Background: Positive Turbulence onset (TO) after atrial premature complexes (APCs) was found temporally related to spontaneous episodes of atrial fibrillation. This study tested the hypothesis that heart rate turbulence (HRT) after APCs is influenced by APC prematurity independently of the prematurity of conducted ventricular complexes.
Methods: We studied 33 patients (mean age = 58 +/- 16 years, 19 men), 11 of whom had structural heart disease, who were referred for electrophysiological studies of supraventricular or ventricular arrhythmias. Sequences of single right atrial extrastimuli were delivered with coupling intervals adjusted to reach 60% prematurity of conducted ventricular complexes. Descriptors of HRT were compared between patients with slow versus fast atrioventricular (AV) conduction of APCs.
Results: The early RR interval dynamics after APCs was prominently modulated by the suppression of sinus node automaticity by the direct effect of APCs. This effect was significantly greater after earlier APCs with longer AV conduction times than after later coupled APCs with shorter AV conduction times.
Conclusions: The early phase of HRT is strongly influenced by the coupling interval of APCs, independently of the prematurity of conducted ventricular complexes. Consequently, the more positive TO preceding spontaneous atrial fibrillation episodes might be an epiphenomenon of incidental short-coupled APCs with delayed AV conduction, likely to trigger atrial fibrillation.