Low skeletal muscle mass is associated with low aerobic capacity and increased mortality risk in patients with coronary heart disease - a CARE CR study

Abstract

Background: In patients with chronic heart failure, there is a positive linear relationship between skeletal muscle mass (SMM) and peak oxygen consumption ( $\dot{V}$ O_2peak ); an independent predictor of all-cause mortality_. We investigated the association between SMM and $\dot{V}$ O_2peak in patients with coronary heart disease (CHD) without a diagnosis of heart failure.

Methods: Male patients with CHD underwent maximal cardiopulmonary exercise testing and dual X-ray absorptiometry assessment. $\dot{V}$ O_2peak, the ventilatory anaerobic threshold and peak oxygen pulse were calculated. SMM was expressed as appendicular lean mass (lean mass in both arms and legs) and reported as skeletal muscle index (SMI; kg m^-2 ), and as a proportion of total body mass (appendicular skeletal mass [ASM%]). Low SMM was defined as a SMI <7·26 kg m^-2 , or ASM% <25·72%. Five-year all-cause mortality risk was calculated using the Calibre 5-year all-cause mortality risk score.

Results: Sixty patients were assessed. Thirteen (21·7%) had low SMM. SMI and ASM% correlated positively with $\dot{V}$ O_2peak (r = 0·431 and 0·473, respectively; P<0·001 for both). SMI and ASM% predicted 16·3% and 12·9% of the variance in $\dot{V}$ O_2peak , respectively. SMI correlated most closely with peak oxygen pulse (r = 0·58; P<0·001). SMI predicted 40·3% of peak $\dot{V}$ O₂ /HR variance. ASM% was inversely associated with 5-year all-cause mortality risk (r = -0·365; P = 0·006).

Conclusion: Skeletal muscle mass was positively correlated with $\dot{V}$ O_2peak in patients with CHD. Peak oxygen pulse had the strongest association with SMM. Low ASM% was associated with a higher risk of all-cause mortality. The effects of exercise and nutritional strategies aimed at improving SMM and function in CHD patients should be investigated.

Keywords: cardiorespiratory fitness; coronary disease; sarcopenia; skeletal muscle.

Figure 1

Partial correlations between appendicular lean mass and $\dot{\mathrm{V}}$ O _2peak (a), VAT (b), and peak $\dot{\mathrm{V}}$O₂/HR (c). Panels d to f show partial correlations between skeletal muscle index and $\dot{\mathrm{V}}$ O _2peak (d), VAT (e) and peak $\dot{\mathrm{V}}$ O ₂/HR (f). Panels G to H show partial correlations between appendicular skeletal mass and $\dot{\mathrm{V}}$ O _2peak (g), VAT (h), and total CPET Duration (i). $\dot{\mathrm{V}}$ O _2peak, peak oxygen uptake; VAT, ventilatory anaerobic threshold; $\dot{\mathrm{V}}$ O ₂/HR, oxygen pulse; CPET, cardiopulmonary exercise test. * = Significant; + = Low muscle mass when defined using skeletal muscle index (<7·26Kg m⁻²); ◊ = Low muscle mass when defined using appendicular skeletal mass (<25·72%); ∆ = Low muscle mass when using either skeletal mass or appendicular skeletal mass.