Left atrial strain and its correlates to cardiorespiratory endurance in HFpEF patients with paroxysmal atrial fibrillation

Abstract Introduction Patients (pts) with paroxysmal atrial fibrillation are at risk for developing heart failure with preserved ejection fraction (HFpEF) and often have an impaired exercise capacity. Since left atrial (LA) pressure plays a major role in the exercise intolerance, we aimed to characterize the contribution of resting LA mechanical properties, assessed by two dimensional speckle tracking echocardiography upon exercise capacity. Purpose To evaluate relationship between LA mechanics, measured by LA strain (LAS) and parameters of exercise capacity in pts with paroxysmal atrial fibrillation. Methods The study included 54 pts (64 ± 10 years, 76 % males) with dyspnea (NYHA≥II), paroxysmal atrial fibrillation and preserved LV ejection fraction (≥50%). The likelihood of HFpEF was estimated using H2FPEF score. During sinus rhythm, all patients underwent speckle tracking echocardiography and cardiopulmonary exercise testing (CPET). Peak oxygen uptake (VO2 peak) served as measure of functional capacity and ventilation/carbon dioxide output slope (VE/VCO2) as surrogate of ventilation/perfusion mismatch. Results LA contractile strain (S) and strain rate (SR) showed significant correlation with VO2 peak (both p < 0.05). LA reservoir, conduit and contractile LAS, all had significant relationship with VE/VCO2 slope (all p<0.050). Pts with LASR above the median had significantly higher VE/VCO2 (p=0.025) and lower VO2 peak (p=0.010). In contrast, no correlations were observed between exercise parameters and LA volumes or any other echocardiographic indices. Conclusions In HFpEF, VO2 peak and VE/VCO2 are closely related to LA contractile strain, suggesting that abnormalities in LA mechanics may contribute to the blunted exercise capacity. Therefore, we speculate that these markers can be used as an echocardiographic surrogate of functional capacity in HFpEF pts. Figure 1: Relationship between left atrial reservoir (LASr) and contractile (LASct) strain and peak oxygen consumption (VO2 peak) and ventilatory efficiency (VE/VCO2 slope). Figure 2: Peak oxygen consumption (VO2 peak) and ventilatory efficiency (VE/VCO2slope) in pts with and without left atrial strain rate above the median.