Correlation of pathologic Q waves on the standard electrocardiogram and the epicardial electrogram of the human heart.

Abstract

To evaluate the relationship between abnormal Q waves on the standard ECG and localized ventricular excitation, unipolar epicardial electrograms were recorded over the left ventricle during aortocoronary bypass surgery in 36 patients. Of 20 without standard ECG Q waves, 6 had abnormal epicardial Q waves, 3 anteriorly and 3 inferiorly. Of 16 patients with standard ECG Q waves, 4 had both precordial and anterior epicardial Q waves while 7 had Q waves in leads III and aVF and inferior epicardial Q waves. Three of the 14 had Q waves in both precordial and inferior leads of the ECG but epicardial Q waves only from the antero-apical region in 2 and only from the inferior wall in 1. Two patients with Q waves in both III and aVF had no epicardial Q waves. The standard electrocardiogram apparently underestimates epicardial Q waves. If Q waves are present in the standard ECG, they correlate with the presence, although not invariably the location of Q waves on the epicardial electrogram.