['Historically, Q-wave myocardial infarction (MI) has been equated with transmural MI. This association have, however, recently been rejected. The endocardial extent of MI is another potential determinant of pathological Q waves, since the first part of the QRS complex where the Q wave appears reflects depolarization of subendocardial myocardium. Therefore, the aim of the present study was to test the hypothesis that endocardial extent of MI is more predictive of pathological Q waves than is MI transmurality and to investigate the relationship between QRS scoring of the ECG and MI characteristics.', 'Twenty-nine patients with reperfused first-time MI were prospectively enrolled. One week after admission, delayed contrast-enhanced magnetic resonance imaging (DE-MRI) was performed and 12-lead ECG was recorded. Size, transmurality and endocardial extent of MI were assessed by DE-MRI. Q waves were identified with Minnesota coding and electrocardiographic MI size was estimated by QRS scoring of the ECG.', 'There was a significant difference between patients with and without Q waves with regard to MI size (P = 0.03) and endocardial extent of MI (P = 0.01), but not to mean and maximum MI transmurality (P = 0.09 and P = 0.14). Endocardial extent was the only independent predictor of pathological Q waves. Endocardial extent of MI was most strongly correlated to QRS score (r = 0.86, P<0.001) of the MI variables tested.'] Is the endocardial extent of reperfused first-time myocardial infarction more predictive of pathologic Q waves than is infarct transmurality : a magnetic resonance imaging study?