Reply to the Editor— The site of origin of the ventricular premature beat in a patient with 2 different P-wave morphologies

I welcome the letter of Drs Alizadeh and Keikhavani concerning the ventricular premature beat (VPB) in our recent article because it gives attention to our ability to locate ectopic ventricular rhythms by giving a close look at their QRS configuration. This is an increasingly important topic in relation to treatment by catheter ablation. While discussing the site of origin of the VPB in relation to QRS configuration, they refer to publications by the clinical electrophysiology group from Birmingham, AL, that contributed extensively to that issue. Two publications are mentioned (references 2 and 3 in their letter) about QRS characteristics favoring a left interventricular septal origin adjacent to the His bundle. I prefer a right ventricular origin on the basis of the following findings: the left bundle branch block QRS configuration; the frontal QRS axis of 0° with a negative QS complex in lead III, and a markedly positive R wave in lead aVL. This is an unlikely axis for impulse formation close to the His bundle, where an intermediate frontal QRS axis is expected. Also, the QS configuration, without initial positivity in lead V₁, does not support a left septal origin. Both the frontal plane QRS axis and the transition from a QS complex in lead V₁ to an R wave in lead V₂ during the VPB reminds one of the delta wave characteristics in a right posteroseptal accessory pathway—findings, in my opinion, supporting a posterior right ventricular origin close to the interventricular septum.