Altered expression of myosin heavy chain in human skeletal muscle in chronic heart failure

To explore further alterations in skeletal muscle in chronic heart failure (CHF), we examined myosin heavy chain (MHC) isoforms from biopsies of the vastus lateralis in nine male patients with class II-III (CHF) (left ventricular ejection fraction (LVEF) 26 +/- 11%, peak oxygen consumption (peak (V) over dot O-2) 12.6 +/- 2 mL.kg(-1).min(-1)) and nine age-matched sedentary normal males (NL). The relative content of MHC isoforms I, IIa, and Ex was determined by gel electrophoresis as follows: The normal sedentary group (NZ) had a higher percent of MHC type I when compared with the patients (NL 48.4 +/- 7% vs CHF patients 24 +/- 21.6%, P < 0.05, no difference between MHC IIa (NL 45.1 +/- 10.5% vs CHF 56.0 +/- 12.5%), and CHF patients had a higher relative content of MHC type IIx than did the normal group (NL 6.5 +/- 9.6% vs CHF 20.0 +/- 12.9%, P < 0.05. Three of nine patients had no detectable MHC type I. In patients relative expression of MHC type I (%) was related to peak (V) over dot O-2, (r = 0.70, P < 0.05). Our results indicate that major alterations in MHC isoform expression are present in skeletal muscle in CHF. These alterations parallel previously reported changes in fiber typing that may affect contractile function in skeletal muscle and possibly exercise performance. The absence of MHC type I in some CHF patients suggests that skeletal muscle changes in this disorder are not solely a result of deconditioning, but may reflect a specific skeletal muscle myopathy in this disorder.