REPETITIVE MONOMORPHIC TACHYCARDIA FROM THE LEFT-VENTRICULAR OUTFLOW TRACT - ELECTROCARDIOGRAPHIC PATTERNS CONSISTENT WITH A LEFT-VENTRICULAR SITE OF ORIGIN

Objectives. This study sought to characterize the electrocardiographic patterns predictive of left ventricular sites of origin of repetitive monomorphic ventricular tachycardia (RMVT). Background. RMVT typicall y arises from the right ventricular outflow tract (RVOT) in patients w ithout structural heart disease. The incidence of left ventricular sit es of origin in this syndrome is unknown. Methods. Detailed endocardia l mapping of the RVOT was performed in 33 consecutive patients with RM VT during attempted radiofrequency ablation. Left ventricular mapping was also performed if pace maps obtained from the RVOT did not reprodu ce the configuration of the induced tachycardia. Results. Pace maps id entical in configuration to the induced tachycardia were obtained from the RVOT in 29 of 33 patients. Application of radiofrequency energy a t sites guided by pace mapping resulted in elimination of RMVT in 24 ( 83%) of 29 patients. In four patients (12%), pace maps obtained from t he RVOT did not match the induced tachycardia. All four patients had a QRS configuration during RMVT with precordial R wave transitions at o r before lead V-2. In two patients, RMVT was mapped to the mediosuperi or aspect of the mitral valve annulus, near the left fibrous trigone; catheter ablation at that site was successful in both. In two patients , RMVT was mapped to the basal aspect of the superior left ventricular septum. Catheter ablation was not attempted because His bundle deflec tions were recorded from this site during sinus rhythm. Conclusions. R MVT can arise from the outflow tract of both the right and left ventri cles. RMVTs with a precordial R wave transition at or before lead V, a re consistent with a left ventricular origin. (C)1997 by the American College of Cardiology.