Incidence of Ventricular Late Potentials inAcute Myocardial Infarction and Evolution at One Year

Signal-averaging electrocardiography (ECG) was performed in 72 consecutive patients (64 male, 8 female; mean age 57 ±11 years) with a first acute myocardial infarction (AMI) to assess the incidence of ventricular late potentials (VLP) during the initial phase of AMI and to determine the relationship between the presence of VLP and the occurrence of ventricular tachycardia or fibrillation (VT/VF) in the setting of AMI. Twenty-two patients (30%) had VLP at initial examination (performed within 96 h after the onset of AMI). No association was found between the presence of VLP and age, location of AMI, left ventricular ejection fraction, peak serum level of cardiac enzymes or the occurrence of VT/VF and death during the initial phase of AMI. VLP were only related to the presence of couplets or runs of nonsustained VT detected by Holter monitoring before hospital discharge (p < 0.05). Among the 66 survivors, 47 (71 %) had a second signal-averaged ECG a mean of 13 months after AMI: in no case (0/15) did VLP disappear during follow-up, but new VLP could be detected in 6 patients ( 19 %) who had initially a normal signal-averaged ECG. We conclude that: (a) signal averaging can be performed in electrically noisy environments such as a coronary care unit; (b) VLP are present in 30% of patients with a first AMI and are detectable early after onset of symptoms; (c) no association is found between VLP and VT/VF occurring during the initial phase of AMI, and (d) in 19% of the cases, VLP develop during the first year after AML