......................................................................

NJIT Mathematical Biology Seminar

Tuesday, March 4, 2008, 4:00pm
Cullimore Hall 611
New Jersey Institute of Technology

......................................................................

Termination and resetting of reentrant cardiac activity

Trine Krogh-Madsen

Division of Cardiology, Weill Mecial College of Cornell University

Implantable cardioverter defibrillators (ICDs) have become standard therapy for many patients at risk for reentrant ventricular tachycardias. By applying one or more series of suprathreshold stimuli, the antitachycardia pacing modality of ICDs successfully terminates ventricular tachycardia in about 90% of attempted trials. However, many aspects of why antitachycardia pacing is successful are unknown.

We conducted numerical simulations to investigate the dynamics of reentry termination, and have in particular studied situations where

(1) the stimulus site is located at some distance away from the reentrant loop, and

(2) the reentrant circuit is sufficiently short that a bifurcation to repolarization alternans occurs.

In the first case, we show that when applying a single stimulus there exists a critical distance below which termination of reentry occurs over a range of values for the timing of the stimulus. This behavior is in fact predicted by a discontinuous window in the phase resetting curve. Above this critical distance, however, termination of reentry due to a single stimulus is impossible.

In the second case, we found that reentry termination is very much facilitated when the ring size is such that there is alternans. The main determinant of the ability to terminate is the spatial gradient of recovery time that the induced waves encounter. Based on these findings, we propose novel algorithms for antitachycardia pacing.