Septal Q waves in surface electrocardiographic lead V6 exclude minimal ventricular preexcitation.

Electrocardiograms of 37 consecutive patients with minimal preexcitation (i.e., PR >120 ms, QRS <120 ms) were compared before and after ablation with electrocardiograms of 37 age-matched patients with atrioventricular nodal reentrant tachycardia. The presence of a septal Q wave could be used to exclude minimal preexcitation with a high degree of reliability in both patients and controls before and after radiofrequency ablation.