Apparatus for artificial cardiac stimulation and method of using same

Abstract

A system for artificial stimulation of the heart of a subject is provided, the system comprising a controller comprising a receiver for receiving signal data, a processor for processing received signal data, and a transmitter for transmitting signal data; a sensing stent for location in the proximal coronary sinus of the subject, the sensing stent electrode comprising a sensing electrode assembly for sensing atrial and/or ventricular signals from the heart of the subject and a transmitting assembly for transmitting signal data to the receiver of the controller; and a stimulation stent for location in a vein of the subject distal of the sensing stent, the stimulation stent comprising a receiver for receiving signal data from the transmitter of the controller and an electrode assembly for providing a stimulating electrical signal to the heart of the subject in response to the data received.

Claims

1. A method for providing stimulation to a heart of a subject, the heart comprising a coronary sinus having a proximal region with an ostium, a left atrium, a left ventricle, an oblique vein and a middle cardiac vein, the method comprising: sensing electrical activity of the heart at the ostium of the proximal region of the coronary sinus using a single sensing stent, the single sensing stent implanted in the coronary sinus, the sensing stent operable for sensing purposes only; transmitting first signal data from the ostium of the coronary sinus to a controller; generating second signal data for providing electrical stimulation to target tissue of the heart in response to the signal data received from the ostium of the coronary sinus transmitting the second signal data to a stimulation stent for stimulation of the target tissue, wherein the stimulation stent is located in a vein of the heart distal of the ostium of the coronary sinus; and providing electrical stimulation to the target tissue of the heart in response to the second signal data, wherein the electrical stimulation is provided to the tissue of the heart distal of the ostium of the coronary; wherein signal data are transmitted from the sensing stent to the controller and from the controller to the stimulation stent remotely without using leads.

2. The method according to claim 1, wherein pacing of the heart is provided at a single site.

3. The method according to claim 1, wherein the second signal data are transmitted to a plurality of stimulation stents.

4. The method according to claim 1, wherein electrical stimulation is provided to the left atrium of the heart.

5. The method according to claim 1, wherein electrical stimulation is provided to a mid to distal location of the coronary sinus.

6. The method according to claim 1, wherein electrical stimulation is provided to the left ventricle of the heart at a plurality of sites.

7. A method for the biventricular pacing of a heart of a subject, the heart comprising a coronary sinus having a proximal region with an ostium, a left ventricle and a right ventricle, the method comprising: sensing electrical activity of the heart at the ostium of the proximal region of the coronary sinus using a single sensing stent, the single sensing stent implanted in the coronary sinus, the sensing stent operable for sensing purposes only; transmitting first signal data from the ostium of the coronary sinus to a controller; generating second signal data for providing electrical stimulation to target tissue of the heart in response to the signal data received from the ostium of the coronary sinus; transmitting the second signal data to a plurality of stimulation stents disposed in a vein of the heart distal of the ostium of the coronary sinus for multisite stimulation of the left ventricle and stimulation stent disposed in a vein of the heart distal of the ostium of the coronary sinus for stimulation of the right ventricle; and providing electrical stimulation to both the left and right ventricles in response to the second signal data, wherein the electrical stimulation is provided to the tissue of the heart distal of the ostium of the coronary sinus; wherein signal data are transmitted from the sensing stent to the controller and from the controller to the stimulation stems remotely without using leads.

Description

(1) Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying drawings, in which:

(2) FIG. 1a is a first perspective view of the exterior of a heart showing the general arrangement of veins;

(3) FIG. 1 b is a second perspective view of the exterior of a heart showing the general arrangement of veins;

(4) FIG. 2 is a diagrammatical representation of the major veins of the heart and showing the placement of stents according to one embodiment of the present invention;

(5) FIG. 3a is a side elevational view of a stimulation stent according to one embodiment of the present invention;

(6) FIG. 3b is a perspective view of the electrode housing of the stent of FIG. 3a;

(7) FIG. 4 is a side elevational view of a stimulation stent according to a second embodiment of the present invention;

(8) FIG. 5 is a side elevational view of a stimulation stent according to a third embodiment of the present invention;

(9) FIG. 6a is a side elevational view of a stimulation stent according to a fourth embodiment of the present invention in a condition to be installed in a larger vein;

(10) FIG. 6b is a side elevational view of the stent of FIG. 6a in a condition when installed in a vein;

(11) FIG. 7a is an elevational view from one end of a stimulation stent according to a fifth embodiment of the present invention in a condition ready to be deployed;

(12) FIG. 7b is an elevational view from one end of the stimulation stent of FIG. 7a in a deployed condition;

(13) FIG. 7c is an elevational view from one end of an alternative arrangement of the stimulation stent of FIG. 7a in a condition ready to be deployed;

(14) FIG. 7d is an elevational view from one end of the stimulation stent of FIG. 7c in a deployed condition;

(15) FIG. 8 is a side view of a stimulation stent according to a sixth embodiment of the present invention and intended for implanting in narrow or constricted veins;

(16) FIG. 9 is a perspective view of a first embodiment of a sensing stent for use in the system and method of the present invention; and

(17) FIG. 10 is a perspective view of a second embodiment of a sensing stent for use in the system and method of the present invention.

(18) Referring to FIGS. 1a and 1b, there is shown in each figure a perspective view of the exterior of a human heart, generally indicated as 2. Indicated on the heart 2 and labelled are the major veins of the heart, in particular the coronary sinus and the tributary veins extending therefrom to the left and right ventricles. The arrangement of the veins is shown in more detail in FIG. 2. In particular, FIGS. 1 and 2 show the coronary sinus and the arrangement of various tributary veins thereof, including the small cardiac vein, the middle cardiac vein, the oblique vein, the posterior cardiac vein and the great cardiac vein.

(19) FIGS. 1 and 2 further show the placement of a system for providing artificial stimulation to tissue of the heart according to one embodiment of the present invention.

(20) The system comprises a sensing stent 4 positioned in a proximal position in the coronary sinus, in particular in the region of the origin of the coronary sinus between the oblique vein and the middle cardiac vein. The sensing stent 4 is a leadless stent implanted in the coronary sinus. The sensing stent 4 functions to sense both atrial and ventricular signals from the electrical activity of the heart and transmit radio frequency data signals 6 to a controller 8 shown in FIG. 2.

(21) The controller 8 has a processor programmed with appropriate software for processing radio frequency signals. Such processing techniques are known in the art and used in existing pacemaker systems. In order to overcome potential issues arising from distance adversely affecting induction coupling transmission, the controller 8 can be placed in a lower chest position in closer proximity to the heart 2. By having no leads attached, the implantation procedure for the controller is simplified, as there is no need to tunnel any hardware subcutaneously, therefore making the implant procedure straightforward.

(22) The controller 8 is programmed and data regarding the performance of the system and the subject exported by means of remote radio frequency communication with a programmer 22.

(23) The system further comprises a plurality of stimulation stents disposed distally of the sensing stent 4 and arranged within veins of the heart as follows:

(24) A first stimulation stent 10 is disposed at the junction between the coronary sinus and the great cardiac vein and is operable to provide stimulation and pacing to the left atrium. In use, the first stimulation stent 10 provides unisite pacing to the left atrium.

(25) A second stimulation stent 12 is disposed within a ventricular branch of the small cardiac vein or in the middle cardiac vein (as illustrated by stent 18) and is operable to provide stimulation and pacing to the right ventricle. In use, the second stimulation stent 12 or 18 provides unisite pacing to the right ventricle.

(26) The system comprises one to three further stimulation stents to provide multisite pacing of the left ventricle, as follows. As shown in FIG. 2, a third stimulation stent 14 is disposed within the lateral cardiac vein; a fourth stimulation stent 16 is disposed within the posterio-lateral cardiac vein; and a fifth stimulation stent 18 is provided within the middle cardiac vein. The stimulation stent 18, in view of its location, is capable of providing stimulation to either the left or right ventricles.

(27) The precise location of the stents within the subject is determined by a range of factors. For example, positioning of a stent will depend upon the size of the target blood vessel. The size of blood vessels will vary from subject to subject, depending upon their age, size and condition. Further, in general, there can be significant differences in the physiology of subjects, for example in the number and size of veins around the heart. These differences lead to differences in the final placement of the stents of the system. Further factors affecting the positioning of the stents include the quality of the electrical signals received from the heart and/or provided to the heart.

(28) Preferably, the stimulation stents are positioned with a sufficient distance between adjacent stents to ensure that different regions of the heart are being stimulated, rather than multiple stimulation of a single site.

(29) Further, it is an advantage of the system of the present invention that the stimulating stents may be located at proximal to mid-vessel positions, compared with stimulating stents of known systems. This in turn allows the stimulating stents to provide stimulation at optimal sites and avoid stimulation of the phrenic nerve.

(30) The sensing stent is implanted in the coronary sinus using known techniques applied to angioplasty or coronary artery stents, in particular using an angioplasty wire and an angioplasty balloon of appropriate size to expand the stents at the desired location. Apparatus and techniques for the insertion of stents in this manner are known in the art. The coronary sinus is conventionally accessed through the right atrium which is most commonly approached through the left venous system at left subclavian vein level. However, the stents could also be delivered via the right femoral vein approach using delivery systems similar to the ones currently used in electrophysiological studies and known in the art. The stimulation stents are implanted in like manner at the location in their respective veins. When implanting the stents of the system, the distally disposed stents are implanted first, with the proximal stents being implanted thereafter, in particular the sensing stent being implanted last.

(31) In particular, the stimulation stents are each delivered via the coronary sinus using a known coronary sinus sheath and a standard 0.014 guide wire. For placement of the stent 12 for stimulation of the right ventricle, the pacing site is accessed via either the small cardiac vein between the right atrium and the right ventricle (as shown in the Figures) or a suitable branch of the middle cardiac vein between the right ventricle and the left ventricle. The decision regarding the best position for the stimulation stent 12 is determined by the implanter and is based on determining the size and anatomy of the aforementioned veins. In subjects with significant conduction deficit, the stent 12 should be implanted first. Alternatively, a temporary right ventricular apical lead can be implanted for the duration of the procedure and be removed after the electrical parameters of all stents have been checked and found to be satisfactory.

(32) The stimulation stent 10 in the distal portion of the coronary sinus for pacing the left atrium is positioned after the stimulation stents 14, 16, 18 have been placed in the target veins of the left ventricle, but preferably before the stimulation stent 12 in the small cardiac vein and the sensing stent 4 in the coronary sinus are positioned as this regime is easier to achieve.

(33) Once the sensing stents have been deployed and all the sensing and pacing parameters checked, the delivery system is withdrawn from the coronary sinus. As the system is leadless, the implanting of the stents occurs without the current concerns that one or more leads may be inadvertently displaced during the removal of the delivery system.

(34) Each stimulation stent 10-18 comprises one or more pairs of electrodes acting as electrical poles for the provision of electrical stimulation to the surrounding tissue. Pacing impedance and threshold are checked remotely and in turn for every pair of pacing poles present on each stimulation stent during the implant procedure. The position of each stent can be adjusted in the vein to achieve best pacing parameters and avoid inadvertent diaphragmatic pacing before being deployed under pressure in its final position. When more than one stimulation stent is used in order to achieve multisite pacing of the left ventricle, as is the case with the embodiment shown in FIGS. 1 and 2, the stimulation stents 14, 16, 18 are programmed to respond simultaneously to the coordinated pulses generated by the controller following atrial sensing provided by the sensing stent. The pacing stimuli for the left ventricle are generated at the same time as the pacing stimulation for the right ventricle, for optimal re-synchronization of the heart function. However, a small delay between the right ventricle and left ventricle pacing may be programmed if necessary, similar to existing pacemaker programming options.

(35) For subjects in atrial fibrillation, where atrial sensing and pacing are not necessary, the stimulation stents 12-18 for the left ventricle and right ventricle would simply be programmed to pace at a rate responsive rate generated by the pacemaker. During atrial fibrillation, atrial impulses are rapid, typically ranging from 250 to 400 beats per minute. The atrioventricular node limits the number of beats reaching the ventricles. However, this process is variable and can be irregular, giving rise to an erratic heart beat. In general, a slower rate transmitted to the ventricles is better, as it enhances the percentage of cardiac resynchronisation. At higher rates, pacemaking systems are generally inhibited and do not function properly to pace the heart. As a result, the CRT function can be lost. The rate at which pulses are transmitted by the atrioventricular node can be regulated, for example by medication or by techniques such as radio frequency ablation. This can ensure that no pulses are transmitted to the ventricles by the atrioventricular node, in turn allowing the system to provide complete CRT to the heart.

(36) In order to optimize the percentage of cardiac resynchronisation therapy to be applied, a standard atrioventricular node radiofrequency ablation may be necessary, as it would be with the known lead-based systems.

(37) In operation of the system, the controller interprets the received data signals 6 and generates a set of radio frequency stimulation data signals 20, which are transmitted to each stimulation stent 10-18. Each stimulation stent responds to the received signals and provides electrical stimulation to the adjacent tissue of the heart through one or more electrodes.

(38) The system is shown in FIGS. 1 and 2 for providing cardiac resynchronisation therapy (CRT) to the heart, in particular with stimulation and pacing of the right atrium and biventricular pacing of both the left and right ventricles, including multisite pacing of the left ventricle.

(39) Turning to FIGS. 3a and 3b, there is shown a first embodiment of a stimulation stent, generally indicated as 102. The stent 102 is shown mounted on an angioplasty balloon 104 on a guide wire 106, in known manner, as it would be when being advanced in the target vein.

(40) The stent 102 comprises a generally cylindrical, expandable stent body 110 of known configuration, shown extending around the balloon 104. When being implanted, the stent body 110 is contracted and the balloon 104 deflated. To install the stent 102 at the target location, the balloon 104 is inflated in known manner, in turn expanding the stent body 110 radially outwards and securing the stent within the blood vessel. The balloon 104 and the guidewire 106 are then deflated and removed, again in known manner.

(41) An electrode housing 112 is mounted to one side of the stent body 110 and extends along and radially outwards from the stent body. The electrode housing is generally wedge-shaped in cross-section, as shown more clearly in FIG. 3b, with the narrower portion of the housing adjacent the stent body 110. The housing 112 holds two pairs of electrodes 114, 116. When installed, the expansion of the stent body 110 urges the electrodes 114, 116 radially outwards and into contact with the inner wall of the vein, in turn allowing electrical stimulation to be provided to the surrounding heart tissue 120. The pairs of electrodes allow for different configurations of stimulation to be applied, as necessary. For example, if phrenic nerve stimulation and twitching is encountered with one pattern of stimulation via one configuration of electrodes, a different combination may be used.

(42) The housing 110 contains further components for the operation of the stimulation stent, including an antenna (not shown for clarity) for receiving radio frequency signals from the controller 8, an electrical circuit 122, and requisite capacitors 124. The stent 102 is arranged to be powered by induction coupling, as is known in the art and, as a result, does not have a local power source, such as a battery.

(43) Turning to FIG. 4, there is shown a second embodiment of a stimulation stent, generally indicated as 202. The stent 202 is shown mounted on an angioplasty balloon 204 on a guide wire 206, in known manner, as it would be when being installed in the target vein.

(44) The stent 202 comprises a generally cylindrical, expandable stent body 210 of known configuration, shown extending around the balloon 204. Installation of the stent is as described above with respect to the embodiment of FIG. 3.

(45) An electrode housing 212 is mounted to one side of the stent body 210 and extends along and radially outwards from one side of the stent body. The housing 212 holds a pair of electrodes 214. When installed, the expansion of the stent body 210 urges the electrodes 214 radially outwards and into contact with the inner wall of the vein, in turn allowing electrical stimulation to be provided to the surrounding heart tissue.

(46) A second housing 218 is disposed on the opposite side of the stent body to the electrode housing 212 and contains further components for the operation of the stimulation stent, including an antenna (not shown for clarity) for receiving radio frequency signals from the controller 8, circuitry 220, and requisite capacitors 222. The stent 202 is arranged to be powered by induction coupling, as is known in the art and, as a result, does not have a local power source, such as a battery. Alternatively, the stent 202 may be provided with a battery located within the housing 212, for example for use with a radio frequency communication system.

(47) Turning to FIG. 5, there is shown a third embodiment of a stimulation stent, generally indicated as 302. The stent 302 is shown mounted on an angioplasty balloon 304 on a guide wire 306, in known manner, as it would be when being installed in the target vein.

(48) The stent 302 comprises a generally cylindrical, expandable stent body 310 of known configuration, shown extending around the balloon 304. Installation of the stent is as described above with respect to the embodiment of FIG. 3.

(49) A generally arcuate electrode housing 312 is mounted to one side of the stent body 310 and extends along and radially outwards from one side of the stent body. The housing 312 holds two pairs of electrodes 314, 316. When installed, the expansion of the stent body 310 urges the electrodes 314, 316 radially outwards and into contact with the inner wall of the vein, in turn allowing electrical stimulation to be provided to the surrounding heart tissue. As described above, the pairs of electrodes may be used in different configurations to optimise the stimulation provided to the tissue.

(50) The housing 312 contains further components for the operation of the stimulation stent, including an antenna (not shown for clarity) for receiving radio frequency signals from the controller 8, an electrical circuit 322, and requisite capacitors 324. The stent 302 is arranged to be powered by induction coupling, as is known in the art and, as a result, does not have a local power source, such as a battery. Alternatively, the stent 302 may be provided with a battery located within the housing 312, for example for use with a radio frequency communication system.

(51) Turning to FIGS. 6a and 6b, there is shown a fourth embodiment of a stimulation stent, generally indicated as 402. The stent 402 is shown in FIG. 6a mounted on an angioplasty balloon 404 on a guide wire 406, in known manner, as it would be when being installed in the target vein.

(52) The stent 402 comprises an expandable stent body 410 having a generally rounded triangular cross-section, shown extending at one around the balloon 404. Installation of the stent is as described above with respect to the embodiment of FIG. 3.

(53) An electrode housing 412 is mounted within the stent body 410 and extends along and radially outwards from one side of the stent body. The housing 412 holds two pairs of electrodes 414, 416. When installed, the expansion of the stent body 410 urges the electrodes 414, 416 radially outwards and into contact with the inner wall of the vein, in turn allowing electrical stimulation to be provided to the surrounding heart tissue.

(54) The housing 412 contains further components for the operation of the stimulation stent, including an antenna (not shown for clarity) for receiving radio frequency signals from the controller 8, an electrical circuit 422, and requisite capacitors 424. The stent 402 is arranged to be powered by induction coupling, as is known in the art and, as a result, does not have a local power source, such as a battery.

(55) Turning to FIGS. 7a and 7b, there is shown a fifth embodiment of a stimulation stent, generally indicated as 502. The stent 502 is shown mounted on an angioplasty balloon 504 on a guide wire 506, in known manner, as it would be when being installed in the target vein.

(56) The stent 502 comprises a generally cylindrical, expandable stent housing 510, shown extending around the balloon 504, on the angioplasty guide wire 506. The stent housing 510 comprises three circumferentially spaced electrode housings 512a, 512b, 512c, evenly spaced at a 120 degree orientation. Disposed between adjacent electrode housings is a flexible casing member 518, with two longitudinal ridges on each side. The electrode housings are attached loosely by a stented mesh to the flexible casing members 518 disposed therebetween. Each electrode housing 512 has a generally wedge-shaped cross-section, with two longitudinal ridges on each side to permit deployment of the electrode housings 512a, 512b and 512c against the flexible casing members 518 in a cam-like action by the action of the expanding balloon 504. The electrode housing 512a holds two pairs of electrodes 514, 516. When installed, the expansion of the balloon 504 using a cam mechanism urges the longitudinal ridges on the wedge-shaped electrode housings 512 radially outwards past the corresponding supporting longitudinal ridges on the flexible casing members 518. Consequently the electrodes 514, 516 in the housing 512a, 512b and 512c are urged into contact with the inner wall of the vein, in turn allowing electrical stimulation to be provided to the surrounding heart tissue. This embodiment allows two final deployment positions of the electrode housings 512, that is first position having a lesser diameter and a second position having a larger diameter, the diameter determined by the relative resting positions of the corresponding ridges on the electrode housings 512 and the flexible casing member 518. The selection of the position of the electrode housings 512 is dictated by the diameter of the target vein.

(57) The electrode housings 512b and 512c contain further components for the operation of the stimulation stent, including an antenna (not shown for clarity) for receiving radio frequency signals from the controller 8, an electrical circuit 522, and requisite capacitors 524. The stent 502 is arranged to be powered by induction coupling, as is known in the art and, as a result, does not have a local power source, such as a battery. The stent of this embodiment is particularly suitable for positioning in larger diameter blood vessels.

(58) As an alternative to providing power to each of the stimulation stents by induction, alternative means may be employed, such as acoustic coupling. Alternatively, or in addition, each stimulation stent may be provided with a local power storage device, in particular a battery. In particular, an alternative arrangement of the embodiment of FIGS. 7a and 7b provides for battery fittings within either of the electrode housings 512, in particular if radiofrequency communication is to be used. For example, the battery may occupy the entire inner space of the housing 512b and the circuitry may be accommodated in the housing component 512c. Alternative arrangements of the components may also be employed.

(59) Referring to FIGS. 7c and 7c, there is shown an alternative arrangement of the stent of FIGS. 7a and 7b. The stent 502 of FIGS. 7c and 7d is similar in design to the stent 502 of FIGS. 7a and 7b, but has only one electrode housing 512. The electrode housing is attached loosely by a stented mesh to the flexible casing member 518. The deployment mechanism of the electrode housing 502 is similar to that of the stent 502 of FIGS. 7a and 7b, which is described above.

(60) The electrode housing 512 contains further components for the operation of the stimulation stent, including an antenna (not shown for clarity) for receiving radio frequency signals from the controller 8, an electrical circuit 522, and requisite capacitors 524

(61) An alternative arrangement of the stent 502 of FIGS. 7c and 7d provides for battery fittings within the electrode housing 512, in particular if radiofrequency communication is to be used. Alternative arrangements of the components may also be employed.

(62) Referring to FIG. 8, there is shown a further embodiment of a stimulation stent for use in the system of the present invention. The stimulation stent, generally indicated as 602, comprises a generally cylindrical, expandable body 604 of known configuration. When being installed, an angioplasty balloon and guide wire (not shown in FIG. 8 for clarity) are used in known manner and as described above. In particular, the stent body 604 is applied around the balloon and, when at the desired location in the vein, the balloon is inflated and the stent body expanded radially outwards, to thereby secure the body within the vein.

(63) The stent 602 further comprises a generally cylindrical housing 606 mounted loosely to one end of the stent body 604 and extending longitudinally therefrom. The stent is installed with the housing 606 extending in a distal direction from the stent body 602. The housing 606 retains components, such as, for example circuitry, an antenna, capacitors and optionally a battery to act as a local power source.

(64) A lead 608 extends from the end of the housing 606 in a distal direction within the vein, when installed, and terminates in an electrode assembly 610 comprising two pairs of electrodes 614, 616.

(65) In use, the stent body 604 is installed in a portion of the target vein proximal of the target pacing site. Being proximal, this portion of the vein is generally larger in diameter and more accessible than the more remote pacing site. Once in situ, the lead 608 and electrode assembly 610 extend distally of the stent body 604 and the housing 606 into the narrower, distal portion of the vein, with the electrode assembly being located at the target site of the electrical stimulation.

(66) Turning now to FIG. 9, there is shown a first embodiment of a sensing stent for implanting in the coronary sinus of the subject. The sensing stent, generally indicated as 702, is shown mounted on an angioplasty balloon 704 attached to a guide wire 706, in known manner, as it would be when being installed at the target location in the coronary sinus.

(67) The sensing stent 702 comprises a generally cylindrical, expandable stent body 710 of known configuration, shown extending around the balloon 704, on an angioplasty wire 706. When being implanted, the stent body 710 is contracted and the balloon 704 deflated. To install the stent 702 at the target location, the balloon 704 is inflated in known manner, in turn expanding the stent body 710 radially outwards and securing the stent within the blood vessel. The balloon 704 is then deflated and removed, again in known manner.

(68) An electrode housing 712 is mounted to one side of the stent body 710 and extends along and radially outwards from one side of the stent body. The housing 712 holds a pair of sensing electrodes 714. When installed, the expansion of the stent body 710 urges the sensing electrodes 714 radially outwards and into contact with the inner wall of the coronary sinus, in turn allowing electrical signals from the atrial and ventricular activity of the heart to be sensed.

(69) A second housing 718 is disposed on the opposite side of the stent body to the electrode housing 712 and contains an antenna and transmitter assembly 720 for transmitting radio frequency signals to the controller 8, and a battery 722.

(70) Finally, referring to FIG. 10, there is shown a second embodiment of a sensing stent for implanting in the coronary sinus of the subject. The sensing stent, generally indicated as 802, is shown mounted on an angioplasty balloon 804 on an angioplasty guide wire 806, in known manner, as it would be when being installed at the target location in the coronary sinus.

(71) The sensing stent 802 comprises a generally cylindrical, expandable stent body 810 of known configuration, shown extending around the balloon 804. The sensing stent 802 is installed in the coronary sinus of the subject in the manner described above in relation to FIG. 9.

(72) A housing 812, having a generally arcuate cross-section, is mounted to one side of the stent body 810 and extends along and radially outwards from the one side of the stent body. The housing 812 holds a pair of sensing electrodes 814. When installed, the expansion of the stent body 810 urges the sensing electrodes 814 radially outwards and into contact with the inner wall of the coronary sinus, in turn allowing electrical signals from the atrial and ventricular activity of the heart to be sensed.

(73) The housing 812 further contains an antenna and transmitter assembly 820 for transmitting radio frequency signals to the controller 8, and a battery 822.