Prognostic Value of Coronary Flow Capacity by 82Rb PET in Patients With Suspected Coronary Artery Disease and Normal Myocardial Perfusion at Semiquantitative Imaging Analysis

BACKGROUND: Coronary flow capacity (CFC) is a measure that integrates hyperemic myocardial blood flow and myocardial flow reserve to quantify the pathophysiological impact of coronary artery disease on vasodilator capacity. We assessed the prognostic value of CFC derived from Rb-82 positron emission tomography/computed tomography in patients with suspected coronary artery disease and normal myocardial perfusion imaging. METHODS: We studied 1967 patients with suspected coronary artery disease and normal myocardial perfusion at the semiquantitative analysis of stress/rest cardiac Rb-82 positron emission tomography/computed tomography imaging. Coronary artery calcium scores were calculated and categorized into 3 groups: 0, 0.1 to 99.9, and >= 100. Patients were classified as having myocardial steal, severely reduced CFC, moderately reduced CFC, mildly reduced CFC, minimally reduced CFC, or normal flow using previously defined thresholds. The outcome end points were myocardial infarction and cardiac death, whichever occurred first. RESULTS: During a mean time of 41 +/- 27 months, 49 events occurred (2.5% cumulative event rate, with an annualized event rate of 0.5% person-years). At multivariable Cox analysis, coronary artery calcium score categories and impaired CFC resulted as independent predictors of events (both P<0.001). The annualized event rate was higher in patients with impaired CFC compared with those with normal CFC (P<0.05). Kaplan-Meier analysis showed that patients with impaired CFC were at the highest risk of events. CONCLUSIONS: In patients with suspected coronary artery disease and normal myocardial perfusion, impaired CFC is associated with a higher risk of cardiac events. Evaluating CFC can help identify patients' candidates for additional therapies to prevent future events.