All ETDs from UAB

Advisory Committee Chair

Andrew E Pollard

Advisory Committee Members

Raymond E Ideker

Jack M Rogers

William M Smith

Gregory P Walcott

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) School of Engineering


Implantable cardioverter defibrillators can terminate accelerated heart rhythms with either high energy shocks or antitachycardia pacing. Shocks are highly effective, but they reduce the quality of life in patients that receive them. Antitachycardia pacing is a train of pulses administered at a rate slightly faster than the arrhythmia rate. These pulses are low energy, and terminate ventricular tachycardia in patients without causing pain. The paced wavefronts penetrate the reentrant circuit, and interact with the underlying reentrant wavefront to block all arrhythmic activity. Currently, these interactions between paced wavefronts and reentrant wavefronts are not well understood. A better understanding of these interactions could lead to improvements in the therapy such that high energy shocks could be avoided. For this purpose, I investigated antitachycardia pacing in a computer simulation of rabbit ventricles, and in an isolated rabbit heart preparation. In both studies a train of pulses was applied during stable anatomic reentry. The modeling study showed that termination required block of the paced wavefront that traveled behind the reentrant wavefront. When this requirement was not met, the arrhythmia was either reset, or destabilized and pushed off of its anatomic anchor. These responses were also observed and confirmed in the isolated rabbit heart preparation. Additionally, the heart preparation supported responses in which the arrhythmia was destabilized, but the new destabilized arrhythmia terminated on the anatomic borders some time after the final pulse in the train. Detailed analysis of these delayed termination responses revealed temporal characteristics very similar to those during delayed termination in patients with implantable cardioverter defibrillators. This suggests that pacing induced shifts of stable anatomic VT to polymorphic VT could be i the mechanism of delayed termination in patients.

Included in

Engineering Commons



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