Left atrial reservoir strain is independently associated with heart failure hospitalization beyond NT-proBNP in HFpEF with non-paroxysmal atrial fibrillation

Introduction Patients with heart failure with preserved ejection fraction (HFpEF) and non-paroxysmal atrial fibrillation (AF) are at high risk of heart failure hospitalization (HFH). In AF, NT-proBNP interpretation is complicated by rhythm- and load-related factors, motivating markers of atrial mechanics. Left atrial reservoir strain (LASr) reflects atrial mechanical function, compliance, and chronic filling-pressure burden. This study assessed whether LASr was independently associated with first HFH beyond NT-proBNP. Methods We retrospectively identified 432 patients with LVEF ≥50%, HFpEF (chiefly HFA-PEFF; invasive wedge pressure in 78, 18.1%), and non-paroxysmal AF from two centers. LASr was measured offline by two-dimensional speckle-tracking echocardiography on a single vendor platform, with at least five cardiac cycles averaged. The primary endpoint was first HFH. Cox models assessed apparent and bootstrap optimism-corrected performance, with proportional hazards diagnostics and sensitivity analyses including adjustment for left atrial volume index (LAVI) and a high-certainty HFpEF cohort. Results During a median follow-up of 31.7 (24.3–37.8) months, 124 patients (28.7%) reached the endpoint. Baseline LASr was lower in these patients (11.1% vs. 14.8%; P < 0.001). After adjustment for clinical variables, log NT-proBNP, LV GLS, and E/e′, LASr remained independently associated with HFH (HR 0.61 per 1-SD increase, 95% CI: 0.49–0.76, equivalent to HR 1.11 per 1% absolute decrease, 95% CI: 1.06–1.16), and the association persisted after further adjustment for LAVI (HR 0.61, 95% CI: 0.49–0.76). Log NT-proBNP (HR 1.32, 95% CI: 1.04–1.68) and E/e′ (HR 1.23, 95% CI: 1.03–1.47) were also independently associated. Adding LASr raised the apparent Harrell C-index from 0.712 to 0.737 and the optimism-corrected C-index from 0.687 to 0.713 (corrected increment 0.027, 95% CI: −0.001 to 0.044). Discussion In HFpEF with non-paroxysmal AF, LASr was independently associated with first HFH after clinical, biomarker, echocardiographic, and left atrial size adjustment, whereas its incremental discrimination beyond NT-proBNP, LV GLS, E/e′, and clinical variables was modest, with an optimism-corrected confidence interval that included zero. This study therefore concludes that lower LASr marks a higher risk of HFH in this population and may complement NT-proBNP, although these retrospective two-center findings, obtained without vital status data, require prospective multicenter validation.