Systems and methods for examining heart tissue employing multiple electrode structures and roving electrodes

We claim:

1. A system for acquiring electrograms comprising

an array of multiple electrodes supported for operative association with a region of heart tissue,

roving second electrode means supported for movement relative to the multiple electrodes for operative association with selected, different regions of endocardial tissue within the heart, and

a processing element coupled to the multiple electrodes and the roving second electrode means for conditioning one of the multiple electrodes and the roving second electrode means to emit a pacing signal and for conditioning the other one of the multiple electrodes and the roving second electrode means to record paced electrograms occurring as a result of the pacing signal.

2. A system according to claim 1

wherein the multiple electrode array is shaded to assume a radially expanded position in operative association with the region of endocardial tissue.

3. A system according to claim 1

wherein the roving second electrode means includes means for remote steering of the roving second electrode means.

4. A system for analyzing electrograms comprising

an array of multiple electrodes supported for operative association with a region of heart tissue,

a roving second electrode supported for movement relative to the multiple electrodes for operative association with selected, different regions of endocardial tissue within the heart,

a processing element coupled to the multiple electrodes and the roving second electrode for conditioning one of the multiple electrodes and the roving second electrode to emit a pacing signal and for conditioning the other one of the multiple electrodes and the roving second electrode to record paced electrograms occurring as a result of the pacing signal, and

means for processing the paced electrograms.

5. A system according to claim 4

wherein the multiple electrode array is shaded to assume a radially expanded position in operative association with the region of endocardial tissue.

6. A system according to claim 4

wherein the roving second electrode includes means for remote steering of the roving second electrode means.

7. A system for analyzing biopotential morphologies in myocardial tissue comprising

an array of multiple electrodes supported for operative association with a region of heart tissue,

a roving second electrode supported for movement relative to the multiple electrodes for operative association with selected, different regions of endocardial tissue within the heart, and

a processing element electrically coupled to the multiple electrodes the roving second electrode including

first means for conditioning the multiple electrodes to sense a sample of biopotentials occurring during a cardiac event of known diagnosis and for creating a template based upon the sensed biopotential sample,

second means for conditioning either one of the multiple electrodes or the roving second electrode to emit a pacing signal and to sense with the multiple electrodes a sample of the paced biopotentials occurring as a result of the pacing signal, and

third means for electronically comparing the paced biopotential sample to the template and generating an output based upon the comparison.

8. A system according to claim 7

wherein the output comprises a matching coefficient indicating how alike the paced biopotential sample is to the template.

9. A system according to claim 7

wherein the third means compares the paced biopotential sample to the template by matched filtering.

10. A system according to claim 7

wherein the third means compares the paced biopotential sample to the template by cross correlation.

11. A system according to claim 7

wherein the third means compares the paced biopotential sample to the template by deriving a norm of the difference.

12. A system according to claim 7

wherein the third means compares the paced biopotential sample to the template by using the template to create a matched filtered paced biopotential sample and by analyzing the symmetry of the matched filtered paced biopotential sample.

13. A system according to claim 7

wherein the sensed biopotential sample of the template comprises an electrogram of a first predetermined duration, and

wherein the sensed paced biopotential sample comprises an electrogram of a second predetermined duration not shorter than the first predetermined duration.

14. A system according to claim 13

wherein the first and second predetermined durations are equal.

15. A system according to claim 14

wherein the first and second predetermined durations comprise one heart beat.

16. A system according to claim 7

wherein the multiple electrode array is shaped to assume a radially expanded position in operative association with the region of endocardial tissue.

17. A system according to claim 7

wherein the roving second electrode includes means for remote steering of the roving second electrode means.

18. A method for examining heart tissue comprising the steps of

locating an array of multiple electrodes in operative association with a region of heart tissue,

moving a roving second electrode means relative to the multiple electrodes for operative association with selected, different regions of endocardial tissue within the heart and

conditioning one of the multiple electrodes and the roving second electrode means to emit a pacing signal and to record with the other one of the multiple electrodes and the roving second electrode means paced electrograms occurring as a result of the pacing signal.

19. A method according to claim 18

and further including the step of processing the paced electrograms.

20. A method for analyzing biopotential morphologies in myocardial tissue comprising the steps of

positioning an array of multiple electrodes in operative association with a region of heart tissue,

moving a roving second electrode means relative to the multiple electrodes for operative association with selected, different regions of endocardial tissue within the heart,

conditioning the multiple electrodes to sense a sample of biopotentials occurring during a cardiac event of known diagnosis and for creating a template based upon the sensed biopotential sample,

conditioning either one of the multiple electrodes or the roving second electrode means to emit a pacing signal and sensing with the multiple electrodes a sample of the paced biopotentials occurring as a result of the pacing signal,

electronically comparing the paced biopotential sample to the template and generating an output based upon the comparison.

21. A method according to claim 20

wherein the output comprises a matching coefficient indicating how alike the paced biopotential sample is to the template.

22. A method according to claim 20

wherein the paced biopotential sample is compared to the template by matched filtering.

23. A method according to claim 20

wherein the paced biopotential sample is compared to the template by cross correlation.

24. A method according to claim 20

wherein the paced biopotential sample is compared to the template by deriving a norm of the difference.

25. A method according to claim 20

wherein the comparison compares the paced biopotential sample to the template by using the input template to create a matched filtered paced biopotential sample and by analyzing the symmetry of the matched filtered biopotential sample.

Description Submit all comments and votes

FIELD OF THE INVENTION

The invention generally relates to systems and methods for pacing and mapping the heart for the diagnosis and treatment of cardiac conditions.

BACKGROUND OF THE INVENTION

Normal sinus rhythm of the heart begins with the sinoatrial node (or "SA node") generating a depolarization wave front. The impulse causes adjacent myocardial tissue cells in the atria to depolarize, which in turn causes adjacent myocardial tissue cells to depolarize. The depolarization propagates across the atria, causing the atria to contract and empty blood from the atria into the ventricles. The impulse is next delivered via the atrioventricular node (or "AV node") and the bundle of HIS (or "HIS bundle") to myocardial tissue cells of the ventricles. The depolarization of these cells propagates across the ventricles, causing the ventricles to contract.

This conduction system results in the described, organized sequence of myocardial contraction leading to a normal heartbeat.

Sometimes aberrant conductive pathways develop in heart tissue, which disrupt the normal path of depolarization events. For example, anatomical obstacles in the atria or ventricles can disrupt the normal propagation of electrical impulses. These anatomical obstacles (called "conduction blocks") can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called "reentry circuits," disrupt the normal activation of the atria or ventricles. As a further example, localized regions of ischemic myocardial tissue may propagate depolarization events slower than normal myocardial tissue. The ischemic region, also called a "slow conduction zone," creates errant, circular propagation patterns, called "circus motion." The circus motion also disrupts the normal depolarization patterns, thereby disrupting the normal contraction of heart tissue.

The aberrant conductive pathways create abnormal, irregular, and sometimes life-threatening heart rhythms, called arrhythmias. An arrhythmia can take place in the atria, for example, as in atrial tachycardia (AT) or atrial flutter (AF). The arrhythmia can also take place in the ventricle, for example, as in ventricular tachycardia (VT).

In treating arrhythmias, it is essential that the location of the sources of the aberrant pathways (call foci) be located. Once located, the tissue in the foci can be destroyed, or ablated, by heat, chemicals, or other means. Ablation can remove the aberrant conductive pathway, restoring normal myocardial contraction.

Today, physicians examine the propagation of electrical impulses in heart tissue to locate aberrant conductive pathways. The techniques used to analyze these pathways, commonly called "mapping," identify regions in the heart tissue, called foci, which can be ablated to treat the arrhythmia.

One form of conventional cardiac tissue mapping techniques uses multiple electrodes positioned in contact with epicardial heart tissue to obtain multiple electrograms. The physician stimulates myocardial tissue by introducing pacing signals and visually observes the morphologies of the electrograms recorded during pacing, which this Specification will refer to as "paced electrograms." The physician visually compares the patterns of paced electrograms to those previously recorded during an arrhythmia episode to locate tissue regions appropriate for ablation. These conventional mapping techniques require invasive open heart surgical techniques to position the electrodes on the epicardial surface of the heart.

Conventional epicardial electrogram processing techniques used for detecting local electrical events in heart tissue are often unable to interpret electrograms with multiple morphologies. Such electrograms are encountered, for example, when mapping a heart undergoing ventricular tachycardia (VT). For this and other reasons, consistently high correct foci identification rates (CIR) cannot be achieved with current multi-electrode mapping technologies.

Another form of conventional cardiac tissue mapping technique, called pace mapping, uses a roving electrode in a heart chamber for pacing the heart at various endocardial locations. In searching for the VT foci, the physician must visually compare all paced electrocardiograms (recorded by twelve lead body surface electrocardiograms (ECG's)) to those previously recorded during an induced VT. The physician must constantly relocate the roving electrode to a new location to systematically map the endocardium.

These techniques are complicated and time consuming. They require repeated manipulation and movement of the pacing electrodes. At the same time, they require the physician to visually assimilate and interpret the electrocardiograms.

Furthermore, artifacts caused by the pacing signals can distort the electrocardiograms. The pacing artifacts can mask the beginning of the Q-wave in the electrocardiogram. In body surface mapping, the morphology of the pacing artifact visually differs from the morphology of the electrocardiogram. A trained physician is therefore able to visually differentiate between a pacing artifact and the electrocardiogram morphology. This is not always the case in endocardial or epicardial mapping, in which there can be a very close similarity between the morphology of the pacing artifact and the bipolar electrogram morphology. Under the best conditions, the pacing artifact and electrogram complex are separated in time, and therefore can be distinguished from one another by a trained physician. Under other conditions, however, the presence of the pacing artifact can sometimes mask the entire bipolar electrogram. In addition, its likeness to the bipolar electrogram often makes it difficult or impossible for even a trained physician to detect the beginning of depolarization with accuracy.

There thus remains a real need for cardiac mapping and ablation systems and procedures that simplify the analysis of electrograms and the use of electrograms to locate appropriate arrhythmogenic foci.

SUMMARY OF THE INVENTION

A principal objective of the invention is to provide improved systems and methods to examine heart tissue morphology quickly and accurately.

One aspect of the invention provides systems and methods using an array of multiple electrodes supported for operative association with a region of heart tissue, in tandem with a roving second electrode supported for movement relative to the multiple electrodes for operative association with selected, different regions of endocardial tissue within the heart.

Another aspect of the invention provides an analog or digital processing element and method usable in association with the multiple electrodes and the roving electrode for conditioning one of the multiple electrodes and the roving electrode to emit a pacing signal, while the other one of the multiple electrodes and the roving electrode records paced electrograms occurring as a result of the pacing signal.

Yet another aspect of the invention provides a processing element and method that input a template of a cardiac event of known diagnosis sensed using an array of multiple electrodes supported for operative contact with a region of heart tissue. The processing element and method input a sample of a cardiac event acquired by pacing from the roving electrode in operative association with a region of endocardial tissue and sensed with the array of multiple electrodes. The processing element and method electronically compare the input sample to the input template and generate an output based upon the comparison. In a preferred embodiment, the output is a matching factor that aids the physician in locating potentially appropriate sites for ablation.

Other features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic view of a system, which embodies the features of the invention, for accessing a targeted tissue region in the body for diagnostic or therapeutic purposes;

FIG. 1B is a diagrammatic view of the system shown in FIG. 1A, with the inclusion of a roving pacing probe and additional features to aid the physician in conducting diagnosis and therapeutic techniques according to the invention;

FIG. 2 is an enlarged perspective view of a multiple-electrode structure used in association with the system shown in FIG. 1;

FIG. 3 is an enlarged view of an ablation probe usable in association with the system shown in FIGS. 1A and 1B;

FIG. 4A is a diagrammatic view of the process controller shown in FIGS. 1A and 1B, which locates by electrogram matching a site appropriate for ablation;

FIG. 4B is a schematic view of a slow conduction zone in myocardial tissue and the circular propagation patterns (called circus motion) it creates;

FIG. 5 is a flow chart showing a pattern matching technique that the process controller shown in FIG. 4A can employ for matching electr