Closed Chest Radiofrequency Ablation of the Sinoatrial Node in Dogs

Transcatheter ablation of the sinoatrial node with radiofrequency energy (0.6 MHZ, 2.5–5 watts) was performed in 10 dogs under fluoroscopic monitoring and autonomic blockade. Sinus function was previously studied in terms of cycle length, recovery time and atrial activation pattern by catheter mapping. Several discharges (8–22) were applied for variable periods of time (maximum 1 minute). Sinus tachycardia and/or sinus arrest during ablation confirmed correct catheter position. Sinus rhythm was abolished in eight dogs. The ectopic rhythm was atrial in six and AV nodal in two dogs. Ectopic atrial cycle length and recovery time were longer than the baseline sinus values: 724 ± 321 versus 509 ± 147, P < 0.05; 1103 ± 775 versus 638 ± 151, P < 0.05 (values in msec). The study was repeated 10–14 days later in six dogs; three maintained the same atrial rhythm, one persisted in sinus rhythm, and one dog changed from atrial to sinus rhythm, whereas another changed from sinus to atrial rhythm. Gross findings revealed transmural lesions in all dogs, without perforation. Histology in chronic dogs showed sinus cell necrosis and its replacement by granulation tissue. In conclusion: sinus function may be abolished by closed chest radiofrequency ablation.