ST‐Segment depression on ambulatory electrocardiography in the early in‐hospital period after acute myocardial infarction predicts early and late mortality: A short‐term and a 3‐year follow‐up study

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Abstract
A surveillance study was conducted to determine the in-hospital and long-term prognostic value of ST-segment depression assessed by ambulatory electrocardiographic monitoring (AEM) during the early in-hospital period after acute myocardial infarction (AMI). ST-segment depression (STD) was determined by computer analysis of 24-h ECG tapes as a horizontal or downsloping change in ST level by ≥ 0.1 mV from the reference base line. The ST level was measured 80 ms after the J point of all normally conducted complexes for ≥ 1 min. All computer-detected ST events were verified by one trained reader. Tapes corresponding to 74 patients were analyzed. In addition, 23 tapes corresponding to age- and gendermatched controls were also analyzed. Patients were divided into two groups: 22 patients (30%) showed STD (Group A), and 52 patients (70%) had no episode of STD (Group B). Among controls, 1 person (4%) showed STD. During the early follow-up period (14 ± 11 days after hospital admission), cardiac events occurred in 11 patients [7 (32%) in Group A and 4 (8%) in Group B, p < 0.01], including 6 cardiac deaths [5 (23%) in Group A and 1 (2%) in Group B, p < 0.01], 3 acute coronary artery bypass surgeries [2 (9%) in Group A and 1 (2%) in Group B, p = NS], and 2 nonfatal myocardial infarctions (both in Group A, p = NS). During a mean follow-up period of 3 years (36 ± 15 months), 18 patients died [10 (45%) in Group A and 8 (15%) in Group B, p = 0.01]. Eleven deaths were sudden [7 (32%) in group A and 4 (8%) in Group B, p <0.01 ]. Eighteen AMI occurred [11 (50%) in Group A and 7 (13%) in Group B, p < 0.005]. Twenty patients underwent revascularization procedures [7 (32%) in Group A and 13 (25%) in Group B, p=NS]. Thirty-eight patients [18 (82%) in Group A and 20 (38%) in Group B, p<0.001] suffered at least one cardiac event during the follow-up period (death, myocardial infarctions, and revascularization therapy). Survival analysis using Kaplan-Meier curves showed that patients with STD (Group A) had shorter survival times (p < 0.001, Log rank test) than those without STD (Group B). The same analysis showed that patients in Group A had shorter survival times free of cardiac events (myocardial infarction, p < 0.001; sudden death, p < 0.001; revascularization therapy, p < 0.05; all cardiac events, p < 0.001) than those in Group B. No coronary events were reported in control persons. A multivariate stepwise regression analysis (Cox's proportional hazards model) of a number of clinical variables, including STD, showed that its presence was the most important factor predicting mortality (p < 0.001, hazards ratio 5.09), followed by the presence of diabetes (p < 0.01, hazards ratio 4.67) and hypertension (p < 0.01, hazards ratio 3.52). The findings of this survey illustrate both the short- and long-term prognostic value regarding mortality and morbidity of STD recorded on AEM during the early in-hospital period after AMI.

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