 10 , at step  410 , the guidewire  510  is advanced through the coronary sinus  520  and into the vein of interest, which, in this at least one embodiment, comprises the posterior vein  522  of the heart  500 . 
     Now referring back to  FIG. 7 , the guidewire  510  inserted into the vein  506  at step  410  may further comprise a plurality of impedance electrodes as previously described herein. In this approach, the guidewire  510  may be used at optional step  411  to determine the size of the vessel of interest through use of the plurality of impedance electrodes disposed thereon. In this manner, a clinician can use the measurements generated by the impedance electrodes to select a properly sized expandable balloon  158  for use in connection with the second catheter  150 . By using a precisely sized expandable balloon  158  and inflation volume, the clinician can ensure that the distal end  154  of the second catheter  150  is securely anchored within the vessel of interest without imposing an undue force on the venous vessel walls. 
     After the guidewire  510  has been advanced into the vessel of interest at step  410  and, optionally, the dimensions of the vessel of interest have been measured at step  411 , the method  400  advances to step  412 . At step  412 , the distal end  154  of the second catheter  150  is inserted into the delivery catheter  508  over the guidewire  510 . Accordingly, the guidewire  510  is slidably received by the at least one lumen  156  of the second catheter  150 . The distal end  154  of the second catheter  150  is then advanced over the guidewire  510  to the region of interest and the expandable balloon  158  of the second catheter  150  is inflated to anchor the distal end  154  within the targeted vessel.  FIG. 11  shows a schematic view of the method  400 , as applied to the heart  500 , after step  412  has been completed. It will be understood that at any point after the distal end  154  of the second catheter  150  is positioned and anchored within the desired location in the targeted vessel, the delivery catheter  508  and the guidewire  510  may be withdrawn from the vein of interest. 
     After the distal end  154  of the second catheter  150  is secured within the targeted vessel, at step  414  the anastomosis between the vein  506  and the artery  502  is formed. Specifically, in at least one approach, the proximal end  20  of the projection cannula  16  of the catheter  10  is coupled with the proximal end  152  of the second catheter  150  by way of the connector  170 . In the at least one embodiment of the system  100  comprising the first graft  185  and the second graft  190 , the connector  170  may be coupled with the catheter  10  and the second catheter  150  via the first graft  185  and the second graft  190  to form an elongated anastomosis. Alternatively, in yet another approach, the connector  185  may be coupled with the catheter  10  via the proximal end  20  of the projection cannula  16  and the second catheter  150  via only the second graft  190 . It will be understood that any combination of the catheter  10 , the second catheter  150  and the first and second grafts  185 ,  190  may be used in connection with the connector  170  to form the desired anastomosis between the vein  506  and the artery  502 . 
     After the anastomosis is formed and the arterial blood is allowed to flow through the anastomosis and thereby through the connector  170 , at step  416  the connector  170  measures the flow rate, pressure and any other desired data of the arterial blood flow. The connector  170  transmits the collected data to the remote module  180  either through intravascularly placed leads or wirelessly, through telemetry or other means. In this manner, a clinician may easily view the blood flow data on the remote module  180  and assess the degree of pressure drop that will be required to preserve and gradually arterialize the vein  506 . 
     At step  418 , the pressure of the arterial blood flow through the system  100  is modified to transmit the desired pressure to the venous system. In this step  418  the pressure modification can be achieved through a clinician modifying the means of regulating the blood flow of the connector  170  through remote means or, in at least one embodiment of the system  100 , inflating the internal expandable balloon of the second catheter  150  using the internal balloon port in order to partially occlude the flow of arterial blood through the at least one lumen  156  of the second catheter  150 . Furthermore, in at least one alternative embodiment of the system  100 , a clinician may deliver a resorbable stenosis configured to achieve the necessary pressure drop into the at least one lumen  156  of the second catheter  150  through means known in the art. 
     Alternatively, as previously described in connection with autoretroperfusion system  100 , the remote module  180  may further comprise a computer or other processing means capable of being programmed to automatically analyze the data received from the connector  170  and, based on such data, determine the proper degree of adjustment required in the blood pressure flowing through the anastomosis. In this embodiment, at step  418 , the remote module  180  automatically adjusts the means of regulating the blood flow of the connector  170  to achieve the optimal pressure drop. In this manner, the desired pressure drop between the arterial system and the venous system is immediately achieved and the risk of venous rupture is significantly reduced. 
     In step  420  the method  400  allows the arterial blood having a modified pressure to irrigate the vein  506  for a period of time such that the vein  506  properly arterializes. For example, and without limitation, the patient&#39;s venous system may be subjected to the reduced arterial pressure for about fourteen days to allow the vein  506  to adapt to the elevated blood pressure flowing therethrough. 
     After arterialization of the vein  506  is achieved, at step  422  the patient may optionally undergo a coronary venous bypass graft surgery and the components of the autoretroperfusion system  100  may be removed. However, as previously discussed, even with a properly arterialized vein  506 , many patients that require retroperfusion therapy may still not be candidates for a coronary vein bypass graft surgery. In the event that the patient is unable to tolerate such a procedure, after the vein  506  has arterialized at step  420 , the method  400  can progress directly to step  424 . At step  424 , the pressure modification of the arterial blood flowing through the second catheter  150  is ceased. Accordingly, pre-arterialized veins  506  are subjected to the full arterial pressure of the blood flowing through the anastomosis and second catheter  150 . In at least one embodiment, a clinician can cease the pressure modification by adjusting the controller  170 . Alternatively, in the at least one embodiment where the controller  170  can be automatically adjusted by the remote module  180 , the remote module  180  can automatically adjust the controller  170  after the veins  506  have pre-arterialized. Further, where the pressure drop is achieved through the use of an internal expandable balloon positioned within the at least one lumen  156  of the second catheter, the clinician may deflate the internal expandable balloon through the internal balloon port and thereafter withdraw the deflated internal expandable balloon through the tertiary lumen of the second catheter and the internal balloon port. In yet another embodiment where a resorbable stenosis is used to achieve the pressure drop in the arterial blood as it flows through the second catheter  150 , the resorbable stenosis can be configured to dissolve after the desired period of time, thereby gradually decreasing the influence the resorbable stenosis has on the pressure of the blood flowing through the at least one lumen  156  of the second catheter over a period of time. Accordingly, the autoretroperfusion system  100  can remain chronically implanted within the patient to deliver oxygen-rich blood to a targeted area of tissue over an extended period of time. 
     Now referring to  FIG. 12 , a flow chart of a method  600  for performing simultaneous selective retroperfusion using the SSA system  300  is shown. While the method  600  is described herein in connection with treating a heart  500  through catheterization of the coronary sinus  520 , it will be understood that the method  600  may be used to perform autoretroperfusion on any organ or tissue in need of retroperfusion treatment. The reference numerals used to identify the steps of method  600  that are included in the description of method  400  designate like steps between the two methods  400 ,  600 . As such, like steps between the two methods  400 ,  600  will not be discussed in detail with respect to the method  600  and it will be understood that such description can be obtained through the description of the method  400 . 
     Method  600 , and the embodiments thereof, can be performed under local anesthesia and does not require arterial sutures. Further, once implanted, the SSA system  300  can deliver simultaneous chronic treatment to multiple ischemic locations as the system  300  is capable of remaining within a patient&#39;s vascular system for an extended period of time and selectively retroperfusion more than one sub-branch of a vein  506 . 
     The method  600  progresses through steps  402  through  410  as previously described in connection with the method  400 . After the guidewire  510  is advanced through the coronary sinus  520  and into the first vein of interest, a second guidewire  610  is inserted at step  602  into the delivery catheter  508  adjacent to the guidewire  510 , and advanced into the lumen of the vein  506  through the distal end of the delivery catheter  510 . The second guidewire  610  is then advanced into a second region of interest by use of x-ray (i.e. fluoroscopy), direct vision, transesophageal echocardiogram, or other suitable means or visualization techniques. The second guidewire  610  is configured similar to the guidewire  510  and is capable of functioning the in the same manner. 
       FIG. 13  shows a schematic view of the method  600  as applied to a heart  500 . Specifically, in this at least one embodiment,  FIG. 13  shows the method  600  at step  602  wherein the guidewire  510  is inserted a first vein of interest, which comprises the posterior vein  522  of the heart  500 , and the second guidewire  610  is inserted into a second vein of interest, which comprises the interventricular vein  622  of the heart  500 . 
     Now referring back to  FIG. 12 , the guidewire  610  inserted into the second vein of interest in step  602  may further comprise a plurality of impedance electrodes as previously described with respect to the guidewire  510 . In this embodiment, the guidewire  610  may be used at optional step  603  to determine the size of the second vessel of interest through use of the plurality of impedance electrodes disposed thereon. In this manner, a clinician can use the measurements generated by the impedance electrodes to select a properly sized expandable balloon  358  for use in connection with the third catheter  350 . By using a precisely sized expandable balloon  358  and inflation volume, a clinician can ensure that the distal end  354  of the third catheter  350  is securely anchored within the second vessel of interest without imposing an undue force on the venous vessel walls. 
     After the guidewire  610  has been advanced into the second vessel of interest at step  602  and, optionally, the dimensions of the second vessel of interest have been measured at step  603 , the method  600  advances to step  412  wherein the second catheter  150  is inserted over the guidewire  510  as described in connection with method  400 . At step  604 , the distal end  354  of the third catheter  350  is inserted into the delivery catheter  508  over the second guidewire  610 . Accordingly, the second guidewire  610  is slidably received by the at least one lumen  356  of the third catheter  350 . The distal end  354  of the third catheter  350  is then advanced over the second guidewire  610  to the second region of interest and the expandable balloon  358  of the third catheter  350  is inflated to anchor the distal end  354  within the targeted vessel.  FIG. 14  shows a schematic view of the method  600  at step  604  as applied to the heart  500 . It will be understood that at any point after the distal ends  154 ,  354  of the second and third catheters  150 ,  350  are positioned and anchored in the desired locations within the targeted vessels, the delivery catheter  508  and the guidewires  510 ,  610  may be withdrawn from the vein  506 . 
     After both the distal end  154  of the second catheter  150  and the distal end  354  of the third catheter  350  are secured within the targeted vessels, the method  600  proceeds to step  414  where the anastomosis is formed between the vein  506  and the artery  502  as described in connection with method  400 . Thereafter, the method  600  advances through steps  416  through  424  as described in connection with the method  400 . Furthermore, at step  418 , it will be recognized that a clinician can independently adjust the pressure drop through the second and third catheters  150 ,  350  in the event that an internal expandable balloon is used in either or both catheters  150 ,  350  or resorbable stenosis are employed within the at least one lumens  156 ,  356  of the second and third catheters  150 ,  350 . Alternatively, in the at least one embodiment where the controller  170  comprises a means for regulating the blood flow through the anastomosis, the pressure of the arterial blood flowing through both the second and third catheters  150 ,  350  may be substantially the same. 
     As described herein, the method  600  may be used to simultaneously and immediately treat two different ischemic areas of a tissue through the use of one minimally to non-invasive procedure. Furthermore, the method  600  can provide no-option patients with a viable treatment option that is not associated with contraindications for congestive heart failure, diabetes, or drug treatment. 
     While various embodiments of devices, systems, and methods for achieving autoretroperfusion of the heart tissue have been described in considerable detail herein, the embodiments are merely offered by way of non-limiting examples of the disclosure described herein. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of this disclosure. It will therefore be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the scope of the disclosure. Indeed, this disclosure is not intended to be exhaustive or to limit the scope of the disclosure. The scope of the disclosure is to be defined by the appended claims, and by their equivalents. 
     Further, in describing representative embodiments, the disclosure may have presented a method and/or process as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps disclosed herein should not be construed as limitations on the claims. In addition, the claims directed to a method and/or process should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present disclosure. 
     It is therefore intended that the disclosure will include, and this description and the appended claims will encompass, all modifications and changes apparent to those of ordinary skill in the art based on this disclosure.