ASSOCIATION BETWEEN LEFT ATRIAL STRAIN AND LEFT ATRIAL VOLUME IN OVERWEIGHT AND OBESE ADULTS: A CROSS-SECTIONAL SPECKLE-TRACKING ECHOCARDIOGRAPHIC STUDY

Abstract

Background: Maximum left atrial (LA) volume indexes structural remodelling in obesity, whereas LA reservoir strain (LASr) measured by speckle-tracking echocardiography indexes atrial function. Whether the two markers move together across the spectrum of elevated body mass index (BMI) is unsettled. Objectives: To compare biplane LA volume and phasic LA strain across BMI strata, and to test whether strain and volume are associated with each other and with BMI independently of age, sex and comorbidity. Materials and Methods: Seventy-five adults with BMI ≥25 kg/m² and preserved left ventricular ejection fraction underwent transthoracic echocardiography at a tertiary centre. Maximum LA volume (LAVmax) and reservoir, conduit and contractile strain were obtained from apical four-chamber, two-chamber and biplane measurements. Participants were grouped as BMI 25.0–30.0 (n = 15), >30.0–35.0 (n = 20) and >35.0 kg/m² (n = 40), and compared using analysis of variance or the Kruskal–Wallis test, Spearman correlation and multivariable linear regression. Results: Mean age was 56.7 ± 9.4 years; 49 participants (65.3%) were men. Biplane LASr fell progressively across BMI groups (median 20.0%, 16.0% and 13.0%; Kruskal–Wallis p < 0.001; p for trend < 0.001), whereas biplane LAVmax did not differ (39.5, 38.5 and 40.3 mL; p = 0.355). BMI correlated inversely with LASr (ρ = −0.496, 95% confidence interval [CI] −0.658 to −0.291; p < 0.001) but not with LAVmax (ρ = 0.179; p = 0.125). LAVmax and LASr were only weakly related (ρ = −0.225; p = 0.053), and this attenuated after adjustment for BMI (partial r = −0.168; p = 0.150). On multivariable regression BMI was the only independent predictor of LASr (B = −0.504% per kg/m², 95% CI −0.766 to −0.242; p < 0.001; adjusted R² = 0.187); no variable predicted LAVmax (model p = 0.610). Impaired LASr (<22%) affected 60 participants (80.0%), LAVmax >32 mL affected 63 (84.0%). Conclusion: In overweight and obese adults with preserved ejection fraction, LA reservoir strain deteriorated as BMI rose, independently of age, sex and comorbidity, whereas LA volume showed no BMI gradient and was not significantly associated with strain. Atrial function tracks adiposity more closely than chamber size does; the two should not be treated as interchangeable.