Left atrial strain correlation with NTproBNP and functional capacity in obese population with preserved or mildly reduced EF: a monocentric study

Background Obesity is an epidemic illness which plays a central role in different cardiovascular pathologies, often leading to heart failure with preserved ejection fraction (HFpEF) or mildly reduced ejection fraction (HFmrEF). Studies showed that the interpretation of natriuretic peptides can be challenging since N-Terminal pro-B-type Natriuretic Peptide (NT-proBNP) levels are falsely lower in obese population, despite clinical and structural signs of disease. It becomes necessary to identify other parameters to early diagnose HF in obese patients. Purpose To investigate the association between NT-proBNP levels and speckle tracking echocardiography (STE), Myocardial Work (MW) indices, renal function and functional capacity tests (6 minutes walking test, 6MWT) in a cohort of overweight or obese patients with HFpEF and HFmrEF. Methods This monocentric retrospective study screened 118 outpatients with left ventricular ejection fraction (LVEF) ≥45%, New York Heart Association class ≥II and BMI ≥27, referred to our hospital for diagnostic echocardiography due to effort or rest dyspnea, after excluding lung etiology. We excluded pacemaker carriers, severe kidney or liver failure and previous cardiac surgery. All patients underwent comprehensive 2D and STE and complete blood test. Functional capacity was assessed by 6MWT. Statistical analyses were performed using Pearson's or Spearman's correlation coefficients. Results in a cohort of 118 symptomatic obese patients (mean age 73.9±11.8 years, mean BMI 32.6 ± 3.7 kg/m²), significant correlations were observed (Table 1). NT-proBNP was inversely related with peak atrial longitudinal strain (global PALS ρ =–0.629, p<0.001), suggesting that reduced atrial compliance is strongly associated with increased myocardial stress as in non-obese population. NT-proBNP also shows moderate inverse correlations with myocardial work indices (Global Work Index, GWI; ρ =–0.389, p<0.001; Global Constructive Work, GCW ρ =–0.321, p<0.001; Global Work Efficiency, GWE; ρ = –0.350, p<0.001) and scarce but significant correlations with Global Longitudinal Strain, (GLS ρ = 0.269, p = 0.003) and Global Wasted Work (GWW ρ=0.216, p=0.024), underlying its rise as myocardial mechanical performance worsens. NT-proBNP maintained a significant association with abnormal kidney function (with estimated glomerular filtration rate r = –0.460, p<0.001). Global PALS positively correlated with 6MWT distance (r=0.278, p=0.002), while GLS did not, highlighting the importance of atrial function in preserving exercise capacity. Conclusions Results confirm that in obese patients with HFpEF or HFmrEF, NT-proBNP maintains a good relationship with atrial function and their combined use can support HF diagnosis, also considering the association with 6MWT, contrary to GLS. Moreover, the significant inverse correlation between NT-proBNP and eGFR confirms the well-established cardio-renal interplay, despite the lower levels of NT-proBNP in obesity.