Block of the mitral-pulmonary isthmus during ablation of a single left-sided accessory pathway causing different patterns of retrograde atrial activation.

The case of a 16-year-old patient with atrioventricular tachycardia caused by a single left anterolateral accessory pathway is reported. When the patient underwent radiofrequency ablation, a lesion on the mitral annulus lateral wall produced changes in the retrograde atrial activation pattern determined by that pathway; changes ranged from a delay in depolarization of the annulus posterior portions to full left atrium counterclockwise activation. Such phenomena were probably caused by a block in the isthmus between the annulus and the lower left pulmonary vein ostium.

Ventricular resynchronization through biventricular cardiac pacing for the treatment of refractory heart failure in dilated cardiomyopathy.

Objective: The biventricular pacing (BVP) approach has good results in the treatment of congestive heart failure (CHF) in patients (pts) with disorders of intraventricular conduction.

Methods: We have applied BVP to 28 pts, with left ventricular pacing using minitoracotomy in 3 pts and the transvenous approach via coronary sinus in 25 pts. The mean duration of the QRS complexes was 187 ms, in the presence of the left branch block in 22 pts, and right branch block + divisional hemiblock in 6 pts.