(Circulation. 2002;105:837.)
© 2002 American Heart Association, Inc.
Clinical Investigation
and Reports
|
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; Michael R. Gold, MD, PhD
From the Division of Cardiology, Department of
Medicine, University of Maryland at Baltimore.
Correspondence to Eric J. Rashba, MD, University of Maryland Medical Center, Division of Cardiology, 22 S Greene St, Room N3W77, Baltimore, MD 21201. E-mail erashba@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