Analysis of posterior mitral annular activation during entrainment and catheter ablation of mitral isthmus ventricular tachycardia using a coronary sinus catheter

A detailed analysis of the ventricular activation along the posterior aspec t of the mitral annulus was made using a multipolar catheter positioned in the coronary sinus in a patient with mitral isthmus ventricular tachycardia (VT) associated with a remote inferior myocardial infarction and prior cry osurgical ablation for the elimination of a different preexisting VT. A cha nge in the timing and sequence of the ventricular activation along the isth mus could be observed during induction of the VT and entrainment pacing. A radiofrequency (RF) current application directed at the posterolateral regi on of the isthmus successfully eliminated this tachycardia. During the RF d elivery, complete conduction block was confirmed by a sudden change in the activation sequence during sinus rhythm.