Analysis of the extension of Q-waves after infarction with body surface map: relationship with infarct size

We aimed to characterize the extension of Q-waves after a first ST-segment elevation myocardial infarction using body surface map (BSM) and its relationship with infarct size quantified with cardiovascular magnetic resonance imaging (CMR).

Thirty-five patients were studied 6 months after a first ST-segment elevation myocardial infarction (23 anterior, 12 inferior). All cases had single-vessel disease and an open artery. The extension of Q-waves was analyzed by means of a 64-lead BSM. Infarct size was quantified with CMR. Absence of Q-waves in BSM was observed in 5 patients (14%), 2 of whom (40%) had >1 segment with transmural necrosis. Absence of Q-waves in 12-lead ECG was observed in 8 patients (23%), 7 of whom (87%) had >1 segment with transmural necrosis. Patients with inferior infarctions (n=12, 34%) showed a larger number of Q-waves in BSM (18+/-7.1 leads) than patients with anterior infarctions (n=23, 66%; 3.7+/-3.6 leads; p<0.0001). When the study group was analysed as a whole, the total number of Q-waves detected in BSM did not correlate with the number of necrotic segments (r=0.15; p=0.4). In anterior infarctions, a number of Q-waves >median (2 leads) was related to a higher number of necrotic segments (5.1+/-2.4 vs. 2+/-2.2 segments; p=0.004). The same was observed in inferior infarctions (median 20 leads: 3.5+/-1.9 vs. 1.2+/-1.2 segments; p=0.03).

In a stable phase after a first ST-segment elevation myocardial infarction, absence of Q-waves does not mean non-transmural necrosis. Using BSM, extension of Q-waves is much higher in inferior infarctions; a separate analysis depending on infarct location is necessary. A major BSM-derived extension of Q-waves is related to larger infarct size both in anterior and in inferior infarctions.