Rates of Referral to Coronary Angiography After Positron Emission Tomography (PET) Myocardial Perfusion Imaging (MPI)

Introduction: The true utility of a test lies on the ability of its results to guide management. Several studies have reported low rates of abnormal perfusion and referral to coronary angiography following SPECT myocardial perfusion imaging (MPI), raising questions of overuse in a low pre-test risk population. Positron emission tomography (PET) MPI is typically reserved for patients unable to exercise, with greater burden of comorbidities and at higher perceived CAD risk. However, the rates of patient referral to angiography after PET MPI are not well known.

Methods: We retrospectively examined all consecutive patients who had a rest/stress Rb-82 PET MPI within our health system between 1/2010 and 12/2016. 90-day referral rates to coronary angiography were determined by medical record review. Known coronary artery disease (CAD) was defined as presence of known atherosclerotic disease on angiography, prior history of myocardial infarction or revascularization. We calculated rates of coronary angiography within 90 days of the PET MPI based on patient history of known CAD at the time of the test and perfusion results.

Results: A total of 19,282 unique patients underwent a PET MPI, with a mean age of 68.6 ± 11.9 years, BMI of 29.5 ± 6.3 kg/m². Of them,53% were male, 30.7% had diabetes,15.7% had peripheral vascular disease, 10.8% prior stroke/TIA and 42.3% had known CAD. The population was highly symptomatic with chest pain reported in 57.0% and dyspnea in 49.8%. The overall referral rate of 90-day coronary angiography was 18.5% (3574); 14.4% (1603/11125) among patients without known CAD and 24.2% (1971/8157) among those with documented prior CAD. Among patients with high-risk ischemia (≥ 10%) on MPI, 64.1% (1930/3011) had angiography within 90 days; the rate was higher in those without known CAD (69.5%; 761/1097) than in those with known CAD (61.2%; 1169/1914).

Conclusions: About 1 in 5 patients undergoing PET MPI are referred for coronary angiography within 90 days of testing, a rate greater than that reported for SPECT MPI, likely due to higher baseline risk of patients undergoing PET MPI testing. While referral rates for coronary angiography varied based on the presence or absence of prior documented clinical CAD and presence of test abnormalities, nearly 36% of patients with moderate-severe ischemia were not referred. Further work is needed to characterize why such patients are not referred for invasive evaluation to optimize the use of PET MPI in this high-risk population.

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