Variability of Holter Electrocardiographic Findings in Patients Fulfilling the Noninvasive MADIT Criteria. Multicenter Automatic Defibrillator Implantation Trial

In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the non-invasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF < or = 0.35. Patients with NSVT underwent programmed ventricular stimulation (PVS); patients were implanted with an ICD if sustained VT or VF was inducible. If NSVT was found in at least two recordings, the arrhythmia was defined as reproducible. In 28 (41%) of the 68 patients, NSVT was found in at least one recording. Seventeen patients revealed NSVT in the first, the remaining 11 in the second registration; no patient had NSVT only in the third Holter. Of the patients with NSVT, 50% had only one, 39% had two, and 11% had three positive recordings. Thus, reproducible NSVT was found in only 50% of the patients with NSVT. Predictors for reproducibility were LVEF > 0.27, NYHA Class I, absence of digitalis therapy, and > 2 NSVT per 24-hour period. Reproducible NSVT was not associated with risk factors such as elevated mean heart rate, reduced heart rate variability, late potentials, or inducibility of sustained VT during PVS. During 17 +/- 9 months of follow-up, seven (10%) patients experienced arrhythmic events: two without and five with previously documented NSVT. In the latter patients, first occurrence of NSVT was consistently in the first Holter; only two of them had reproducible NSVT. In postinfarction patients, the risk factor NSVT exhibits marked spontaneous variability, especially in those with a low number of NSVT per 24-hour period, LVEF < 0.27 or NYHA III, which limits its clinical value as a selection criterion for PVS. Reproducibility of NSVT itself does not seem to be an independent risk factor.