Haines, Phillip

Introduction: Impaired left atrial (LA) function may limit optimal cardiac performance, reflecting both LA load and atrial dysfunction in HFpEF. The link between MRI-derived LA characteristics and exercise capacity in HFpEF has not been studied. Hypothesis: We hypothesized that total LA emptying fraction (LAEF) is reduced in HFpEF vs. healthy controls and LA functional impairment would be correlated with LV diastolic dysfunction, vascular dysfunction, and exercise intolerance. As LA hypertension may increase right ventricular load and limit increases in pulmonary perfusion with exercise, the correlation of LAEF with ventilatory efficiency (VE/VCO2 slope) was also examined. Methods: Baseline exercise, echo, and cardiac MRI data from RELAX (a study of sildenafil in HFpEF) in patients in sinus rhythm with a measureable LAEF by MRI (n=100) were utilized. Healthy volunteers (n=21) were included for comparison. LAV was measured by the biplane area-length method using 2-/4-chamber SSFP CMR. LAEF was defined as total (ΔLAVmax-min), passive/conduit (ΔLAVmax-before atrial contraction ), and active (ΔLAVbefore atrial contraction-min), each divided by maximal LAV. Results: As compared to controls, LAEF (particularly passive conduit function) was reduced in HFpEF (Table 1). In HFpEF, patients with lower LAEF had a larger LA, more echo diastolic dysfunction, higher PA systolic pressure and NT-proBNP, reduced aortic distensibility, worse exercise capacity, and ventilatory inefficiency (Table 2). Conclusions: LA function is impaired in HFpEF, may serve as a marker of chronic LA hypertension and may contribute to impaired exercise intolerance and ventilatory inefficiency.