Prognostic implications of cardiac 82-rubidium positron emission tomography in angina patients with no perfusion defects

Abstract Background Myocardial perfusion imaging with 82-Rubidium positron emission tomography (82Rb-PET) is increasingly used in the assessment of stable coronary artery disease (CAD). Among other variables, it provides quantitative measures of myocardial blood flow (MBF) which has shown the prognostic significance of coronary microvascular dysfunction (CMD), also in patients without perfusion defects. However, other 82Rb-PET variables may also be of prognostic significance in these patients. Purpose The purpose of this study was to evaluate the prognostic value of 82Rb-PET in patients with symptoms suggestive of CAD but no perfusion defects. Methods A study was conducted with 3726 consecutive patients who underwent 82Rb-PET on the suspicion of stable CAD between January 2018 and August 2020. After exclusion of patients with regional perfusion defects, we examined the association of 82Rb-PET derived parameters with a composite endpoint: all-cause mortality, hospitalization for unstable angina pectoris, acute myocardial infarction, heart failure or ischemic stroke in 2175 patients. CMD was defined as myocardial blood flow reserve (MBFR) <2. Analyses were further stratified to assess differences across gender. Results Resting and stress MBF were higher in women, while MBFR was lower and CMD more prevalent (30.5% among women versus 25.3% among men, p=0.008). Over a median follow-up of 1.7 years (IQR 1.1–2.5 years) a total of 148 events were observed. In unadjusted analyses, MBF during stress, MBFR, left ventricular ejection fraction (LVEF), LVEF-reserve, heart rate reserve and Ca-score were associated with adverse outcomes in both genders (Figure 1). A joint multivariable Cox model, for both genders, adjusted for patient characteristics, cardiovascular risk factors and 82Rb-PET variables showed reduced MBFR <2 (HR 1.75, 95% CI 1.24–2.48), resting LVEF (HR 1.38 per 10% decrease, 95% CI 1.24–1.54) and LVEF-reserve (HR 1.19 per 5% decrease, 95% CI 1.07–1.31) to be significant predictors of outcomes (Figure 2). Results were consistent in subgroups defined by gender, previous history of ischemic heart disease (IHD), reduced LVEF and atrial fibrillation. Conclusion MBFR, LVEF and LVEF-reserve derived from 82Rb-PET are predictors of adverse outcome and provide prognostic information in patients with no perfusion defects. This may aid in identifying patients at risk and provide opportunity of prevention. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Department of Cardiology, Bispebjerg Frederiksberg Hospital, Copenhagen