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Talk Abstract
Seminar on Industrial Problems
Exploring the Mechanisms of Cardiac Defibrillation Via Mathematical Modeling
March 19, 1999

Presented by:

Matthew G. Fishler
Staff Scientist
St. Jude Medical, Inc.
Cardiac Rhythm Management Division

Talk and refreshments will be in Lind Hall Seminar Room at 10:10 am.

The heart utilizes biochemically-generated electrical currents to directly control its mechanical function. Normally, this electrical activity is regular and orderly as it propagates through the heart, thereby generating the strong and coordinated mechanical action required to pump blood through the body (and especially to the brain). Occasionally, however, this electrical pattern is disrupted and transformed into a persistent and uncoordinated electrical "storm" called fibrillation. Without external intervention, fibrillation is fatal. Cardiac defibrillation is the process by which a strong electric shock is delivered to the heart in order to terminate fibrillation and return the heart to its normal life-sustaining rhythm.

Despite the clear clinical benefits of defibrillation, there are several facets of the defibrillation process which remain unexplained or poorly understood. Beyond the inherent basic science aspect, it is anticipated that unraveling these mysteries might lead to subsequent improvements in the efficiency and/or efficacy of defibrillation. To this end, mathematical modeling of cardiac tissue and shock/tissue interactions has been a valuable tool for formulating and testing hypotheses regarding various mechanisms of defibrillation, as well as for gaining insights into the defibrillation process that are unattainable via other modalities. This talk will first present an overview of cardiac defibrillation and the several approaches for modeling various aspects of the shock/tissue interaction. This will be followed by a more in-depth treatment of one particular open question of defibrillation (how does a shock defibrillate the bulk myocardium?) and how modeling has been instrumental in exploring this question. Finally, additional open questions regarding cardiac defibrillation and which are amenable to mathematical modeling will be summarized.

Movie of Fribrillation (4.4M)

Slide Presentation

Table of Contents

Exploring the Mechanisms of Cardiac Defibrillation Via Mathematical Modeling

St. Jude Medical, Inc.

Transvenous Defibrillation

Defibrillation Research

Modeling Defibrillation Research Question

Modeling Defibrillation One-Dimensional Cable Example

Modeling Defibrillation One-Dimensional Cable Example

Modeling Cardiac Tissue One-Dimensional Cable Analysis

Modeling Cardiac Tissue Generalized Bidomain Equations

Modeling Cardiac Tissue Generalized Bidomain Equations

Modeling Cardiac Tissue Choosing a Solution Technique

Modeling Cardiac Tissue Bidomain Hybrid Simulation Engine

Modeling Defibrillation Insite via Generalized Activating Function

Modeling Defibrillation Mechanisms of Far-Field Excitation

Syncytial Heterogeneities Definition

Syncytial Heterogeneities Research Questions

Syncytial Heterogeneities Simple & Compound Heterogeneities

Syncytial Heterogeneities Simulation Results

Syncytial Heterogeneities Results: Diastolic Thresholds

Syncytial Heterogeneities Results: Diastolic Strength-Duration Curves

Syncytial Heterogeneities Results: Strength-Interval Curves

Syncytial Heterogeneities Conclusions

Syncytial Heterogeneities Future Work

Future of Cardiac Modeling