Chasing Red Herrings
Making Sense of the Colors While Mapping
A 50-year-old man presented with sustained wide complex tachycardia and was treated with cardioversion. He gave a history of 2 such episodes within the past 7 years, requiring cardioversion each time. Ten years previously, he had undergone surgical repair of tetralogy of Fallot. Review of operative notes indicated that the procedure included patch closure of the ventricular septal defect, right ventricular outflow tract resection, repair with a transannular patch, and pulmonary valve replacement with a porcine valve.
Editor’s Perspective see p 557
ECG recorded during the tachycardia showed a regular wide complex tachycardia at a rate of 240 beats per minute of left bundle branch block morphology with left axis deviation. ECG in sinus rhythm showed PR interval of 200 ms, right bundle branch block with normal axis, and QRS duration of 170 ms. Echocardiography showed mild right ventricular dilatation with normal left and right ventricular function. The ventricular septum was intact, there was no pulmonary regurgitation, and the peak gradient across the pulmonary valve was 32 mm Hg.
Mapping was performed using an electroanatomic system (CARTO 3, Biosense Webster, Diamond Bar, CA). Wide complex tachycardia at a cycle length of 260 ms with the same morphology as the clinical tachycardia was induced during catheter placement and could not be pace terminated. ventriculo-atrial dissociation and negative His-ventricular interval confirmed ventricular tachycardia. Surface ECG was used …