Interaction of impaired myocardial flow reserve and extent of myocardial ischemia assessed using 13N-ammonia positron emission tomography imaging on adverse cardiovascular outcomes

Abstract

BackgroundMyocardial flow reserve (MFR) and the extent of myocardial ischemia identify patients at high risk of major adverse cardiovascular events (MACEs). Associations between positron emission tomography (PET)-assessed extent of ischemia, MFR, and MACEs is unclear. MethodOverall, 640 consecutive patients with suspected or known coronary artery disease undergoing 13N-ammonia myocardial perfusion PET were followed-up for MACEs. Patients were categorized into three groups based on myocardial ischemia severity: Group I (n = 335), minimal (myocardial ischemia < 5%); Group II (n = 150), mild (5–10%); and Group III (n = 155), moderate-to-severe (> 10%). ResultsCardiovascular death and MACEs occurred in 17 (3%) and 93 (15%) patients, respectively. Following statistical adjustment for confounding factors, impaired MFR (global MFR < 2.0) was revealed as an independent predictor of MACEs in Groups I (hazard ratio [HR], 2.89; 95% confidence interval [CI], 1.48–5.64; P = 0.002) and II (HR, 3.40; 95% CI 1.37–8.41; P = 0.008) but was not significant in Group III (HR, 1.15; 95% CI 0.59–2.26; P = 0.67), with a significant interaction (P < 0.0001) between the extent of myocardial ischemia and MFR. ConclusionImpaired MFR was significantly associated with increased risk of MACEs in patients with ≤ 10% myocardial ischemia but not with those having > 10% ischemia, allowing a clinically effective risk stratification.