Sympathetic predominance of cardiac autonomic regulation in patients with left free wall accessory pathway and orthodromic atrioventricular reentrant tachycardia.

AIMS The aim of this study was to compare cardiac autonomic regulation in patients with a history of paroxysmal supraventricular tachyarrhythmias, such as atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia, and healthy controls. METHODS AND RESULTS Seventeen patients with paroxysmal atrioventricular nodal reentrant tachycardia (atrioventricular nodal reentrant tachycardia group), 14 patients with overt preexcitation and paroxysmal atrioventricular reentrant tachycardia caused by a left free wall accessory pathway (atrioventricular reentrant tachycardia group) and 14 healthy control subjects, were studied. The patients and the controls were age and gender matched. Cardiac autonomic regulation was assessed by means of frequency domain analysis of heart rate variability at rest, during head-up tilt, active standing, treadmill exercise and after exercise. The high frequency component (0.15-0.5 Hz) of heart rate variability tended to be lower and the low frequency component (0.04-0.15 Hz) tended to be higher among the atrioventricular reentrant tachycardia patients than in atrioventricular nodal reentrant tachycardia patients and controls. The difference reached statistical significance at rest (P < 0.05) and during standing (P < 0.05 atrioventricular reentrant tachycardia vs atrioventricular nodal reentrant tachycardia and P < 0.01 atrioventricular reentrant tachycardia vs controls). Accordingly, the low-to-high frequency ratio--the marker of cardiac sympathetic regulation--was higher in atrioventricular reentrant tachycardia patients than in atrioventricular nodal reentrant tachycardia patients (P < 0.05 at rest and during standing) and controls (P < 0.01 during standing). CONCLUSION The cardiac autonomic status in atrioventricular reentrant tachycardia patients was suggestive of a higher sympathetic tone than in atrioventricular nodal reentrant tachycardia patients or healthy controls. This may be related to inhomogeneous ventricular activation in the presence of antegrade conduction via the accessory atrioventricular pathway.