T wave alternans as a predictor of spontaneous ventricular tachycardia in a canine model of sudden cardiac death.
BACKGROUND
We recently developed an ambulatory canine model of spontaneous ventricular tachycardia (VT) and sudden cardiac death by creating myocardial infarction, complete AV block, and infusion of nerve growth factor to the left stellate ganglion. Whether or not T wave alternans is associated with the spontaneously occurring episodes of VT in our model was unclear.


RESULTS
Through intracardiac electrograms obtained from an implantable cardioverter defibrillator, we manually measured T wave amplitudes prior to VT and while the dogs were at rest (baseline, no VT). Of the 79 VT episodes analyzed, 28 (35.4%) exhibited repolarization alternans. In contrast, only 3 (4.7%) of 64 baseline data cases displayed alternans (P < 0.0001). The magnitude of T wave alternans for dogs that died of sudden cardiac death, dogs that did not die suddenly, and for the total 28 episodes that exhibited repolarization alternans were 4.8 +/- 2.8 mm, 4.9 +/- 3.5 mm, and 4.9 +/- 3.3 mm, respectively (P = NS). We also found the sensitivity, specificity, positive predictive value, negative predictive value, and relative risk of repolarization alternans in predicting VT to be 35.4%, 95.3%, 90.3%, 54.5%, and 1.98, respectively. The ventricular rate prior to VT (65 +/- 11 beats/min) was significantly higher than that at rest (49 +/- 12 beats/min; P < 0.0001).


CONCLUSIONS
T wave alternans often occurred immediately before the onset of VT in dogs with myocardial infarction, complete AV block, and nerve growth factor infusion to the left stellate ganglion. Increased sympathetic activity might be responsible for the occurrence of the T wave alternans.
Tsai
Jerome
J
Department of Medicine, Cedars-Sinai Medical Center, and University of California Los Angeles, 90048-1865, USA.
Cao
Ji-Min
JM
Zhou
Shengmei
S
Swissa
Moshe
M
Cates
Adam W
AW
Kenknight
Bruce H
BH
Chen
Lan S
LS
Karagueuzian
Hrayr S
HS
Chen
Peng-Sheng
PS
D000818:Animals; D016757:Death, Sudden, Cardiac; D017147:Defibrillators, Implantable; D004285:Dogs; D004562:Electrocardiography; D006352:Heart Ventricles / Q000503:physiopathology; D011237:Predictive Value of Tests; D018570:Risk Assessment; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology