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 r
eentrant tachycardia. The presence of a septal Q wave could be used to excl
ude minimal preexcitation with a high degree of reliability in both patient
s and controls before and after radiofrequency ablation.