Sex-specific diagnostic and prognostic value of a resting biventricular myocardial blood flow ratio measured by PET in chronic coronary syndromes

Abstract

Quantitative cardiac PET is well established for assessing left ventricular (LV) ischaemia, but the clinical significance of right ventricular (RV) myocardial blood flow (MBF) remains unclear. We investigated the diagnostic and prognostic value of the ratio between RV and LV resting MBF (MBFRV/LV) as a potential PET-based marker of abnormal RV loading, with a focus on sex-specific differences. A clinical cohort of 783 symptomatic subjects with known or clinically suspected chronic coronary syndromes referred for cardiac 15O-water PET was retrospectively included. MBFRV/LV was analysed in relation to traditional risk factors, comorbidities associated with manifest cardiac disease, echocardiography, biomarkers, stress PET findings, and major adverse cardiac events (MACE: acute heart failure [HF] hospitalization or cardiovascular death). MBFRV/LV was narrowly regulated in low-risk subjects (mean 51±8%). It increased progressively with traditional risk factors—particularly in females—and was independently associated with hypertension, obesity, and LV ischaemia. Higher MBFRV/LV correlated with NT-proBNP and echocardiographic markers of diastolic dysfunction, including elevated E/e′ and RV systolic pressure. A value above 67% predicted MACE (HR 4.5 [95% CI 2.8–7.3]) and remained independently prognostic after adjustment for HF history, LV ejection fraction, and myocardial flow reserve (MFR). In females without known HF, MBFRV/LV predicted outcomes independently of MFR. The RV/LV perfusion ratio derived from standard PET imaging reflects sex-specific vulnerability to adverse ventricular loading. MBFRV/LV identifies patients—especially females—with increased HF risk, independent of LV systolic or microvascular function, and may serve as a novel marker of HF pathophysiology.