The Presence of a Q Wave in Lead V5 Excludes Manifest Preexcitation

Background The degree of preexcitation in patients with the Wolff‐Parkinson‐White syndrome may vary depending on autonomic tone, heart rate, pathway location, and atrioventricular node conduction. When subtle, preexcitation may be difficult to detect with a 12‐lead electrocardiogram (ECG). Furthermore, the pattern of preexcitation may be mimicked in patients with QRS widening and rapid atrioventricular node conduction. Methods We studied 50 patients with manifest accessory pathways who underwent electrophys‐iological study and pathway ablation. Pre‐ and postablation ECGs for the presence or absence of a Q wave in leads V 5 and V 6 were studied. ECGs from an additional 19 patients were used to validate the observations. Results We found that no patient with preexcitation had a Q wave in lead V 5 and only 1 of 50 patients had a Q wave in V 6 . This was a reproducible finding in the 26 patients with multiple ECGs obtained on separate days. The results were validated in an additional 19 patients none of whom had a Q wave in V 5 , and 1 had a Q wave in V 6 . Conclusions The presence of a Q wave in lead V 5 reliably excludes manifest preexcitation.