Myocardial technetium-99m sestamibi single-photon emission tomography as a prognostic tool in coronary artery disease : multivariate analysis in a long-term prospective study

To date several studies have evaluated the accuracy of thallium-201 myocardial scan in risk stratification of coronary artery disease (CAD), while reports using technetium-99m methoxyisobutylisonitrile (MIBI), a tracer particularly suited to single-photon emission tomographic (SPET) imaging, are lacking. To rectify this omission, a prospective study was started in 1988 and at present 176 consecutive, and thus unselected, patients have been enrolled. All of them have been submitted to stress-rest MIBI SPET for the diagnosis or evaluation of CAD; 147 patients (121 males and 26 females, aged 53±9 years) have completed a surveillance period of at least 36 months following the scintigraphic study (range 36–60 months, mean 43). Sixty-one patients had a documented previous myocardial infarction. The mean pretest likelihood of CAD was 44% in the patients without prior infarction. The main anamnestic, clinical, EKG and scintigraphic findings were evaluated and statistically correlated with the incidence of ensuing cardiac events using both univariate (chi-square test) and multivariate analysis (logistic regression model). Twenty-nine patients suffered from a cardiac event during the follow-up period (i.e. three cardiac deaths, six myocardial infarctions and 20 cases of unstable angina). Statistical multivariate analysis identified MIBI scan as the only highly significant and independent prognostic predictor [P=0.006, relative risk (RR)=17.62]. In detail, the most important scintigraphic parameters were the presence of a reversible defect (P=0.0089, RR=5.11) and the extension of the stress perfusion defect (P=0.0255, RR=3.27). The presence of typical angina proved to be a slightly significant predictor (P=0.051, RR=2.45), while no other examined parameter showed a significant correlation with a bad prognosis. In conclusion, MIBI SPET can be considered a useful tool in the risk stratification of CAD patients. The presence of a reversible perfusion defect or an extensive defect appears responsible for a clear increase in the probability of subsequent cardiac events, thus indicating a more aggressive therapeutic approach to be appropriate.