Diagnostic value of Q-waves in inferior myocardial infarction

Forty-eight patients with proved, healed, inferior myocardial infarction were studied to determine the electrocardiographic characteristics of this syndrome, the correlation between electrocardiographic abnormalities and angiographic findings, and to determine the value of recording Lead III during inspiration to identify abnormal Q-waves.The diagnosis of inferior myocardial infarction (IMI) was established by the presence of two of the following three criteria: (1) past history of acute infarction, associated with typical acute electrocardiographic changes and compatible clinical data, (2) total occlusion or more than 80 per cent occlusion of the right coronary artery, and (3) contraction abnormalities of the inferior left ventricular wall.Fifteen per cent of patients with inferior myocardial infarction had diagnostic Q-waves in all the three limb Leads II, III, and aV_F, and 29 per cent of patients had no diagnostic Q-waves in any of the three limb leads. Relative frequency of diagnostic Q-waves in inferior myocardial infarction were found to be 70, 43, and 15 per cent in Leads III, aV_F, and II, respectively.One hundred per cent correlation was noted between left ventricular inferior wall asynergy and presence of diagnostic Q-waves in all the limb Leads II, III, and aV_F, but the correlation was low (54 per cent) when none of the limb Leads II, III, and aV_F revealed diagnostic Q-waves.Obtaining Lead III in deep inspiration to differentiate an abnormal Q-wave due to inferior myocardial infarction from a benign Q-wave was not found to be a reliable measure and could result in false-negative diagnosis of inferior myocardial infarction in a significant number of patients.