RELATIONSHIP BETWEEN LATE POTENTIALS AND THE PREDISCHARGE ELECTROCARDIOGRAPHIC PATTERN IN PATIENTS WITH ACUTE ANTERIOR WALL MYOCARDIAL-INFARCTION

Hypothesis: The presence of late potentials on the signal-averaged ele ctrocardiogram (SAECG) identifies patients at high risk for developmen t of ventricular tachyarrhythmias after myocardial infarction (MI). Me thods: The electrocardiogram and left ventricular function in 65 patie nts recovering from a first acute anterior wall MI were analyzed. We c ompared the pattern of the ST segment (isoelectric or elevated) and of the T wave (positive or negative) with the SAECG using an orthogonal bipolar lead configuration (X, Y, Z) with bidirectional Butterworth fi ltering (Simson's method). Results: Abnormal SAECG was found in 17 (26 %) patients; 11 of 18 patients with ST elevation had abnormal SAECG, a nd only 6 of 47 patients with isoelectric ST segment developed abnorma l SAECG (p<0.0001, odds ratio = 10.74). Of 19 patients with positive T waves, 10 had abnormal SAECG, and abnormal SAECG was found in 7 of 46 patients with negative T waves (p<0.003, odds ratio = 5.27). When bot h parameters were considered together, 9 of 12 patients with ST elevat ion and positive T wave developed abnormal SAECG, and 35 of 40 patient s with isoelectric ST and negative T wave had normal SAECG (p<0.0002). Left ventricular ejection fraction was similar in patients with abnor mal SAECG (43 +/- 14%) and normal SAECG (46 +/- 11%). Conclusion: Thes e findings suggest that patients with anterior wall MI and a predischa rge pattern of ST elevation and positive T wave have a higher incidenc e of abnormal SAECG and therefore may have a worse prognosis, especial ly related to the subsequent development of ventricular arrhythmias.