The outcome of patients with a first non-Q wave acute myocardial infarction presenting with ST segment depression, ST segment elevation, or no ST deviations on the admission electrocardiogram

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Abstract

We evaluated the prognosis of patients with a first non-Q wave myocardial infarction according to their admission electrocardiogram. Hospital and 1-year mortality rates in patients with ST elevation (15%, and 21% respectively) and ST depression (17%, and 27% respectively) were similar and significantly higher than in patients with no ST changes (3%, and 10% respectively). Likewise, the adjusted hospital and 1-year mortality risks of patients with ST elevation or depression were comparable but higher than the corresponding mortality risk of patients with no ST deviations. The cumulative 5-year mortality rate was highest among patients with ST segment depression (51%) compared to patients with ST elevation (34%) or no ST deviation (21%), (p<0.001 for both comparisons). The adjusted 5-year mortality risk of patients with ST depression was higher (HR: 1.83, 95% C.I., 1.17–2.83) compared to patients with baseline ST elevation (HR–1.33, 95% C.I., 0.83–2.12) or patients with no ST changes (reference group). Patients with baseline ST segment elevation and coexistent ST segment depression in other electrocardiogram leads, had a higher in-hospital mortality rate (19%) compared to counterparts without concomitant ST depression (10%) and a tendency for higher in-hospital mortality risk but not for subsequent 1- and 5-year mortality risks. Conclusions: Patients with a first non-Q wave MI with ST elevation or depression on admission have similar hospital and 1-year mortality risk, but the long-term mortality risk is higher among patients with ST segment depression. Patients with ST elevation and concomitant ST segment depression are at increased risk for mortality during the index hospitalization.

Introduction

The increased frequency of non-Q wave acute myocardial infarction (AMI) in the reperfusion era 1, 2, 3, 4, and the poor post discharge prognosis of this type of infarction 5, 6, make early risk stratification in this group of patients to be of great clinical importance.

ST segment depression in the electrocardiogram was previously reported to be an important predictor for mortality in patients with AMI 7, 8, 9. However, the importance of ST segment depression in patients with non-Q wave AMI is controversial. Several studies showed that ST segment depression was associated with increased mortality or other cardiac events compared to no ST segment depression 10, 11, 12, 13, 14. In one of these studies the univariate association between ST segment depression and mortality disappeared after adjustment for other confounding variables [10]. In another study this association was present for cardiac events but not for mortality [13]. Some of the studies included a large proportion of patients with previous infarction, more often associated with increased mortality 10, 11, 12. The aim of the present study was to compare the short- and long-term prognosis of patients with a first non-Q wave AMI presenting with ST segment depression versus those with ST elevation or no ST changes on the admission electrocardiogram.

Section snippets

Study population

The Secondary Prevention Reinfarction Israeli Nifedipine Trial (SPRINT) registry contains data on 5,839 consecutive patients with AMI hospitalized in 13 coronary care units in Israel between July 1981 and August 1983. Among 4808 hospital survivors, 2138 patients were enrolled in the SPRINT study. The detailed methods and results of this trial have been published [15]. Demographic and medical data from hospitalization and 1-year post discharge follow-up were collected for all the 5839 patients

Results

Among the 4,314 patients with a first AMI, 610 patients (14%) had a non-Q wave infarction. Sixty one patients lacking admission electrocardiograms were excluded from the present analysis (see Methods).

Among the remaining 549 patients, 236 (43%) had ST segment elevation, 186 patients (34%) had ST depression, and 127 patients (23%) displayed only T wave changes or no electrocardiographic abnormalities on the admission electrocardiogram. Among the 236 patients with ST segment elevation, 130 (55%)

Discussion

The most important findings of the present study are: 1) The presence of ST segment deviation (elevation or depression) on the admission electrocardiogram of patients with a first non-Q wave acute myocardial infarction, was associated with increased mortality risk during the index hospitalization, and after 5-years of follow-up, compared to patients with no ST changes. 2) After multivariate adjustment for possible confounders, the in-hospital and 1-year mortality risk were similar in patients

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    1

    For the SPRINT Study Group: see appendix Eur Heart J 1988;9:354–64.

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