Myocardial perfusion reserve (MPR) is a more sensitive predictor for cardiac death than left ventricular ejection fraction and extent of viability, based on a study in this month’s Journal of Nuclear Medicine.
Since PET is a “powerful tool” to assess myocardial viability, it is often used in ischemic heart disease patients to evaluate which patients should be revascularized, according to the study authors.
Not all patients treated on the basis of PET-proven viability benefit from revascularization, but MPR predicts survival in patients not undergoing revascularization, wrote Riemer H.J.A. Slart, MD, of the department of nuclear medicine and molecular imaging at the University Medical Center Groningen in Groningen, the Netherlands, and colleagues. Therefore, they investigated whether MPR is related to survival in ischemic heart disease patients after a PET-driven intervention.
Between 1995 and 2003, 119 consecutive patients (96 men) with chronic ischemic heart disease underwent a PET-driven revascularization procedure based on ischemia-viability assessment with PET. Those patients were followed for all-cause mortality and major cardiovascular events.
One hundred nineteen patients underwent a PET-driven revascularization procedure (67 percutaneous coronary interventions, 52 coronary artery bypass grafts) because of angina complaints. The mean age was 67 years; global left ventricle MPR was 1.54. MPR intertertile boundaries were 1.34 and 1.67.
Significantly more cardiac deaths were observed in the lowest and middle MPR tertiles than in the highest tertile, the study authors wrote. The age- and sex-corrected hazard ratio for the middle tertile was 8.3 and for the lowest tertile 23.6.
After left ventricular ejection fraction and viability were added to the model, the researchers reported that MPR remained significant, with hazard ratios of 6.5 and 18.5, whereas neither left ventricular ejection fraction nor viability reached significance in this model. Comparable results were found for major adverse cardiac events, with hazard ratios of 3.15 and 8.24.
“The advantage of PET is that on top of viability, absolute myocardial perfusion can be measured. In addition, MPR can be assessed using vasodilator substances,” Slart and colleagues wrote. “The question remains whether epicardial revascularization has a large effect on the small vasculature. Left ventricular ejection fraction in our study was low and, as can be expected, did not discriminate with respect to prognosis. Apparently, MPR on top of a low left ventricular ejection fraction can be used to further determine prognosis in these patients.”