Published Online
on January 14, 2002

A more recent version of this article appeared on February 19, 2002

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Submitted on September 24, 2001
Revised on December 11, 2001
Accepted on December 19, 2001

Effects of Selective Autonomic Blockade on T-Wave Alternans in Humans

Eric J. Rashba MD^*, Michael Cooklin MD, Karen MacMurdy MD, Neal Kavesh MD, Malcolm Kirk MD, Samantha Sarang RN, Robert W. Peters MD, Stephen R. Shorofsky MD, PhD, and Michael R. Gold MD, PhD

From the Division of Cardiology, Department of Medicine, University of Maryland at Baltimore.

^* To whom correspondence should be addressed. E-mail: erashba{at}medicine.umaryland.edu.

Background—T-wave alternans (TWA) is an important noninvasive measure of ventricular arrhythmia vulnerability. This study tested the hypothesis that the autonomic nervous system influences TWA measurement in high-risk subjects with coronary artery disease.

Methods and Results—T-wave alternans was measured in 60 patients with coronary artery disease, left ventricular dysfunction, and inducible sustained ventricular tachycardia during electrophysiological studies. All patients had TWA measured at baseline with atrial pacing at 100 bpm (600 ms), 109 bpm (550 ms), and 120 bpm (500 ms). After a 10-minute recovery period, TWA was measured again after sympathetic blockade (esmolol, n=20), parasympathetic blockade (atropine, n=20), or no intervention (control subjects, n=20). The prevalence of significant TWA was unchanged compared with baseline after atropine infusion and in the control group. In contrast, the amplitude of TWA in the vector magnitude lead was significantly reduced after esmolol infusion (P<0.001), and the number of positive TWA tests was reduced by 50% (70% versus 35%, P<0.05).

Conclusions—Our findings have important implications for the use of TWA to risk-stratify patients for life-threatening ventricular arrhythmias and provide a new potential mechanism for the reduction in sudden cardiac death conferred by ß-blockers among patients with coronary artery disease and congestive heart failure.

Key words: tachyarrhythmias • nervous system, sympathetic • electrophysiology

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