Catheter Ablation in the Canine Coronary Sinus Using Radiofrequency Energy

This study was performed to evaluate the effects of radiofrequency catheter ablation in the coronary sinus as a potential means of eliminating conduction over left‐sided accessory pathways in humans. Radiofrequency current at a frequency of 500 kHz was delivered by electrode catheter to two sites in the coronary sinus of each often dogs. Left coronary arteriography with venous phase visualization of the coronary sinus was performed before, immediately after, and 2 weeks following ablation. Unipolar electrograms from the ablating electrode were recorded before and immediately after ablation. Coronary arteriography revealed no evidence of damage to the adjacent left circumflex coronary artery or its branches as a result of ablation. Contrast visualization of the coronary sinus showed persistent contrast staining following ablation at two of the ablated sites. Angiographically apparent stenosis of the coronary sinus was seen both acutely and chronically in two cases. Unipolar electrogram recordings from the ablating electrode showed an increase in atrial repolarization voltage (atrial current of injury) of 1.53 ± 1.03 mV (P = 0.00004), and an increase in ventricular repolarization voltage of 0.73 ± 0.84 mV (P = 0.005). There was a 23% decrease in amplitude of atrial electrograms (P = 0.006) and a 7% decrease in amplitude of ventricular electrograms (P = 0.02) recorded from the ablating electrode following ablation. Lesions could be identified grossly and microscopically at 16 of the 20 ablated sites. Perforation of the coronary sinus did not occur. Microscopical observation showed normal healing with granulation tissue and fat necrosis extending outward from the coronary sinus involving the atrial epicardium in 13 lesions, the ventricular epicardium in 5 lesions, and the adventitia of the left circumflex coronary artery in 5 lesions. No medial or intimal involvement of the coronary artery was seen. The coronary sinus itself showed luminal organized thrombus in 4 lesions, with near occlusion of the lumen in 1 case. Radiofrequency ablation in the coronary sinus thus results in lesions of a size and extent that would be expected to successfully ablate some left‐sided accessory pathways if delivered in humans. Monitoring of the unipolar electrogram provides insight into the extent of injury during ablation. In some cases, thrombosis of the coronary sinus occurs, the long‐term effects of which are not known.