Left atrioventricular ratio (LA:LV): using left ventricular size as the reference for identifying maladaptive left atrial remodelling

Introduction Remodelling of the left atrium (LA) and left ventricle (LV) occurs in response to pathological and physiological stimuli, yet their inter-dependence is often overlooked in clinical practice. The left atrioventricular ratio (LA:LV)—the ratio of maximal LA end-systolic volume (LAESV) to LV end-diastolic volume (LVEDV)—may offer valuable context for distinguishing physiological from pathological cardiac remodelling. Methods and results This study evaluated LA:LV, assessed via echocardiography, and cardiorespiratory fitness assessed as peak oxygen uptake (VO2peak) in a multi-centre international cohort spanning the cardiorespiratory fitness spectrum. Exercise capacity in healthy participants was categorized by VO2 peak quartiles, and cardiac structural differences were analysed. Among 2943 adults (1600 healthy, 1343 pathology), healthy individuals had a median LA:LV of 0.49 [0.38, 0.61], consistent with LVEDV being roughly twice the LAESV. Pathology revealed higher LA:LV ratios [0.53 (0.38–0.75), P < 0.001], with marked elevations amongst AF [0.60 (0.45–0.78)] and HFpEF [0.70 (0.51–0.88)]—a 30% increase vs. healthy adults. The highest indexed LA volumes occurred in the highest VO₂ peak quartile [Q4: 36 (28–46) mL/m²], while the LA:LV ratio was highest in Q1 [0.53 (0.42–0.69)]. Among participants with elevated LAVi (≥34 mL/m²), concordance with elevated LA:LV ratio (≥0.75) varied markedly by fitness level: ∼60% in Q1-Q2 vs. only 7% in Q4, highlighting the importance of fitness context when interpreting LA enlargement. Conclusion The LA:LV ratio effectively discriminates between adaptive and maladaptive atrial remodelling. LA:LV is typically ∼0.5. Lower ratios correlate with higher functional capacity and physiological remodelling, whereas ratios ≥0.75 may indicate pathological remodelling and warrant consideration of atrial pathology.