Abstract
BackgroundImpaired coronary flow reserve is considered an early manifestation of coronary artery disease, even in vessels free of angiographic stenosis. However, the role of hyperemic myocardial blood flow (HMBF) using Positron Emission Tomography (PET) is not well determined. The aim of this analysis is to determine whether noninvasive HMBF in patients with suspected or known coronary artery disease adds incremental prognostic value over clinical variables.MethodsWe included 5,770 consecutive patients (mean age 61±12years, 45% females) who underwent rubidium-82 rest/stress positron emission tomography for clinical indications. The scans were interpreted for the presence of perfusion defects as well as systolic function. Hyperemic myocardial blood flow was measured as well as Coronary Flow Reserve (CFR). Patients were followed up for a median duration of 2.2 years for incident cardiac death or myocardial infarction (CDMI).ResultsThe median HMBF was 2.6 ml/gm/min. A total of 32% of the patients had evidence of perfusion defects. Over the follow-up period, A total of 290 (5%) patients developed CDMI (8.7% in those with HMBF below 2.6 ml/gm/min. vs. 1.1% in the other group, 0<0.0001). In multivariate analysis, Both HMBF (HR 0.38, 95% CI 0.31 - 0.45, P<0.0001) and CFR (HR 0.67, 95% CI 0.58 - 0.67, P<0.0001) were independently associated with increased risk of CDMI (95% confidence interval, 3.1-6.1 P<0.0001). HMBF improved model discrimination over CFR (Area under the curve increased from 0.822 to 0.837, p=0.014). CFR did not add discriminatory value over HMBF.ConclusionNoninvasively measured hyperemic myocardial blood flow with positron emission tomography is an independent predictor of cardiac death or myocardial infarction in patients with known or suspected coronary artery disease. It adds prognostic value over CFR.