Clinical impact of a formula-based fat-free mass index in male patients with chronic heart failure

Background Loss of fat-free mass (FFM) is a hallmark of sarcopenia and is associated with adverse outcomes in heart failure (HF). Dual-energy X-ray absorptiometry (DEXA) is considered a reference method for body composition assessment; however, its limited availability and practical constraints, particularly in patients with advanced HF, may restrict its routine use. Purpose This study aims to investigate whether a simple formula-based FFM index (FFMI) provides reliable body composition assessment and prognostic performance compared with DEXA-derived FFMI in male patients with chronic HF. Methods A total of 187 male patients with chronic HF (68 ± 11 years, left ventricular ejection fraction 37 ± 13%) from the Studies Investigating Co-morbidities Aggravating Heart Failure (SICA-HF) were enrolled. Formula-based FFMI (FFMIcalc) was derived using the Deurenberg equation to estimate body fat percentage (1.20 × [BMI] + 0.23 × [Age] – 16.2), followed by FFM calculation and indexing to height squared. DEXA-based FFMI (FFMIdexa) was calculated as total body lean mass plus bone mass divided by height squared. Patients were stratified according to the median value of each FFMI measure. The primary endpoint was defined as all-cause mortality. Results During a median follow-up of 6.2 years, 80 patients (42.8%) died. FFMIcalc strongly correlated with FFMIdexa (r=0.77, p<0.0001), although FFMIcalc was significantly lower (18.77 vs. 19.86 kg/m²; mean difference 1.09 kg/m², p<0.0001). The difference between FFMIcalc and FFMIdexa was more pronounced in patients with oedema (β=-0.35 kg/m², 95% CI -0.59 to -0.11, p=0.004). Patients with low FFMIcalc had higher mortality than those with high FFMIcalc (log-rank p=0.004), and this association was independent of oedema status (both strata: log-rank p=0.04). In contrast, FFMIdexa was not associated with mortality (log-rank p=0.41). Multivariable analysis, including cardiac function, HF severity, and major clinical risk factors, confirmed the association between lower FFMIcalc and higher mortality (adjusted hazard ratio 1.39 per 1-SD decrease in FFMIcalc, p=0.01), with no interaction by age (median-split; p=0.44), BMI (median-split; p=0.79), and oedema status (p=0.78). Conclusions In male patients with chronic HF, formula-based FFMI is strongly correlated with DEXA-derived FFMI and is independently associated with long-term mortality. The prognostic value of FFMIcalc is consistent irrespective of age, BMI, or oedema status. These findings support the clinical use of a simple, readily available anthropometric approach to complement DEXA for risk stratification in chronic HF.