Quantitative analysis of coronary endothelial function with generator-produced 82Rb PET: comparison with 15O-labelled water PET

Endothelial dysfunction is the earliest abnormality in the development of coronary atherosclerosis. Rb-82 is a generator-produced positron emission tomography (PET) myocardial perfusion tracer that is becoming more widely used. We aimed to (1) develop a method for quantitative assessment of coronary endothelial function using the myocardial blood flow (MBF) response during a cold pressor test (CPT) in smokers, measured using Rb-82 PET, and (2) compare the results with those measured using O-15-water PET. MBF was assessed at rest and during the CPT with Rb-82 and O-15-water in nine controls and ten smokers. A one-compartment model with tracer extraction correction was used to estimate MBF with both tracers. CPT response was calculated as the ratio of MBF during the CPT to MBF at rest. At rest, measurements of MBF for smokers vs controls were not different using O-15-water (0.86 +/- 0.18 vs 0.70 +/- 0.13, p = 0.426) than they were using Rb-82 (0.83 +/- 0.23 vs 0.62 +/- 0.20, p = 0.051). Both methods showed a reduced CPT response in smokers vs controls (O-15-water, 1.03 +/- 0.21 vs 1.42 +/- 0.29, p = 0.006; Rb-82, 1.02 +/- 0.28 vs 1.70 +/- 0.52, p < 0.001). There was high reliability [intraclass correlation coefficients: 0.48 (0.07, 0.75)] of MBF measurement between Rb-82 and O-15-water during the CPT. Using a CPT, Rb-82 MBF measurements detected coronary endothelial dysfunctions in smokers. Rb-82 MBF measurements were comparable to those made using the O-15-water approach. Thus, Rb-82 PET may be applicable for risk assessments or evaluation of risk factor modification in subjects with coronary risk factors.