CA2098716A1

CA2098716A1 - Apparatus for controlling heart rate

Info

Publication number: CA2098716A1
Application number: CA002098716A
Authority: CA
Inventors: Rahul Mehra
Original assignee: Individual
Current assignee: Medtronic Inc
Priority date: 1991-01-07
Filing date: 1991-11-13
Publication date: 1992-07-08
Also published as: EP0566588A1; AU9090191A; AU647564B2; US5129394A; WO1992011900A1; EP0566588A4

Abstract

A method and apparatus for sensing in vivo blood pressure proportional to the left ventricular pressure for detecting ventricular tachyarrhythmias or the cardiovascular status in congestive heart failure, and/or for adjusting the rate of a pacemaker. A lead (76) with a pressure sensor (118) near its distal end is placed transvenously through the coronary sinus and located in the coronary vein. When in place, a bulge or an inflatable balloon proximal to the pressure sensor may be used to acutely occlude the coronary vein (80) until the sensor fibroses in. The balloon may be reinflated prior to pressure measurements. The pressure that is sensed in that location is proportional to the left ventricular pressure. Values representing the left ventricular pulse, systolic and diastolic pressures, as well as the differentiated rate of change (i.e., dP/dt), gross rate of change (.delta.P/.delta.t) and mean or average of such pressure values are all or selectively developed by sofware algorithms and implemented in microprocessor based control circuitry.

Description

W092/~900 2~ PCT/~91/0~481 , .

METHOD AND APPA~ATUS FOR CONTROLLIN6 HEART RATE
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a method and apparatus for deriving pressure signals relative to the blood pressure within the left ventricle of a patient's heart and employing those signals to control pacing rate of a pacemaker in response to the physiologic needs of the cardiovascular lO system and/or to confirm the existence of a pathologic tachyarrhythmia and trigger the delivery of an appropriate therapy, such as anti-tachyarrhythmia pacing, cardioversion or de~ibrillation.

2. Descri~tion of the Prior Art Advances in the treatments of bradyarrhythmias (slo~
heart beat) and tachyarrhythmias (fast heart beat) with implanted devices capable of detecting each condition and providing the appropriate therapy resulted in numerous advances in the art since simple fixed rate pacemaker were 20 first implanted about thirty years ago. The control of the heart's rhythm by monitoring both electrical and mechanical heart function has been a goal of researchers in the field over that same period of time. For example, the 1961 pamphlet by Dr. Fred Zacouto, Paris, France, "Traitement 2~ D'~rgence des Differents Types de Syncopes Cardia~ues du Syndrome de Morgangni-Adams-Stokes", (National Library of Medicine), describes an automatic pacemaker and defibrillator responsive to the presence or absence of the patient's blood pressure in conjunction with the rate OL the 30 patient's electrocardiogram. ~ery generally, a simple algorithm employing the patient's heart rate as evidenced by the electrical R-waves and the patient's blood pressure pulse ~as employed to: (1) operate a pacemake~ pulse generator at a fixed rate in the presence of both signals .

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:. . . : : , .: ~, WO92/11900 PCT/USg1/0848 2~71f~ 2 recurring at less than a minimum rate or escape interval;
(2) trigger the delivery of a defibrillation shock to the heart in the presence of a heart rate exceeding a tachyarrhythmia detect upper rate threshold in conjunction 5 with the absence of a blood pressu-e signal over a variable period ~such as thirty seconds); and, (3) inhibit both the pacemaker and defihrillator in the presence of both ~-waves and blood pressure pulses recurring at a frequency exceeding the lower rate threshold but falling below the lO tachyarrhythmia detect threshold. It was long recognized earlier in medicine that the patient's blood pressure and electrocardiogram constituted the two most familiar and direct diagnostic tools for assessing the condition of the patient's cardiovascular system.
In this regard, it was also recognized early in the history of cardiac pacing that the patient dependent upon fixed rate pacing stimulation suffered cardiovascular insufficiency as his heart was able to increase its output (cardiac output) by only a limited amount in response to 20 physiologic need. In normal hearts, the cardiovascular system responds to physiologic need by increasing both the heartbeat rate and its volume and systolic pressure (thereby increasin~ stroke volume and cardiac output) in response to physiologic need and as the heartbeat rate is limited in the 25 pacing dependent patient to the fixed pacer rate, the heart's blood pressure and volume could increase proportional to physiologic need only to a limited extent.
Thus, it was suggested by Juhasz in his 1965 article "Development of Implanted Cardiac Pacemakers", Diqest of 6th 30 Int'l Conf. on Medical Electrics and Bioloqical Engineerinq, 1965, Tokyo, pp. 85-86, that blood pressure, among other parameters of the cardiovascular system, could be used as a forward transfer control value to vary pacing rates as a function of the bloGd pressure value, thus releasing the 35 heart from the constraint imposed by the fixed ~ase or lower ... . .... i ~

~WO92~11900 2 n 9 ~ 71 ;S PCT/~S91/08481 pacing xate and allowing it to beat up to the pulse generator~s upper pacing rate limit.
These early researchers were followed by numerous examples of the use of pressure signals of one form or 5 another to control pacing rate or verify the presence of a tachyarrhythmia and trigger the delivery of appropriate therapies. For example, it has been proposed to sense pressure in the right atrium and to utilize a signal derived therefrom to affect and control ri~ht ventricular pacing as lO disclosed in Cohen U.S. Patent No. 3,358,690. In addition, tne Zacouto U.S. Patent No. 3,857,399 (Figure l9) discloses a pressure sensor on an extension of a pacing lead adapted to be forced into or through the ventricular septum to measure the intramyocardial pressure within the septum, 15 and/or the actual left ventricular pressure. The signal derived from one or both of these sensors represents an average or mean pressure that varies over relatively long periods of time in a manner similar to that d~scribed in the Kresh PCT Publication No. W087/0l947. More recently, the 20 publication o~ Todd J. Cohen, entitled "A Theoretical Right Atrial Pressure Feedback Heart Rate Control System to Restore Physiologic Control to a Rate Limited Heart", PACE, Vol. 7, pp. 671~677, July-August, 1984, discloses a system for comparing the mean right atrial pressure signal with a 25 baseline signal and developing an error signal which, after processing, is used to control the pacing rate.
In addition, the microprocessor based implantable pacemaker and ventricular pressure sensing lead disclosed in Koning et al, U.S. Patent No. 4,566,456, relates right 30 ventricular systolic prPssure, the gross rate of change over time of the pressure (~P/~t) and/or the time derivative (dP/dt) of the systolic pressure with the rate needed to produce the desired cardiac output. Koning, in one algorithm, de~e_ts the right ventricular systolic pressure 35 peak valves, averages N peak values and compares the current - . -~ : .

WO92/11900 2 0 g 8 7 1 ~ 4 PCT/VS91/0~ ~

average to the preceding stored average value to detect the change in average pressure over time (~P/~t). That signal is employed to "look up" a ~R or pacing rate change used to modify the pacing rate R.
More recently, Cohen U.S. Patent No. 4,899,751 discloses a pacing system relying on a pressure signal from a pressure sensor located in the cardiovascular system, including the four chambers of the heart, coupled with signal processing circuitry for developing short term and lO long term mean (or average) pressure related control signalstherefrom. The escape interval or rate o~ the pacemaker is controlled as a function of the difference between the short term and long term mean pressure values. Cohen, U.S. Patent No. 4,899,752, provides a somewhat different algorithm in 15 that the current mean pressure values are compared against fixed threshold values and the difference is employed to modify the pacing rate.
Medtronic U.S. Patents 4,407,296, 4,432,372 and 4,485,813 describe various transvenous pressure sensors with 20 associated pacing electrodes adapted to be positioned in a heart chamber to develop pressure values to control the operation of rate responsive pacemakers or to detect pathologic tachyarrhythmias and trigger the delivery o~
appropriate therapies.
2S In regard to the use of a blood pressure related signal detected within a heart chamber to confirm the detection of a tachyarrhythmia and trigger the delivery of an appropriate therapy, the initial system proposed by Mirowski et al in U.S. Patent No. Re 27,757 relied upon the decrease in the 30 amplitude of a pulsatile (systolic) right ventricular pressure signal below a threshold over a predetermined period of time (~P/~t) to commence the charging of a high energy output capacitor and deliver a shock to the heart i, the pressure signal did not increase above the thres;.~id 35 during the charging time. The short lived pressure sensor : ,: - . : .
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~92/11900 2 ~ ~ o 7 1 ~ PCT/US91/0~]
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available to Mirowski at that time was abandoned in favor of electrocardiogram rate and morphology detection.
More recently, the use of intramyocardial pressure and left ventricular pressure has been explored by a research 5 group from Belgium (see, for example, the paper by Denys et al entitled "Ventricular Defibrillation Detection by Intramyocardial Pressure Gradients" in PROCEEDINGS OF THE
SEVENTH WORLD SYMPOSIUM ON CARDIAC PACING, pp. 821-826, Verlag, 1983, and subse~uent papers, such as "Automatic 10 Defibrillator, Antitachy Pacemaker and Cardioverter", COMPUTERS AND CARD~OLOGY, IEEE COMPUTER SOCIETY PRESS, pp.
45-48, October 7--10, 1986, and other papers by this group.
This group has advocated the use of left ventricular impedance or pressure or a left ventricular pressure related 15 signal over right ventricular pressure, and they resorted to use of ventricular intramyocardial pressure because of the difficulty of directly measuring pressure in the left ventricle and atrium.
In addition, a Japanese group has published papers such 20 as "Design for an Implantable Defibrillator Using a Novel Heartbeat Sensor", 3apanese Journal of Medical and Bioloaical Enqineerina, 1984, pp. 43-48, by Makino et al.
The Japanese group's sensor detects the pressure in the right ventricle using a catheter born electrode, or 2~ microphone, heartbeat sensor. The absence of a heartbeat for 3.5 seconds causes the fibrillation detector to switch the high voltage converter into operation.
The comparison of a current average pressure value to a longèr term average control value derived from the heart 30 during normal sinus rhythm to detect ventricular arrhythmias and trigger cardioversion/defibrillation therapies in response to a significant decrease in the current value was proposed by Olson et al, in "Automati~ Detection of Ventricular Fibrillation with Chrcnic Pressure Sensors", 35 (abstract), J~CC, Vol. 7, No. 2, February , 1986, p. 182A.

W092/11900 - - PCT/USg1/0848l 2~9~7~f~ 6 More recently Cohen, U.S. Patent No. 4,774,950, describes a system employing mean pressure values from any of the four chambers of the heart represe~tative of the long-term mean base line pressure and the short-term current 5 mean pressure to indicate or confirm the indication of a tachyrhythmia and to trigger cardioversion/defibrillation shoc~ therapies when the difference between the two mean pressure values exceeds a predetermined threshold valueO
The truest indication of the degree of hemodynamic lo compromise of the malfunctioning heart is the left ventricular pressure which is measurable only with some difficulty. For example, Zacouto, Xresh, the Belgian group and Cohen (in the '751 and '950 patents) all have sought in one way or another to determine the left ventricular 15 pressure by locating a pressure sensor within the left ventricle or within the myocardial tissue. Placing and retaining a pressure sensor in either location involves some risk that the high pressure, left ventricular chamber will be breached at the point of penetration causing the patient 20 to hemorrhage as expressly commented on by the Belgian group. Thus with current technology, it is undesirable to so situate a pressure sensing transducer. However, the desirability of measuring is directly as possible the left atrial or ventricular blood pressure remains high.

SUMMARY OF THE I~ENTION
According to the invention, there is provided an implantable apparatus for developing various pressure values proportional to the left ventricular pulse, systolic, and diastolic pressures, as well as the differentiated rate of 30 change (dP/dt), gross rate of change (~P/~t) and mean or average of such pressure values by indirectly measuring without invading the left chambers or the myocardium in order to det~rm ne the adequacy of the pumping action of the heart and control the operation of a rate responsive ;

WO92/11900 2 a ~ lj 71~ PC~/US51/0~81 ~. ...

bradycardia treating pacemaker and/or the operation of a sys~em for pacing, cardioverting and/or defibrillating to correct tachyarrhythmias.

According to the present invention, there is provided a 5 method and apparatus ~or controlling cardiac tachyarrhythmias by passing an electrical current through the heart which comprises disposing at least first and second electrodes in relation to the heart, disposing a pressure transducer within the coronary sinus or a coronary 10 vein adjacent to the l~ft heart chambers, detecting a signal proportional to the left heart chamber blood pressure signals by said pressure transducer and providing a first signal in response to normal heart pumping and a second signal in response to abnormal heart pumping characteristic 15 of hemodynamic insufficiency, and supplying cardioversion or defibrillation energy to said heart in response to said second signal by application of stimulating pulses across said electrode.
More specifically, the first and second signals may be 20 related to one or more of the aforementioned pressure values. In addition, the first and second signals may be derived by comparing the current pressure signals (or values) to a fixed baseline pressure signal (or value) or to a baseline pressure signal (or value) derived from a series 25 of normal pressure signals (or values) detected (or derived) from the pressure sensor.
According to the present invention, there is provided a further method and apparatus for providing electrical energy to the heart to maintain and/or restore cardiac output at a 30 value meeting the patient's physiologic or metabolic requirements, wherein the method and apparatus is realized by: implanting a pulse generator and control circuitry which may be realized by a software driven microprocesao~
within the patient's body; coupling a lead system to the :. - ..................... . .

, ~, , , W092/11900 . ~ PCT/US91/08481 ~`~g ~r~lif; 8 pulse generator to situate an electrogram sensing and stimulating electrode in or adjacent to the ventricle and a pressure sensor within the coronary sinus or deep cardiac vein; periodically measuring the pressure within the vessel 5 in order to develop a pressure related signal of any of the aforementioned pressure values representative of the left ventricular pressure; processing the signal representative of the left ventricular pressure in order to develop a control signal for operating the pulse generator to restore 10 or regulate cardiac output.
More particularly, the method and the apparatus of the present invention may be implemented with a electrogram sensing or pacing electrode and/or a cardioversion/defibrillation electrode on the body of the 15 lead bearing the pressure sensor adapted to be disposed in the coronary sinus or coronary vein. A mechanism for blocking the great cardiac vein until the pressure sensor is securely fibrosed into the vessel may be provided and take the form of a radially disposed collar or expandable balloon 20 member located proximally to the pressure sensor and adapted to be expanded at implant or prior to pressure measurement.
Pressure measurements may be made on a continuing basis, with pressure measurements initiated in response to sensed or paced ventricular contractions. Alternatively, if 25 the pressure measurement is to be used only for detection of tachyarrhythmias, or discrimination of tachyarrhythmias from high sinus rates, pressure measurements may be initiated ln response to the detection of high heart rates.
Alternatively, pressure measurements may be taken 30 intermittently, under control of a real time clock within the pulse generator.
The signal processing alyorithm may provide for measuring and storing baseline pressure values for subsequent comparison to current pressure values and 35 providing a pacing rate control or :
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: ~ -." ' wo 9~ 900 2 D ~ ~7~ ~ PCT/US91/0~81 -cardioversion/defibrillation therapy triggering signal in response to the difference between the two signals. In this regard, the electrogram or R-wave rate may be employed to place bounds on the function of the system in treating ~rady 5 and tachyarrhythmias.
From a somewhat different point of view, the invention can be seen as a method and apparatus for treating a malfunctioning heart by providing electrical pulse energy to the heart to restore or maintain cardiac output in response lO to at least one hemodynamic pressure value related to the pressure values in the left chambers of the heart, measured by means of a pressure sensor located within the coronary sinus, great cardiac vein, or other coronary vein. Changes of pressure values are employed to vary the frequency of 15 pacing energy-pulses within upper and lower rate limits, whereas diminished or nonexistent pressure values are employed to trigger the delivery of cardioversion/defibrillation energy stimulation pulses. The method and apparatus may be implemented in a microprocessor 20 based dual chamber rate responsive pacemaker and tachyrhythmia control system.
More specifically, the present invention contemplates a method and apparatus for regulating cardiac pacing rate in response to a patient's left heart blood pressure which 25 comprises: disposing at least first and second electrodes in relation to the heart; disposing a pressure transducer within the coronary sinus region of the heart adjacent to the left heart chambers; detecting pressure by said pressure transducer and providing a pressure signal related thereto;
30 developing a current blood pressure value from a series of current pressure signals; providing a baseline blood pressure value; comparing the current blood pressure value to the baseline blood pressure value and develQping a difference vaiue; deriving a rate control signal from said 35 difference value; and supplying pacing energy stimulation ., ~ ~:. - :

WO92/l1900 2~ `7~6 - PCT/US91/0848~_ pulses to said electrodes at a rate established by said rate control signal. The method and apparatus for providing a baseline blood pressure value may further comprise developing said baseline blood pressure value from a 5 baseline series of blood pressure signals greater in number than said series of current blood pressure signals.
Alternatively, the baseline blood pressure may be a fixed value. This method and apparatus may employ any of the aforementioned pressure values.

BRIEF DESCRIPTION OF THE DRAWINGS
The above and still further objects, features and advantages of the present invention will become apparent from the following detailed description of the presently preferred embodiments, taken in conjunction with the 15 accompanying drawings, and, in which:
Fig. 1 illustrates the correlation between the electrocardiogram and the corresponding pressure wave forms taken the left ventricular cavity ~LV) and from the coronary sinus (CS).
Fig. 2 is a partial plan view of a first embodiment of the pressure transducer bearing coronary sinus pacing and/or cardioversion lead of the present invention;
Fig. 3 is a partial plan view of a second embodiment of a pressure transducer bearing coronary sinus pacing and/or 25 cardioversion lead of the present invention;
Figs. 4A - 4B are simplified drawings of a cutaway anterior view of the heart showing the arrangement of the pulse generator and leads comprising the system that performs the technique of the present invention wherein the 30 pacing and/or cardioversion leads of the present invention are situated within the coronary sinus; and Fig. 5 is a block diagram of one form of pulse generator which may be adapted to be used in a systPm embodying the present invention.

'' ' WO92/11900 ~ ~,9 8`7 ~i PCT/US9i/0848~
. 1 1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the following description of the preferred embodiments of the present invention, it will be understood that the illustrated embodiments encompass both the 5 detection and treatment of brady and tachyarrhythmias, whereas the invention may be used advantageously in either system alone. Consequently, although the drawings illustrate the advantageous uses of the invention in combination, it will be understood the detection of the left 10 chamber pressure by way of a pressure transducer situated a coronary vein may be employed advantageously as stated hereinbefore, in a first system for controlling the pacing rate of a bradycardia pacing pulse generator, or ~he detection of cardiac insufficiency in order to detect or 15 confirm the detection of a hemodynamically compromising tachyarrhythmia and to trigger the appropriate therapy or in a third system embodying all of the features of both the bradycardia and tachyarrhythmia detection and treatment systems.
Figure 1 shows a simulated EXG tracing, with illustrative wave forms illustrating the corresponding pressure waves as measured in the left ventricle (LV) and the occluded coronary sinus or cardiac vein (Cs). As can be seen by these tracings, the pressure in an occluded coronary 25 vein is proportional to the pressure in the left ventricle.
Measurements of the pressure in the coronary vein thus provide a workable substitute for direct measurement of pressure within the left ventricular cavity.
Turning then to Fig. 2, the distal portion of the 30 pacing/cardioversion/pressure sensing lead of the present invention ls depicted in a first embodiment. In Fig. 2, the distal portion 110 includes an elongated relatively high surface area cardioversion coil electrode 112 wrapped about the outer insulation 114 proximal to th~ solid spherical 35 occluding member 11~. The pressure transducer 118 and .
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W092/1~900 2 0 9 ~ 2 PCT/US~1/08481 optional first and second pacing/sensing electrodes 120 and 122 are located distally from the occluding member 116.
Alternately, atrial pacing and/or sensing electrodes may be placed proximal to the coil electrode 112 such that they are 5 located adjacent the opening of the coronary sinus into the right atrium, when the lead is implanted. Pacing and sensing electrodes may be omitted and may be dispensed with entirety, if separate atrial or ventricular pacing and/or sensing electrodes are provided on other leads. The distal lo end 124 of the lead is fabricated of tapered insulating material which is flexible in order to guide the depicted distal portion of the lead into the coronary sinus and then into a coronary vein.
The bipolar pacingtsensing electrodes 120 and 122 in 15 the lead of Fig. 1 are coupled through conductors within the lead body to pacing/sensing circuitry within a pulse generator to detect the near field EGM and provide a heart rate signal and cardioversion synchronization signal in a manner well known in the prior art. The pressure transducer 20 118 may take the form of the pressure transducer illustrated and described in the Medtronic U.S. Patent No. 4,485,813, also incorporated herein by reference in its entirety.
The occluding member 116 is depicted in Fig. 2 as a solid somewhat spherically shaped protrusion extending 25 outwardly about the outer surface of the insulating sheath 114 and is provided to occlude the coronary vein until the lead fibroses in. It will be understood that the occluding member 116 may not be necessary inasmuch as the overall size of the lead body extending distally from the occluding 30 member 116 may well fill and stretch the lumen of the selected coronary vein. In either case, if the vein is fibrosed or otherwise stretched tightly over the pressure transducer 118, the pressure transducer 118 will detect pressure propc~ ,.al to the left ventricular pressure wave 35 or pulse due to the location of the thebesian veins : ., , - ~ -: ~ .
,~

WO9~/11900 ~ a~ ~ 7 l 6 PCT/US91/08481 extending into the left ventricle accessible through the coronary sinus.
A commonly assigned U~ S. Patent No. 4, 932, 407 issued to Williams (incorporated herein by reference in its entirety) 5 depicts a lead similar to that shown in Fig. 2, except that it does not include the occluding member 116 and pressure sensor 118. The lead disclosed in the Williams patent is also intended to be introduced into the coronary sinus to situate the cardioversion electrode 112 deep within the 10 great cardiac vein to provide one cardioversion electrode in a system comprising one or two further electrodes spaced in or about the heart.
Turning now to Fig. 3, the second preferred embodiment of the pressure transducer bearing coronary sinus lead of 15 the present invention is illustrated. In Fig. 3, the distal portion 210 does not include a cardioversion electrode section, it depicts only a unipolar pace sense electrode 220 and illustrates an inflatable occluding member 216 rather than the ~olid occluding member 116 of Fig. 2. The 20 embodiment depicted in Fig. 3 thus presents an alternative design for the lead although it will be understood that features from both the Fig. 2 and Fig. 3 embodiments may be combined or eliminated in practice of the present invention.
In Fig. 3, the inflatable occluding member 216 is 25 accessed from the proximal end of the l~ad (not shown) by the lumen 226 extending from the proximal end of the lead to an access port 228 inside the balloon occluding member 216. In practice, it would be contemplated that the lead depicted in Fig. 2 would be transvenously 30 advanced into the coronary sinus and from the coronary sinus into a coronary vein until adequate pressure signals representative of the pressure of the left ventricular chamber are detected, whereupon the balloon member may be partially or completely inflated by saline solution.

WO92/11900 2 0 g 8 71 ~ PCTtUS91/0~81 14 ;-:
- The leads illustrated in Figures 2 and 3 show two forms of leads useful for practicing the present invention.
~owever, it is envisioned that other types of leads bearlng pressure sensors may also be useful in the context of the 5 present invention. As noted above, pacing and/or sensing electrodes may be located in a more proximal position, or may be dispensed with entirely. Depending upon the diameter of the lead body, an occluding section, 116, 216, may be dispensed with entirely, or it may take a different form.
10 Similarly, the particular pressure sensor illustrated may be replaced with other types of pressure sensors, and still remain within the scope of the invention. As such, the leads illustrated in Figures 2 and 3 should be considered exemplary, rather than limiting with regard to the scope of 15 the invention.
Turning now to Figs. 4A - 4B, the preferred embodiments of the present invention may be embodied in a system incorporating dual chamber pacing and/or cardioversion comprising a pulse generator and the leads of Figs. 2 or 3 20 or variations of those leads, as well as further leads and stimulating electrodes arranged about the heart. Figs. 4A -4B illustrate but one possible electrode combination to be employed with the pressure transducer bearing coronary sinus leads of the present invention.
Fig. 4A shows a cutaway view of the human heart in which the electrode leads have been mounted in their expected positions of use to provide a completely endocardial, transvenous defibrillation lead system.
Ventricular lead 70 may take the form of the lead 3C illustrated in Fig. 1 of the aforementioned Williams patent.
Alternatively, it may be a defibrillation lead of the type employing one or more cylindrical electrodes adjacent its distal end, as illustrated in U.S. Patent No. 4,355,646, issued to Kallok et al. This patent is a'so incorporated 35 herein by reference in its entirety. In this view, it can .

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WO92/11900 ~ ~ 9 ~ 7 ~ PCT/US91/0~81 : 1~
be seen that the ventricular lead 70 passes through the atrium 69, and is secured in the apex of the right ventricle 71. Defibrillation lead 70 includes at least one elongated electrode surface 74 and located within the right ventricle 5 71 and a bipolar electrode pair for ventricular pacing and sensing comprising a helical electrode 66 and a ring electrode 68.
The pressure sensor bearing coronary sinus lead 76 is shown passing through the superior vena cava, into the 10 opening of the coronary sinus 75, through the great caxdiac vein 80, and extending around the base of the left ventricle 77. When so mounted, the elongated defibrillation electrode 78 extends ~rom a point adjacent the opening of the coronary sinus 75 and into the great cardiac vein 80. This provides 15 a large surface area defibrillation electrode which is generally well spaced from the ventricular defibrillation electrode 74 and provides good current distribution in the area of the left ventricle 77. It is desirable to extend the electrode 78 around the heart as far as possible.
20 However, it is important not to extend the electrode 78 downward through the great vein 80 toward the apex 79 of the heart, as this will bring the coronary sinus and right ventricular electrodes into close proximity to one another, interfering with proper current distribution. Generally, 25 the distal end of the electrode 78 should be roughly adjacent the left atrial appendage.
The pressure sensor 118 is shown in Fig. 3A located within the coronary vein 80 ad~acent to the left ventricle.
In this position, pressure proportional to the systolic and 30 diastolic pressure of the left ventricle may be sensed.
In the electrode system illustrated in Flgures ~A and 4B, the optional pacing and/or sensing electrodes 120, 124 are dispensed with in view of the inclusion of ventricular pacing electrodes 66 ~nd 68 on lead 70. In the event that 35 dual chamber pacing is desired, a set of atrial pacing .
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WO92/11900 ~ ~ ~ $ 7 ~ ~ PCT/US91/08481 and/or sensing electrodes should be provided. These may, for example, take the form of a pair of ring electrodes or a single ring electrode located on the body of the coronary sinus lead 76, adjacent to the opening of the coronary sinus 5 into the right atrium. sensing electrodes appropriate for this application are disclosed in the lead illustrated in Fig. 2 of the above-cited Williams patent. Alternatively, atrial pacing and/or sensing electrodes may be separately provided, in the form of either a unipolar or bipolar lO cardiac pacing lead, of any of the numerous types known to the art.
Fig. 4B shows a stylized cross-section of the heart, intended to illustrate the relative locations of the ventricular and coronary sinus electrodes. In this view, it 15 can be seen that the right ventricular electrode 74 (visible in cross-section) is located within the right ventricular cavity 82, while the coronary sinus electrode 78 encircles the left ventricular cavity 86. In this view, it can be seen that a substantial percentage of the tissue of the left 20 ventricle is located between electrode 74 and electrode 78, and that the pressure sensor 118 is located adjacent to the left ventricular cavity 86.
Turning now to Fig. 5, a block diagram of the major components of an automatic implantable device for detecting 25 and treating brady and tachyarrhythmias is depicted. It is contemplated that such a device would be implemented in analog and digital microcircuits under the control of a central microprocessorlmemory block lO powered by high (for cardioversion and defibrillation) and low (for the remaining 30 circuitry on pacing therapies) power sources in block 12.
The high power pulse yenerator block 14 would include the cardioversion and defibrillation pulse generator circuitry coupled by output terminals to two or more cardioversion/defibrillation electrodes to apply 35 synchronized cardioversion or unsynchronized defibrillation WO92/11900 ~ ~ 9 ~ ~1 6 PCT/US91/08481 shocks to the electrodes situated in or about the heart in a manner well known in the art.
It is contemplated that the implantable device depicted in Fig. 5 would function under the control of a resident 5 operating program or software retained in memory within the microprocessor/memory block lO and would be programmable by an external programmer/receiver (not illustrated in Fig. 5) communicating with the implanted device by radio frequency energy received or transmitted by antenna 16 under the lO control of the programming and data transmission block 18 and reed swltch 20 which is responsive to an external magnet. The programming and data transmitting block 18 would be capable of receiving programming instructions and directing them to the memory within microprocessor/memory 15 block lO as well as transmitting data stored within the memory block lO as well as an electrogram representing the patient's atrial and ventricular activity in a manner well known in the pacing art.
The timing of all processing functions, including the 20 determination of atrial and ventricular cycle lengths, is controlled by system clocks within microprocessor/memory lO
driven by crystal oscillator ~2 in a manner well known in the prior art of implantable digital pacemakers. The remaining blocks of Fig. 4 include the isolation/protection 25 or interface block 24 which operates to direct ventricular, and optionally atrial pacing stimuli from the pacing pulse generator block 26 to respective ventricular and atrial output terminals which in turn are coupled through pacing leads to bipolar pacing electrodes situated in or near the 30 ventricle, and optionally the atrium of the heart, respectively. In addition, the interface 24 (when unblanked) couples the atrial and ventricular electrograms (or P-waves and R-waves respectively) to the sense amplifier block 28. Interface 24 is blanked or preYcnted from passing 35 any signals picked up on the bipolar atrial and ventricular ' , - , 2~9~7~ &

pacing/sensing electrodes to the sense amplifier block 28 during short blanking intervals following the delivery of an atrial or ventricular pacing stimulus in a fashion well known in the pacing art.
~urthermore, the interface 24 disconnects or shorts out the pacing/sensing electrodes during the delivery and for a short period after the delivery of a cardioversion/defibrillation shock by application of a control signal to the interface 24 by the 10 cardioversion/defibrillation pulse generator block 14.
The P-waves and R-waves transmitted through the interface 24 to the sense amplifiers 28 are amplified and shaped to generate atrial and ventricular signals AS and VS, respectively, which are conducted to microprocPssor/memory 15 lO in order to- derive the atrial and ventricular cycle lengths, the AV delay interval, and other intervals which may be appropriate to the overall function of the device. A
further signal from the pressure sensor 118, 218 representative of left chamber blood pressure is also 20 applied to the microprocessor/memory 10 in order to control the bradyarrhythmia pacing rate in DDDR, W IR or other rate responsive mode of operation and to augment detection of tachyarrhythmias.
The microprocessor/memory 10 responds to atrial and 25 ventricular AS and Vs signals by generating appropriatP
atrial and ventricular refractory and blanking intervals which are in turn applied to the sense amplifier block 28 during certain windows of time following each respective AS
and VS signal in a fashion well known in the pacing art.
It is contemplated that the system depicted in Fig. 4 may be programmed to operate in any of the known bradycardia single or dual chamber pacing modes. The signal from the physiologic sensor 32 may be employed to modify the atrial and ventricular escape intervals to allow for a certain 35 range of atrial and ventricular pacing depending upon the :: ; - :; -WO92/11900 ~ ~ 9 ~ 7 ~ 6 PCT/U~91/0~81 ,.. - . .
.. `. 19 le~el of the patient's activity in a fashion well know~ in the bradycardia pacing art. Suffice it to say, that atrial and ventricular escape intervals established in memory are compared against the atrial and ventricular cycle lengths 5 encountered in the patient and, if a bradycardia condition exists, the microprocessor/memory 10 applies atrial and ventricular pace trigger signals AT and VT through analog rate limiter block 30 to the pacing pulse generator 26 which responds by developing the respective A pace and V pace 10 signals. Analog rate limiter 30 operates telemetry atrial and ventricular pacing rates to a safe high rate into effect an appropriate upper rate behavior in the event that the spontaneous atrial rate exceeds the programmed upper rate limit in a fashion well known in the pacing art.
It is moreover contemplated that the microprocessor memory block 10 may be programmed to provide a regimen of successive treatment therapies to treat any tachyarrhythmia that is not corrected to sinus rhythm by the delivery of the first therapy in the regimen. The successive therapies may 20 be programmed to be more aggressive and may include both pacing energy and cardioversion defibrillation shock therapies.
~ he system as described i5 rendered operational by resident software within the microprocessor/memory block 10 25 which is capable of distinguishing normal sinus rhythm within the acceptable upper and lower rate limits of the main brady pacing routine and distinguishing various types of tachyarrhythmias in accordance with algorithms known in the art.
The signals derived from the pressure sensors 118 or 218 and applied to the microprocessor/memory 10 of Fig. 4 may be employed to develop pulse, systolic and diastolic pressure values, long term mean or average values of these ~.-essure values or both, sho-t term mean or average values 35 of the same pressures, the time derivatives (dP/dt) of the . ,, ' ~ ~ ' ' ' , -- ~

WO92/11900 ~9~7~ PCT/US91/0~81 pressure signals and corresponding mean or average valu~s thereof over short and long terms and the gross rate of change (~P/~t) of same as all is described in the prior art referenced above. The microprocessor/ memory 10 may include 5 specific circuits for differentiating the pressure signal, measuring the peak pulse, systolic and diastolic pressures and the mean and gross rate of change of these values. For example, the calculation of the mean blood pressure may be carried out in various manners. For instance, the 10 microprocessor/ memory 10 may consist of a mean ~alue rectifying circuit having a suitable time constant including two peak detecting amplifiers which are connected to the signal from the pressure transducer with opposite polarities so that the one amplifier produces an output signal 15 representing the systolic blood pressure, whereas the other amplifier produces an output signal representing the diastolic blood pressure. These two output signals are supplied to an analog summing circuit which sums the signals according to the equation:

mean Pdj~stoLic ~ 2 (P5yst~ic ~ Pdjasto~

This is an approximate expression for the mean blood pressure P~an based upon a substitution of a triangular curve for the pulse wave. These pressure values may be employed in any of the algorithms described in the 25 aforementicned prior art to develop a pacing rate control system or to detect or confirm the detection of a hemodynamically compromising tachyarrhythmia. Thus, the algorithms disclosed in the aforementioned U.S. Patent Nos.
4,566,456, 4,774,950, 4,899,751 and the Olson et al abstract 30 are incorporated herein by reference.
The ability of the system in Figure 4 to distinguish high rates which res~lt in hemodynamic compromise, from high ventricular rates accompanied by normal hemodynamic WO92/11~00 2 ~ ~ ~ 71 ~ PCT/US9l/08481 .

~operation or only moderate hemodynamic compromise can be used to select the aggressiveness of the cardioversion therapy to be applied. For example, in the presence of high ventricular rate, within a predetermined range believed 5 to be generally indicative of ventricular tachycardia, and in the presence of normal, or only somewhat compromised hemodynamic functions, the first anti-tachyarrhythmia therapy attempted may be an anti~tachyarrhythmia pacing therapy such as burst pacing, decremental overdrive pacing, 10 or multiple pulse pacing methods, of any of the types known to the art. The degree to which hemodynamic function has been compromised is a useful indicator of how rapidly cardioversion must be effected, and with greater hemodynamic compromise, a greater degree of aggressiveness for the 15 initial anti-tachyarrhythmia therapy provided is desirable.
Similarly, the entire sequence of therapies to be employed may be specified based on the degree of hemodynamic compromise detected by the pressure sensor, with a more rapid increase in the aggressiveness of the sequential 20 therapies specified in response to detection of greater hemodynamic compromise. The therapy sequence may be specified after a single measurement made prior to the first therapy or may be updated by later pressure measurements ta~en after initiation of antitachyarrhythmia therapy.
2~ The present invention pro~ides a significant advancement in the treatment of patients having malfunctioning hearts through the detection of left heart chamber pressure values without invading the myocardium or the left heart chambers or high pressure vessels. The 30 systems of the present invention operate automatically to process the left heart related pressure values to develop pacing rate control and cardioversion detection signals effective to distinguish normal heart function from abnormal heart function in a vari~ty of situations. Although not 35 expressly illustrated, hereinbefore it will be understood . . ..

.

WO92/11900 PCT/US91/0~81~
~` ~ 22 ~" `
-that the principles of the present invention may be applied as well to the detection and treatment of congestive heart failure by either electrical stimulation or dispensing of drugs. In this regard, it will be understood that the 5 pressure transducer bearing coronary sinus lead of the present invention may be employed with an implantable drug dispenser of the type described in Ellinwood U.S. Patent No.
4,003,379 to control the delivery of ~lectrical stimulation and/or drugs in the treatment of congestive heart failure.
It is to be understood that the foregoing detailed description and accompanying illustrations have been set out by way of example, not by way of limitation. Numerous other embodiments and variants are possible, without departing from the spirit and scope of the invention defined in the 15 appended claims.

': ': ' ' ~ ~ .

.

Claims

What is claimed is:

1. A method for controlling cardiac tachyarrhythmias by passing an electrical current through the heart which comprises:
disposing at least first and second electrodes in relation to the heart;
disposing a pressure transducer within the coronary sinus region of the heart adjacent to the left heart chambers;
detecting a signal proportional to the left heart chamber blood pressure by said pressure transducer and providing a first signal in response to detection of normal heart pumping and a second signal in response to detection of abnormal heart pumping, characteristic of hemodynamic insufficiency; and supplying cardioversion energy to said heart in response to said second signal by application of stimulating pulses across said electrodes.

2. The method of claim 1 wherein said step of disposing at least first and second electrodes further comprises the step of providing at least one of said electrodes in said coronary sinus region in specific relation with said pressure transducer.

3. The method of claims 1 or 2 wherein said detecting step includes detecting a pressure proportional to left ventricular systolic blood pressure.

4. The method of claims 1 or 2 wherein said detecting step includes detecting a pressure proportional to left ventricular pulse pressure.

5. The method of claims 1 or 2 wherein said detecting step includes detecting a signal proportional to left ventricular peak to peak blood pressure.

6. The method of claims 1 or 2 wherein said detecting step includes detecting differentiated time rate of change (dP/dt) pressure values.

7. The method of claims 1 or 2 wherein said detecting step includes detecting time rate of change (?P/?t) pressure values.

8. The method of claim 1 wherein said step of disposing a pressure transducer in the coronary sinus or coronary vein-region further comprises:
providing a pressure transducer in the distal portion of a lead body adapted to be inserted into the coronary sinus and from the coronary sinus into a coronary vein; and transvenously advancing said distal portion of said lead body through the superior vena cava, the right atrium, the coronary sinus, and into said coronary vein.

9. The method of claim 8 further comprising the step of:
occluding the coronary vein proximal to the location of the pressure transducer when said pressure transducer is situated in the coronary vein.

10. The method of claim 9 wherein said step of occluding the coronary vein further comprises the step of:
providing an occluding member on said lead proximal to said pressure transducer.

11. Apparatus for controlling cardiac tachyarrhythmias by passing an electrical current through the heart which comprises:
means for disposing at least first and second electrodes in relation to the heart;
means for disposing a pressure transducer within the coronary sinus or coronary vein of the heart adjacent to the left heart chambers;
means for detecting a pressure proportional to left heart chamber blood pressure by said pressure transducer and providing a first signal in response to normal heart pumping and a second signal in response to abnormal heart pumping characteristic of hemodynamic insufficiency; and means for supplying cardioverting energy to said heart in response to said second signal by application of stimulating pulses by means of said first and second electrodes.

12. The apparatus of claim 11 wherein said means for disposing at least first and second electrodes further comprises means for providing at least one of said electrodes in said coronary sinus region in specific relation with said pressure transducer.

13. The method of claims 11 or 12 wherein said means for detecting pressure includes means for detecting pressure proportional to left ventricular systolic blood pressure.

14. The method of claims 11 or 12 wherein said means for detecting pressure includes means for detecting pressure proportional to left ventricular pulse pressure.

15. The method of claims 11 or 12 wherein said means for detecting pressure includes means for detecting pressure proportional to left ventricular peak to peak blood pressure.

16. The method of claims 11 or 12 wherein said means for detecting pressure includes means for detecting differentiated time rate of change (dP/dt) pressure values.

17. The method of claims 11 or 12 wherein said means for detecting pressure includes means for detecting gross time rate of change (?P/?t) pressure values.

18. The apparatus of claim 11 wherein said means for disposing a pressure transducer in the coronary sinus or coronary vein region further comprises:
means for providing a pressure transducer in the distal portion of a lead body adapted to be inserted into the coronary sinus and from the coronary sinus into a coronary vein.

19. The apparatus of claim 18 further comprising:
means for occluding said coronary vein proximal to the location of the pressure transducer when said pressure transducer is situated in said coronary vein.

20. The apparatus of claim 19 wherein said means for occluding the coronary vein further comprises:
means for providing an occluding member on said lead proximal to said pressure transducer.

21. A method for regulating cardiac pacing rate in response to a patient's left heart blood pressure which comprises:
disposing at least first and second electrodes in relation to the heart;

disposing a pressure transducer within the coronary sinus region of the heart adjacent to the left heart chambers;
detecting pressure signals by said pressure transducer;
providing a pacing rate control signal derived from said pressure signals; and supplying pacing energy stimulation pulses to said electrodes at a rate established by said rate control signal.

22. The method of claim 21 wherein said step of disposing at least first and second electrodes further comprises the step of providing at least one of said electrodes in said coronary sinus region in specific relation with said pressure transducer.

23. The method of claim 21 wherein said step of disposing a pressure transducer in the coronary sinus region further comprises:
providing a pressure transducer in the distal portion of a lead body adapted to be inserted into the coronary sinus and from the coronary sinus into a coronary vein; and transvenously advancing a distal portion of said lead body through the superior vena cava, the right atrium, the coronary sinus, and into a coronary vein.

24. The method of claims 21 or 23 wherein said step of detecting pressure signals includes detecting pressure signals proportional to left ventricular systolic blood pressure.

25. The method of claims 21 or 23 wherein said step of detecting pressure signals includes detecting pressure signals proportional to left ventricular pulse pressure.

26. The method of claims 21 or 23 wherein said step of detecting pressure signals includes detecting left pressure signals proportional to ventricular peak to peak blood pressure.

27. The method of claims 21 or 23 wherein said step of detecting pressure signals includes detecting differentiated time rate of change (dP/dt) pressure values.

28. The method of claims 21 or 23 wherein said step of detecting pressure signals includes detecting time rate of change (?P/?t) pressure values.

29. The method of claim 21 further comprising the step of:
occluding said coronary vein proximal to the location of said pressure transducer when said pressure transducer is situated in said coronary vein.

30. The method of claim 29 wherein said step of occluding said coronary vein further comprises the step of:
providing an occluding member on said lead proximal to said pressure transducer.

31. Apparatus for regulating cardiac pacing rate in response to a patient's left heart blood pressure which comprises:
means for disposing at least first and second electrodes in relation to the heart;

means for disposing a pressure transducer within the coronary sinus region of the heart adjacent to the left heart chambers;
means for detecting pressure signals by said pressure transducer and providing a pacing rate control signal derived from the pressure signal; and means for supplying pacing energy stimulation pulses to said electrodes at a rate established by said rate control signal.

32. The apparatus of claim 31 wherein said means for disposing at least first and second electrodes further comprises means for providing at least one of said electrodes in said coronary sinus region in specific relation with said pressure transducer.

33. The apparatus of claim 32 wherein the means for disposing a pressure transducer in the coronary sinus region further comprises:
means for providing a pressure transducer in the distal portion of a lead body adapted to be inserted into the coronary sinus and from the coronary sinus into a coronary vein.

34. The apparatus of claims 31 or 33 wherein said means for detecting pressure signals includes means for detecting signals proportional to left ventricular systolic blood pressure.

35. The apparatus of claims 31 or 33 wherein said means for detecting pressure signals includes means for detecting signals proportional to left ventricular pulse pressure.

36. The apparatus of claims 31 or 33 wherein said means for detecting pressure signals includes means for detecting signals proportional to left ventricular peak to peak blood pressure.

37 The apparatus of claims 31 or 33 wherein said means for detecting pressure signals includes means for detecting differentiated time rate of change (dP/dt) pressure values.

38. The apparatus of claims 31 or 33 wherein said means for detecting pressure signals includes means for detecting gross time rate of change (?P/?t) pressure values.

39. The apparatus of claim 31 further comprising:
means for occluding said coronary vein proximal to location of said pressure transducer when said pressure transducer is situated in said coronary vein.

40. The apparatus of claim 39 wherein said means for occluding said coronary vein further comprises:
means for providing an occluding member on said lead proximal to the pressure transducer.