Relationships between cardiac function, functional capacity, and patient-reported health status remain incompletely defined in heart failure, with implications for endpoint selection in clinical trials. In a post hoc analysis of the randomized cardiac microcurrent (C-MIC) II trial published in ESC Heart Failure, correlations among these domains were evaluated in patients with advanced heart failure with reduced ejection fraction (HFrEF) receiving guideline-directed medical therapy.

The analysis included 65 ambulatory patients with non-ischemic dilated cardiomyopathy, New York Heart Association (NYHA) Class III-IV symptoms, and baseline left ventricular ejection fraction (LVEF) of 25–35%. Associations between changes in Kansas City Cardiomyopathy

Questionnaire Overall Summary Score (KCCQ-OSS), 6-minute walk distance (6MWD), LVEF, and peak oxygen uptake (peak VO2) were assessed over 6 months using Pearson correlation coefficients with 95% confidence intervals (CI).

From baseline to 6 months, changes in KCCQ-OSS and 6MWD showed modest correlations with core laboratory-assessed LVEF (r=0.39; 95% CI: 0.16–0.58; p=0.0015 and r=0.39; 95% CI: 0.15-0.58; p=0.0022). Changes in KCCQ-OSS and 6MWD were strongly correlated (r=0.63; 95% CI: 0.46-0.76; p<0.0001). No significant correlation was observed between changes in KCCQ-OSS or 6MWD and peak VO2 (p=0.06 and p=0.30). Changes in LVEF and peak VO2 showed modest correlation (r=0.41; 95% CI: 0.16-0.61; p=0.002), while baseline correlations with peak VO2 increased at 6 months for LVEF (r=0.56; 95% CI: 0.35-0.71; p<0.0001).

These findings indicate that cardiac function, functional capacity, and health status represent related but distinct domains in advanced heart failure.