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Background:The pathogenesis of the occurrence of late potentials (LP) has not been fully elucidated. Deletion polymorphism in the Angiotensin I-converting enzyme (ACE) gene may relate the myocardial remodeling after the myocardial infarction (MI). The purpose of this study was to evaluate the significance of ACE gene polymorphism for the occurrence of LPs after MI. Methods:A 287 base pair (bp) insertion/deletion polymorphism in intron 16 of the ACE gene was determined by polymerase chain reaction and LPs were also examined by signal-averaged ECG in 136 patients with MI. Polymorphism of the ACE gene was characterized by three genotypes: II, ID, and DD. Signal-averaged ECG were recorded using X, Y, Z leads and LP were defined by timedomain analysis as low amplitude potentials exceeding 20 ms after the QRS-end and filtered QRS >115 ms. Results:Positive LPs were noted in 40 of 136 patients with MI. No differences could be detected between patients with LP-positive and LP-negative for the location of MI, the success rate of reperfusion therapy, and left ventricular end-diastolic volume (126 2 40 vs 113 I+_ 43 mL/m*). In patients with LP-positive compared with those in LP-negative, filtered QRS was significantly higher (135 2 8 vs 107 2 8 ms), left ventricular ejection fraction was lower (47 2 12 vs 54% 2 1 1 %), and peak was higher (3602 I+_ 2928 vs 2614 I+_ 2360 IU/L). The frequency of ACE/ DD genotype was associated with patients with LP-positive (18 of DD, 18 of ID, and 4 of II for patients with LP-positive, while 25 of DD, 42 of ID, and 29 of II for patients with LP-negative). In the study population, the ACE / DD genotype was associated with patients with LP-positive when compared with the ACE ID& II genotype (x2 = 4.7, P = 0.03).Conclusion: ACVDD genotype of the ACE gene may be associated with the occurrence of LP after MI. A.N.E. 1996;1(4):405-410 late potential; signal-averaged ECC; ACE gene polymorphism; myocardial infarction Many groups have demonstrated that high frequency analysis of the signal-averaged surface ECG can detect low amplitude signals in the terminal portion of the body surface QRS of myocardial in-farction (MI) with ventricular tachycardia (VT).1-4 These signals have been labeled as arrhythmogenic ventricular activity or the late potentials (LP) and correlate with the fragmented activity, which is ob-This work was supported in part by a grant-in-aid 07670801