Patent Publication Number: US-11660096-B2

Title: Operating a vessel occlusion catheter

Description:
CROSS-REFERENCES TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 16/382,649, filed on Apr. 12, 2019, which is a continuation of U.S. patent application Ser. No. 15/177,457 filed on Jun. 9, 2016, which is a continuation of U.S. patent application Ser. No. 13/689,929 filed Nov. 30, 2012, which is a division of U.S. patent application Ser. No. 13/688,725 filed on Nov. 29, 2012, which is a division of U.S. patent application Ser. No. 12/786,822 filed on May 25, 2010, which claims priority to European Patent Application No. 10 450 019.4 filed on Feb. 16, 2010. The entire contents of these previous applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This document relates to systems and methods for inflating and deflating a balloon of a vessel occlusion catheter device arranged in a body vessel. 
     BACKGROUND 
     Balloon catheters have been used for a number of medical applications. A balloon catheter comprises a balloon which can be brought from the deflated state into the expanded state by the introduction of a fluid, and from the expanded state back into the deflated state by evacuation. The fluid may be comprised of a gas or a liquid. 
     Balloon catheters are, for instance, used for the balloon dilatation of constricted blood vessels in the context of a percutaneous transluminal angioplasty. In that case, a balloon attached to a vascular catheter is advanced within a blood vessel as far a to a pathologically constricted vascular site, and the balloon is deployed on the constricted site under a high pressure (6 to 20 bar). This causes the constrictions, which are primarily due to arteriosclerotic vascular sclerosis, to be dilated until they will no longer, or less strongly, impair the blood flow. 
     Balloon catheters may, however, also be employed in the context of a pressure-controlled intermittent occlusion of a body vessel and, in particular, the coronary sinus. Methods for the pressure-controlled intermittent occlusion of the coronary sinus are, for instance, described in the documents EP 609914 A1, EP 230996 A2, EP 1406683 A2, EP 1753483 A1, EP 1755702 A1 and WO 2008/064387 A1. In those methods, the coronary sinus is cyclically occluded and released again by using a balloon, the occlusion of the coronary sinus, during the occlusion phases, inducing a pressure increase and hence a retroperfusion of blood via the respective vein into the nutritive capillaries of the ischemic region so as to enable a redistribution of flow into those regions. Upon release of the occlusion, the retroperfused blood is flushed out while metabolic waste products are, at the same time, discharged. The pressure in the occluded coronary sinus is each measured during the occlusion phases, the release of the occlusion as well as the initiation of the occlusion occurring as a function of the measured pressure values. 
     As opposed to a balloon dilatation in the context of a percutaneous transluminal angioplasty, the pressure-controlled intermittent occlusion of a blood vessel and, in particular, the coronary sinus does not aim to inflate the balloon with such a high pressure as to cause an irreversible deformation and, in particular, expansion of the respective vascular region. The inflation of the balloon rather is to be controlled in a manner that the balloon exerts a pressure on the vessel wall, which will just do to occlude the blood vessel to a sufficiently safe extent and prevent blood from flowing past the balloon. If too high a pressure is fed to the balloon, this will cause too strong a radial expansion of the blood vessel, whereby the respective mechanical load on the vessel wall may lead to irreversible damage, which is to be prevented anyhow. On the other hand, too small a pressure supply to the balloon would save the vessel wall, yet the balloon would not completely occlude the vessel. 
     SUMMARY 
     Some embodiments of a system or method for controlling the inflation of a balloon catheter arranged in a blood vessel can provide a process by which it is feasible to control the filling of the balloon in such a manner that the vessel wall will not be overstressed while safely occluding of the blood vessel. 
     In particular embodiments, some systems and methods for operating a vessel occlusion catheter may include a control and inflation device to control the filling of the balloon in such a manner that the vessel wall will not be irreversible deformed while the safe occlusion of the blood vessel is achieved. For example, a coronary sinus occlusion catheter may include a balloon device that is repeatedly inflated and deflated to intermittently occlude the coronary sinus. A control system for the occlusion catheter can include the control and inflation device having components to inflate and deflate the balloon device in a safe manner that reduces the likelihood of overstressing the vessel wall of the coronary sinus. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a portion of a system for treating heart tissue, in accordance with some embodiments. 
         FIG.  2    is a perspective view of another portion of the system of  FIG.  1   . 
         FIG.  3    is a block diagram of a control and inflation device of the system of  FIG.  2   . 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Referring to  FIGS.  1 - 2   , some embodiments of a system  100  for treating heart tissue can include a coronary sinus occlusion catheter  120  and a control system  140  ( FIG.  2   ). In particular embodiments, the control system  140  can be configured to control the operation of the catheter  120  for providing pressure-controlled intermittent coronary sinus occlusion (PICSO) and to receive heart sensor data for display. The coronary sinus occlusion catheter  120  includes a distal tip portion  121  (leading to a distal end depicted in  FIG.  1   ) and a proximal portion  131 , which includes a proximal hub  132  that is coupled to the control system  140  via a number of fluid or sensor lines  133 ,  134 , and  135 . Accordingly, the control system  140  may be employed to operate one or more components at the distal tip portion  121  of the coronary sinus occlusion catheter  120  while also receiving one or more sensor signals that provide data indicative of heart characteristics (e.g., coronary sinus pressure, electrocardiogram (ECG) information, and the like). 
     Briefly, in use, the distal tip portion  121  of the coronary sinus occlusion catheter  120  can be arranged in a coronary sinus  20  of a heart  10  and thereafter activated to intermittently occlude the blood flow exiting from the coronary sinus  20  and into the right atrium  11 . During such an occlusion of the coronary sinus  20 , the venous blood flow that is normally exiting from the coronary sinus  20  may be redistributed into a portion of heart muscle tissue  30  that has been damaged due to blood deprivation. For example, the portion of heart muscle tissue  30  can suffer from a lack of blood flow due to a blockage  35  in a coronary artery  40 . As a result, the arterial blood flow to the affected heart muscle tissue  30  via a local artery  41  can be substantially reduced such that the heart muscle tissue  30  becomes ischemic or otherwise damaged. Further, because the arterial blood flow is reduced, the venous blood flow exiting from the local vein  21  is likewise reduced. Other branch veins  22  located at different regions along the heart  10  may continue to receive blood flow, thereby creating a supply of venous blood flow exiting through the coronary sinus  20 . In some embodiments, the coronary sinus occlusion catheter  120  can be delivered into the coronary sinus  20  and thereafter activated so as to intermittently occlude the coronary sinus  20  before, during, or after treating the blockage  35  on the arterial side. Such an occlusion can cause the venous blood flow to be redistributed to the local vein  21  and then into the portion of heart muscle tissue  30  can suffer from a lack of blood flow due to a blockage  35  in a coronary artery  40 . As such, the ischemic or otherwise damaged heart muscle tissue  30  can be treated (e.g., reduction of border zone infarct size) with the redistributed venous blood flow in that the heart muscle tissue  30  receives an improved redistribution of flow before, during, and after the blockage  35  is repaired or removed to restore normal coronary arterial blood flow. 
     Furthermore, in use, the control system  140  ( FIG.  2   ) is configured to provide automated control of an occlusion component (e.g., an inflatable balloon  122  or the like) of the coronary sinus occlusion catheter  120 . As described in more detail below, the control system  140  includes a computer processor that executes computer-readable instructions stored on a computer memory device so as to activate or deactivate the occlusion in the coronary sinus  20  in accordance with particular patterns. For instance, the control system  140  can be configured to activate the occlusion component of the catheter  120  in the coronary sinus  20  as part of a predetermined pattern of occlusion periods and release periods that is independent of the coronary sinus pressure, or as part of a pressure-dependent pattern that is at least partially defined by the coronary sinus pressure readings during the procedure. In addition, the control system  120  is equipped with a display device  142  having a graphical user interface that provides a cardiologist or other user with time-sensitive, relevant data indicative of the progress of a coronary sinus occlusion procedure and the condition of the heart  10 . As such, the user can readily monitor the patient&#39;s condition and the effects of intermittently occluding the coronary sinus  20  by viewing the graphical user interface while contemporaneously handling the coronary sinus occlusion catheter  120  other heart treatment instruments (e.g., angioplasty catheters, stent delivery instruments, or the like). It should be understood from the description herein that, in some embodiments, the control system  140  and the coronary sinus occlusion catheter  120  can be used as part of a system for treating the heart muscle tissue before, during, and after the blockage  35  is repaired or removed to restore normal coronary arterial blood flow. 
     Referring in more detail to  FIG.  1   , the coronary sinus occlusion catheter  120  can be delivered via the venous system to the coronary sinus  20  before, during, or after repairing or treating the blockage  35  the coronary artery  40 . In such circumstances, the portion of heart muscle tissue  30  that is damaged due to lack of arterial blood flow (as a result of the blockage) can be treated with a supply of venous blood while the normal arterial blood flow is restored (as a result of repairing or removing the blockage  35 ). 
     The system  100  may include a guide member  110  that is advanced through the venous system of the patient and into the right atrium  11 . The guide member  110  in this embodiment comprises a guide sheath having a lumen extending between a distal end  111  ( FIG.  1   ) and a proximal end (not shown). In alternative embodiments, the guide member  110  can include a guide wire having an exterior surface extending between the distal end and the proximal end. Optionally, the guide member  110  includes a steerable mechanism to control the orientation of the distal end so as to steer the distal end  111  through the venous system and into the right atrium  11 . Also, the guide member  110  can include one or more marker bands along the distal end  111  so that the position of the distal end can be monitored during advancement using an imaging device. 
     After the guide member  110  is advanced into the right atrium  11 , the distal end  111  may be temporarily positioned in the coronary sinus  20 . From there, the distal tip portion  121  of the coronary sinus occlusion catheter  120  can be slidably advanced along the guide member  110  for positioning inside the coronary sinus  20 . In the embodiments in which the guide member  110  comprises a guide sheath, the distal tip portion  121  of the coronary sinus occlusion catheter  120  can slidably engage with an interior surface of the lumen during advancement toward the coronary sinus  20 . In the alternative embodiments in which the guide member  110  comprises a guide wire structure, the distal tip portion  121  of the coronary sinus occlusion catheter  120  can slidably advance over the exterior surface of the guide wire (e.g., a lumen of the catheter  120  passes over the guide wire) during advancement toward the coronary sinus  20 . After the coronary sinus occlusion catheter  120  reaches the coronary sinus  20 , the distal end  111  of the guide member  110  can be withdrawn from the coronary sinus  20  and remain in the right atrium  11  during use of the coronary sinus occlusion catheter  120 . 
     Still referring to  FIG.  1   , the distal tip portion  121  of the coronary sinus occlusion catheter  120  that is positioned in the coronary sinus  20  includes an occlusion component  122 , which in this embodiment is in the form of an inflatable balloon device. The occlusion component  122  can be activated so as to occlude the coronary sinus  20  and thereby cause redistribution of the venous blood into the heart muscle tissue  30  that is damaged due to a lack of arterial blood flow. As described in more detail below, the inflatable balloon device  122  can be in fluid communication with an internal lumen of the coronary sinus occlusion catheter  120 , which is in turn in communication with a pneumatic subsystem of the control system  140  ( FIG.  2   ). As such, the control system  140  can be employed to expand or deflate the balloon device  122  in the coronary sinus. 
     The distal tip portion  121  also includes a one or more distal ports  129  that are positioned distally forward of the inflatable balloon device. In the depicted embodiments, the distal ports  129  face is a generally radially outward direction and are substantially uniformly spaced apart from one another along the circumference of the distal tip. As described in more detail below, the distal ports  129  may all be in fluid communication with a single pressure sensor lumen extending through the coronary sinus occlusion catheter  120 . Accordingly, the coronary sinus pressure can be monitored via a pressure sensor device that is in fluid communication with the distal ports  129 . 
     Referring now to  FIG.  2   , the proximal portion  131  of the coronary sinus occlusion catheter  120  and the control system  140  are positioned external to the patient while the distal tip portion  121  is advanced into the coronary sinus  20 . The proximal portion  131  includes the proximal hub  132  that is coupled to the control system  140  via a set of fluid or sensor lines  133 ,  134 , and  135 . As such, the control system  140  can activate or deactivate the occlusion component  122  at the distal tip portion  121  of the coronary sinus occlusion catheter  120  while also receiving one or more sensor signals that provide data indicative of heart characteristics (e.g., coronary sinus pressure, electrocardiogram (ECG) information, and the like). 
     The proximal hub  132  of the coronary sinus occlusion catheter  120  serves to connect the plurality of fluid or sensor lines  133 ,  134 , and  135  with the portion of the coronary sinus occlusion catheter  120  that extends into the patient&#39;s venous system. For example, the first line  133  extending between the control system  140  and the proximal hub  132  comprises a fluid line through which pressurized fluid (e.g., helium, another gas, or a stable liquid) can be delivered to activate the occlusion component (e.g., to inflate the inflatable balloon device  122 ). The fluid line  133  is connected to a corresponding port  143  of the control system  140  (e.g., the drive lumen port in this embodiment) so that the line  133  is in fluid communication with the control and inflation device  200  (refer to  FIG.  3   ) at least partially housed in the control system  140 . The proximal hub  132  joins the first line  133  with a balloon control lumen extending through the coronary sinus occlusion catheter  120  and to the inflatable balloon device  122 . 
     In another example, the second line  134  extending between the control system  140  and the proximal hub  132  comprises a balloon sensor line that is in fluid communication with the interior of the inflatable balloon device  122  so as to measure the fluid pressure within the balloon device  122 . The proximal hub  132  joins the second line  134  with a balloon pressure lumen extending through the coronary sinus occlusion catheter  120  and to the inflatable balloon device  122 . The pressure of the balloon device  122  may be monitored by a component of the control and inflation device  200  (refer to  FIG.  3   ) at least partially housed in the control system  140 . The balloon sensor line  134  is connected to a corresponding port  144  of the control system  140  so that a pressure sensor arranged within the control system  140  can detect the fluid pressure in the balloon device  122 . Alternatively, the pressure sensor may be arranged in the distal tip portion  121  or the in the proximal hub  132  such that only a sensor wire connects to the corresponding port  144  of the control system  140 . 
     The proximal hub also connects with a third line  135  extending from the control system  140 . The third line  135  comprises a coronary sinus pressure line that is used to measure the fluid pressure in the coronary sinus both when the balloon device  122  is inflated and when it is deflated. The proximal hub  132  joins the third line  135  with a coronary sinus pressure lumen extending through the coronary sinus occlusion catheter  120  and to the distal ports  129  that are forward of the balloon device  122 . As such, the coronary sinus pressure lumen  125  and at least a portion of the third line  135  may operate as fluid-filled path (e.g., saline or another biocompatible liquid) that transfers the blood pressure in the coronary sinus  20  to pressure sensor device  136  along a proximal portion of the third line  135 . The pressure sensor device  136  samples the pressure measurements (which are indicative of the coronary sinus pressure) and outputs an sensor signal indicative of the coronary sinus pressure to the corresponding port  145  of the control system  140  for input to an internal control circuit (which may include one or more processors that execute instructions stored on one or more computer memory devices housed in the control system  140 ). As described in more detail below, the coronary sinus pressure data are displayed by the graphical user interface  142  in a graph form so that a cardiologist or other user can readily monitor the trend of the coronary sinus pressure while the coronary sinus  20  is in an occluded condition and in an non-occluded condition. Optionally, the graphical user interface  142  of the control system  140  can also output a numeric pressure measurement on the screen so that the cardiologist can readily view a maximum coronary sinus pressure, a minimum coronary sinus pressure, or both. In alternative embodiments, the pressure sensor device  136  can be integrated into the housing of the control system  140  so that the third line  135  is a fluid-filled path leading up to the corresponding port  145 , where the internal pressure sensor device (much like the device  136 ) samples the pressure measurements and outputs a signal indicative of the coronary sinus pressure. 
     Still referring to  FIG.  2   , the system  100  may include one or more ECG sensors  149  to output ECG signals to the control system  140 . In this embodiment, the system  100  includes a pair of ECG sensor pads  149  that are adhered to the patient&#39;s skin proximate to the heart  10 . The ECG sensors  149  are connected to the control system  140  via a cable that mates with a corresponding port  149  along the housing of the control system  140 . As described in more detail below, the ECG data can be displayed by the graphical user interface  142  in a graph form so that a cardiologist or other user can readily monitor the patient&#39;s heart rate and other characteristics while the coronary sinus is in an occluded condition and in an non-occluded condition. Optionally, the graphical user interface  142  of the control system  140  can also output numeric heart rate data (based on the ECG sensor data on the screen so that the cardiologist can readily view the heart rate (e.g., in a unit of beats per minutes). The ECG sensor signals that are received by the control system  140  are also employed by the internal control circuit so as to properly time the start of the occlusion period (e.g., the start time at which the balloon device  122  is inflated) and the start of the non-occlusion period (e.g., the start time at which the balloon device  122  is deflated). 
     As shown in  FIG.  2   , the coronary sinus occlusion catheter  120  is delivered to the heart  10  via a venous system using any one of a number of venous access points. Such access points may be referred to as PICSO access points in some embodiments in which the coronary sinus occlusion catheter  120  is controlled to perform a PICSO procedure for at least a portion of the time in which the catheter  120  is positioned in the coronary sinus  20 . For example, the guide member  110  and the distal tip portion  121  can be inserted into the venous system into an access point at a brachial vein, an access point at a subclavian vein, or at an access point at a jugular vein. From any of these access points, the guide member  110  can be advanced through the superior vena cava and into the right atrium  11 . Preferably, the guide member  110  is steered into an ostial portion of the coronary sinus  20 , and then the distal tip portion  121  of the catheter  120  is slidably advanced along the guide member  110  and into the coronary sinus  20  before the guide member  110  is backed out to remain in the right atrium  11 . In another example, the guide member  110  and the distal tip portion  121  can be inserted into the venous system into an access point at a femoral vein. In this example, the guide member  110  can be advanced through the inferior vena cava and into the right atrium  11 . As previously described, the distal tip portion  121  of the catheter  120  is slidably advanced along the guide member  110  and into the coronary sinus  20  before the guide member  110  is backed out to remain in the right atrium  11 . 
     In some embodiments, the blockage  35  in the heart may be repaired or removed using a percutaneous coronary intervention (PCI) instrument such as an angioplasty balloon catheter, a stent delivery instrument, or the like. The PCI instrument may access the arterial system via any one of a number of PCI access points, as shown in  FIG.  2   . In some implementations, the PCI instrument can be inserted into the arterial system into an access point at a femoral artery, an access point at a radial artery, or an access point at a subclavian artery. Thus, as previously described, some embodiments of the system  100  may employ a PICSO access point into the venous system while a PCI access point is employed to insert a PCI instrument into the arterial system. 
     Referring now to  FIG.  3   , some embodiments of the control system  140  include the control and inflation device  200  having components to inflate and deflate the balloon device  122  of the catheter  120 . As previously described, the control system may further include one or more processors (not shown in  FIG.  3   ) that are configured to execute various software modules stored on at least one memory device (not shown in  FIG.  3   ). In some embodiments, a balloon inflate and deflate software module can be stored on the memory device to provide computer-readable instructions that, when executed by one of the processors (such as an embedded microprocessor), causes the control and inflation device  200  to inflate or deflate the balloon device  122  at selected times. In some embodiments, the balloon inflate and deflate software module stored on the memory device can implement a customized algorithm that calculates and updates the time periods during which the coronary sinus is in an occluded state and in a non-occluded state based upon the coronary sinus pressure measurements. In such circumstances, the coronary sinus  20  is not occluded and non-occluded according to a predetermined pattern of inflated times and deflated times that are independent of the patient, but instead the coronary sinus pressure measurements at least partially dictate the time periods during which the coronary sinus is in an occluded state and in a non-occluded state. In alternative modes, the balloon inflate and deflate software module stored on the memory device may cause the coronary sinus  20  to be occluded and non-occluded according to a predetermined pattern of inflated times and deflated times that are independent of the patient and the coronary sinus pressure measurements. The processors of the control system  140  may include, for example, microprocessors that are arranged on a motherboard so as to execute the control instructions of the control system  140 . The memory device of the control system  140  may include, for example, a computer hard drive device having one or more discs, a RAM memory device, that stored the various software modules. 
     As shown in  FIG.  3   , the control and inflation device  200  can be configured to promptly inflate or deflate the balloon device  122 . The balloon device  122  is connected to the connection  203  of the control and inflation device via an inflation lumen  202 . The pressure in the inflation lumen  202  can be measured via a schematically illustrated pressure measuring device  204 . A further measurement for the balloon pressure can be obtained via a further pressure measuring device  205 . The pressure measuring device  205  is connected with the balloon  122  via a separate pressure measuring lumen  206 . 
     The control and inflation device comprises a pressure tank  207 , which can be connected via the control valves  208  or  224  either with the connection  203  via line  209  or with the fluid loop via line  210 . Pressure measuring devices for measuring the pressure prevailing in the pressure tank  207  are designated by reference numbers  232  and  233 . Furthermore, a pump  211  is provided in parallel with a stop valve  212  (and, optionally, a throttle valve). A conductive connection between the pump  211  and the vacuum tank  216  can be established via a stop valve  214  and a line  215 . The condensate possibly collecting in the vacuum tank  216  is schematically indicated at  217  and can be pumped off via a stop valve  218  by the aid of the condensate pump  219 . Connection lines  220  and  221  can be brought into a conductive connection with the vacuum tank  216  via a stop valve  222 . In order to determine the pressure prevailing in the vacuum tank  216  a pressure measuring device  226  is provided. 
     An emergency valve is denoted by  223 . 
     The feed-in for the fluid loop takes place via line  227 , to which a fluid reservoir  230 , e.g. a helium cylinder, may be connected via a throttle valve  228  and a stop valve  229 . 
     In the following, the mode of functioning of the control and inflation device will be explained in more detail. 
     Set-Up Mode: 
     In the set-up mode, all components of the system are initially filled with air or the like, and the valves are closed. 
     Evacuation: 
     In the evacuation mode, the whole system is evacuated. To this end, the stop valves  223  and  229  are closed, whereas all other valves are open. The air possibly present in the system is evacuated by the aid of the condensate pump  219 , the air possibly present in the system escaping along arrow  231 . The balloon  122  is also evacuated and deflated. 
     In the evacuated state a leak-tightness test can be conducted. In particular the leak-tightness of the control and inflation device, the balloon and the catheter as well as possible further volumes connected thereto can be checked, whereby the components can be regarded as tight if the evacuated state is maintained over a predetermined period of time. 
     System Filling: 
     The system is then filled with a fluid, e.g. helium, from the fluid reservoir  230 . To this end, valves  208 ,  212 ,  214 ,  228  and  229  are in the opened state. All other valves are closed. As long as the stop valve  229  is opened, the system is filled with helium from the reservoir  230  such that the pressure tank  27 , the pump  211 , lines  210  and  215  as well as the vacuum tank  216  are being uniformly filled with helium. 
     Biasing: 
     After having terminated the filling procedure, stop valve  229  is closed and valve  212  is, furthermore, closed. Valve  208  remains in the state connecting the pressure tank  207  with line  210 . In order to bias the system, the pump  211  is set in operation, pressing fluid from the vacuum tank  216  into the pressure tank  207 . The process is carried out until a released fluid amount has reached the pressure tank  207  and a predetermined pressure difference has adjusted between the vacuum tank  216  and the pressure tank  207  or a predetermined pressure has been reached in the pressure tank  207 , respectively. It may, for instance, be proceeded in a manner that a pressure of 3 bar is reached in the pressure tank  207 , while the pressure in the vacuum tank  216  is reduced to 0.6 bar. After having completed the biasing of the system, all valves are closed. 
     Balloon Inflation: 
     To inflate the balloon  122 , valve  224  is opened so that the pressure tank  207  is connected with the connection  203 , and hence with the balloon  122 , via line  209 . Pressure equalization consequently occurs between the pressure tank  207  and the balloon  122 , with valve  224  being maintained in the opened position until full pressure equalization between the pressure tank  207  and the balloon  122  has occurred. After full pressure equalization has been achieved, the balloon  122  and the pressure tank  207  are under the same pressure, for instance under a pressure of 1.2 bar. 
     Balloon Evacuation: 
     To evacuate the balloon, valve  222  is opened and valve  224  is closed, thereby disconnecting the pressure tank  207  from the connection  203 . The balloon  122  is then directly connected with the vacuum tank  216  such that the evacuation of the balloon  122  is caused by pressure equalization between the balloon  122  and the vacuum tank  216 . After full pressure equalization has been achieved, the balloon  122  and the vacuum tank  216  are under the same pressure, the pressure level being, for instance, 0.8 bar, yet in any case less than 1 bar. 
     The cycle of inflating and evacuating the balloon  122  can be repeated any number of times. For a renewed inflation of the balloon  122 , the system may again be biased, to which end valve  222  is closed and valve  14  is opened. As before, valve  208  is in an open state in which the pressure tank  207  is connected with line  210  and valve  224  is closed. When the pump  211  is set in operation, fluid is sucked from the vacuum tank  216  and pressed into the pressure tank  207 . To fill the balloon  122 , valve  214  is again closed and valves  208  and  224  are switched such that the pressure tank  207  is connected with the connection  203 , and hence with the balloon  122 . After a pressure equalization of the pressure tank  207  and the balloon  122 , the balloon is again filled. The evacuation of the balloon is again effected by switching valves  208  and  224  and opening valve  222  so as to connect the balloon  122  with the vacuum tank  216 , thus causing fluid to flow from the balloon  122  into the vacuum tank  216  until pressure equalization between the balloon  122  and the vacuum tank  216  has occurred. 
     It should be apparent from the description herein that both the filling of the balloon  122  and the evacuation of the balloon  122  are simply effected due to a full pressure equalization with the pressure tank  207 , on the one hand, and with the vacuum tank  216 , on the other hand. The fluid is simply recirculated so as to enable a particularly economical mode of operation and a reduction of the energy consumption. 
     As a security measure valves  208  and  224  are blocked to each other in a hardware manner such that they cannot both be opened or both be closed at the same time. 
     As a further security measure the emergency valve  223  is opened if a pressure overload is detected based on the measurements of the pressure measurement devices  204 ,  205 ,  213 ,  225 ,  232 ,  233  and  234 . 
     System Cleaning: 
     For cleaning purposes, valve  222  is opened and valve  208  is placed into a position in which the pressure tank  207  is connected with line  210 . All other valves are closed. Condensate possibly collecting in the vacuum tank  216  can subsequently be pumped off by the vacuum-condensate pump  219 . 
     The method of cyclically filling the balloon  122  can be realized in the form of a control algorithm which can be realized as a hardware circuit (electronic wiring with relays and flipflops) or software in a microcontroller. Typically, the realization is a software type realization, such as the software module as previously described. 
     The control algorithm can function as follows (when the computer software instructions are executed by the processor) to perform the following operations:
         Determining the volume of the catheter with the balloon being in a deflated state based on at least two subsequent pressure measurements with two different pressures in the pressure tank  207 . Thereby at least four measurement values (pressures at  204  and  205 ) are measured.   Measuring the pressures at  204  for a predetermined pressure at  232 .   Stepwise raising the pressure in the pressure tank  207  until a predetermined or selected target value for the pressure at  204  is attained.       

     This is performed in the form of a control algorithm that is implemented as software instructions stored on a computer-readable memory device in the control system  140 . In some embodiments, the control and inflation device  200  advantageously comprises a multi processor system, a pneumatic fluid circuit and an embedded PC for controlling an MIMI for the application specific representation and evaluation of application and measurement data during one treatment. The multi processor system comprises at least two independent electronic circuits which monitor the security relevant function in a fail-safe manner. 
     According to some embodiments described herein, a method for determining a patient- and/or catheter-specifically optimized fluid amount for filling a balloon of a balloon catheter arranged in a body vessel to inflate the former is provided. The method may include the following steps: 
     a) evacuating the balloon, 
     b) providing a defined starting amount of fluid and using this starting amount for filling the balloon as well as measuring the balloon starting pressure, 
     c) providing a fluid amount increased relative to the preceding amount and using the increased amount for filling the balloon as well as measuring the balloon pressure, resulting from the filling or measuring variations thereof, 
     d) comparing the measured balloon pressure or the variations thereof with a predetermined target value and repeating step c) until the balloon pressure or the variations thereof has reached said target value, 
     e) storing the last-provided fluid amount as a reference value for inflating the balloon. 
     The aforementioned method can be used to determine a patient- and/or catheter-specifically optimized fluid amount for filling the balloon during the preparation of the occlusion procedure. Thus, prior to performing the patient&#39;s treatment, the optimum fluid amount for filling the balloon can be determined by the aforementioned method, with the optimum fluid amount determined being used as a reference value for the subsequent treatment of the patient, and the control and inflation device  200  for the balloon catheter  122  being adjusted to the patient- or catheter-specific value in this manner. During the subsequent occlusion cycles, the value determined using the aforementioned method is maintained or adjusted in order to take into account changes of the circumstances occurring during treatment. Adjusting the patient- and/or catheter-specifically determined value will be appropriate if, for example, the pressure conditions in the occluded vessel have changed, if the visco-elasticity of the vessel has changed, or if the treatment is shifted to another vessel site. 
     At the beginning of the method, the balloon  122  may be evacuated in order to bring the balloon  122  to a defined pressure level which serves as the starting point for the subsequent method steps. According to step b), a defined starting amount of fluid is provided and the starting amount is used for filling the balloon, whereupon the balloon pressure resulting from said starting amount is measured. According to step c), the preceding fluid amount can be increased and the balloon pressure resulting from the increased fluid amount is measured. The determined balloon pressure is compared with a predetermined target value, and the fluid amount used for filling the balloon may be gradually increased until the balloon pressure has reached the predetermined target value. A target value may, for instance, be an absolute value of at least 70 mm Hg, in particular approx. 80 mm Hg, independent of the patient concerned. The target value may, however, also be chosen as a function of the patient and, for instance, lie 10% above the maximum pressure resulting in the respective patient during the occlusion in the occluded vessel. 
     In order to achieve the predetermined target value, a differently strong inflation of the balloon (e.g., a differently large amount of introduced fluid) may be employed as a function of the visco-elasticity of the vessel, other patient-dependent factors and the catheter type. The gradual approach during the introduction of the fluid into the balloon  122  as in correspondence with the invention prevents the pressure in the balloon to exceed a predetermined target value. By defining as a reference value the fluid amount introduced into the balloon and corresponding to the target value, a pressure measurement in the balloon may (in some circumstances) be obviated during the subsequent inflation procedure, and the inflation procedure may be exclusively controlled on account of the introduced fluid amount. By limiting the introduced fluid amount, simple control of the inflation procedure is feasible while safeguarding against inadmissible operating states such as, in particular, inadmissible pressure states. If the reference value is be adjusted during subsequent inflating procedures, the balloon pressure may be continuously determined so that deviations of the balloon pressure from the target value can be detected, whereby the reference value is adjusted, if the detected deviation exceeds a predetermined limit of tolerance. 
     In some embodiments, a continuous pressure measurement is also useful, if the balloon pressure shall be monitored not only with regard to the holding of the target value but also with regard to exceeding a security relevant upper limit. Such an upper limit orients itself at values which are deemed as being permissive with regard to the operating security of the catheter, e.g. with respect to the bursting of the balloon or the coronary sinus vessel, and can have values of e.g. between 90 and 120 mm Hg. If the upper limit value is exceeded, the system can be stopped immediately. 
     According to an alternative embodiment, variations of the balloon pressure may be determined and analyzed instead of the absolute pressure prevailing in the balloon. Pressure variations can occur, if the balloon is inflated to an extent that the balloon touches the vessel wall, whereby the blood flow in the small gap between the balloon approaching the vessel wall and the vessel wall cause characteristic flow conditions that result in pressure variations in the balloon. Such pressure variations indicate that the balloon reaches the vessel wall. 
     According to some embodiments, the aforementioned steps b) to d) may comprise establishing a pressure-volume curve from the balloon starting volume resulting from using the starting amount and from the balloon starting pressure as well as the balloon volumes respectively resulting from using the gradually increased fluid amounts and from the respective balloon pressures. By way of the pressure-volume curve, it is feasible in a simple manner to observe and track the gradual approach to the optimum balloon filling, the course of the pressure-volume curve as a rule being such that in a first region, in which the balloon does not yet touch the vessel wall, the introduced fluid volume rises at a nearly constant or slightly increasing pressure and in a second region, in which the balloon abuts on the vessel wall, the internal pressure of the balloon significantly rises at every increase of the introduced fluid volume. 
     According to some embodiments, the balloon  122  may be evacuated prior to every performance or repetition of the aforementioned step c). Such an operation may ensure that a defined starting state is provided for each of the gradual increases in the fluid amount introduced into the balloon  122  in the course of the gradual approach to the target value of the balloon pressure, the balloon  122  after every evacuation being filled with a fluid amount increased relative to the preceding amount. In order to achieve the same evacuation state at every evacuation procedure, the balloon pressure may be measured during the evacuation of the balloon and said evacuation is effected until a predetermined negative pressure is reached. The predetermined negative pressure may be chosen to be the same at each evacuation. During the evacuation of the balloon  122 , the pressure can additionally also be measured in the negative pressure source being responsible of the evacuation of the balloon. Advantageously, the pressure in the vacuum tank  216  can be measured in order to monitor if a predetermined negative pressure is attained. 
     The evacuation of the balloon  122  prior to each increase of the fluid amount introduced into the balloon  122  may also result in the balloon  122  being regularly deflated in the course of the method according to the invention, thus preventing too long an impairment or interruption of the flow in the concerned body vessel (e.g., the coronary sinus in some embodiments). 
     According to particular embodiments, it is provided that the increase in the fluid amount may be gradually effected by a value which is preferably the same at every increase. 
     According to some embodiments, the inflation of the balloon  122  is effected in that the starting amount of fluid and the respectively increased fluid amount are dosed into the pressure tank  207  and the balloon  122  is filled exclusively due to full pressure equalization between the pressure tank  207  and the balloon  122 . The fluid is thus not directly filled into the balloon, since this would entail the risk of an uncontrolled amount of fluid entering the balloon in the event of a malfunction. If, as is preferably provided, the fluid is at first dosed into the pressure tank  207 , the fluid amount can be precisely controlled and a malfunction would only result in the pressure tank  207  being filled with an excessive amount, which would, however, be detected or checked prior to the inflation of the balloon  122 . With the respectively provided amount of fluid dosed into the pressure tank  207 , filling of the balloon  122  is simply effected by opening the connection between the pressure tank  207  and the balloon  122 , thus causing the balloon  122  to fill exclusively due to a full pressure equalization between the pressure tank  207  and the balloon  122 . 
     According to an exemplary mode of operation, the pressure measured in the pressure tank  207  can be used for controlling the dosing of the desired amount of fluid into the pressure tank  207 . With regard to the amount of fluid stored as a reference value, this means that the pressure that prevails due to the filling of the pressure tank  207  with the reference amount of fluid is stored as the reference pressure and the filling is carried out until the reference pressure is reached so that the control of the filling procedure of the pressure tank  207  is simplified. 
     According to a further mode of operation, it is provided that the balloon pressure is measured via a catheter lumen  206  separate from the catheter lumen  202  provided for filling. This will lead to an enhanced safety, in particular, if the balloon pressure is also measured in the catheter lumen provided for filling. In this manner, two independent pressure measurements are available, and possible malfunctions can be concluded from a comparison of these pressure values. 
     According to particular embodiments described herein, a method for inflating and evacuating the balloon  122  of the balloon catheter  120  is provided, in which the balloon  122  is connected with a positive pressure source for inflation and with a negative pressure source for evacuation and which is characterized in that the pressure tank  207  which is filled with fluid under positive pressure is provided as said positive pressure source, and that the inflation of the balloon  122  is effected exclusively due to a full pressure equalization between the pressure tank  207  and the balloon  122 . By the inflation of the balloon  122  being effected exclusively due to a full pressure equalization between the pressure tank  207  and the balloon  122 , malfunctions such as overfilling of the balloon  122  beyond the maximum pressure may be effectively avoided. The pressure tank  207  is initially filled with a predetermined fluid amount, said fluid amount being measured such that a predetermined filling state and pressure state will result in the balloon  122 . When the connection between the prefilled pressure tank  207  and the balloon  122  is opened, a predetermined filling state of the balloon  122  will adjust due to the full pressure equalization between the pressure tank  207  and the balloon  122 , thus causing the body vessel (e.g., the coronary sinus) to be occluded. By the filling of the balloon  122  being exclusively effected due to a full pressure equalization between the pressure tank  207  and the balloon  122 , separate regulation and control measures can be obviated during filling, and an inadmissible filling state of the balloon may be prevented in that only the fluid amount initially dosed into the pressure tank  207  will reach the connection line and the balloon  122  because of the subsequent pressure equalization. 
     An additional control can be advantageously performed, if the inflation time is monitored. In case the inflation time lies below a lower limit value such as, e.g., 0.2 sec, an error message will be generated or the system shuts down. A too fast inflation might result in damage of the vessel. In case the inflation time lies above a predetermined upper limit value such as, e.g., 0.50 sec, an error message is also generated or the system shuts down. An inflation that lasts too long may result in that the blood flow in the respective vessel is impeded for a too long time. 
     A further control can advantageously be carried out when the deflation time is monitored. If the deflation time lies below a predetermined lower limit value such as, e.g., 0.5 sec, an error message is generated or the system shuts down. If the balloon collapses too fast, this might possibly lead to damage of the vessel. 
     In some embodiments, a cycle comprising the evacuation and inflation of the balloon may be advantageously performed by a sequence of the following steps: 
     a) connecting the balloon with a negative pressure source to evacuate the balloon, in particular to a predetermined negative pressure, 
     b) interrupting the connection between the balloon and the negative pressure source, 
     c) dosing a predetermined fluid amount into the pressure tank, thus filling the latter with fluid under positive pressure, 
     d) opening the connection between the pressure tank and the balloon, whereby the inflation of the balloon is exclusively effected due to a full pressure equalization between the pressure tank and the balloon, 
     e) closing the connection between the pressure tank and the balloon after full pressure equalization has occurred. 
     In an example mode of operation of this method, the vacuum tank  216  may be employed as said negative pressure source, the fluid preferably being recirculated between the vacuum tank  216 , the pressure tank  207  and the balloon  122 , thus offering the advantage that no new fluid need be fed into the loop even with a plurality of inflation and evacuation cycles. An advantageous mode of operation in this respect provides that the filling of the pressure tank  207  comprises the suction of fluid from the vacuum tank  216  forming the negative pressure source. 
     In some circumstances, it is further provided that the filling of the pressure tank  207  is effected by the aid of the pump  211  arranged between the pressure tank  207  and the vacuum tank  216 . 
     The method can be advantageously carried out in that the fluid system comprising the pressure tank  207 , the pump  211 , the vacuum tank  216  and the balloon  122  as well as the connection lines is filled with such an amount of fluid that the pressure within the system is smaller than 2 bar at a full pressure equalization of all components. This will lead to a substantial enhancement of the operating safety, since it is ensured that an uncontrolled fluid amount will not enter the balloon  122  even if all of the safety valves or other safety devices have failed. In the most extreme case, pressure equalization would take place within the whole system at a valve failure, which, due to the overall quantity of the fluid present within the system, would result in a pressure of &lt;2 bar so that an accordingly deflated state of the balloon  122  would be obtained. 
     According to a further aspect, the control and inflation device  200  of the control system  140  may comprise a connection for the inflation lumen  202  (refer also to the drive lumen  133  in  FIG.  2   ) of the balloon catheter  120 , wherein switching valves are arranged in a manner that the connection for the inflation lumen  202  is alternately connectable with the vacuum tank  216  and with the pressure tank  207 . In a preferred manner, it is provided the pressure tank  207  is alternately connectable with the connection for the inflation lumen  202  and, via the pump  211 , with the vacuum tank  216 . 
     In some embodiments, the connection for a catheter lumen separate from the inflation lumen is provided, which is connected with a pressure measuring device. 
     In some embodiments, the pressure tank  207 , the pump  211  and the vacuum tank  216  preferably form a closed fluid loop together with the inflation lumen  202  of the catheter. The closed loop preferably comprises a connection for filling the loop with fluid. 
     According to some embodiments, a control inflation apparatus for the balloon catheter  120  is provided comprising the pressure tank  207  for fluid, a dosing unit (e.g., the pump  211 ) for dosing fluid into the pressure tank  207 , the connection  202  for a filling lumen of the balloon catheter  120 , which connection can be connected to the pressure tank  207  via a switchable valve  24 , at least one pressure measuring device for measuring the fluid pressure prevailing in the balloon  122  of the balloon catheter  120 , and a control circuit to which the measuring values of the pressure measuring device are fed and which cooperates with the dosing unit for dosing a defined fluid amount into the pressure tank as a function of the pressure measurement values. 
     In one aspect, the control circuit cooperates with the switchable valve such that the switchable valve is closed if the dosing unit doses fluid into the pressure tank. The dosing unit can be comprised of a pump for example. 
     According to a further aspect, a pressure measuring device measuring the fluid pressure prevailing in the pressure tank can be provided, the measuring values of which are fed to the control circuit whereby a storage is provided for an upper pressure target value and the control circuit cooperates with the dosing unit such that dosing of fluid into the pressure tank is terminated if the pressure measured in the pressure tank reaches the pressure target value. 
     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of the invention. Accordingly, other embodiments are within the scope of the following claims.