Abstract 14503: Prevalence and Correlates of Impaired Myocardial Blood Flow Reserve in Patients With Normal Myocardial Perfusion Rubidium-82 Positron Emission Tomography
Introduction: We performed the current study to determine the prevalence and correlates of abnormal myocardial blood flow reserve (MBFR) in a large consecutive series of patients with an apparently normal rubidium-82 (82Rb) rest/stress positron emission tomography (PET) perfusion study using spatially-relative visual interpretation.
Methods: We quantitated MBFR (defined as stress/rest MBF ratio) using commercially-available software (ImagenQ, CVIT, Kansas City, MO) in consecutive patients referred for clinically indicated 82Rb PET. Retrospectively we identified all 495 patients who had no known CAD and normal scans (summed stress score ≤ 3). Mean age was 66 years, 62% were female, and 23%, 76%, 70%, 14%, 44% and 42% respectively had diabetes, hypertension, dyslipidemia, smoking, family history of CAD and obesity. Three analyses were performed: multivariate analysis to identify independent correlates of MBFR; univariate comparison of patients in the lowest tertile of MBFR versus the remainder; and the percentage of patients with MBFR below an arbitrary threshold of lower limits of normal (< 2).
Results: Multivariate predictors of a lower MBFR were age (odds ratio −0.11 per 10 years, CI [−0.18, −0.05], p = 0.0008), smoking (OR −0.31, CI [−0.54, −0.09], p = 0.007) and CACS > 400 (OR −0.22, CI [−0.41, −0.03], p = 0.02). Mean MBFR was 1.5+/−0.2, 2.1+/−0.1, and 2.9+/−0.5 from lowest to highest tertile. Patients in the lowest tertile were older, had a higher prevalence of diabetes and hypertension, and had higher levels of coronary artery calcium (CAC) and lower BMI. Of the total cohort, 43% had an abnormal MBFR based on a definition of < 2 as abnormal.
Conclusion: A high percentage of patients with an apparently normal 82Rb PET have impaired MBFR. Because the correlates of abnormal MBFR are those typically associated with CAD risk, it is likely that abnormal MBFR may identify patients at higher risk despite a normal PET myocardial perfusion imaging scan.
- © 2010 by American Heart Association, Inc.