SYMPATHETIC PREDOMINANCE OF CARDIAC AUTONOMIC REGULATION IN PATIENTS WITH LEFT FREE-WALL ACCESSORY PATHWAY AND ORTHODROMIC ATRIOVENTRICULARREENTRANT TACHYCARDIA

Aims The aim of this study was to compare cardiac autonomic regulation in patients with a history of paroxysmal supraventricular tachyarrhyt hmias, such as atrioventricular nodal reentrant tachycardia and atriov entricular reentrant tachycardia, and healthy controls. Methods and Re sults Seventeen patients with paroxysmal atrioventricular nodal reentr ant tachycardia (atrioventricular nodal reentrant tachycardia group), 14 patients with overt preexcitation and paroxysmal atrioventricular r eentrant tachycardia caused by a left free wall accessory pathway (atr ioventricular reentrant tachycardia group) and 14 healthy control subj ects, were studied. The patients and the controls were age and gender matched. Cardiac autonomic regulation was assessed by means of frequen cy domain analysis of heart rate variability at rest, during head-up t ilt, 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 h igher among the atrioventricular reentrant tachycardia patients than i n atrioventricular nodal reentrant tachycardia patients and controls. The difference reached statistical significance at rest (P<0.05) and d uring standing (P<0.05 atrioventricular reentrant tachycardia vs atrio ventricular nodal reentrant tachycardia and P<0.01 atrioventricular re entrant tachycardia vs controls). Accordingly, the low-to-high frequen cy ratio - the marker of cardiac sympathetic regulation - was higher i n atrioventricular reentrant tachycardia patients than in atrioventric ular nodal reentrant tachycardia patients (P<0.05 at rest and during s tanding) and controls (P<0.01 during standing). Conclusion The cardiac autonomic status in atrioventricular reentrant tachycardia patients w as suggestive of a higher sympathetic tone than in atrioventricular no dal reentrant tachycardia patients or healthy controls. This may be re lated to inhomogeneous ventricular activation in the presence of anteg rade conduction via the accessory atrioventricular pathway.