Reduced Myocardial Flow Reserve Is Associated With Diastolic Dysfunction and Decreased Left Atrial Strain in Patients With Normal Ejection Fraction and Epicardial Perfusion.

INTRODUCTION: Coronary microvascular dysfunction (MVD) may contribute to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). Using myocardial flow reserve (MFR) measured by positron emission tomography (PET) as an assessment of microvascular function, we hypothesized that abnormal MFR is associated with LV diastolic dysfunction (DD) and reduced LV and LA strain in patients with risk factors for HFpEF and normal epicardial perfusion on cardiac PET.

METHODS AND RESULTS: Retrospective study of patients without heart failure who underwent cardiac rubidium-82 PET and echocardiography. Global MFR was calculated as the ratio of global stress to rest myocardial blood flow. Echocardiographic measures of diastolic function were recorded. Global longitudinal LA and LV strain were measured with a 2-dimensional speckle-tracking technique. Relationships among MFR and echocardiographic measures were assessed with linear regression, analysis of variance, and test for trend. Seventy-three patients (age 64 ± 11 years, 52% male) were identified with no epicardial perfusion defect on cardiac PET and an ejection fraction ≥50%. Decreased MFR was associated with LV DD (P = .02) and increased E/e', an estimation of LV filling pressure (low E/e' [<8] vs. high E/e' [>15], P < .001). MFR was associated with LA strain independent of age, gender, and common comorbidities (adjusted β = 2.6% per unit MFR, P = 0.046); however, MFR was only marginally related to LV strain.

CONCLUSIONS: In patients with risk factors for HFpEF, MVD assessed with MFR was associated with DD, increased estimated LV filling pressure, and abnormal LA strain.