T wave alternans during exercise and atrial pacing in humans.
BACKGROUND
Evidence is accumulating that microvolt T wave alternans (TWA) is a marker of increased risk for ventricular tachyarrhythmias. Initially, atrial pacing was used to elevate heart rate and elicit TWA. More recently, a noninvasive approach has been developed that elevates heart rate using exercise.


RESULTS
In 30 consecutive patients with a history of ventricular tachyarrhythmias, the spectral method was used to detect TWA during both atrial pacing and submaximal exercise testing. The concordance rate for the presence or absence of TWA using the two measurement methods was 84%. There was a patient-specific heart rate threshold for the detection of TWA that averaged 100 +/- 14 beats/min during exercise compared with 97 +/- 9 beats/min during right atrial pacing (P = NS). Beyond this threshold, there was a significant and comparable increase in level of TWA with decreasing pacing cycle length and increasing exercise heart rates.


CONCLUSIONS
The present study is the first to demonstrate that microvolt TWA can be assessed reliably and noninvasively during exercise stress. There is a patient-specific heart rate threshold beyond which TWA continues to increase with increasing heart rates. Heart rate thresholds for the onset of TWA measured during atrial pacing and exercise stress were comparable, indicating that heart rate alone appears to be the main factor of determining the onset of TWA during submaximal exercise stress.
Hohnloser
S H
SH
Department of Cardiology, J.W. Goethe University, Frankfurt, Germany.
Klingenheben
T
T
Zabel
M
M
Li
Y G
YG
Albrecht
P
P
Cohen
R J
RJ
D000328:Adult; D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods; D003327:Coronary Disease / Q000503:physiopathology; D005080:Exercise Test / Q000379:methods; D005240:Feasibility Studies; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000503:physiopathology