Abstract 4367325: Correlation and Complementary Prognostic Value of 82Rb PET-Derived Myocardial Flow Reserve and Echocardiography-Assessed Diastolic Dysfunction

Background: Coronary microvascular dysfunction (CMD) is increasingly recognized as a key contributor to diastolic dysfunction, the key pathology in heart failure with preserved ejection fraction (HFpEF). Objective: We studied the relationship between, and clinical implications of, CMD, assessed using myocardial flow reserve (MFR), and diastolic dysfunction. Methods: We included 861 symptomatic patients who underwent same-day transthoracic echocardiography and 82 Rubidium PET within 24 hours. Patients with LVEF <50% or perfusion defects were excluded. Diastolic dysfunction was assessed and graded according to the ASE guidelines, and MFR was calculated as the ratio of stress and rest myocardial blood flow. The primary outcome was a composite of all-cause death and heart failure (HF) hospitalizations. Results: Of the included 861 patients, the median age was 67 years, 54.9% were female, and 34.7% had diastolic dysfunction. MFR was inversely correlated with key echocardiographic markers of diastolic dysfunction, including E/e′ (r = –0.34), Estimated PASP (r = –0.35), and mitral A velocity (r = –0.31). Over a median follow-up of 1.34 years, 85 events occurred. The highest event rate was observed in patients with both impaired MFR (<2) and grade II/III diastolic dysfunction, with an adjusted hazard ratio (HR) of 6.21 (95% CI: 2.76–13.93) ( Figure 1 ). The simultaneous addition of MFR and diastolic dysfunction grade significantly improved predictive fit (P-value from likelihood ratio test: <0.001), with an increase in the C-index from 0.768 in the base model to 0.818 in the combined model. Combined assessment also improved risk-stratification over separate assessment of each variable (P-value of <0.001 vs MFR alone and 0.006 vs diastolic dysfunction grade alone)( Table 1 ). Conclusion: CMD demonstrated a significant correlation with diastolic dysfunction. Both were independently associated with adverse outcomes, and their combined assessment markedly enhanced risk stratification in patients without overt ischemia. These findings highlight the complementary roles of PET and echocardiography in evaluating HFpEF-related physiology and prognosis.