Vescovo G, Serafini F, Dalla Libera L, Leprotti C, Facchin L, Tenderini P, Ambrosio G B
First Department of Internal Medicine, Venice City Hospital, Italy.
Am Heart J. 1998 Jan;135(1):130-7. doi: 10.1016/s0002-8703(98)70353-9.
Patients with congestive heart failure (CHF) have a reduced exercise capacity because of the early appearance of fatigue and dyspnea. Qualitative changes in the skeletal muscle composition and metabolism can be responsible for the origin of symptoms
We correlated the myosin heavy chain (MHC) composition of the gastrocnemius in 20 patients with different degrees of CHF to NYHA class, diuretic consumption, echocardiographic parameters, and expiratory gases measured during cardiopulmonary exercise testing. MHC composition was determined electrophoretically in skeletal muscle needle microbiopsies and the percent distribution was calculated by densitometry. Maximal cardiopulmonary exercise testing was performed on a treadmill with a modified Naughton protocol. A capnograph was used.
There was no correlation between ejection fraction, left ventricular end systolic diameter, left ventricular end diastolic diameter, and MHC composition. We found a significant positive correlation between the percentage of MHC 1 (slow aerobic isoform) and NYHA class (r2 = 0.62, p < 0.0001), peak VO2 (r2 = 0.5, p < 0.0004), ventilatory threshold (VT) (r2 = 0.33, p = 0.008) and O2 pulse (peak VO2/HR) (r2 = 0.40, p = 0.003). There was a negative correlation between both MHC2a (fast oxidative) and MHC2b (fast glycolytic) with peak VO2 (r2 = 0.38, p = 0.004 and r2 = 0.37, p = 0.004, respectively), VT (r2 = 0.2, p = 0.046 and r2 = 0.34, p = 0.007, respectively), and O2 pulse (peak VO2/HR) (r2 = 0.39, p = 0.003 and r2 = 0.23, p = 0.03). NYHA class was also correlated positively with MHC2a and MHC2b (r2 = 0.46, p = 0.001 and r2 = 0.41, p < 0.006, respectively) and negatively with the same clinical and functional parameters.
The correlation between the magnitude of the MHC shift from the slow aerobic to the fast glycolytic and fast oxidative with both functional and objective measurements of exercise capacity (peak VO2, VT, O2 pulse) seem to suggest that changes in skeletal muscle composition may play a determining role in exercise tolerance in patients with CHF.
充血性心力衰竭（CHF）患者由于疲劳和呼吸困难过早出现，运动能力降低。骨骼肌组成和代谢的质性变化可能是症状产生的原因。
我们将20例不同程度CHF患者腓肠肌的肌球蛋白重链（MHC）组成与纽约心脏协会（NYHA）心功能分级、利尿剂使用情况、超声心动图参数以及心肺运动试验期间测得的呼出气体进行了关联分析。通过骨骼肌针吸活检电泳法测定MHC组成，并通过密度测定法计算百分比分布。采用改良的诺顿方案在跑步机上进行最大心肺运动试验。使用了二氧化碳分析仪。
射血分数、左心室收缩末期内径、左心室舒张末期内径与MHC组成之间无相关性。我们发现MHC 1（慢氧化型异构体）百分比与NYHA心功能分级（r2 = 0.62，p < 0.0001）、峰值VO2（r2 = 0.5，p < 0.0004）、通气阈值（VT）（r2 = 0.33，p = 0.008）和氧脉搏（峰值VO2/心率）（r2 = 0.40，p = 0.003）之间存在显著正相关。MHC2a（快氧化型）和MHC2b（快糖酵解型）与峰值VO2（分别为r2 = 0.38，p = 0.004和r2 = 0.37，p = 0.004）、VT（分别为r2 = 0.2，p = 0.046和r2 = 0.34，p = 0.007）以及氧脉搏（峰值VO2/心率）（分别为r2 = 0.39，p = 0.003和r2 = 0.23，p = 0.03）之间均呈负相关。NYHA心功能分级与MHC2a和MHC2b也呈正相关（分别为r2 = 0.46，p = 0.001和r2 = 0.41，p < 0.006），与相同的临床和功能参数呈负相关。
MHC从慢氧化型向快糖酵解型和快氧化型转变的程度与运动能力的功能和客观测量指标（峰值VO²、VT、氧脉搏）之间的相关性似乎表明，骨骼肌组成的变化可能在CHF患者的运动耐力中起决定性作用。
