Abstract 5690: Idiopathic Catecholamine-sensitive Epicardial Ventricular Tachycardia At The Crux Of The Heart
Idiopathic ventricular tachycardia (VT) has been described from the epicardial surface of the left ventricle (LV), usually near the summit of the LV in the outflow tract. Ablation of these VTs may be possible by delivery of energy within the coronary venous system or directly on the epicardial surface. We describe a distinct syndrome of focal epicardial VT induced by catecholamine infusion that arises from the crux of the heart. Among 340 cases of idiopathic VT referred for catheter ablation, 4 patients were identified with a clinical syndrome of catecholamine sensitive VT that was mapped to the epicardial surface at the crux of the heart. There were 3 males and 1 female (age 31–79 yrs, mean 58). VT was sustained in all patients and associated with syncope or near syncope in 3 of 4 pts. The LVEF was >0.55 in 3 pts and mildly depressed (0.45) in 1 pt. In all pts VT could be induced with programmed stimulation or burst pacing from the right ventricular apex but required the infusion of isoproterenol for induction in 3. The VT was very rapid with a mean cycle length of 264 msec. The surface ECG during VT demonstrated a left superior axis QRS morphology in all pts, with an abrupt precordial tansition from V1 to V2 in 3 pts and R waves across the precordium in one. The precordial maximal deflection index was > 0.55 in all pts (mean 0.67). The site of earliest activation during intracardiac mapping occurred at the crux of the heart with activation in the middle cardiac vein or proximal coronary sinus recorded 20 –50 msec (mean −38 msec) prior to the onset of the surface QRS. Catheter ablation with irrigated RF was attempted within the middle cardiac vein or proximal coronary sinus in all pts and was successful in 1. In 2 of 3 remaining pts, percutaneous epicardial RF ablation was attempted and was successful. Simultaneous coronary angiography demonstrated the site of earliest activation within 5–10 mm of the proximal posterior descending coronary artery (PDA). There was no acute narrowing of the PDA in any pt following ablation. Idiopathic VT may arise from the epicardial surface at the crux of the heart in close proximity to the PDA. This syndrome can result in very rapid, catecholamine sensitive VT, and may require careful attention to the PDA during ablation.