The impact of obesity on myocardial flow reserve and its prognostic utility

Background: Obesity is a major cardiovascular risk factor associated with coronary microvascular dysfunction, which can be noninvasively assessed using myocardial flow reserve (MFR) on positron emission tomography (PET). As impaired MFR identifies high-risk patients, we assessed whether body mass index (BMI) modifies the association between MFR and cardiovascular outcomes. Methods: Consecutive patients with no known coronary artery disease who had a clinically indicated PET were enrolled and followed prospectively for incident outcomes (all-cause death, major adverse cardiovascular events (MACE), and heart failure admissions). Multivariable-adjusted Cox proportional hazards models were used to study the association between MFR, and incident events stratified by BMI categories. Results: The study population consisted of 3397 patients; median (IQR) age 67 (59-74) years, 55.2% female, 63.9% White, 17.6% with a BMI of 18.5-<25 kg/m², 27.5% with a BMI of 25-<30 kg/m², 38.6% with a BMI of 30-<40 kg/m², and 16.3% with a BMI of ≥40 kg/m². The median (IQR) MFR was 2.35 (1.96-2.80). Over a median (IQR) follow-up time of 1.34 (.43-2.43) years, there were 125 incident events (56 MACE, 6 HF admissions, and 70 deaths). In adjusted analyses, a .1-unit increase in MFR was significantly associated with decreased incident outcomes; HR (95% CI):0.91 (95% CI .84-.99) for BMI 18.5–<25 kg/m², .88 (.83-.94) for BMI 25–<30 kg/m², .93 (.87-.99) for BMI 30–<40 kg/m², and .88 (.76-1.01) for BMI ≥40 kg/m². There was no significant interaction between MFR and BMI; P = .381. Conclusion: PET-derived global MFR is inversely associated with subsequent cardiovascular outcomes in all BMI categories.