Lack of prognostic implications of spontaneously occurring or stimulation induced atrial tachyarrhythmias in patients with dilated cardiomyopathy.

A prospective study was undertaken in 102 patients with idiopathic dilated cardiomyopathy to assess the significance of spontaneous and inducible atrial tachyarrhythmias (ATA). Twenty-six patients were in chronic atrial fibrillation (group I) and 76 patients were in sinus rhythm (group II); 14 patients in group II had a clinical history of ATA or episodes of ATA during Holter monitoring. An electrophysiological study was systematically performed. Programmed atrial stimulation was carried out in group II, and used up to two atrial premature stimuli from the right atrium at 2 cycle lengths (sinus cycle length--10%, 600 ms) and then one atrial extrastimulus under infusion of 1 to 4 micrograms. min-1 of isoproterenol. Programmed ventricular stimulation was performed in groups I and II. Sustained atrial tachyarrhythmia (ATA) was induced in 33 patients in group II (42%); isoproterenol infusion facilitated the induction of ATA in only one other patient, who had exercise-related ATA. Eleven patients in group II with spontaneous ATA had inducible sustained ATA. The sensitivity of programmed atrial stimulation to reproduce an ATA was 78.5% and its specificity 64.5%. Inducible ATA was related to a shorter atrial effective refractory period (209 +/- 25 ms vs 228 +/- 32, P less than 0.02). Inducible and spontaneous ATAs were related to older age but not to the existence of spontaneous or inducible ventricular tachycardia; they did not have prognostic significance: the left ventricular ejection fraction and the prognosis were similar in patients with spontaneous or inducible ATA and those without ATA.(ABSTRACT TRUNCATED AT 250 WORDS)