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Prognosis

Patients with a first non-Q-wave myocardial infarction had more re-infarctions, more coronary insufficiency, less congestive heart failure, and similar mortality rates as patients with a first Q-wave myocardial infarction

ACP J Club. 1993 Mar-April;118:52. doi:10.7326/ACPJC-1993-118-2-052


Source Citation

Berger CJ, Murabito JM, Evans JC, Anderson KM, Levy D. Prognosis after first myocardial infarction. Comparison of Q-wave and non-Q-wave myocardial infarction in the Framingham Heart Study. JAMA. 1992 Sep 23/30;268:1545-51.


Abstract

Objective

To compare a first Q-wave with non-Q-wave myocardial infarction (MI) for the incidence of re-infarction, cardiac death, and of other cardiac events in patients enrolled in the Framingham Heart Study.

Design

Inception cohort followed for a mean of 5.1 years.

Setting

Population-based study in Framingham, Massachusetts.

Patients

363 patients (mean age 67 y, 62% men) who had a first-recognized MI. 77% were Q-wave infarctions. Exclusion criteria were left bundle branch block, ventricular pacemakers, or coronary bypass surgery. Follow-up was > 99%.

Assessment of prognostic factors

Height, weight, blood pressure, smoking history, blood glucose, and plasma total cholesterol were assessed at biennial visits. Interim MIs were identified by medical history and 12-lead electrocardiograms (ECGs), as well as by hospital chart review for admission history, cardiac enzymes, and serial ECGs, and were classified for Q-wave and non-Q-wave status.

Main outcome measures

Re-infarction and death from coronary heart disease. Secondary outcomes were coronary insufficiency, congestive heart failure, sudden death, and all-cause mortality.

Main results

Patients having a first non-Q-wave MI had a higher rate of re-infarction compared with those having a Q-wave infarction (45% vs 27% at 10 years {absolute difference 18%, 95% CI 6% to 30%}*; P = 0.02). The higher rate of re-infarction after non-Q-wave infarctions was significant only in men (33% vs 13% {absolute difference 20%, CI 6% to 34%}*; P = 0.005); and for those < 65 years of age (P = 0.02, relative odds ratio [OR] 2.4, CI 1.1 to 5.1). The incidence of coronary heart disease deaths after infarctions did not differ (44% vs 51%). Multivariate analysis identified 2 independent predictors of re-infarction: non-Q-wave infarctions (relative OR 1.8, CI 1.1 to 3.1) and baseline hypertension (relative OR 1.8, CI 1.1 to 3.2). Q-wave status did not influence the incidence of sudden death or all-cause mortality. Rates increased for congestive heart failure after Q-wave infarctions (P = 0.05) and for the development of coronary insufficiency after non-Q-wave infarctions (P = 0.03).

Conclusions

Patients having first non-Q-wave myocardial infarctions had more re-infarctions, developed more coronary insufficiency, had less congestive heart failure, and had similar mortality rates when compared with patients having first Q-wave myocardial infarctions.

Source of funding: Not stated.

For article reprint: Dr. J.M. Murabito, Framingham Heart Study, 5 Thurber Street, Framingham, MA 01701, USA. FAX 617-735-4921.

*Numbers calculated from data in article.


Commentary

This report from the Framingham Study provides an interesting perspective on outcome associated with a first Q-wave and non-Q-wave MI. The clinical axiom that non-Q-wave infarction is necessarily associated with a low mortality rate has been corrected. The collection of data using the Framingham cohort ensures quality of ascertainment but has the drawback of involving a population with a very high level of medical care (medical therapy and coronary bypass grafting). The extent that this may have changed the outcomes was not addressed by the study. The study also occurred before the advent of thrombolytic therapy, which may alter the relevance of its findings.

Overall, the results support the general notion that non-Q-wave infarction often involves incomplete occlusion of the epicardial coronary vessel, a situation that is unstable with substantial risk for further ischemia and complete occlusion. In the reperfusion era, many Q-wave infarctions are now also associated with a patent infarct artery.

An important caveat concerning this study is that it included patients with a first infarction and without left bundle branch block. Patients with multiple infarction and an already abnormal QRS complex are much more likely to have non-Q-wave infarction associated with multivessel disease and severe left ventricular dysfunction. These patients have an extremely poor prognosis.

The clinical implications of these results are that regardless of the ECG findings, every patient with acute MI should be evaluated for left ventricular function, inducible ischemia, and risk factors for progression of disease.

Robert M. Califf, MD
Duke UniversityDurham, North Carolina, USA