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SPECT myocardial perfusion imaging (MPI) can pick up perfusion defects that don't show up with normal cardiac stress testing and can predict cardiovascular death or morbidity out to 10 years, researchers found.

Half of 650 patients with known or suspected heart disease and normal exercise ECGs had an abnormal SPECT MPI, and 20% had indications that the ischemia was reversible, reported Arend F.L. Schinkel, MD, of the Erasmus MC Thoraxcenter in Rotterdam, the Netherlands, and colleagues.

The summed rest score, which accounts for the amount of infarcted myocardium, was an independent predictor of death, whereas the summed stress score, which measures both infarcted and ischemic myocardium, was an independent predictor of major adverse cardiac events (MACE), they wrote in a study published in the November European Heart Journal: Cardiovascular Imaging.

In the nearly 10 years of follow-up, 23% of patients died, 11% had a nonfatal MI, 14% underwent CABG, and 22% underwent PCI.

The summed rest score predicted mortality, with a hazard ratio of 1.15 (95% CI 1.08 to 1.22, P<0.001). And the summed stress score predicted MACE with a hazard ratio of 1.09 (95% CI 1.04 to 1.13, P<0.001).

"Several lines of evidence, collected with different approaches, demonstrate that a functional assessment as obtained by perfusion imaging is superior to clinical and ECG assessment in prognostic stratification of patients with known or suspected ischemic heart disease," wrote Danilo Neglia, MD, and Alessia Gimelli, MD, of Fondazione Toscana Gabriele Monasterio in Pisa, Italy, in an accompanying editorial.

"On this basis, stress/rest myocardial perfusion abnormalities should be obtained -- whenever possible -- before coronary angiography in order to guide decision-making," they said.

They added that the summed rest score "may be a better predictor of mortality than the left ventricular ejection fraction alone."

One of the problems with this approach, they said, is that when facilities are tightening their budgets, a functional risk assessment after a normal ECG may seem redundant.

Neglia and Gimelli pointed to a survey by the European Society of Cardiology that indicated an underutilization of this type of noninvasive functional testing. Such underutilization results in many patients without significant disease undergoing diagnostic catheterization.

To help stratify patients to SPECT MPI, Neglia and Gimelli suggested having a "better definition of pre-test probability of disease based on new predicting models incorporating clinical data, risk factors, and possibly biohumoral markers in order to exclude patients with very low probability."

In addition, attention should be paid to lower the radiation dose of SPECT imaging as much as possible. One way to do that is to avoid a rest exam when the stress test is positive.

For this study, Schinkel and colleagues included 650 consecutive patients who underwent exercise ECG and subsequent exercise SPECT MPI. All patients had known or suspected coronary artery disease. The mean age was 56 and 66% were men.

A total of 8% of the 324 patients with an abnormal SPECT test had completely reversible perfusion defects, 12% had partially reversible defects, and 30% had fixed defects. However, just having an abnormal SPECT test increased the risk of death (P=0.02) or MACE (P<0.0001), wrote Schinkel and colleagues.

Despite the recognized limitations of exercise ECG in patients with known or suspected CAD, European guidelines recommend the test as the initial evaluation.

In the multivariable analysis, Schinkel and colleagues found that SPECT testing provided incremental prognostic information over clinical data and exercise ECG for prediction of future events.

Along with the summed rest score, other significant predictors of death were age (HR 1.09, per one unit increment) and smoking (HR 1.95).

And in addition to the summed stress score, other significant predictors of MACE were age (HR 1.03, per one unit increment), male gender (HR 1.47), and previous MI (HR 1.53).

The study is limited because catheter angiography -- the reference gold standard -- was not routinely performed in these patients. Also, the use of attenuation correction may have improved the accuracy of SPECT imaging.

From the American Heart Association:

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