Differences in skeletal muscle between men and women with chronic heart failure

Men with chronic heart failure (CHF) have alterationsin their skeletal muscle that are partially responsible for a decreased exercise tolerance. The purpose of this study was to investigate whether skeletal muscle alterations in women with CHF are similar tothose observed in men and if these alterations are related to exerciseintolerance. Twenty-five men and thirteen women with CHFperformed a maximal exercise test for evaluation of peak oxygen consumption (O₂) and resting leftventricular ejection fraction, after which a biopsy of the vastuslateralis was performed. Twenty-one normal subjects (11 women, 10 men)were also studied. The relationship between muscle markers and peakO₂ was consistent for CHF men and women.When controlling for gender, analysis showed that oxidative enzymes andcapillary density are the best predictors of peak O_2. These results indicatethat aerobically matched CHF men and women have no differences inskeletal muscle biochemistry and histology. However, when CHF groupswere separated by peak exercise capacity of 4.5 metabolic equivalents(METs), CHF men with peak O₂ >4.5METs had increased citrate synthase and 3-hydroxyacyl-CoA dehydrogenasecompared with CHF men with peak O₂ <4.5METs. CHF men with a lower peak O₂ hadincreased capillary density compared with men with higher peakO₂. These observations were notreproduced in CHF women. This suggests that differences may existin how skeletal muscle adapts to decreasing peakO₂ in patients with CHF.