Key Points
- To determine myoglobin concentration in skeletal muscle fibers of chronic heart failure (CHF) patients and calculate its effects on oxygen buffering and facilitated diffusion.
- Obtained vastus lateralis muscle biopsies from 9 CHF patients and 5 healthy control subjects.
- Quantified fiber cross-sectional area, myoglobin concentration, and succinate dehydrogenase (SDH) activity across type I and type II fibers using calibrated histochemistry.
- Calculated oxygen buffering capacity and the critical extracellular oxygen tension required to prevent core anoxia (Po2(crit)).
- Myoglobin concentration did not differ significantly between CHF and controls in type I (0.69 ± 0.11 vs. 0.70 ± 0.09 mM) or type II fibers (0.52 ± 0.07 vs. 0.49 ± 0.07 mM), whereas SDH activity was significantly reduced in CHF across both fiber types (P < 0.01).
- Calculated oxygen buffering capacity was significantly higher in CHF than controls in type I (11.4 ± 2.1 vs. 7.8 ± 0.9 s, P < 0.01) and type II fibers (13.6 ± 3.9 vs. 7.5 ± 1.0 s, P < 0.01).
- Critical oxygen tension (Po2(crit)) was significantly lower in CHF type II fibers compared to controls (6.1 ± 2.8 vs. 14.7 ± 6.2 Torr, P < 0.01), but remained similar in type I fibers (10.3 ± 0.9 vs. 11.5 ± 3.3 Torr).
Structured PICO
PPopulation9 chronic heart failure (CHF) patients and 5 control subjects
CComparator5 control subjects
OOutcomeMyoglobin concentration in skeletal muscle fibers (vastus lateralis)surrogate
Reduced exercise tolerance in chronic heart failure is not due to myoglobin deficiency, as myoglobin concentrations are preserved while oxidative capacity (SDH activity) is reduced.