CARDIAC DENERVATION AFTER RADIOFREQUENCY ABLATION OF SUPRAVENTRICULARTACHYCARDIAS

Inappropriate sinus tachycardia and atrial arrhythmias have been repor ted after radiofrequency ablation. Previous studies have suggested tha t cardiac denervation is a possible explanation for these rhythm distu rbances. The aim of this study was to investigate possible alterations in autonomic innervation of the heart after ablation using the techni ques of heart rate variability (HRV) analysis and metaiodobenzylguanid ine (I-123 MIBG) scintigraphy. The subjects of this study were 30 cons ecutive patients aged 25 to 40 years, without structural heart disease , who underwent radiofrequency ablation of atrioventricular nodal slow pathways, and posteroseptal and left lateral accessory pathways becau se of symptomatic recurrent reentrant tachycardias. Time and frequency domain analysis of HRV after ablation revealed a significant reductio n in the indexes of the mean of all 5-minute standard deviation of RR intervals (p = 0.042), low frequency (p = 0.0005), and total frequency (p = 0.008) compared with preablation values in the group of patients who underwent atrioventricular nodal slow pathway ablation. Patients who underwent ablation of a posteroseptal accessory pathway also had s ignificant attenuation of the indexes of standard deviation about the mean RR interval (p = 0.03), standard deviation of 5-minute mean RR in tervals (p = 0.006), and low-frequency (p <0.0001)land high-frequency (p <0.0001) components. Significant I-123 MIBG map defects, indicating efferent cardiac sympathetic denervation, were also found in the same groups of patients: atrioventricular nodal group (p = 0.0024), poster oseptal accessory pathway group (p = 0.0007). None of the above change s in HRV and 123-I MIBG scintigraphy were seen in patients who underwe nt ablation of left lateral accessory pathways. We conclude that radio frequency ablation in the anterior, mid-, and posterior regions of the low intraatrial septum may disrupt sympathetic fibers located in thes e regions, causing cardiac sympathetic denervation. The density of the se fibers appear to be less along the left atrioventricular groove. (C ) 1998 by Excerpta Medica, Inc.