WO2002022206A1

WO2002022206A1 - A method and apparatus for left ventricular pacing via a right ventricular endocardial approach

Info

Publication number: WO2002022206A1
Application number: PCT/US2001/028413
Authority: WO
Inventors: Hongpyo H. Lee
Original assignee: Lee Hongpyo H
Priority date: 2000-09-12
Filing date: 2001-09-11
Publication date: 2002-03-21

Abstract

A pacing lead (10) of the invention is characterized by a screw-in tip (12) that is longer than conventional tips ans is provided with an electrically active distal electrode (14), which is insulated from the proximal part of the screw tip of the pacemaker lead. This electrically active distal screw-in tip is extended from the right ventricular septal endocardium (22) into the left side of the interventricular septum (26) and is used for left ventricular pacing with optional properly synchronized right ventricular pacing. In the illustrated embodiment the lead is shown as being comprised of a lead through which a stylet (13) is disposed, the stylet engaging a follower nut (15) with external threading which in turn engages internal threading (17) provided in the interior surface of the lead. Rotation of the stylet rotates the follower nut to advance or retract the nut within the threading to allow advancement of the tip at least more than halfway through the entire septum.

Description

A METHOD AND APPARATUS FOR LEFT VENTRICULAR PACING VIA A RIGHT VENTRICULAR ENDOCARDIAL APPROACH

Background of the Invention

1. Field of the Invention

The invention relates to the field of cardiac pacing and in particular to pacing of the left ventricle.

2. Description of the Prior Art

Congestive heart failure (CHF) is one of most rapidly growing major health problems, afflicting four million people in the United States, with 400,000 new cases and 300,000 deaths annually. CHF presents a clinical picture of poor cardiac pump function due to decreased cardiac contractile disorders, such as diffuse idiopathic cardiomyopathy or end stage coronary disease with multiple myocardial infarctions. There are several effective medications, but they are not completely satisfactory in many patients.

The heart is characterized by widely spread complex electric conduction networks which ensure rapid and orderly depolarization of heart muscle. This orderly depolarization triggers coordinated cardiac contractions for an efficient cardiac pump function. An extensive cardiac disease process frequently damages this complex conduction system, resulting in slow zigzag, non-orderly myocardial depolarization through muscle conduction, instead of orderly rapid depolarization through the regular conduction network. This electric asynchrony is manifested as a wide left bundle branch block (LBBB) pattern in an electrocardiogram (ECG) and causes an uncoordinated cardiac contraction sequence, which results in more inefficiency on existing poor cardiac pump function.

The rationale for using a pacemaker in CHF is to resynchronize the cardiac electric depolarization (inter and intraventricular, especially left intraventricular, because of its dominance in the cardiac pump function) by pacing on proper cardiac sites. This electric resynchronization improves cardiac function by achieving better coordination of cardiac contraction sequence. The usual right ventricular pacing alone cannot improve electric asynchrony of left ventricle, but proper left ventricular (single or multiple sites) or biventricular pacing has shown significant electromechanical improvement.

However, the placement of a permanent left ventricular (left ventricle) pacemaker lead has been limited by technical difficulties and relatively high risks, preventing wide spread clinical trial of this cardiac resynchronization therapy.

The first technique used was the epicardial approach, but its main limitation is the need for thoracotomy and general anesthesia, which carries a high risk for CHF patient.

The current approach is transvenous pacing lead insertion into a tributary of coronary sinus over the left ventricular free wall, but technical difficulties frequently result in improper lead placement. Finally, an endocardial approach via an atrial transseptal route was also proposed, but this technique appears too difficult and risky for practical usage. The left ventricle is much more muscular and generates five times more pumping pressure than the right ventricle. Electrophysiological dysfunction in the left ventricle can thus be corresponding more significant to the functioning of the heart than other heart portions. While being the dominant portion of the heart, the left ventricle has been rarely paced, however, because of the anatomical difficulty of accessing or implanting a pacemaker lead in it.

What is needed is a method and apparatus whereby left ventricular pacing can be made easier and safer.

Brief Summary of the Invention The invention is a method of pacing a heart having a left ventricle and a right ventricle which are separated by a septum. The method comprises the steps of disposing a distal end of a pacing lead into the right ventricle in contact with the septum at a selected site using conventional transvenous approaches. A tip is extended from the distal end of the pacing lead to penetrate the septum by a selected distance. The tip extends into the septum toward the left ventricle. The tip has a tip electrode. An electrical signal is applied to the tip and tip electrode to pace the left ventricle. The step of extending a tip from the distal end of the pacing lead screws the tip into the septum, although it is to be expressly understood that any type of penetrating now known or later devised may be employed, such a anchoring, hooking, puncturing, pronging, screwing or pinching.

The step of extending a tip from the distal end of the pacing lead extends the tip or at least its tip electrode at least more than half way through the septum toward the left ventricle.

The pacing lead has a distal electrode and the step of extending a tip from the distal end of the pacing lead brings the distal electrode on the pacing lead into contact with a right ventricle wall of the septum. Depending on the signal applied and the location in the septum of the tip electrode, the step of applying an electrical signal to the tip to pace the left ventricle may also pace the right ventricle. On the other hand the right ventricle may be paced through a separate distal electrode on the pacing lead independently from pacing of the left ventricle through the tip electrode. In this case, the right ventricle is paced through the distal electrode on the pacing lead independently from pacing of the left ventricle through the tip electrode. Typically, pacing the right ventricle through a separate distal electrode is synchronized with pacing of the left ventricle.

The invention is also defined as an apparatus for pacing a heart having a left ventricle and a right ventricle which are separated by a septum. The apparatus comprises a pacing lead having a distal end adapted to be disposed into the right ventricle in contact with the septum at a selected site. A tip can be extended from the distal end of the pacing lead to penetrate the septum by a selected distance. The tip extends into the septum toward the left ventricle. The tip has a tip electrode so that an electrical signal applied to the tip paces the left ventricle. In the illustrated embodiment the tip is a screw tip which is characterized by a distal portion which is conductive, which is exposed to provide the tip electrode, and which is embedded into or at least partially through the septum. The mechanism for advancing or retracting the tip may take anyone of a wide variety of conventional forms associated with screw or embedding cardiac tips with the modification according to the invention of being extendable to a sufficient distance into or through the septum wall to pace or stimulate the left ventricle.

An insulating layer is provided on the tip so that the tip is conductive, the distal portion of the tip is uninsulated, and all remaining portions of the tip are covered by the insulating layer. The pacing lead further comprises a distal electrode. The distal electrode of the pacing lead is electrically insulated from the tip. A pacemaker is coupled to the tip and to the distal electrode for selectively applying separate electrical signals to both the tip and to the distal electrode. The pacemaker applies the separate electrical signals to both the tip and to the distal electrode in predetermined synchronization with each other. The pacing lead is either a unipolar or bipolar pacing lead.

Although the method has been described grammatically as steps, it must be expressly understood that the invention is not limited under 35 USC 112 to the disclosed method, but is defined solely by the following claims without necessary limitation to the illustrated embodiment. Turn now to the following drawings wherein like elements are referenced by like numerals.

Brief Description of the Drawings Fig. 1 is a side cross-sectional view of a human heart in which a lead has been implanted according to the invention to pace the left ventricle.

Fig. 2 is an enlarged side cross-sectional view of the distal end of a pacing lead disposed against the right ventricle wall of the septum according to the invention in which a screw tip is fully retracted, but the distal end of the pacing lead is placed against the right ventricle wall of the septum.

Fig. 3 is the side cross-sectional view of Fig. 2 in which the screw tip is advanced into the septum toward the left ventricle wall.

The invention and its various embodiments are better understood by now turning to the following detailed description of the preferred embodiments. Detailed Description of the Preferred Embodiments

A pacing lead of the invention is characterized by a longer screw-in tip than is conventional and is provided with an electrically active distal electrode, which is insulated from the proximal part of the screw tip of the pacemaker lead. This electrically active distal screw-in tip is extended from the right ventricular septal endocardium into the left side of the interventricular septum and is used for left ventricular pacing with optional properly synchronized right ventricular pacing. This is done by usual transvenous technique. The method for tip extension into the septum may be any currently known or modified means such as in the illustrated embodiment. In the illustrated embodiment the lead in shown as being comprised of a lead through which a stylet is disposed. A stylet is engaged to a follower nut with external threading, which engages internal threading provided in the interior surface of the lead. Rotation of the stylet rotates the follower nut to advance or retract the nut within threading. The lineal extent of internal threading which is provided is sufficient to allow advancement of the tip at least more than halfway through the entire width the septum. In the illustrated embodiment the electrically active distal electrode of the tip is comprised of the exposed portion of the metallic tip while the remaining portion of the tip is covered with the electrical insulator. An electrical pin is coupled at its proximal end to a pacemaker, which is typically subcutaneously implanted in the upper chest.

Pacemaker leads with active screw-in tips have been used for over a decade with great ease and success to secure or anchor a pacemaker lead tip into stable contact with the endocardium. Current screw-in tips are typically about 2mm in length. According to the invention the length of the screw-in tip is altered to allow extension of the tip into the septum toward the left ventricle by a distance to allow electrical stimulation to the left ventricle. The septum may in some cases be approximately 2 cm thick, thus requiring a screw-in tip approximately 1 cm longer or longer. One of the commonly used screw-in tips presently used for pacing is described and shown by Bisping, "Implantable Electrode," U.S. Patent 4,233,992 (1980), and Bisping, "Implantable Lead Assembly with Extendable Screw-in Electrode," U.S. Patent 4,886,074 (1989), which are incorporated herein by reference. See also Dutcher, "Body-lmplantable Lead with Protected, Extendable Tissue Securing Means," U.S. Patent 4,217,913 (1980), and Bradshaw, et.al, "Active Fixation Mechanism for Lead Assembly of an Implantable Cardiac Stimulator," U.S. Patent 4,858,623 (1989), which are incorporated herein by reference. The Bisping lead and screw-in tip or any other conventional lead and screw-in tip now known or later devised can be modified according to the invention to be used left ventricle pacing. The exact form of the lead, while important, is nonetheless ancillary to the main thrust of the invention which is directed to left ventricle pacing through septum by access through the right ventricle as shown in Fig. 1. Heart 11 has a lead 10 disposed into right atrium 13 in a conventional manner and extending into right ventricle 24 to septum 16. Tip 14 is extended from distal tip 20 of lead 10 and penetrates or extends into septum 16 by a distance sufficient to stimulate a selected pathway in left ventricle 17. Tip 14 will be implanted at a location which is determined by the physician to be for best left ventricular pacing.

Fig. 2 is a diagrammatic side view of the invention showing a lead 10 which is characterized by a longer screw-in tip 12 with an electrically active small distal electrode 14, insulated from the proximal part of screw 12 of pacemaker lead 10. In the illustrated embodiment lead 10 in shown as being comprised of a lead 11 through which a stylet 13 is disposed. A stylet 13 is engaged to a follower nut 15 with external threading, which engages internal threading 17 provided in the interior surface of lead 11. Rotation of stylet 13 rotates follower nut 15 to advance or retract nut 15 within threading 17. The lineal extent of internal threading 17 provided is sufficient to allow advancement of tip 12 at least more than halfway through the entire width septum 16. In the illustrated embodiment electrically active distal electrode 14 of tip 12 is comprised of the exposed portion of metallic tip 12 on the remaining portion of tip 12 is covered with the electrical insulator. However, it is entirely within the scope of the invention that other structural combinations between tip electrode 14 and tip 12 may be realized, such as a conductive tip 14 coupled to a nonconductive tip 12, which tip 14 is electrically connected to means such as a conductive strip or core embedded within nonconductive tip 12, which is coupled at its proximal end to a pacemaker 32, which is typically subcutaneously implanted in the upper chest. Fig. 3 is side cross sectional diagrammatic view of lead 10 of Fig. 2 in which tip 12 has been advanced by rotating follower nut 15. In the illustrated view of Fig. 3, tip 12 has been advanced so that electrically active electrode tip 14 is positioned in the left side of septum 16. When tip 12 is screwed into septum 16, lead 10 is positioned with its distal electrode 20 adjacent right ventricular wall 22. Advancement of tip 12 into septum 16 insures that distal electrode 20 remains in intimate contact with adjacent right ventricular wall 22. It is to be expressly understood that the mechanism for advancing or retracting tip 12 is meant to include any mechanism for advancing or retracting tip 12 from or into the distal end 28 of lead 10 now known or later devised. For example, the degree of screw can be varied from almost straight to markedly pitched. A screw mechanism need not be used, but a straight needle which has a fixed or extendable distal anchor can also be used. In all cases tip 12 is made of an appropriate material so that it moves easily with the contractions of septum 16 without fatigue or embrittlement.

Tip 12 is adapted to being and is screwed into the interventricular septum 16 and is advanced to or toward the left ventricle side 18 of septum 16. Left ventricle pacing can be performed either as unipolar or bipolar pacing as is conventionally practiced. See for example, Helland, etal., "Bipolar Active Fixation Lead for Sensing and Pacing of the Heart," U.S. Patent 5,545,201 (1996), incorporated herein by reference. Pacemaker lead pole 20 is in contact with the endocardium of right ventricle and can be used for right ventricle pacing as unipolar or bipolar electrode. Split bipolar pacing between the left ventricle and right ventricle septum walls 26 and 22 respectively can also be performed. Lead 10 may include additional electrodes as are well known in the art such as proximal ring electrode 30 which may be used for sensing or bipolar operation.

The length of screw-tip 12, including its electrically active portion 14, which extends into septum 16 depends on the thickness of interventricular septum 16, which is normally about 1cm, but this is highly variable. Lead 10 can be easily positioned perpendicularly against septum 16 in right ventricle cavity 24, using a variety of techniques including fluoroscopy, a preformed sheath and steerable guide- stylet so that screw-tip 12 can be screwed into the left ventricle side 26 of septum 16. This septal pacing will mimic the normal septal depolarization from left septum 26 to right septum 22 and may substantially improve the coordination of left ventricular contraction by itself. If needed, simultaneous or nonsimultaneous pacing of another left ventricular site, such as the left lateral basal wall, in addition to the described left septal pacing may further augment the electromechanical improvement.

Again the advantage of this lead is that it permits easy and reliable left ventricle pacing, and optional right ventricle pacing with a single lead via a routine transvenous approach. Because left ventricle pacing can be realized by a penetrating electrode 14 disposed into septum 16 from the right ventricle, which electrode 14 is located at or near left ventricle wall 18, conventional methods of approach, which are well known and well tested, as well as being within the skill of the ordinary pacemaker surgeon, can be successfully used to implant lead 10. Multiple chamber pacings can be done easily and any of the means now known to the art or later devised can be employed. See for example, Struble, etal., "Multiple Channel, Sequential Cardiac Pacing System, "U.S. Patent 6,081 ,748 (2000) which is incorporated herein by reference.

Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations.

The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself.

The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination. Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.

Claims

I claim: 1. A method of pacing a heart having a left ventricle and a right ventricle which are separated by a septum comprising: disposing a distal end of a pacing lead into said right ventricle in contact with said septum at a selected site; extending a tip from said distal end of said pacing lead to penetrate said septum by a selected distance, said tip extending into said septum toward said left ventricle, said tip having a tip electrode; and applying an electrical signal to said tip to pace said left ventricle

2. The method of claim 1 where extending a tip from said distal end of said pacing lead screws said tip into said septum.

3. The method of claim 1 where extending a tip from said distal end of said pacing lead extends said tip at least half way through said septum toward said left ventricle.

4. The method of claim 1 where extending a tip from said distal end of said pacing lead extends said tip at least more than half way through said septum toward said left ventricle.

5. The method of claim 1 where said pacing lead has a distal electrode and where extending a tip from said distal end of said pacing lead brings said distal electrode into contact with a right ventricle wall of said septum.

6. The method of claim 1 where extending a tip from said distal end of said pacing lead anchors said tip into said septum.

6. The method of claim 1 where applying an electrical signal to said tip to pace said left ventricle also paces said right ventricle.

7. The method of claim 1 further comprising pacing said right ventricle through a separate distal electrode on said pacing lead independently from pacing of said left ventricle through said tip electrode.

8. The method of claim 5 comprising pacing said right ventricle through said distal electrode on said pacing lead independently from pacing of said left ventricle through said tip electrode.

9. The method of claim 8 where pacing said right ventricle through a separate distal electrode is synchronized with pacing of said left ventricle.

10. The method of claim 9 where pacing said right ventricle through a separate distal electrode is synchronized with pacing of said left ventricle.

11. An apparatus for pacing a heart having a left ventricle and a right ventricle which are separated by a septum comprising: a pacing lead having a distal end adapted to be disposed into said right ventricle in contact with said septum at a selected site; a tip extendible from said distal end of said pacing lead to penetrate said septum by a selected distance, said tip extending into said septum toward said left ventricle, said tip having a tip electrode so that an electrical signal applied to said tip paces said left ventricle.

12. The apparatus of claim 11 where said tip is a screw tip in which a distal portion is conductive and exposed to provide said tip electrode.

13. The apparatus of claim 12 where only said distal portion of said tip is conductive and all remaining portions of said tip are nonconductive.

14. The apparatus of claim 13 further comprising an insulating layer on said tip, and where said tip is conductive, said distal portion of said tip is uninsulated, and all remaining portions of said tip are covered by said insulating layer.

15. The apparatus of claim 11 where said pacing lead further comprises a distal electrode.

16. The apparatus of claim 15 where said distal electrode of said pacing lead is electrically insulated from said tip.

17. The apparatus of claim 11 further comprising a pacemaker coupled to said tip and to said distal electrode for selectively applying separate electrical signals to both said tip and to said distal electrode.

18. The apparatus of claim 17 where said pacemaker applies said separate electrical signals to both said tip and to said distal electrode in predetermined synchronization with each other.

19. The apparatus of claim 11 where said pacing lead is either a unipolar or bipolar pacing lead.