Decrease in exhaled hydrogen as marker of congestive heart failure

Hydrogen excretion is thought to be related to systemic antioxidation activity. H₂ selectively reduces the hydroxyl radical of free hydrogen (·OH), a highly cytotoxic form of reactive oxygen species, in cultured cells.

We investigated whether exhaled H₂ decreased during night sleep, reflected ·OH production and was associated with heart failure severity. We enrolled 108 patients with chronic heart failure (CHF) and 15 control participants without CHF. H₂ concentration was measured by gas chromatography in exhaled breath collected before sleep and in the morning after overnight fasting. Overnight change in H₂ concentration (ΔH₂) was calculated. Mitochondrial morphology evaluated by transmission electron microscopy in endomyocardial biopsies collected from 18 patients with dilated cardiomyopathy.

ΔH₂ was significantly lower in patients with CHF compared with controls (-4.3±1.0 vs 2.0±2.1 ppm, p=0.030) and was positively correlated with cardiac index (CI; r = -0.285, p=0.003). Patients with a ΔH₂<0 ppm had a significantly lower CI compared with those who had a ΔH₂>0 ppm (2.85±0.61 vs 3.24±0.65 L/min/m², p=0.005). ΔH₂ was negatively correlated with both the percentage of vacuole-containing mitochondria and indices of cristae remodelling (r = -0.61, p=0.007).

Decrease in exhaled H₂ during night sleep was associated with CHF severity. ΔH₂ warrants investigation as marker of CHF severity.