Patent Publication Number: US-9409012-B2

Title: Pacemaker integrated with vascular intervention catheter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/074,048, filed on Jun. 19, 2008, under 35 U.S.C. §119(e), which is hereby incorporated by reference. 
     This application is related to commonly assigned, U.S. patent application Ser. No. 11/113,828, entitled “METHOD AND APPARATUS FOR PACING DURING REVASCULARIZATION”, filed on Apr. 25, 2005, now U.S. Pat. No. 7,962,208, U.S. patent application Ser. No. 11/468,875, entitled “INTEGRATED CATHETER AND PULSE GENERATOR SYSTEMS AND METHODS”, filed on Aug. 31, 2006, now abandoned, U.S. Patent Application Ser. No. 61/074,032, entitled “PACING CATHETER WITH EXPANDABLE DISTAL END”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,035, entitled “PACING CATHETER FOR ACCESS TO MULTIPLE VESSELS”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,042, entitled “PACING CATHETER RELEASING CONDUCTIVE LIQUID”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,055, entitled “TRANSVASCULAR BALLOON CATHETER WITH PACING ELECTRODES ON SHAFT”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,060, entitled “PACING CATHETER WITH STENT ELECTRODE”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,064, entitled “VASCULAR INTERVENTION CATHETERS WITH PACING ELECTRODES”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,064, entitled “EXTERNAL PACEMAKER WITH AUTOMATIC CARDIOPROTECTIVE PACING PROTOCOL”, filed on Jun. 19, 2008, U.S. Patent Application Ser. No. 61/074,024, entitled “METHOD AND DEVICE FOR PACING AND INTERMITTENT ISCHEMIA”, filed on Jun. 19, 2008, which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This document relates generally to cardiac pacing systems and particularly to a system for delivering cardioprotective pacing during revascularization procedure. 
     BACKGROUND 
     The heart is the center of a person&#39;s circulatory system. It includes an electro-mechanical system performing two major pumping functions. The left portions of the heart draw oxygenated blood from the lungs and pump it to the organs of the body to provide the organs with their metabolic needs for oxygen. The right portions of the heart draw deoxygenated blood from the body organs and pump it to the lungs where the blood gets oxygenated. These pumping functions are resulted from contractions of the myocardium (cardiac muscles). In a normal heart, the sinoatrial node, the heart&#39;s natural pacemaker, generates electrical impulses, called action potentials, that propagate through an electrical conduction system to various regions of the heart to excite the myocardial tissues of these regions. Coordinated delays in the propagations of the action potentials in a normal electrical conduction system cause the various portions of the heart to contract in synchrony to result in efficient pumping functions. A blocked or otherwise abnormal electrical conduction and/or deteriorated myocardial tissue cause dyssynchronous contraction of the heart, resulting in poor hemodynamic performance, including a diminished blood supply to the heart and the rest of the body. The condition in which the heart fails to pump enough blood to meet the body&#39;s metabolic needs is known as heart failure. 
     Myocardial infarction (MI) is the necrosis of portions of the myocardial tissue resulted from cardiac ischemia, a condition in which the myocardium is deprived of adequate oxygen supply and metabolite removal due to an interruption in blood supply caused by an occlusion of a blood vessel such as a coronary artery. The necrotic tissue, known as infarcted tissue, loses the contractile properties of the normal, healthy myocardial tissue. Consequently, the overall contractility of the myocardium is weakened, resulting in an impaired hemodynamic performance. Following an MI, cardiac remodeling starts with expansion of the region of infarcted tissue and progresses to a chronic, global expansion in the size and change in the shape of the entire left ventricle. The consequences include a further impaired hemodynamic performance and a significantly increased risk of developing heart failure. 
     When a blood vessel such as the coronary artery is partially or completely occluded, a revascularization procedure such as percutaneous transluminal coronary angioplasty (PTCA) can be performed to reopen the occluded blood vessel. However, the revascularization procedure itself involves a temporary occlusion of the coronary artery. Reperfusion that follows the reopening of the occluded blood vessel is also known to cause cardiac injury, known as reperfusion injury. In addition, plaques dislodged and displaced by the revascularization procedure may enter small blood vessels branching from the blood vessel in which the revascularization is performed, causing occlusion of these small blood vessels. The revascularization procedure may also cause distal embolization, i.e., obstruction of the artery caused by the plaque dislodged during the procedure. Therefore, there is a need for minimizing cardiac injury associated with MI and the subsequent revascularization procedure. 
     SUMMARY 
     Cardioprotective pacing is applied to prevent and/or reduce cardiac injury associated with myocardial infarction (MI) and revascularization procedure. Pacing pulses are generated from a pacemaker and delivered through one or more pacing electrodes incorporated onto one or more percutaneous transluminal vascular intervention (PTVI) devices during the revascularization procedure. The pacemaker controls the delivery of the pacing pulses by automatically executing a cardioprotective pacing protocol. 
     In one embodiment, a cardiac pacing system for use during revascularization of a blood vessel includes a pacemaker integrated into a PTVI device. The PTVI device includes a proximal end portion, a distal end portion configured to be placed in the blood vessel, an elongate shaft coupled between the proximal end portion and the distal end portion, and a plurality of pacing electrodes. The pacemaker includes a flexible circuit substrate affixed to the PTVI device. A flexible pacemaker circuit including an electronic circuit is built on the flexible circuit substrate. The flexible pacemaker circuit delivers cardiac pacing pulses through the plurality of pacing electrodes of the PTVI device. 
     In one embodiment, a method for delivering cardioprotective pacing during revascularization is provided. Pacing pulses are delivered from a flexible pacemaker circuit integrated into a PTVI device. The flexible pacemaker circuit includes an electronic circuit built on a flexible circuit substrate affixed to the PTVI device. 
     This Summary is an overview of some of the teachings of the present application and not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and appended claims. Other aspects of the invention will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof. The scope of the present invention is defined by the appended claims and their legal equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate generally, by way of example, various embodiments discussed in the present document. The drawings are for illustrative purposes only and may not be to scale. 
         FIG. 1  is an illustration of an embodiment of a system providing for pacing during revascularization and portions of an environment in which the system is used. 
         FIG. 2  is a block diagram illustrating an embodiment of a pacemaker providing for pacing during revascularization. 
         FIG. 3  is a timing diagram illustrating an embodiment of a cardioprotective pacing protocol. 
         FIG. 4  is an illustration of an embodiment of a guide catheter with pacing electrodes. 
         FIG. 5  is an illustration of an embodiment of a guide wire with pacing electrodes. 
         FIG. 6  is an illustration of an embodiment of an angioplasty catheter with pacing electrodes. 
         FIG. 7  is an illustration of an embodiment of a distal portion of the guide catheter with pacing electrodes. 
         FIG. 8  is an illustration of another embodiment of a distal portion of the guide catheter with pacing electrodes. 
         FIG. 9  is an illustration of another embodiment of a distal portion of the guide catheter with pacing electrodes. 
         FIG. 10  is an illustration of an embodiment of a distal portion of the guide wire with pacing electrodes. 
         FIG. 11  is an illustration of another embodiment of a distal portion of the guide wire with pacing electrodes. 
         FIG. 12  is an illustration of an embodiment of a distal portion of the angioplasty catheter with a balloon and pacing electrodes. 
         FIG. 13  is an illustration of an embodiment of a proximal portion of the angioplasty catheter with pacing electrodes. 
         FIG. 14  is an illustration of an embodiment of a pacing catheter including a sheath and a pacing lead having an expandable distal end. 
         FIG. 15  is an illustration of an embodiment of the distal end portion of a pacing lead of the pacing catheter of  FIG. 14 . 
         FIG. 16  is an illustration of another embodiment of the distal end portion of a pacing lead of the pacing catheter of  FIG. 14 . 
         FIG. 17  is an illustration of another embodiment of the distal end portion of a pacing lead of the pacing catheter of  FIG. 14 . 
         FIG. 18  is an illustration of an embodiment of a percutaneous transluminal vascular intervention (PTVI) device assembly including a pacing lead and a balloon catheter. 
         FIG. 19  is an illustration of an embodiment of a pacing catheter including multiple pacing leads for access to multiple blood vessels. 
         FIG. 20  is an illustration of an embodiment of a catheter of the pacing catheter of  FIG. 19 . 
         FIG. 21  is an illustration of an embodiment of a pacing catheter releasing conductive liquid and an injection device. 
         FIG. 22  is an illustration of another embodiment of a pacing catheter releasing conductive liquid. 
         FIGS. 23A-B  are an illustration of another embodiment of a pacing catheter releasing conductive liquid. 
         FIG. 24  is an illustration of an embodiment of a pacemaker integrated into a PTVI device. 
         FIG. 25  is an illustration of an embodiment of the pacemaker of  FIG. 24 . 
         FIG. 26  is an illustration of another embodiment of a pacemaker integrated into a PTVI device. 
         FIG. 27  is an illustration of another embodiment of a pacemaker integrated into a PTVI device. 
         FIG. 28  is an illustration of another embodiment of a pacemaker integrated into a PTVI device. 
         FIG. 29  is an illustration of an embodiment of an angioplasty catheter including pacing electrodes on the shaft. 
         FIG. 30  is an illustration of an embodiment of a sleeve of the angioplasty catheter of  FIG. 29 . 
         FIG. 31  is an illustration of another embodiment of an angioplasty catheter including pacing electrodes on the shaft. 
         FIG. 32  is an illustration of another embodiment of an angioplasty catheter including pacing electrodes on the shaft. 
         FIG. 33  is an illustration of another embodiment of an angioplasty catheter including pacing electrodes on the shaft. 
         FIG. 34  is an illustration of an embodiment of a pacing catheter assembly including a stent catheter with a stent electrode. 
         FIG. 35  is an illustration of an embodiment of the distal end portion of the stent catheter of  FIG. 34 . 
         FIG. 36  is an illustration of another embodiment of the distal end portion of the stent catheter of  FIG. 34 . 
         FIG. 37  is an illustration of another embodiment of the distal end portion of the stent catheter of  FIG. 34 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description provides examples, and the scope of the present invention is defined by the appended claims and their legal equivalents. 
     It should be noted that references to “an”, “one”, or “various” embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. 
     In this document, “revascularization” includes reopening of a completely or partially occluded blood vessel using percutaneous transluminal vascular intervention (PTVI) procedure, such as a percutaneous transluminal coronary angioplasty (PTCA) procedure performed in response to cardiac ischemia or myocardial infarction (MI), using PTVI devices such as those discussed in this document. 
     This document discusses a pacing system that delivers pacing pulses through one or more PTVI devices to a patient receiving a revascularization procedure. In an application, the pacing system provides for acute pacing cardioprotection therapy, also referred to as pacing postconditioning, during the revascularization procedure. The acute pacing cardioprotection therapy includes the delivery of pacing pulses before, during, and/or after the temporary occlusion of a coronary artery to prevent and/or reduce cardiac injury associated with MI and the subsequent revascularization procedure. The pacing system is capable of delivering the acute pacing cardioprotection therapy without substantially interfering with the revascularization procedure. In another application, the pacing system also provides for ischemic cardioprotection therapy. The ischemic cardioprotection therapy includes intermittent occlusion of the coronary artery, for example, by periodically inflating and deflating a balloon of a PTVI device. 
     To deliver pacing pulses during the revascularization procedure, one or more pacing electrodes are incorporated onto the one or more PTVI devices. Examples of such PTVI devices include guide wires, guide catheters, and angioplasty catheters such as dilatation balloon catheters, stent delivery systems, brachytherapy devices, atherectomy devices, and distal embolization protection devices. A pacemaker connected to the one or more PTVI devices generates the pacing pulses. In one embodiment, the pacemaker controls the delivery of the acute pacing cardioprotection therapy by automatically executing a cardioprotective pacing protocol specifying a pacing sequence including alternating pacing and non-pacing periods, or alternating pacing modes. In one embodiment, the pacemaker is an external pacing device such as a pacing system analyzer (PSA). In another embodiment, the pacemaker is integrated into the one of the one or more PTVI devices. 
       FIG. 1  is an illustration of an embodiment of a system  100  providing for pacing during revascularization and portions of an environment in which system  100  is used. System  100  includes a PTVI device  110 , a pacemaker  122 , and a cable  121  connecting PTVI device  110  and pacemaker  122 . When needed, system  100  also includes a reference electrode  119 , which is a surface electrode, such as a skin patch electrode, connected to a lead  120 . Lead  120  is connected to a connector  118  allowing its connection to cable  121 . 
     PTVI device  110  is used during a revascularization procedure and includes a distal end portion  111  for intravascular placement and a proximal end portion  112 . Proximal end portion  112  includes a proximal end device  114  and pacing connectors  116 A-B. Proximal end device  114  includes various connectors and other structures allowing manipulation of PTVI device  110  including the percutaneous transluminal insertion of the device and operation of an angioplasty device at distal end  111 . Pacing connectors  116 A-B provide for electrical connections between pacemaker  122  and PTVI device  110  through cable  121 . In the illustrated embodiment, PTVI device  110  is a PTCA device used in a PTCA procedure. During the PTCA procedure, an opening  105  is made on a femoral artery  104  in a patient&#39;s body  102 . PTVI device  110  is inserted into femoral artery  104  and advanced to an aorta  106  and then to a right coronary artery  107 , which is narrowed or blocked. The angioplasty device at distal end  111  is then used to open up the blocked right coronary artery  107 . In another embodiment, PTVI device  110  is used to open up a blocked left coronary artery  108 . 
     Distal end portion  111  of PTVI device  110  includes one or more pacing electrodes to allow pacing pulses to be delivered to a heart  101  during the PTCA procedure. In one embodiment, pacing pulses are delivered through two pacing electrodes on distal end portion  111  of PTVI device  110 . In another embodiment, pacing pulses are delivered through a pacing electrode on distal end portion  111  of PTVI device  110  and surface electrode  119  functioning as the return electrode for pacing. 
     Pacemaker  122  delivers pacing pulses by executing a cardioprotective pacing protocol. In one embodiment, the cardioprotective pacing protocol specifies a cardioprotective pacing sequence for preventing arrhythmias and cardiac injuries associated with the revascularization procedure. In one embodiment, pacemaker  122  is an external pacemaker such as a PSA. In another embodiment, pacemaker  122  includes an implantable pacemaker adapted for external use. 
     It is to be understood that  FIG. 1  is for illustrative, but not restrictive, purposes. For example, the physical structure of proximal end portion  112  depends on functional and ease-of-use considerations. Proximal end device  114  represents a structure that accommodates all the mechanical connection and access requirements, which depend on the specific configuration and function of PTVI device  110 . In one embodiment, proximal end device  114  includes an integrated device as illustrated in  FIG. 1 . In another embodiment, proximal end device  114  branches out into multiple connectors and/or other devices. Pacing connectors  116 A-B represent a structure that accommodates all the electrical connections required for delivering pacing pulses from pacemaker  122  to PTVI device  110 . The number of pacing connectors depends on the number of pacing electrodes incorporated onto PTVI device  110  and how it is to be connected to cable  121 . In one embodiment, when more than one electrical connection is needed for delivering the pacing pulses, proximal end portion  112  includes branched-out pacing connectors such as pacing connectors  116  and  117  as illustrated in  FIG. 1 . In another embodiment, proximal end portion  112  includes a single connector providing for multiple, independent electrical connections. 
     Pacemaker 
       FIG. 2  is a block diagram illustrating an embodiment of an external pacemaker  222  that provides for pacing during revascularization. External pacemaker  222  is an embodiment of pacemaker  122  and includes a pacing output circuit  224 , a user interface  228 , and a control circuit  226 . Pacing output circuit  224  delivers pacing pulses to PTVI device  110  through cable  121 . User interface  228  allows a user to control the delivery of the pacing pulses by controlling pacing parameters and/or timing of the delivery. Control circuit  226  controls the delivery of the pacing pulses. In one embodiment, external pacemaker  222  is a PSA including a chassis that houses pacing output circuit  224  and control circuit  226 . User interface  228  is incorporated onto the chassis. 
     In the illustrated embodiment, control circuit  226  includes a pacing protocol module  227 , which enables control circuit  226  to control the delivery of the pacing pulses by automatically executing a pacing protocol. To provide an acute pacing cardioprotection therapy, the pacing protocol specifies a cardioprotective pacing sequence that includes alternating pacing and non-pacing periods or alternating pacing modes for delivering pacing during a revascularization procedure such as a PTCA procedure. 
     In one embodiment, pacing protocol module  227  is configured to be detachably connected to external pacemaker  222 . In a specific embodiment, pacing protocol module  227  includes a memory device that stores the cardioprotective pacing protocol, and control circuit  226  is capable of automatically executing the cardioprotective pacing protocol when pacing protocol module  227  is connected to external pacemaker  222 . In another specific embodiment, in addition to the memory device that stores the cardioprotective pacing protocol, pacing protocol module  227  includes a user interface that allows the user to adjust parameters of the cardioprotective pacing protocol and/or control circuitry that supplement the functions of control circuit  226  for automatically executing the cardioprotective pacing protocol. In various embodiments, other pacing protocol modules are provided for automatically executing pacing protocols using external pacemaker  222 . In various embodiments, the user is provided with external pacemaker  222  and pacing protocol modules for executing pacing protocols such as the cardioprotective pacing protocol, cardiac resynchronization therapy (CRT) pacing protocol, and cardiac remodeling control therapy (RCT) pacing protocol. Compared to a PSA that requires the user to manually adjust pacing parameters during a test or therapy session, the automatic execution of the pacing protocol increases the accuracy of pacing control and reduces or eliminates the need for the user to control the delivery of the pacing pulses, so that the user can be more attentive to the response of the patient and/or the revascularization procedure. 
       FIG. 3  is a timing diagram illustrating an embodiment of the cardioprotective pacing protocol that specifies a cardioprotective pacing sequence. The cardioprotective pacing sequence is initiated after a time interval  301  that starts when the insertion of PTVI device into body  102  is completed. Time interval  301  expires before, during, and/or after an ischemic event that occurs when the blood vessel targeted by the revascularization procedure is substantially occluded by PTVI device  110 . In one embodiment, the cardioprotective pacing sequence is applied repeatedly, before, during, and/or after the occlusion of the blood vessel, during the revascularization procedure. 
     As illustrated in  FIG. 3 , the cardioprotective pacing sequence includes alternating pacing and non-pacing periods. Each pacing period is a pacing duration during which the pacing pulses are delivered in a predetermined pacing mode. The non-pacing period is a non-pacing duration during which no pacing pulses is delivered. In one embodiment, during each pacing period, rapid, asynchronous pacing is applied. In other words, pacing pulses are delivered at a rate substantially higher than the patient&#39;s intrinsic heart rate without being synchronized to the patient&#39;s intrinsic cardiac contractions. For illustrative purpose only,  FIG. 3  shows a cardioprotective pacing sequence that includes two cycles of alternating pacing and non-pacing periods: pacing period  302 A, non-pacing periods  303 A, pacing period  302 B, and non-pacing periods  303 B. In one embodiment, the number of the cycles of alternating pacing and non-pacing periods is programmable, and each of the pacing and non-pacing periods is programmable. In one embodiment, the cardioprotective pacing sequence is initiated before the ischemic event and includes approximately 1 to 4 cycles of alternating pacing and non-pacing periods. The pacing period is in a range of approximately 30 seconds to 20 minutes. The non-pacing period is in a range of approximately 30 seconds to 20 minutes. In a specific example, the cardioprotective pacing sequence initiated before the ischemic event includes 3 cycles of alternating pacing and non-pacing periods each being approximately 5-minute long. In one embodiment, the cardioprotective pacing sequence is initiated during the ischemic event and includes approximately 1 to 4 cycles of alternating pacing and non-pacing periods. The pacing period is in a range of approximately 30 seconds to 20 minutes. The non-pacing period is in a range of approximately 30 seconds to 20 minutes. In a specific example, the cardioprotective pacing sequence delivered during the ischemic event includes 3 cycles of alternating pacing and non-pacing periods each being approximately 5-minute long. In one embodiment, the cardioprotective pacing sequence is initiated after the ischemic event and includes approximately 1 to 4 cycles of alternating pacing and non-pacing periods. The pacing period is in a range of approximately 10 seconds to one minute. The non-pacing period is in a range of approximately 10 seconds to one minute. In one specific example, the cardioprotective pacing sequence delivered after the ischemic event includes 2 to 4 cycles of alternating pacing and non-pacing periods each being approximately 30-second long. 
     In various other embodiments, the cardioprotective pacing sequence includes pacing at one or more atrial tracking or other pacing modes. Examples of pacing modes used in such a cardioprotective pacing sequence include VDD, VVI, and DDD modes. In various embodiments, the VVI and DDD modes are delivered with a lower rate limit higher than the patient&#39;s intrinsic heart rate. In one embodiment, pacing therapy is delivered with pacing mode and/or other pacing parameters selected to create or augment mechanical stress on the myocardium or particular regions of the myocardium. In another embodiment, pacing therapy is delivered to prevent restenosis. In another embodiment, pacing therapy is delivered to treat an arrhythmia during the revascularization procedure, for example, when the patient experiences bradycardia during the procedure. 
     In various embodiments, during the pacing periods, the delivery of the pacing pulse is controlled according to a stress augmentation pacing mode, and during the non-pacing periods of the cardioprotective pacing sequence, no pacing pulse is timed to be delivered according to a non-pacing mode. When a pacing pulse is timed to be delivered, it will be delivered unless inhibited by an inhibitory event such as a detected intrinsic cardiac depolarization occurring before the scheduled delivery of the pacing pulse during a cardiac cycle. Under the non-pacing mode according to which no pacing pulse is timed to be delivered, the non-delivery is due to programming rather than inhibition by a detected inhibitory event. Under the stress augmentation pacing mode, pacing pulses are delivered to augment mechanical stress on the myocardium of the heart to a level effecting cardioprotection against myocardial injury. In various embodiments, the stress augmentation pacing mode is a standard or non-standard pacing mode with pacing parameter values selected for the desired level of myocardial stress augmentation according to the patients&#39; needs, conditions, and responses. Examples of the stress augmentation pacing mode includes an atrial tracking pacing mode with a relatively short atrioventricular (AV) delay, a bradycardia pacing mode with a pacing rate substantially higher than the patient&#39;s intrinsic heart rate, and an asynchronous pacing mode with a pacing rate substantially higher than the patient&#39;s intrinsic heart rate. 
     In one embodiment, the pacing pulses are delivered according to the cardioprotective pacing protocol through PTVI device  110  during the revascularization procedure. After the revascularization procedure, if an implantable pacemaker is implanted into the patient, pacing therapy is delivered to heart  101  through one or more implantable leads from the implantable pacemaker. The pacing therapy includes delivering pacing pulses according to a pacing sequence that is substantially identical or similar to the cardioprotective pacing sequence applied during the revascularization procedure. The pacing sequence is delivered according to a predetermined schedule, such as on a predetermined periodic basis. This prevents or reduces possible cardiac injury after the revascularization, including cardiac injury and occurrences of arrhythmia caused by ischemic events including myocardial infarction that may be experienced by the patient after the implantation of the implantable pacemaker. 
     PTVI Device with Pacing Electrode(s) 
       FIGS. 4-6  illustrate a PTVI device assembly that includes a guide catheter, a guide wire, and an angioplasty catheter. During a revascularization procedure such as a PTCA procedure, the guide catheter is inserted into the patient first, followed by the guide wire through a lumen of the guide catheter. The angioplasty catheter includes a lumen that accommodates a portion of the guide wire, thereby allowing the angioplasty catheter to be inserted into the patient through the guide catheter and over the guide wire. The guide catheter, guide wire, and angioplasty catheter are inserted in such a way that allows an angioplasty device, such as a balloon, of the angioplasty catheter to be placed in the portion of a blocked blood vessel that is to be reopened during the revascularization procedure. 
       FIG. 4  is an illustration of an embodiment of a guide catheter  410 . Guide catheter  410  is an embodiment of PTVI device  110  and has an elongate shaft  413  between a distal end portion  411  and a proximal end portion  412 . Distal end portion  411  is configured for intravascular placement and includes a distal tip  435 . A lumen  430  extends within shaft  413  and has a proximal opening in proximal end portion  412  and a distal opening at distal tip  435 . Lumen  430  accommodates at least a portion of the angioplasty catheter. Distal end portion  411  includes pacing electrodes  432 A-B. In the illustrated embodiment, electrode  432 A is incorporated onto distal tip  435 . Conductor  433 A is connected between pacing electrode  432 A and a connector  416 A. Conductor  433 B is connected between pacing electrode  432 B and a connector  416 B. Connectors  416 A-B are each part of proximal end portion  412 . In one embodiment, conductors  433 A-B each extend longitudinally within shaft  413 . In another embodiment, conductors  433 A-B each extend longitudinally on the outer surface of shaft  413  and are insulated. 
     In one embodiment, guide catheter  410  has a length in a range of approximately 50 cm to 150 cm. Shaft  413  has an outer diameter in a range of approximately 0.5 mm to 8 mm, and lumen  430  has a diameter in a range of approximately 0.4 mm to 7 mm. Conductors  433 A-B are made of a metallic material such as stainless steel or an alloy of nickel, titanium, cobalt, gold, and/or silver chloride. Elongate shaft  413  is made of a material such as silicone, polyurethane, Teflon, or polytetrafluoroethylene (PTFE). Electrodes  432 A-B are made of a metallic material such as platinum or an iridium alloy. 
       FIG. 5  is an illustration of an embodiment of a guide wire  510 . Guide wire  510  is an embodiment of PTVI device  110  and has an elongate shaft  513  between a distal end portion  511  and a proximal end portion  512 . Distal end portion  511  is configured for intravascular placement and includes a distal tip  535 . Distal end portion  511  includes pacing electrodes  532 A-B. In the illustrated embodiment, electrode  532 A is incorporated onto distal tip  535 . Conductor  533 A is connected between pacing electrode  532 A and a connector  516 A. Conductor  533 B is connected between pacing electrode  532 B and a connector  516 B. Connectors  516 A-B are each part of proximal end portion  512 . In one embodiment, conductors  533 A-B each extend longitudinally within shaft  513 . In another embodiment, conductors  533 A-B each extend longitudinally on the outer surface of shaft  513  and are insulated. In one embodiment, one of connectors  533 A-B is the core of guide wire  510 . 
     In one embodiment, guide wire  510  has a length in a range of approximately 30 cm to 300 cm. Shaft  513  is an elongate cylindrical shaft having a diameter in a range of approximately 0.2 mm to 1.5 mm. Conductors  533 A-B are made of a metallic material such as stainless steel or an alloy of nickel, titanium, and/or cobalt. Elongate shaft  513  is made of a material such as silicone, polyurethane, Teflon, or polytetrafluoroethylene (PTFE). Electrodes  532 A-B are made of a metallic material such as platinum, an iridium alloy, gold, or silver chloride. 
       FIG. 6  is an illustration of an embodiment of an angioplasty catheter  610 . Angioplasty catheter  610  is an embodiment of PTVI device  110  and has an elongate shaft  613  between a distal end portion  611  and a proximal end portion  612 . A lumen  631  longitudinally extends within shaft  613  to accommodate at least a portion of a guide wire such as guide wire  510 . Distal end portion  611  is configured for intravascular placement and includes a distal tip  635  and an angioplasty device  634 . Angioplasty device  634  has one end approximately adjacent to distal tip  635  and another end coupled to shaft  613 . In one embodiment, angioplasty device  634  includes an adjustable portion that has controllable expandability and contractibility. In the illustrated embodiment, angioplasty device  634  includes a balloon that is inflated and deflated through a lumen longitudinally extending within shaft  613  and connected between the chamber of the balloon and a connector  614  at proximal end portion  612 . The balloon is inflatable using an air or liquid pump connected to that connector. In various embodiments, angioplasty device  634  includes a balloon or other device that allows for application of an angioplasty therapy such as vascular dilatation, stent delivery, brachytherapy (radiotherapy), atherectomy, or embolic protection. In one embodiment, distal tip  635  is a tapered tip that facilitates the insertion of angioplasty catheter  610  into a blood vessel. Distal end portion  611  includes pacing electrodes  632 A-B. In the illustrated embodiment, pacing electrode  632 A is approximately adjacent to one end of angioplasty device  634 , and pacing electrode  632 B is approximately adjacent to the other end of angioplasty device  634 . A conductor  633 A extends longitudinally within shaft  613  and is connected between pacing electrode  632 A and a pacing connector  616 A, which is part of proximal end portion  612 . A conductor  633 B extends longitudinally within elongate shaft  613  and is connected between pacing electrode  632 B and a pacing connector  616 B, which is also part of proximal end portion  612 . In an alternative embodiment, pacing connectors  616 A-B are physically integrated into one multi-conductor connector. Proximal end portion  612  also includes a proximal end device  614 . In various embodiments, connector  614  includes a structure that accommodates all the mechanical connection and access requirements for angioplasty catheter  610 , which depend on the function of angioplasty device  634 . In one embodiment, connector  614  includes an integrated device. In another embodiment, connector  614  branches out into multiple connectors and/or other devices. 
     In one embodiment, angioplasty catheter  610  has a length in a range of approximately 50 cm to 150 cm. Shaft  613  is an elongate cylindrical shaft having a diameter in a range of approximately 1 mm to 5 mm. In one embodiment, angioplasty device  634  has an adjustable, substantially cylindrical or semi-spherical shape with a maximum diameter in a range of approximately 1 mm to 10 mm when fully expanded and a maximum diameter in a range of approximately 0.5 mm to 5 mm when fully contracted. In one embodiment, conductors  633 A-B are each made of a metallic material such as stainless steel or an alloy of nickel, titanium, and/or cobalt. Electrodes  632 A-B are each made of a metallic material such as platinum or an iridium alloy. Elongate shaft  613  has a tubular outer shell made of a material such as silicone, polyurethane, Teflon, or polytetrafluoroethylene (PTFE). 
     Guide catheter  410 , guide wire  510 , and angioplasty device  610  are illustrated in  FIGS. 4-6  for illustrative but not restrictive purposes. For example, one or more pacing electrodes can be distributed on each of these PTVI devices in any way allowing delivery of pacing pulses to desirable locations. In various embodiments, one or more pacing electrodes are incorporated onto one or more of guide catheter  410 , guide wire  510 , and angioplasty device  610  for delivering pacing pulses through the PTVI device assembly including these three devices. In one embodiment, one or more defibrillation electrodes are also incorporated onto one or more of guide catheter  410 , guide wire  510 , and angioplasty device  610  for delivering defibrillation shocks through the PTVI device assembly. In one embodiment, one or more pacing electrodes such as one of more of pacing electrodes  432 A-B,  532 A-B, and  632 A-B are made of conductive radiopaque material to function as one or more radiopaque markers for locating guide catheter  410 , guide wire  510 , and/or angioplasty device  610  using fluoroscopy. 
     In one embodiment, angioplasty device  610  includes a balloon. Guide wire  510  remains within lumen  631  when the balloon is inflated. The inflated balloon is over pacing electrodes  532 A-B. When being deflated, the balloon is retracted to expose electrodes  532 A-B, thereby allowing delivery of pacing pulses. In one embodiment, shaft  613  includes a portion having an adjustable length that is shortened to expose electrodes  532 A-B when the balloon is deflated. 
     In one application during a PTCA procedure for reopening, for example, right coronary artery  107 , guide catheter  410  is inserted into femoral artery  104  and advanced to aorta  106  until distal tip  435  reaches the point where right coronary artery  107  branches from aorta  106 . Guide wire  510  is introduced through lumen  430  of guide catheter  410  until distal end  535  is in right coronary artery  107 . Angioplasty catheter  610  is then introduced through lumen  430  over guide wire  510  until angioplasty device  634  (balloon) is in the portion of right coronary artery  107 . In one embodiment, the acute pacing cardioprotection therapy is delivered using electrodes  432 A-B as soon as guide catheter  410  is in place for the PTCA procedure. In one embodiment, when the PTVI device assembly including guide catheter  410 , guide wire  510 , and angioplasty device  610  are in place for the PTCA procedure, the acute pacing cardioprotection therapy is delivered using one or more pairs of pacing electrodes selected from electrodes  432 A-B,  532 A-B,  632 A-B, and  119 . 
     In one embodiment, the PTVI device assembly allows for combined pacing cardioprotection therapy and ischemic cardioprotection therapy. For example, the ischemic cardioprotection therapy is applied by intermittently occluding a blocked vessel by inflating and deflating angioplasty device  634  (balloon) of angioplasty catheter  610 , in addition to delivering the pacing cardioprotection therapy through the one or more pairs of pacing electrodes. 
     Various embodiments of the PTVI devices and the pacemaker are discussed below as examples illustrating the pacing system for delivering the acute pacing cardioprotection therapy during a revascularization procedure. In general, such a pacing system includes a pacemaker capable of delivering pacing pulses according to a cardioprotective pacing protocol, such as discussed above with reference to  FIG. 3 , and one or more PTVI devices each including one or more pacing electrodes. In one embodiment, the one or more PTVI devices includes devices used to perform the revascularization procedure, such as guide catheters, guide wires, and angioplasty catheters, that are modified to allow delivery of the acute pacing cardioprotection therapy. In another embodiment, the one or more PTVI devices includes one or more devices that are not required to perform the revascularization procedure itself but configured to allow delivery of pacing pulses during the revascularization procedure. In various embodiments, the PTVI devices have sizes identical or similar to those discussed above, and are constructed using materials identical or similar to those discussed above. 
       FIGS. 7-13  illustrate several specific embodiments of guide catheter  410 , guide wire  510 , and angioplasty device  610 . In various embodiments, pacing pulses are delivered during a revascularization procedure using any PTVI device with at least one pacing electrode, alone or in combination with any other PTVI device(s) each with at least one pacing electrode and/or electrode(s) placed in or on the patient receiving the revascularization procedure. 
       FIG. 7  is an illustration of an embodiment of a distal portion of a guide catheter  710  showing its distal end portion  711  and elongate shaft  713 . Guide catheter  710  is another embodiment of guide catheter  410 . As shown in  FIG. 7 , distal end portion  711  includes a distal tip  735  where a lumen  730  ends with its distal opening. Lumen  730  is configured to accommodate at least a portion of an angioplasty catheter such as angioplasty catheter  610  and allow the angioplasty device of the angioplasty catheter to exit from guide catheter  710 . Pacing electrodes  732 A-B are incorporated onto distal tip  735 , adjacent to the distal opening of lumen  730 . Pacing electrodes  732 C-D are incorporated onto shaft  713 . Conductors  733 A-D provide for electrical connections allowing pacing pulses to be delivered to pacing electrodes  732 A-D when the pacemaker is connected to the proximal end of guide catheter  710 . In various other embodiments, guide catheter  710  includes any number of pacing electrodes incorporated onto distal end portion  711  and/or shaft  713 . In various embodiments, any one or more of the pacing electrodes incorporated onto guide catheter  710  are selected for delivering the pacing pulses during a revascularization procedure. 
       FIG. 8  is an illustration of an embodiment of a distal end portion of a guide catheter  810  showing its distal end portion  811  and elongate shaft  813 . Guide catheter  810  is another embodiment of guide catheter  410 . As shown in  FIG. 8 , distal end portion  811  includes a distal tip  835  where a lumen  830  ends with its distal opening. Lumen  830  is configured to accommodate at least a portion of an angioplasty catheter such as angioplasty catheter  610  and allow the angioplasty device of the angioplasty catheter to exit from guide catheter  810 . A pacing electrode  832  configured as a coil electrode is incorporated onto distal end portion  811  near distal tip  835 . A conductor  833  provides for electrical connection allowing pacing pulses to be delivered to pacing electrode  832  when the pacemaker is connected to the proximal end of guide catheter  810 . In various other embodiments, guide catheter  810  includes any number of coil electrodes incorporated onto distal end portion  811  and/or shaft  813 . In various embodiments, any one or more coil electrodes incorporated onto guide catheter  810  are selected for delivering the pacing pulses during a revascularization procedure. 
       FIG. 9  is an illustration of an embodiment of the distal portion of a guide catheter  910  showing its distal end portion  911  and elongate shaft  913 . Guide catheter  910  is another embodiment of guide catheter  410 . As shown in  FIG. 9 , distal end portion  911  includes a distal tip  935  where a lumen  930  ends with its distal opening. Lumen  930  is configured to accommodate at least a portion of an angioplasty catheter such as angioplasty catheter  610  and allow the angioplasty device of the angioplasty catheter to exit from guide catheter  910 . A pacing electrode  932 A is configured as a collar electrode and incorporated onto distal tip  935 . Another pacing electrode  932 B is configured as another collar electrode and incorporated onto shaft  913 . Two layers of tubular metal braid each extend within guide catheter  910  and connect to one of pacing electrodes  932 A-B. These two layers of tubular metal braid function as conductors  933 A-B, which provide for electrical connections allowing pacing pulses to be delivered to pacing electrodes  932 A-B when the pacemaker is connected to the proximal end of guide catheter  910 . In various other embodiments, guide catheter  910  includes any number of collar electrodes incorporated onto distal end portion  911  and/or shaft  913 . In various embodiments, any one or more collar electrodes incorporated onto guide catheter  910  are selected for delivering the pacing pulses during a revascularization procedure. 
       FIG. 10  is an illustration of an embodiment of the distal portion of a guide wire  1010  showing its distal end portion  1011  and elongate shaft  1013 . Guide wire  1010  is another embodiment of guide wire  510  and is formed by a conductor  1033  covered by an insulation layer  1043 . In the illustrated embodiment, distal end portion  1011  includes a distal tip  1035  and a pacing electrode  1032  formed by an opening in insulation layer  1043  that exposes a portion of conductor  1033 . Pacing pulses are delivered through conductor  1033  to the patient through opening/electrode  1032  when the pacemaker is connected to the proximal end of guide wire  1010 . In various other embodiments, insulation layer  1043  includes any number of openings functioning as electrodes on distal end portion  1011  and/or shaft  1013 . 
       FIG. 11  is an illustration of an embodiment of the distal portion of a guide wire  1110  showing its distal end portion  1111  and elongate shaft  1113 . Guide wire  1110  is another embodiment of guide wire  510  and is formed by a plurality of conductors covered by an insulation layer. In the illustrated embodiment, guide wire  1110  includes conductors  1133 A-B that are insulated to form shaft  1113  and exposed to form pacing electrodes  1132 A-B at distal end portion  1111 . Pacing electrodes  1132 A-B include exposed portions of conductors  1133 A-B in a helical form extending to a distal tip  1135  of guide wire  1110 . In one embodiment, pacing electrodes  1132 A-B are separated from each other to be used as an anode and a cathode for delivering the pacing pulses when the pacemaker is connected to the proximal end of guide wire  1110 . In various other embodiments, guide wire  1110  includes one, two, or more than two conductors with their distal end portions exposed and configured to function as one, two, or more electrically separated pacing electrodes. 
       FIG. 12  is an illustration of an embodiment of the distal portion of an angioplasty catheter  1210 . Angioplasty catheter  1210  is another embodiment of angioplasty catheter  610 . Distal end portion  1211  includes a balloon  1234  coupled between a distal tip  1235  and an elongate shaft  1213 . In the illustrated embodiment, balloon  1234  includes perfusion channels  1236 A-B and cutting blades  1232 E-F. Perfusion channels  1236 A-B each include a lumen having a proximal opening and a distal opening to allow blood to flow through balloon  1234  when it is inflated. In one embodiment, when balloon  1234  is inflated, the lumen has a diameter that allows the distal end portion of a pacing lead to enter its proximal opening and exit from its distal opening such that one or more pacing electrodes of the pacing lead are placed distal to the lumen. Cutting blades  1232 E-F cut plaques in a blood vessel as balloon  1234  is being inflated in that blood vessel. In one embodiment, cutting blades  1232 E-F are each made of metal and used as a pacing electrode. In various embodiments, balloon  1234  is a perfusion balloon including one or more perfusion channels and/or a cutting balloon including one or more cutting blades. Angioplasty catheter  1210  also includes pacing electrodes  1232 A-D. Pacing electrode  1232 A is incorporated onto distal tip  1235 . Pacing electrode  1232 B is incorporated onto shaft  1213 . Pacing electrodes  1232 C-D are incorporated onto balloon  1234 . In one embodiment, one or more of pacing electrodes  1232 A-D are made of radiopaque material to function as one or more radiopaque markers for locating distal end portion  1211  using fluoroscopy. Conductors  1233 A-F provide for electrical connections allowing pacing pulses to be delivered to pacing electrodes  1232 A-F when the pacemaker is connected to the proximal end of angioplasty catheter  1210 . In the illustrated embodiment, angioplasty catheter  1210  includes pacing electrodes  1232 A-F. In various embodiments, angioplasty catheter  1210  includes any one or more of pacing electrodes  1232 A-F as well as other one or more pacing electrodes incorporated onto distal end portion  1211  and/or shaft  1213 . In various embodiments, any one or more pacing electrodes incorporated onto angioplasty catheter  1210  are selected for delivering the pacing pulses during a revascularization procedure. 
     A potential advantage for using one or more of pacing electrodes  1232 C-F for delivering pacing pulses is that when balloon  1234  is inflated, the pacing electrodes are pressed onto the vascular wall to form stable electrical contacts. In one embodiment, a pacing lead that is substantially identical or similar to guide wire  510  is introduced along the side of angioplasty catheter  1210 , with its one or more pacing electrodes placed over balloon  1234  such that when balloon  1234  is inflated, the one or more pacing electrodes of that pacing lead is securely pressed onto the vascular wall to form a stable electrical contact for delivering pacing pulses. 
       FIG. 13  is an illustration of an embodiment of the proximal portion of an angioplasty catheter  1310  showing a proximal end portion  1312  and an elongate shaft  1313 . In the illustrated embodiment, angioplasty catheter  1310  includes conductors  1333 A-D connected between ring connectors  1316 A-D in proximal end portion  1312  and pacing electrodes in the distal end portion of angioplasty catheter  1310 . In various embodiments, angioplasty catheter  1310  includes one or more conductors and ring connectors, depending on the number of pacing electrodes. A lumen  1330  extends longitudinally within angioplasty catheter  1310  to accommodate a guide wire such as guide wire  510  and/or to allow inflation and deflation of a balloon at the distal end portion. Lumens  1339 A-D each accommodates one of conductors  1333 A-D. 
       FIGS. 14-37  illustrate various specific examples of PTVI devices that include pacing electrodes to allow an acute pacing cardioprotection therapy to be delivered during a revascularization procedure. In various embodiments, each of these PTVI devices may function as one of the guide catheter, guide wire, and angioplasty catheter as discussed above, or a PTVI pacing device that is otherwise not required for the revascularization procedure. In various embodiments, pacing pulses are delivered from an external pacemaker connected to one or more PTVI devices with pacing electrodes, or from a pacemaker incorporated onto a PTVI device. 
     Example: Pacing Catheter with Expandable Distal End 
       FIGS. 14-18  illustrate various embodiments of a pacing catheter including an expandable distal end including one or more pacing electrodes. When expanded in a blood vessel during a revascularization procedure, the distal end is stabilized in the blood vessel to provide reliable electrical contact(s) between the one or more pacing electrodes and the vascular wall for delivering pacing pulses. 
       FIG. 14  is an illustration of an embodiment of a pacing catheter  1410 . Pacing catheter  1410  is a PTVI device assembly including a sheath  1410 A and a pacing lead  1410 B. Sheath  1410 A includes a sheath proximal end portion  1412 A, a sheath distal end portion  1411 A configured for intravascular placement and including a distal tip  1435 A, an elongate sheath shaft  1413 A coupled between proximal end portion  1412 A and distal end portion  1411 A, and a lumen  1430 A. Lumen  1430 A extends within shaft  1413 A and has a proximal opening  1441 A at proximal end portion  1412 A and a distal opening  1440 A at distal tip  1435 A. In one embodiment, sheath  1410 A is a guide catheter for use in a revascularization procedure. In the illustrated embodiment, sheath  1410 A includes a pacing electrode  1432 A incorporated onto distal end portion  1411 A, a connector  1416 A incorporated onto proximal end portion  1412 A, and a conductor  1433 A providing for electrical connection between pacing electrode  1432 A and connector  1416 A. In various other embodiments, sheath  1410 A includes any number of pacing electrodes, or no pacing electrode. 
     Pacing lead  1410 B includes a lead proximal end portion  1412 B, an expandable lead distal end portion  1411 B configured for intravascular placement, and an elongate lead shaft  1413 B coupled between proximal end portion  1412 B and distal end portion  1411 B. Pacing lead  1410 B is configured to allow distal end portion  1411 B to enter lumen  1430 A through proximal opening  1441 A and exit from lumen  1430 A through distal opening  1440 A by being pushed into lumen  1430 A, and retract into lumen  1430 A through distal opening  1440 A and exit lumen  1430 A from proximal opening  1441 A by being pulled from lumen  1430 A. Distal end portion  1411 B includes a pacing electrode  1432 B. Pacing lead  1410 B includes a connector  1416 B electrically connected to pacing electrode  1432 B via a conductor  1433 B extending through shaft  1413 B. In one embodiment, pacing electrode  1432 B is incorporated onto distal end portion  1411 B. In another embodiment, pacing electrode  1432 B includes the entire distal end portion  1411 B or a substantial portion thereof. Distal end portion  1411 B is in a contracted state while being placed in lumen  1430 A and in an expanded state after exiting from lumen  1430 A. In one embodiment, distal end portion  1411 B expands upon exiting from lumen  1430 A and contracts upon retracting into lumen  1430 A. In one embodiment, distal end portion  1411 B is self-expandable and is in an expanded state when not being restrained. When being placed in a blood vessel and in its expanded state, distal end portion  1411 B provides for a stable electrical contact between pacing electrode  1432 B and the vascular wall for delivering pacing pulses. 
     In various embodiments, pacing lead  1410 B includes one or more pacing electrodes, one or more connectors, and one or more conductors extending through shaft  1413 B and connecting between one of the one or more pacing electrodes and one of the one or more connectors.  FIGS. 15-17  illustrate various embodiments of distal end portion  1411 B each including one or more pacing electrodes. 
       FIG. 15  is an illustration of an embodiment of a lead distal end portion  1511 B of a pacing lead  1510 B, which is another embodiment of pacing lead  1410 B. Pacing lead  1510 B includes a pacing electrode  1532 B at distal end portion  1511 B connected to a conductor  1533 B extending in an elongate lead shaft  1513 B. Pacing electrode  1532 B is formed by a wire that springs into a coil upon exiting from lumen  1430 A from distal opening  1440 A. The coil has a diameter suitable for stabilizing lead distal end  1511 B in a blood vessel. 
       FIG. 16  is an illustration of an embodiment of a lead distal end portion  1611 B of a pacing lead  1610 B, which is another embodiment of pacing lead  1410 B. Pacing lead  1610 B includes a pacing electrode  1632 B at distal end portion  1611 B connected to a conductor  1633 B extending in an elongate lead shaft  1613 B. Pacing electrode  1632 B includes a Guglielmi Detachable Coil (GDC®). GDC is a coil made of memory material that is restrained during delivery into the body and expands when it is no longer restrained. The coil is electrically sensitive such that it is detached from its delivery device by passing a low-amplitude electrical current through the delivery device. Thus, pacing electrode  1632 B expands upon exiting from lumen  1430 A from distal opening  1440 A and is disconnected from shaft  1613 B after the delivery of the pacing pulses. 
       FIG. 17  is an illustration of an embodiment of a lead distal end portion  1711 B of a pacing lead  1710 B, which is another embodiment of pacing lead  1410 B. In the illustrated embodiment, pacing lead  1710 B includes pacing electrodes  1732 BA and  1732 BB at distal end portion  1711 B connected to conductors  1733 BA and  1733 BB extending in an elongate lead shaft  1713 B. Conductors  1733 BA and  1733 BB at distal end  1711 B are substantially unbiased while being restrained in lumen  1430 A and biased when distal end portion  1711 B has exited from lumen  1430 A from distal opening  1440 A. The biased portion of conductors  1733 BA and  1733 BB are made of one or more memory materials and configured to be suitable for stabilizing distal end portion  1711 B in a blood vessel when biased. In various embodiments, distal end portion  1711 A includes a plurality of wires each being substantially unbiased when being restrained in lumen  1430 A and biased when not being restrained. The plurality of wires forms one or more pacing electrodes. 
       FIG. 18  is an illustration of an embodiment of a PTVI device assembly  1810  including a pacing lead  1810 B and a balloon catheter  1810 A. Balloon catheter  1810 A is an angioplasty catheter including a catheter proximal end portion  1812 A, a catheter distal end portion  1811 A configured for intravascular placement and including a catheter distal tip  1835 A and a balloon  1834 A, an elongate catheter shaft  1813 A between proximal end portion  1812 A and distal end portion  1811 A. A pacing electrode  1832 A is incorporated onto distal tip  1835 A. A conductor  1833 A extends within shaft  1813 A and provides for electrical connection between pacing electrode  1832 A and a connector  1816 A at proximal end portion  1812 A. 
     Pacing lead  1810 B includes a lead proximal end  1812 B, a lead distal end  1811 B including a distal tip  1835 B, and an elongate lead shaft  1813 B between proximal end portion  1812 B and distal end portion  1811 B. A pacing electrode  1832 B is incorporated onto distal tip  1835 B. A conductor  1833 B extends within shaft  1813 B and provides for electrical connection between pacing electrode  1832 B and a connector  1816 B at proximal end portion  1812 B. 
     To deliver pacing pulses using pacing electrodes  1832 A and  1832 B, pacing lead  1810 B is placed such that pacing electrode  1832 B is over balloon  1834 A when distal end portions  1811 A and  1811 B are positioned in the intended pacing site in a blood vessel. When balloon  1834 A is inflated, pacing electrode  1832 B is pressed by balloon  1834 A onto the interior wall of the blood vessel to provide a stable electrical contact for delivering the pacing pulses. In one embodiment, PTVI device assembly  1810  allows for delivering combined ischemic cardioprotection therapy by inflating and deflating balloon  1834 A and pacing cardioprotection therapy by delivering cardioprotective pacing via electrodes  1832 A and  1832 B. 
     Example: Pacing Catheter for Access to Multiple Vessels 
       FIGS. 19 and 20  illustrate various embodiments of a pacing catheter through which multiple pacing leads are introduced into multiple blood vessels. The pacing catheter includes exit ports arranged according to the anatomy of a portion of the vascular system where the intended pacing sites are located, such that the pacing leads exit from the pacing catheter through the exit ports into the blood vessels in which the pacing electrodes are to be placed. For example, after the pacing catheter is inserted into a major blood vessel, such as the vessel to be reopened during a revascularization procedure, the pacing leads exit from the exit ports to enter the major blood vessel and/or one or more blood vessels branching from the major blood vessel. 
       FIG. 19  is an illustration of an embodiment of a pacing catheter  1910 . Pacing catheter  1910  is a PTVI device assembly including multiple pacing leads for access to multiple vessels. In the illustrated embodiment, pacing catheter  1910  includes pacing leads  1910 A and  1910 B and a catheter  1910 C. 
     Pacing lead  1910 A includes a lead proximal end portion  1912 A including a connector  1916 A, a lead distal end portion  1911 A configured for intravascular placement and including a lead distal tip  1935 A, and an elongate lead shaft  1913 A coupled between lead proximal end portion  1912 A and lead distal end portion  1911 A. A pacing electrode  1932 A is incorporated onto distal tip  1935 A. A connector  1933 A provides for electrical connection between pacing electrode  1932 A and connector  1916 A. 
     Pacing lead  1910 B includes a lead proximal end portion  1912 B including a connector  1916 B, a lead distal end portion  1911 B configured for intravascular placement and including a lead distal tip  1935 B, and an elongate lead shaft  1913 B coupled between lead proximal end portion  1912 B and lead distal end portion  1911 B. A pacing electrode  1932 B is incorporated onto distal tip  1935 B. A connector  1933 B provides for electrical connection between pacing electrode  1932 B and connector  1916 B. 
     Catheter  1910 C includes a catheter proximal end portion  1912 C including a connector  1916 C, a catheter distal end portion  1911 C configured for intravascular placement and including a catheter distal tip  1935 C, and an elongate catheter shaft  1913 C coupled between catheter proximal end portion  1912 C and catheter distal end portion  1911 C. A pacing electrode  1932 C is incorporated onto distal tip  1935 C. A connector  1933 C provides for electrical connection between pacing electrode  1932 C and connector  1916 C. Catheter  1910 C includes one or more entry ports  1943 C at proximal end portion  1912 C, exit port  1942 CA at distal tip  1935 C, and exit port  1942 CB on shaft  1913 C. To deliver pacing pulses, distal ends  1911 A-B of pacing leads  1910 A-B are inserted into catheter  1910 C through entry port(s)  1943 C and exit through exit ports  1942 CA-B. Exit ports  1942 CA-B are positioned to allow distal ends  1911 A-B to enter two blood vessels where pacing electrodes  1932 A-B are to be placed. In one embodiment, exit port  1942 CA is positioned on catheter  1910 C to allow pacing electrode  1932 A to be placed in a main blood vessel into which catheter  1910 C is placed, and pacing electrode  1932 B is to be placed in another blood vessel branched from the main blood vessel. 
     In one application, exit ports  1942 CA-B are positioned to allow distal end portions  1911 A-B to enter the left anterior descending (LAD) coronary artery and the right coronary artery. 
     In various embodiments, PTVI device assembly  1910  includes two or more pacing leads that are introduced through catheter  1910 C, which includes two or more exit ports each allow one of the pacing leads to exit into a blood vessel. Each of the two or more pacing leads includes one or more pacing electrodes. 
       FIG. 20  is an illustration of an embodiment of a catheter  2010 C, which is an embodiment of catheter  1910 C. Catheter  2010 C includes a catheter proximal end portion  2012 C, a catheter distal end portion  2011 C configured for intravascular placement and including a catheter distal tip  2035 C, and an elongate catheter shaft  2013 C coupled between catheter proximal end portion  2012 C and catheter distal end portion  2011 C. Catheter  2010 C includes entry ports  2043 CA-B at proximal end portion  2012 C, exit port  2042 CB at distal tip  2035 C, exit port  2042 CA on shaft  2013 C, and guiding channels  2044 CA-B each including a lumen extending within a portion of shaft  2013 C. Guiding channel  2044 CA includes a lumen connecting entry port  2043 CA and exit port  2042 CA. Guiding channel  2044 CB includes a lumen connecting entry port  2043 CB and exit port  2042 CB. To deliver the pacing pulses, pacing leads  1910 A-B are each placed using one of guiding channel  2044 CA-B, with the distal tip entering one of entry port  2043 A-B and exiting from one of exit port  2042 A-B. 
     Example: Pacing Catheter Releasing Conductive Liquid as Electrode 
       FIGS. 21-23  illustrate various embodiments of a pacing catheter that includes a pacing electrode and releases a conductive liquid into a blood vessel to provide a conductive medium between a pacing electrode of the vascular wall of the blood vessel. This conductive medium increases electrical conductivity between the pacing electrode and the target tissue, thereby lowering the pacing energy required to capture the heart. In various embodiments, the conductive liquid has an electrical conductivity that is substantially higher than the electrical conductivity of blood. 
       FIG. 21  is an illustration of an embodiment of a pacing catheter  2110  (cross-sectional view), which releases a conductive liquid  2146 , and an injection device  2150 . Pacing catheter  2110  is a PTVI device including a proximal end portion  2112 , a distal end portion  2111  configured for intravascular placement and including a distal tip  2135 , an elongate shaft  2113  coupled between proximal end portion  2112  and distal end portion  2111 , a lumen  2148  extending within shaft  2113 , and exit ports  2147 A-B. Lumen  2148  has a proximal opening  2149  at proximal end portion  2112  and connects to exit ports  2147 A-B. Conductive liquid  2146  is injected into lumen  2148  from injection device  2150  through proximal opening  2149  and exits into a blood vessel from lumen  2148  through exit ports  2147 A-B. 
     Pacing catheter  2110  includes a pacing electrode  2132  incorporated onto distal tip  2135 , a connector  2116  at proximal end portion  2112 , and a conductor  2133  providing for electrical connection between pacing electrode  2132  and connector  2116 . After being released into the blood vessel, conductive liquid  2146  improves electrical conductivity between pacing electrode  2132  and the vascular wall, thereby reducing the impedance between the pair of anode and cathode through which pacing pulses are delivered. In one embodiment, conductive liquid  2146  includes saline. In one embodiment, conductive liquid  2146  is radiopaque. In one embodiment, conductive liquid  2146  includes saline and radiopaque contrast liquid, such as a mixture of approximately 50% of saline and 50% of the radiopaque contrast liquid. 
     In one embodiment, exit ports  2147 A-B are configured to allow controllable release of conductive liquid  2146  into the blood vessel. In one embodiment, exit ports  2147 A-B each include electrically activated polymer (EAP) functioning as a valve that is controlled by an electric field applied using electrode  2132 . While one pacing electrode  2132  and two exit ports  2147 A-B are shown in  FIG. 21  for illustrative purposes, in various embodiments, pacing catheter  2110  includes any number of pacing electrode(s) and any number of exit port(s) arranged to release conductive liquid to increase the electrical conductivity between the pacing electrode(s) and the target tissue for pacing. 
       FIG. 22  is an illustration of an embodiment of a pacing catheter  2210  releasing conductive liquid  2146 . Pacing catheter  2210  is a PTVI device including a proximal end portion  2212 , a distal end portion  2211  configured for intravascular placement and including a distal tip  2235  and a drip balloon  2234 , an elongate shaft  2213  coupled between proximal end portion  2212  and distal end portion  2211 , a lumen  2248  extending within shaft  2213 , and exit ports  2247 A-D. Lumen  2248  has a proximal opening  2249  at proximal end portion  2212  and connects to exit ports  2247 A-D. Conductive liquid  2146  is injected into lumen  2248  from injection device  2150  through proximal opening  2249  and exit into a blood vessel from lumen  2248  through exit ports  2147 A-D. 
     Pacing catheter  2210  includes a pacing electrode  2232  incorporated onto drip balloon  2234 , a connector  2216  at proximal end portion  2212 , and a conductor  2233  providing for electrical connection between pacing electrode  2232  and connector  2216 . Drip balloon  2234  includes a wall  2251  forming a chamber  2252  to contain conductive liquid  2146 . Wall  2251  includes holes functioning as exit ports  2247 A-D, which allow for dripping of conductive liquid  2146  from chamber  2252  to the blood vessel. In one embodiment, the holes are opened to allow for dripping of conductive liquid  2146  to the blood vessel when drip balloon  2234  is inflated. After being released into the blood vessel, conductive liquid  2146  improves electrical conductivity between pacing electrode  2232  and the vascular wall. 
     In one embodiment, injection device  2150  injects conductive liquid  2146  into chamber  2252  through lumen  2248  to inflate drip balloon  2234  and withdraws conductive liquid  2146  from chamber  2252  through lumen  2248  to deflate drip balloon  2234 . This allows for delivering combined ischemic cardioprotection therapy by inflating and deflating drip balloon  2234  and pacing cardioprotection therapy by delivering cardioprotective pacing via pacing electrode  2232  and conductive liquid  2146 . 
     While four exit ports  2247 A-D are shown in  FIG. 22  for illustrative purposes, pacing catheter  2210  includes any number of exit port(s). In one embodiment, pacing catheter  2210  allows for delivering combined ischemic cardioprotection therapy by inflating and deflating drip balloon  2234  and pacing cardioprotection therapy by delivering cardioprotective pacing via electrodes  2232  and conductive liquid  2146 . 
       FIG. 23A  is a side view, and  FIG. 23B  is a cross-sectional view, illustrating an embodiment of a pacing catheter  2310  releasing conductive liquid  2146 . Pacing catheter  2310  is a PTVI device including a proximal end portion  2312 , a distal end portion  2311  configured for intravascular placement and including a distal tip  2335 , and an elongate shaft  2313  coupled between proximal end portion  2312  and distal end portion  2311 . Pacing catheter  2310  includes an inner tube  2354  including a lumen  2348  and an outer tube  2353  accommodating at least a portion of inner tube  2354 . Inner tube includes inner orifices  2347 BA-B. Outer tube  2353  includes outer orifices  2347 AA-B. The release of conductive liquid  2146  from lumen  2348  is controlled by rotating inner tube  2354  relative to outer tube  2353  to create an opening by aligning inner orifices  2347 BA-B and outer orifices  2347 AA-B. Lumen  2348  has a proximal opening  2349  at proximal end portion  2312  and connects inner orifices  2347 BA-B. Conductive liquid  2146  is introduced into lumen  2348  from injection device  2150  through proximal opening  2349 . When aligned, orifices  2347 AA and  2347 BA form an exit port, and orifices  2347 BA and  2347 BB form another exit port, to allow conductive liquid  2146  to flow from lumen  2348  to the blood vessel. 
     Pacing catheter  2310  includes a pacing electrode  2332  incorporated onto distal end portion  2311 , a connector  2316  at proximal end portion  2312 , and a conductor  2333  providing for electrical connection between pacing electrode  2332  and connector  2316 . After being released into the blood vessel, conductive liquid  2146  improves electrical conductivity between pacing electrode  2332  and the vascular wall. 
     While two pairs of inner and outer orifices forming two exit ports are shown in  FIG. 23  for illustrative purposes, pacing catheter  2310  includes any number of pairs of inner and outer orifices forming any number of exit ports. 
     Example: Pacemaker Integrated with PTVI Device 
       FIGS. 24-28  illustrate various embodiments of a pacemaker and pacing electrodes integrated with a PTVI device. Such an integrated pacemaker-PTVI device eliminates the need for connecting a separate pacemaker to a PTVI device, thereby simplifying the equipment setup for pacing during a revascularization procedure. 
       FIG. 24  is an illustration of an embodiment of a pacemaker  2456  integrated with a PTVI device  2410 . PTVI device  2410  includes a proximal end portion  2412 , a distal end portion  2411  configured for intravascular placement and including a distal tip  2435 , and an elongate shaft  2413  coupled between proximal end portion  2412  and distal end portion  2411 . In the illustrated embodiment, pacemaker  2456  is incorporated onto shaft  2413 . Pacing electrodes  2432 A-B are incorporated onto distal end portion  2411  and electrically connected to pacemaker  2456  via conductors  2433 A-B. In various embodiments, PTVI device  2410  includes any number of pacing electrodes incorporated onto one or more of distal end portion  2411  and shaft  2413 . Examples of PTVI device  2410  include a guide wire, a guide catheter, and an angioplasty catheter. In various embodiments, pacemaker  2456  is integrated into any of the PTVI devices discussed in the document. 
       FIG. 25  is an illustration of an embodiment of a pacemaker  2556 . Pacemaker  2556  is an embodiment of  2456  and includes a flexible pacemaker circuit including an electronic circuit  2559  and a battery  2558  both built on a flexible circuit substrate  2557 . Flexible circuit substrate  2557  is affixed to PTVI device  2410 . In one embodiment, electronic circuit  2559  includes a pacing output circuit such as pacing output circuit  224  and a control circuit such as control circuit  226 . In one embodiment, battery  2558  is a solid state battery, such as a solid state lithium battery, deposited on flexible circuit substrate  2557 . In one embodiment, battery  2558  is capable of providing electronic circuit  2559  with energy for delivering pacing pulses according to the cardioprotective pacing protocol for about 10 minutes. 
     In one embodiment, electronic circuit  2559  includes a control circuit that initiates the delivery of pacing pulses when pacing electrodes  2432 A-B contact blood, such as when distal end portion  2411  exits from a guide catheter or other sheath. In another embodiment, electronic circuit  2559  is communicatively coupled to an external device via a wired or wireless communication link, and initiates the delivery of pacing pulses in response to a command received from the external device. In another embodiment, electronic circuit  2559  includes a switch that is mechanically controlled through a string, a sheath, or other mechanical link extending within or over PTVI device  2410 . The switch allows initiation, suspension, and/or termination of the delivery of pacing pulses at proximal end portion  2412 . In one embodiment, the duration of the delivery of pacing pulses is programmed into electronic circuit  2559 . For example, the electronic circuit  2559  is programmed to execute the cardioprotective pacing protocol discussed above with reference to  FIG. 3 , and the delivery of the pacing pulses is terminated when the pacing sequence specified by the cardioprotective pacing protocol is completed. In circumstances of emergency, such as when fibrillation is detected, the delivery of pacing pulses is stopped by a command from the external device or the mechanically controlled switch, whichever is available, or by removing PTVI device  2410  from the patient. 
       FIG. 26  is an illustration of an embodiment of pacemaker  2456  integrated with a PTVI device  2610 . PTVI device  2610  is another embodiment of PTVI device  2410  and includes a proximal end portion  2612 , a distal end portion  2611  configured for intravascular placement and including a distal tip  2635 , and an elongate shaft  2613  coupled between proximal end portion  2612  and distal end portion  2611 . Pacemaker  2456  is incorporated onto proximal end portion  2612 . Pacing electrodes  2432 A-B are incorporated onto distal end portion  2611  and electrically connected to pacemaker  2456  via conductors  2633 A-B. 
       FIG. 27  is an illustration of an embodiment of pacemaker  2456  integrated with a PTVI device  2710 . PTVI device  2710  is another embodiment of PTVI device  2410  and includes a proximal end portion  2712 , a distal end portion  2711  configured for intravascular placement and including a distal tip  2735 , and an elongate shaft  2713  coupled between proximal end portion  2712  and distal end portion  2711 . Pacemaker  2456  is incorporated onto shaft  2713 . A pacing electrode  2732 A is incorporated onto distal end portion  2711  and electrically connected to pacemaker  2456  via a conductor  2733 A. Another pacing electrode  2732 B is incorporated onto shaft  2713  and electrically connected to pacemaker  2456  via a conductor  2733 B. 
       FIG. 28  is an illustration of an embodiment of a pacemaker  2856  integrated into a PTVI device  2810 . PTVI device  2810  is another embodiment of PTVI device  2410  and includes a proximal end portion  2812 , a distal end portion  2811  configured for intravascular placement and including a distal tip  2835 , and an elongate shaft  2813  coupled between proximal end portion  2812  and distal end portion  2811 . Pacemaker  2856  includes a flexible pacemaker circuit including electronic circuit  2559 , solid state battery  2558 , and pacing electrodes  2832 A-B, all of which built on flexible circuit substrate  2557 . In other words, pacemaker  2856  includes pacemaker  2456  and pacing electrodes  2832 A-B built on a flexible circuit substrate, where pacing electrodes  2832 A-B are electrically connected to pacemaker  2456 . 
     PTVI devices  2410 ,  2610 ,  2710 , and  2810  are discussed above for illustrative purposes. In various embodiment, a pacemaker such as pacemaker  2456  or  2856  and two or more pacing electrodes are integrated into a PTVI device for delivering pacing pulses during a revascularization procedure. In various embodiments, the PTVI device with which the pacemaker is integrated includes any PTVI device discussed in this document. In one embodiment, such a PTVI device including built-in pacemaker and pacing electrodes are constructed as a disposable device for a single use. 
     Example: Angioplasty Catheter with Pacing Electrodes on Shaft 
       FIGS. 29-33  illustrate various examples of one or more pacing electrodes incorporated onto the shaft of an angioplasty catheter such as a balloon catheter. In its expanded state, such as when a balloon is inflated, the angioplasty device at the distal end portion of the angioplasty catheter functions as an anchor to stabilize the location of the pacing electrode(s) in a blood vessel. In one embodiment, the one or more pacing electrodes are displaceable along the shaft of the angioplasty catheter. This allows, for example, the pacing site(s) to be positioned upstream and away from the infarcted region, thereby lowering the energy required to capture the heart by delivering pacing pulses to normal tissue, which is known to be less conductive than infarct tissue. In another embodiment, the angioplasty catheter includes an outer shell made of conductive material, and at least a portion of the outer shell functions as a pacing electrode. 
       FIG. 29  is an illustration of an embodiment of an angioplasty catheter  2910 . Angioplasty catheter  2910  is a PTVI device that includes a proximal end portion  2912 , a distal end portion  2911  configured for intravascular placement and including an angioplasty device  2934  and a distal tip  2935 , and an elongate shaft  2913  coupled between proximal end portion  2912  and distal end portion  2911 . In the illustrated embodiment, a sleeve  2960  is placed over shaft  2913 . Pacing electrodes  2932 A-B are incorporated onto sleeve  2960  and electrically connected to connectors  2916 A-B at proximal end portion  2912  via conductors  2933 A-B. Sleeve  2960  includes a first lumen  2961  and a second lumen  2962 . Lumen  2961  is configured to accommodate a portion of shaft  2913  and allow sleeve  2960  with electrodes  2932 A-B to slide over shaft  2913 . Conductors  2933 A-B each have an adjustable length, displaceable along shaft  2913 , or otherwise flexible to allow the displacement of sleeve  2960  over shaft  2913 . Lumen  2962  is configured to receive a push wire  2963  for moving sleeve  2960  along shaft  2913 . 
     In one embodiment, angioplasty device  2934  includes a balloon. When inflated, balloon  2934  functions as an anchor to stabilize the locations of pacing electrodes  2932 A-B. For example, after expanding balloon  2934 , electrodes  2932 A-B are positioned by sliding sleeve  2960  along shaft  2913 . In various embodiments, angioplasty catheter  2910  includes one or more sleeves over shaft  2913 . Each sleeve includes one or more pacing electrodes. 
       FIG. 30  is an illustration of an embodiment of a sleeve  3060 , which is an embodiment of sleeve  2960  and is configured to be placed over shaft  2913 . Sleeve  3060  is a flexible C-shaped sleeve including a slit  3063 , a first lumen  3061 , a second lumen  3062 , and pacing electrodes  2932 A-B. Slit  3063  extends longitudinally along sleeve  3060  to allow sleeve  3060  to be pushed onto shaft  2913  and peeled away from shaft  2913 . Lumen  3061  is configured to accommodate a portion of shaft  2913  and allow sleeve  3060  to slide along a portion of shaft  2913 . Lumen  3062  is configured to receive a push wire allowing sleeve  3060  to be pushed to slide along shaft  2913 . 
       FIG. 31  is an illustration of an embodiment of an angioplasty catheter  3110 , which is another embodiment of angioplasty catheter  2910 . Angioplasty catheter  3110  is a PTVI device that includes a proximal end portion  3112 , a distal end portion  3111  configured for intravascular placement and including angioplasty device  2934  and a distal tip  3135 , and an elongate shaft  3113  coupled between proximal end portion  3112  and distal end portion  3111 . In the illustrated embodiment, pacing electrodes  3132 A-B, each configured as a stent, are placed over shaft  3113  and electrically connected to connectors  3116 A-B at proximal end portion  3112  via conductors  3133 A-B. In one embodiment, pacing electrodes  3132 A-B are each configured as a flexible stent. In one embodiment, conductors  3133 A-B each have an adjustable length, displaceable along shaft  3113 , or otherwise flexible to allow the displacement of pacing electrodes  3132 A-B over shaft  3113 . In various embodiments, angioplasty catheter  3110  includes one or more pacing electrodes configured as one or more stents over shaft  3113 . 
       FIG. 32  is an illustration of an embodiment of an angioplasty catheter  3210 . Angioplasty catheter  3210  is a PTVI device that includes a proximal end portion  3212 , a distal end portion  3211  configured for intravascular placement and including an angioplasty device  3234  and a distal tip  3235 , and an elongate shaft  3213  coupled between proximal end portion  3212  and distal end portion  3211 . In the illustrated embodiment, shaft  3213  includes an outer shell  3265  that includes a conductive portion functioning as a pacing electrode  3232 A. Pacing electrode  3232 A is electrically connected to a connector  3216 A at proximal end portion  3212 . In one embodiment, outer shell  3265  includes a flexible metal tube. In one embodiment, pacing electrode  3232 A includes approximately the entire outer shell  3265 , or a substantial portion of outer shell  3265 . In the illustrated embodiment, angioplasty catheter  3210  also includes an elongate conductive inner portion  3266  extending through approximately the enough length of angioplasty catheter  3310 . Inner portion  3266  includes an exposed conductive distal end functioning as another pacing electrode  3232 B. Pacing electrode  3232 B is electrically connected to a connector  3216 B at proximal end portion  3212 . In one embodiment, inner portion  3266  is a flexible metal wire. In another embodiment, inner portion  3266  is a flexible metal tube. In one embodiment, angioplasty device  3234  includes a balloon. Inner portion  3266  is a flexible metal tube with a lumen that allows for inflation and deflation of balloon  3234 . When inflated, balloon  3234  functions as an anchor to stabilize the location of pacing electrodes  3232 A-B. For example, after expanding balloon  3234 , electrodes  3232 A-B are positioned by sliding sleeve  3260  along shaft  3213 . 
       FIG. 33  is an illustration of an embodiment of an angioplasty catheter  3310 , which is another embodiment of angioplasty device  3210 . Angioplasty catheter  3310  is a PTVI device that includes a proximal end portion  3312 , a distal end portion  3311  configured for intravascular placement and including an angioplasty device  3234  and a distal tip  3335 , and an elongate shaft  3313  coupled between proximal end portion  3312  and distal end portion  3311 . Angioplasty catheter  3310  differs from angioplasty catheter  3210  in that shaft  3313  includes an outer shell  3365  that is coated with an insulation material to leave one or more exposed areas functioning as one or more pacing electrodes. In the illustrated embodiment, outer shell  3365  is coated with the insulation material to leave an exposed area functioning as a pacing electrode  3332 A, which is electrically connected to connector  3216 A at proximal end portion  3312 . 
     In various embodiments, angioplasty catheters  2910 ,  3110 ,  3210 , and  3310  each allow one or more pacing electrodes to be positioned by moving along and within a blood vessel after an expandable angioplasty device such as a balloon is expanded to function as an anchor. In one application, the one or more pacing electrodes are placed according to the pacing energy required, such as by locating the pacing site(s) associated with approximately minimum amplitude or width of the pacing pulses. In various embodiments, angioplasty catheters  2910 ,  3110 ,  3210 , and  3310  each allow for delivering combined ischemic cardioprotection therapy by inflating and deflating a balloon of the catheter and pacing cardioprotection therapy by delivering cardioprotective pacing via one or more of the pacing electrodes of the catheter. 
     Example: Pacing Catheter with Stent Electrode 
       FIGS. 34-37  illustrate various examples of pacing electrode constructed as a stent or incorporated onto a stent. The stent is connected to a PTVI catheter. After being used for delivering pacing pulses during a revascularization procedure, the stent is disconnected from the PTVI catheter to stay in the patient, or removed from the patient with the PTVI catheter. In various embodiments, the pacing pulses are delivered when the stent is in its expanded state in a blood vessel for a stable electrical contact between the pacing electrode and the vascular wall of the blood vessel. 
       FIG. 34  is an illustration of an embodiment of a pacing catheter  3410 . Pacing catheter  3410  is a PTVI device assembly including a stent catheter  3410 A, a sheath  3410 C, and a guide wire  3410 D. 
     Stent catheter  3410 A includes a catheter proximal end portion  3412 A, a catheter distal end portion  3411 A configured for intravascular placement and including a stent  3468 , an elongate catheter shaft  3413 A coupled between proximal end portion  3412 A and distal end portion  3411 A, and a catheter lumen  3430 A extending within shaft  3413 A between proximal end portion  3412 A and distal end portion  3411 A. Stent  3468  includes a pacing electrode  3432 A. A conductor  3433 A electrically connects pacing electrode  3432 A to a connector  3416 A at proximal end portion  3412 A. In the illustrated embodiment, another pacing electrode  3432 B is incorporated onto shaft  3413 A. Another conductor  3433 B electrically connects pacing electrode  3432 B to a connector  3416 B at proximal end portion  3412 A. 
     Sheath  3410 C includes a sheath proximal end portion  3412 C, a sheath distal end portion  3411 C configured for intravascular placement, an elongate sheath shaft  3413 C coupled between proximal end portion  3412 C and distal end portion  3411 C, and a sheath lumen  3430 C extending within shaft  3413 C between proximal end portion  3412 C and distal end portion  3411 C. Lumen  3430 C has a diameter accommodating a portion of stent catheter  3410 A, including shaft  3413 A and stent  3468  in its restrained state. Lumen  3430 C has a proximal opening  3443 C at distal end portion  3412 C and a distal opening  3442 C at distal end portion  3411 C. In one embodiment, sheath  3410 C is a guide catheter used in a revascularization procedure. In the illustrated embodiment, a pacing electrode  3432 C is incorporated onto distal end portion  3411 C. A conductor  3433 C electrically connects pacing electrode  3432 C to a connector  3416 C at proximal end portion  3412 C. 
     Guide wire  3410 D includes a guide wire proximal end portion  3412 D, a guide wire distal end portion  3411 D including a guide wire distal tip  3435 D, and an elongate guide wire shaft  3413 D coupled between proximal end portion  3412 D and distal end portion  3411 D. In the illustrated embodiment, a pacing electrode  3432 D is incorporated onto distal tip  3435 D. A conductor  3433 D electrically connects pacing electrode  3432 D to a connector  3416 D at proximal end portion  3412 D. 
     In one embodiment, stent catheter  3410 A is a stent delivery catheter, and stent  3468  is detachably connected to shaft  3413 A to be permanently implanted in a blood vessel after the pacing pulses are delivered during the revascularization procedure. In another embodiment, stent catheter  3410 A is dedicated for pacing during the revascularization procedure, and stent  3468  is non-detachably connected to shaft  3413 A to be removed from the blood vessel after the pacing therapy is completed. 
     In one embodiment, stent  3468  includes metal mesh functioning as pacing electrode  3432 A. In another embodiment, pacing electrode  3432 A is an electrode attached onto the mesh of stent  3468 . 
     In various embodiments, stent  3468  is expandable and contractible by pushing and pulling sheath  3410 C and/or stent catheter  3410 A. Stent  3468  exits from lumen  3430 C through distal opening  3442 C by pulling sheath  3410 C toward the proximal direction (away from the patient) and/or pushing stent catheter  3410 A toward the distal direction (toward the patient). In one embodiment, stent  3468  is self-expandable upon exiting from sheath  3410 C through distal opening  3442 C. Stent  3468  is also retractable into lumen  3430 C through distal opening  3442 C by pushing sheath  3410 C toward the distal direction (toward the patient) and/or pulling stent catheter  3410 A toward the proximal direction (away from the patient). 
     In various embodiments, pacing catheter  3410  includes pacing electrode  3432 A and one or more of pacing electrodes  3432 B-D. In one embodiment, as illustrated in  FIGS. 35 and 36  below, stent  3468  includes two pacing electrodes, and pacing electrodes  3432 B-D are optional. 
       FIG. 35  is an illustration of an embodiment of a distal end portion  3511 A of a stent catheter  3510 A, which is another embodiment of stent catheter  3410 A. Distal end portion  3511 A includes a stent  3568 . Pacing electrodes  3532 A-B are each affixed onto the mesh of stent  3568  and connected to one of conductors  3533 A-B extending through a catheter shaft  3513 A. 
       FIG. 36  is illustration of an embodiment of a distal end portion  3611 A of a stent catheter  3610 A, which is another embodiment of stent catheter  3410 A. Distal end portion  3611 A includes a stent  3668 . Pacing electrodes  3632 A-B each include a portion of the mesh of stent  3668  and connected to one of conductors  3633 A-B extending through a catheter shaft  3613 A. The two mesh portions forming pacing electrodes  3632 A-B are electrically insulated from each other. 
       FIG. 37  is an illustration of an embodiment of a distal end portion  3711 A of a stent catheter  3710 A, which is another embodiment of stent catheter  3410 A. Distal end portion  3711 A includes a stent  3768  detachably connected to a catheter shaft  3713 A through a connector  3769 . Stent  3768  is capable of functioning as a pacing electrode  3732 A when being connected to shaft  3713 A through connector  3769 , which also provides electrical connection between pacing electrode  3732 A and a conductor  3733 A extending through shaft  3713 A. Connector  3769  is dissolvable by electrolysis when exposed to the blood. In one embodiment, connector  3769  is dissolved by applying an electrical current through it while being exposed to the blood. This allows stent  3768  to be disconnected from shaft  3713 A and stay in the blood vessel after the pacing pulses are delivered during the revascularization procedure. 
     It is to be understood that the above detailed description, including the various examples of PTVI devices and external pacemakers, is intended to be illustrative, and not restrictive. In general, cardioprotective pacing is applied to prevent or reduce cardiac injury associated with ischemia by using one or more pacing electrodes incorporated onto any intravascular device and a pacemaker that is capable of delivering pacing pulses by executing a cardioprotective pacing protocol. Other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.