Prediction of myocardial infarction versus cardiac death by stress echocardiography

The echocardiography literature to date has considered cardiac death and myocardial infarction (MI) as a combined end point. The purposes of the present study were to evaluate the differential prognosis of nonfatal MI versus cardiac death in patients undergoing stress echocardiography and to effectively risk stratify patients using the appropriate combination of functional, ischemic, and infarction data.

The authors evaluated 3,259 patients (mean age, 59 +/- 13 years; 48% men) undergoing stress echocardiography. Follow-up (mean, 2.8 +/- 1.1 years) for confirmed nonfatal MI (n = 91) and cardiac death (n = 105) was obtained.

Multivariate analysis showed that the strongest predictor of cardiac death was a low ejection fraction (chi(2) = 37.3, P < .0001), and the strongest predictor of nonfatal MI was the extent of ischemia (chi(2) = 12.3, P < .0001). The relationship between ejection fraction and cardiac death rate was an exponential curve (y = 16.91e(-0.50x); r = -0.99, P < .0001). Among patients with ejection fractions > 30% (the low-risk to intermediate-risk groups), peak wall motion score index (WMSI) was able to further risk stratify patients into a very low risk group (peak WMSI = 1.0; cardiac death rate, 0.26% per year) and a higher risk group (peak WMSI > 1.7; cardiac death rate, 2.56% per year). However, patients with ejection fractions < 30% had high cardiac death risk regardless of peak WMSI category.

In patients referred for stress echocardiography, the integration of functional information (on the basis of ejection fraction) and ischemic and infarction data (on the basis of WMSI) effectively risk stratifies patients for the outcome-specific end points of cardiac death and nonfatal MI.