Myocardial Flow Reserve, an Independent Prognostic Marker of All-Cause Mortality Assessed by 82Rb PET Myocardial Perfusion Imaging: A Danish Multicenter Study

BACKGROUND:Rubidium-82 positron emission tomography (Rb-82 PET) myocardial perfusion imaging is used in clinical practice to quantify regional perfusion defects. Additionally, Rb-82 PET provides a measure of absolute myocardial flow reserve (MFR), describing the vasculature state of health. We assessed whether Rb-82 PET-derived MFR is associated with all-cause mortality independently of the extent of perfusion defects. METHODS:We conducted a multicenter clinical registry-based study of patients undergoing Rb-82 PET myocardial perfusion imaging on suspicion of chronic coronary syndromes. Patients were followed up in national registries for the primary outcome of all-cause mortality. Global MFR & LE;2 was considered reduced. RESULTS:Among 7169 patients studied, 38.1% were women, the median age was 69 (IQR, 61-76) years, and 39.0% had MFR & LE;2. A total of 667 (9.3%) patients died during a median follow-up of 3.1 (IQR, 2.6-4.0) years, more in patients with MFR & LE;2 versus MFR >2 (15.7% versus 5.2%; P<0.001). MFR & LE;2 was associated with all-cause mortality across subgroups defined by the extent of perfusion defects (all P<0.05). In a Cox survival regression model adjusting for sex, age, comorbidities, kidney function, left ventricular ejection fraction, and perfusion defects, MFR & LE;2 was a robust predictor of mortality with a hazard ratio of 1.62 (95% CI, 1.31-2.02; P<0.001). Among patients with no reversible perfusion defects (n=3101), MFR & LE;2 remained strongly associated with mortality (hazard ratio, 1.86 [95% CI, 1.26-2.73]; P<0.01). The prognostic value of impaired MFR was similar for cardiac and noncardiac death. CONCLUSIONS:MFR & LE;2 predicts all-cause mortality independently of the extent of perfusion defects. Our results support the inclusion of MFR when assessing the prognosis of patients suspected of chronic coronary syndromes.