Myocardial Flow Reserve, an Independent Prognostic Marker of All-Cause Mortality Assessed by <sup>82</sup> Rb PET Myocardial Perfusion Imaging: A Danish Multicenter Study
Signe Højstrup, Kim Wadt Hansen, Ulrik Talleruphuus, Lisbeth Marner, Louise Hougesen Bjerking, Lars Jakobsen, Evald Høj Christiansen, Kirsten Bouchelouche, Niels Wiinberg, Kasper Guldbrandsen, Søren Galatius, Eva Prescott
Abstract
BACKGROUND: Rubidium-82 positron emission tomography ( 82 Rb PET) myocardial perfusion imaging is used in clinical practice to quantify regional perfusion defects. Additionally, 82 Rb PET provides a measure of absolute myocardial flow reserve (MFR), describing the vasculature state of health. We assessed whether 82 Rb 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 82 Rb 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 ≤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 ≤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 ≤2 versus MFR >2 (15.7% versus 5.2%; P <0.001). MFR ≤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 ≤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 ≤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 ≤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.