Prognostic Significance and Evolution of Late Ventricular Potentials in the First Year After Myocardial Infarction: A Prospective Study

• Published in: Pacing and clinical electrophysiology 1989-01, Vol.12 (P1), p.41-51
• Main Authors: Verzoni, Alessandro, Romano, Salvatore, Pozzoni, Luigi, Tarricone, Diego, Sangiorgio, Stefano, Croce, Luigi
• Format: Article
• Language: English
• Subjects: Arrhythmias, Cardiac - etiology; Arrhythmias, Cardiac - mortality; Death, Sudden - etiology; Electrocardiography; Female; Follow-Up Studies; Humans; late potentials; Male; Middle Aged; Monitoring, Physiologic; myocardial infarction; Myocardial Infarction - complications; Myocardial Infarction - mortality; Prognosis; Prospective Studies; Risk Factors; Signal Processing, Computer-Assisted; Stroke Volume; sudden death; ventricular arrhythmias
• ISSN: 0147-8389; 1540-8159
• DOI: 10.1111/pace.1989.12.p1.41

We performed a prospective study of the high‐frequency components of the terminal portion of the QRS complex in 220 patients who survived acute myocardial infarction. Signal‐averaged electrocardiograms (SA‐ECGs) were performed before hospital discharge (16 ± 6 days) and then serially at regular intervals over the following year. SA‐ECGs were processed using a 40 Hz high‐pass bidirectional filter. Duration of “filtered” QRS (D‐normal value < 120 ms), duration of the low‐amplitude signals. (D40 ‐ n.v. < 39 ms) and last 40 ms voltage of the QRS complex (V40 ‐ n.v.> 20 µV) were measured. Late potentials (LPs) were defined as the presence of two or more abnormal values. In addition, 24‐hour Holter monitoring was performed in 208 patients and left ventricular ejection fraction (LVEF) was determined by scintigraphy in 111. Sixty‐two patients (group 1) had LPs, 158 had normal SA‐ECGs (group 2). Spontaneous normalization of SA‐ECGs occurred in 20% of patients after 6 months, although the mean values of D, D40 and V40 did not change significantly and the reproducibility was very good for all the indexes during all the follow‐up controls. Three patients had sudden death and three presented again with spontaneous, sustained ventricular tachycardia. Five of 62 (8%) group 1 patients had an arrhythmic event compared with one of 158 patients (0.6%) in group 2. The sensitivity of SA‐ECGs as a predictor of arrhythmic events was 83% with a specificity of 73%. Patients with subsequent arrhythmic events had longer filtered QRS (133 ± 19 vs 104 ± 16 ms; P < 0.001), longer duration of the low‐amplitude signals (54 ± 15 vs 33 ± 14 ms; P < 0.01), and lower voltages in the last 40 ms of the filtered QRS (11 ± 3 vs 36 ± 25 µV; P < 0.02) and, moreover, higher peak CK values and lower LVEF than those without such events. In conclusion, SA‐ECGs provide important prognostic information in identifying patients at risk of arrhythmic events after myocardial infarction although dynamic changes of LPs are observed during the first year after myocardial infarction.