Global and segmental absolute stress myocardial blood flow in prediction of cardiac events. [${}^{15}$O] water positron emission tomography study

We evaluated the value of reduced global and segmental absolute stress myocardial blood flow (sMBF) quantified by [${}^{15}$O] water positron emission tomography (PET) for predicting cardiac events in patients with suspected obstructive coronary artery disease (CAD). Global and segmental sMBF during adenosine stress were retrospectively quantified in 530 symptomatic patients who underwent [${}^{15}$O] water PET for evaluation of coronary stenosis detected by coronary computed tomography angiography. Cardiovascular death, myocardial infarction, or unstable angina occurred in 28 (5.3%) patients at a 4-year follow-up. Reduced global sMBF was associated with events (area under the receiver operating characteristic curve 0.622, 95% confidence interval (95% CI) 0.538-0.707, p = 0.006). Reduced global sMBF (< 2.2 ml/g/min) was found in 22.8%, preserved global sMBF despite segmentally reduced sMBF in 35.3%, and normal sMBF in 41.9% of patients. Compared with normal sMBF, reduced global sMBF was associated with the highest risk of events (adjusted hazard ratio (HR) 6.970, 95% CI 2.271-21.396, p = 0.001), whereas segmentally reduced sMBF combined with preserved global MBF predicted an intermediate risk (adjusted HR 3.251, 95% CI 1.030-10.257, p = 0.044). The addition of global or segmental reduction of sMBF to clinical risk factors improved risk prediction (net reclassification index 0.498, 95% CI 0.118-0.879, p = 0.010, and 0.583, 95% CI 0.203-0.963, p = 0.002, respectively). In symptomatic patients evaluated for suspected obstructive CAD, reduced global sMBF by [${}^{15}$O] water PET identifies those at the highest risk of adverse cardiac events, whereas segmental reduction of sMBF with preserved global sMBF is associated with an intermediate event risk.