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
mfishler@ventritex.com

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 DefibrillationResearch Question Modeling Defibrillation One-Dimensional Cable Example Modeling Defibrillation One-Dimensional Cable Example Modeling Cardiac TissueOne-Dimensional Cable Analysis Modeling Cardiac TissueGeneralized Bidomain Equations Modeling Cardiac TissueGeneralized Bidomain Equations Modeling Cardiac TissueChoosing a Solution Technique Modeling Cardiac TissueBidomain Hybrid Simulation Engine Modeling DefibrillationInsite via Generalized Activating Function Modeling DefibrillationMechanisms of Far-Field Excitation Syncytial HeterogeneitiesDefinition Syncytial HeterogeneitiesResearch Questions Syncytial HeterogeneitiesSimple & Compound Heterogeneities Syncytial HeterogeneitiesSimulation Results Syncytial HeterogeneitiesResults: Diastolic Thresholds Syncytial HeterogeneitiesResults: Diastolic Strength-Duration Curves Syncytial HeterogeneitiesResults: Strength-Interval Curves Syncytial HeterogeneitiesConclusions Syncytial HeterogeneitiesFuture Work Future of Cardiac Modeling

 

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