Objective: To derive and validate a clinical prediction rule that identifies patients after myocardial infarction who have preserved left ventricular systolic function.
Design: Retrospective analysis of a prospective cohort study, with a derivation set to generate a clinical prediction rule and a validation set to test the prediction rule.
Setting: Urban tertiary care hospital.
Patients: 314 consecutive patients admitted with myocardial infarction who had one or more of the following tests to determine left ventricular ejection fraction: transthoracic echocardiography, contrast left ventriculography, or radionuclide ventriculography.
Measurements: Left ventricular ejection fractions were determined by transthoracic echocardiography, contrast left ventriculography, and gated blood pool scan.
Results: Multivariate analysis of patients in the derivation set yielded the following rule: The left ventricular ejection fraction is predicted to be 40% or more in patients who have 1) an interpretable electrocardiogram, 2) no previous Q-wave myocardial infraction, 3) no history of congestive heart failure, and 4) an index myocardial infarction that is not a Q-wave anterior infarction. In the derivation and the validation sets, the positive predictive value of the prediction rule was more than 0.98.
Conclusions: A simple clinical prediction rule using easily obtained historical and electrocardiographic data reliably identifies a substantial percentage of patients after myocardial infarction (40% in our hospital) who are likely to have preserved left ventricular systolic function. If validated in other patient populations, application of this prediction rule in clinical practice could result in a substantial decrease in the cost of treating uncomplicated myocardial infarction.