The 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging guidelines report that approximately 20% of diastolic dysfunction is indeterminate and has limited diagnostic accuracy. Left atrial strain may help accurately categorize diastolic dysfunction; however, its exact roles remain unclear. This study investigated the impact of left atrial reservoir strain (LARS) and its association with exercise capacity in patients with indeterminate diastolic function.

Among 687 patients who underwent cardiopulmonary exercise tests and supine bicycle stress echocardiography for symptoms including dyspnea, chest pain, valvular heart disease, and other cardiovascular problems, 118 with indeterminate diastolic function were analyzed after excluding those with atrial fibrillation and significant valvular heart disease. Poor exercise tolerance was defined as peak oxygen consumption (pVO2) <14 mL/kg/min.

Key diastolic dysfunction indices showed no statistical differences between patients with pVO2 <14 mL/kg/min and ≥14 mL/kg/min. Only LARS was independently associated with pVO2 (β=0.12 [0.09–0.15], p<0.001) in patients with indeterminate diastolic function. Receiver-operating characteristic curves highlighted LARS as a strong predictor of impaired pVO2 among all echocardiographic variables (area under the curve: 0.871 [0.776–0.966]), with an optimal cut-off value of 21% after adjusting for clinical variables. Logistic analysis showed that patients with ≤21% LARS had significantly reduced exercise capacity (odds ratio, 12.77; 95% confidence interval, 3.83–48.65; p<0.001).

LARS is significantly associated with pVO2 in patients with indeterminate diastolic function. Impaired LARS is a robust predictor of exercise intolerance; measuring LARS enhances diastolic-function assessment accuracy, potentially improving individualized diastolic-dysfunction management and treatment.