"Atypical" posteroseptal accessory pathway in Wolff-Parkinson-White syndrome.
The posteroseptal accessory pathway in the Wolff-Parkinson-White syndrome is associated with a delta wave that is negative in the inferior electrocardiographic (ECG) leads and the occurrence of the earliest retrograde atrial activation near the orifice of the coronary sinus during atrioventricular (AV) reentrant tachycardia. Seventy-two patients with a posteroseptal accessory pathway underwent epicardial mapping before operative ablation. The earliest epicardial activation occurred at the posterosuperior process of the left ventricle in all patients. Dissection of the posteroseptal region (right atrial-left ventricular sulcus) resulted in permanent loss of preexcitation in 69 patients and failure to abolish preexcitation permanently in 3. At reoperation in two patients, preexcitation was abolished by discrete cryoablation of the left side of the interatrial septum near the AV node approached through the atrial septum in the normothermic beating heart. At reoperation, one patient had extensive AV node dissection. All patients have had permanent loss of preexcitation. The vast majority of posteroseptal accessory pathways ("typical") are epicardial and ablated by dissection of the posteroseptal region. Rarely, posteroseptal accessory pathways are "atypical" in that they are intraseptally located near the AV node on the left atrial endocardial surface.