Defibillator electrogram T wave alternans as a predictor of spontaneous ventricular tachyarrhythmias in defibrillator recipients

BACKGROUND: Although T wave alternans (TWA) and the T wave peak-to-end (Tpte) interval are associated with vulnerability to ventricular tachyarrhythmia (VT), no previous reports have demonstrated that TWA immediately precedes spontaneous VT in the human ambulatory setting. METHODS AND RESULTS: Stored electrograms from the implantable cardioverter defibrillators (ICD) of 74 patients (59 males, 55.3+/-12.2 years) were analyzed. TWA (DeltaT amplitude), Tpte interval, QT interval, and RR intervals were measured from magnified digital images immediately before spontaneous VT (VT(Clinical); n=73), or immediately after ICD shocks during artificially-induced VT (VT(Induced); n=74) or inappropriate shocks (Shock(Inapp); n=6). (1) TWA was significantly greater in VT(Clinical) than VT(Induced) (P<0.01) or Shock(Inapp) (P<0.001), but Tpte was not (P=NS). (2) In the VT(Clinical) group, TWA was significantly greater in patients with ischemic VT than in those with non-ischemic cardiomyopathy or idiopathic VF (P<0.05). (3) In the same patient, the TWA for VT(Clinical) was significantly greater than that for VT(Induced) (P