Purpose: Endothelial dysfunction is the earliest abnormality in the development of coronary atherosclerosis. 82Rb 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 82Rb PET, and (2) compare the results with those measured using 15O-water PET.
Methods: MBF was assessed at rest and during the CPT with 82Rb and 15O-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.
Results: At rest, measurements of MBF for smokers vs controls were not different using 15O-water (0.86±0.18 vs 0.70±0.13, p=0.426) than they were using 82Rb (0.83±0.23 vs 0.62±0.20, p=0.051). Both methods showed a reduced CPT response in smokers vs controls (15O-water, 1.03±0.21 vs 1.42±0.29, p=0.006; 82Rb, 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 82Rb and 15O-water during the CPT.
Conclusion: Using a CPT, 82Rb MBF measurements detected coronary endothelial dysfunctions in smokers. 82Rb MBF measurements were comparable to those made using the 15O-water approach. Thus, 82Rb PET may be applicable for risk assessments or evaluation of risk factor modification in subjects with coronary risk factors.