Signal-averaged electrocardiography in survivors of first acute myocardial infarction: a pre-hospital discharge study.

ABSTRACT

Ninety one consecutive survivors of a first acute myocardial infarction (MI) were studied prior to hospital discharge, in order to observe the relationship of signal-averaged electrocardiography (SAECG) to thrombolytic therapy, site of infarction and left ventricular function. Sixty six patients received thrombolytic agents and the remaining had conventional therapy. The overall incidence of abnormal SAECG was 27 percent and 16 percent with high-pass 40 Hz and 25 Hz filters respectively. The SAECG (40Hz) was abnormal in 12 of 25 patients (48%) who did not receive thrombolytic therapy and in 13 of 66 (20%) who were thrombolysed (p < 0.01). When patients were classified according to the site of myocardial infarction, 6 out of 10 patients (60%) with anterior MI who were not thrombolysed had abnormal SAECG as compared to 10 of 51(20%) who received this treatment (p < 0.01), with no significant difference among inferior myocardial infarction patients. The mean (+/- SEM) ejection fraction (EF%) of anterior myocardial infarction patients was 31 +/- 3 percent in those with abnormal SAECG when compared to 39 +/- 2 percent in patients with normal SAECG (p < 0.05). Similarly, in patients with inferior myocardial infarction, the mean EF among these respective groups was 41 +/- 2 and 47 +/- 2 percent (p < 0.05). The mean echocardiographic score, which reflected regional LV wall motion abnormality, was not different between patients with anterior infarction when the groups with abnormal and normal SAECG were compared (9.1 +/- 0.6 versus 6.4 +/- 0.4), but differed significantly between inferior infarction patients (5.8 +/- 0.7 versus 4.6 +/- 0.4 respectively; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)