Left Atrial Mechanics and Functional Capacity in HFpEF pts with Paroxysmal Atrial Fibrillation

Abstract

Type of funding sources: None. Exercise capacity and ventilatory efficiency are often impaired in heart failure patients with preserved ejection fraction (HFpEF). Since left atrial (LA) pressure, particularly during exercise plays a major role in the exercise intolerance observed in these patients, we aimed to characterize the contribution of resting LA mechanical properties, assessed by two-dimensional speckle tracking echocardiography upon exercise capacity. To evaluate relationship between LA mechanics, measured by LA strain (LAS) and parameters of exercise capacity, assessed by cardiopulmonary exercise testing (CPET) in HFpEF patients with dyspnea and paroxysmal atrial fibrillation (AF). The study included 23 consecutive patients (63 ± 8 years, 83 % males) with dyspnea (NYHA≥II), paroxysmal AF and preserved LV ejection fraction (≥50%), referred for elective pulmonary vein ablation. The probability of HFpEF was estimated using H2FPEF score. During sinus rhythm, all patients underwent speckle tracking echocardiography and cardiopulmonary exercise testing by treadmill. Peak oxygen uptake (VO2max) served as measure of functional capacity and ventilation/carbon dioxide output (VE/VCO2) slope as surrogate of ventilation/perfusion mismatch. Out of all the echocardiographic indices, only LA contractile strain and strain rate showed significant correlation with peak VO2 (both p < 0.05). All three strain components of LA phasic function, i.e. reservoir, conduit and contractile LAS, had significant relationship with VE/VCO2 slope (all p<0.050). Patients with LA strain rate above the median had significantly higher VE/VCO2 slope (p=0.025) and lower peak VO2 (p=0.010). In contrast, no correlations were observed between exercise parameters and LA volumes or LA emptying fraction or any other echocardiographic indices. In HFpEF patients, VO2 max and VE/VCO2 slope are closely related to LA contractile strain, suggesting that abnormalities in LA mechanics may contribute to the blunted exercise capacity observed. Therefore, these markers can be used as an echocardiographic surrogate of functional capacity in HFpEF patients with paroxysmal AF.