On improvement of exercise tolerance in patients with chronic heart failure, with special reference to local muscle training

Abstract: ON IMPROVEMENT OF EXERCISE TOLERANCE IN PATIENTS WrrH CHRONIC HEART FAILURE With special reference to local muscle traimng Thesis by Allan Gordon, MD, Division of Cardiology at the Department of Medicine, Karolinska Institutet, Huddinge University Hospital, S-14186 Huddinge, Sweden Reduced heart pump function and skeletal muscle abnormalities are considered important determinants for the low physical exercise capacity in chronic heart failure. Because of reduced ventricular function, traditional physical rehabilitation with whole body training may cause underperfusion and low local work intensity, thereby producing suboptimal conditions for skeletal muscle training. The specific aims of the investigation on patients with chronic heart failure were: To quantify the effect of high-intensity local endurance and strength training on the structure and function of knee extension muscles and to determine if this type of training might improve exercise capacity . To determine muscle strength in the major muscle groups of the arm and leg and the time course of the muscle twitch compared to healthy individuals. Also, to establish whether muscle force production during maximal single and repeated contractions of major muscle groups is affected by poor activation. To evaluate effects of creatine supplementation on ejection fraction, symptom-limited exercise capacity and skeletal muscle strength. To determine if there are any differences in skeletal muscle adaptation and exercise capacity using one or two legged knee extensor endurance training. To investigate if the health-related quality of life is decreased and if knee extensor endurance training can improve their quality of life. To investigate the systemic effects of local knee extensor endurance training on ventilation and neurohormonal activity. Training effects were studied in chronic heart failure patients after 8 weeks using an exercise-model where only the knee extensor leg muscles were engaged in the work. Effects of creatine after one week of supplementation was evaluated. The conclusions are: Chronic heart failure patients adapts to localised muscle training with improved f unctional capacity of the quadriceps femoris muscle. This may be related to an increased muscle cross-sectional area, a greater capillary density and increased mitochondrial enzyme activity in the quadriceps femoris muscle. The localised training effect was accompanied by a transfer effect to an increased whole body work capacity. Voluntary strength in the major muscle groups of the arm and leg is well maintained. These patients may possess muscles that are faster to contract and less resistant to fatigue. This increased fatigability is not due to poor muscle activation. Skeletal muscle creatine levels are similar to those of healthy volunteers. Creatine supplementation for one week increases muscle strength and endurance by 10-20%. Enhanced muscle function occurs primarily in subjects with low basal levels of creatine. Skeletal muscle changes in chronic heart failure are not irreversible. The major factors contributing to these changes and exercise limitation are cardiac dysfunction and deconditioning. In this group of patients different degrees of local activation, i.e. one- or two-legged knee extensor exercise do not seem to differ in terms of the effects on oxidative capacity and exercise capacity. Thus, in patients with chronic heart failure, exercise modes in which a limited ventricular function does not limit skeletal muscle function to any major extent, the musculature shows sign of a plasticity similar to that of healthy subjects. Chronic heart failure patients exhibit a globally reduced health-related quality of life compared to healthy controls. Local muscle training can improve this reduced quality of life. As two-legged knee extension training showed a tendency to better improvement in submaximal exercise capacity and in the quality of life than one-legged training, the effects on the quality of life appear to be exercise- related, in addition to a possible placebo effect. Local muscle training in patients with chronic heart failure leads to improved ventilation connected with decreased lactate concentrations suggesting beneficial conditioning of ventilatory reflexes. This type of training also seems to exert further systemic effects, such as reduced sympathetic stress. The levels of plasma catecholamines are generally lower during quadriceps activation than the plasma catecholamines levels reported to be induced by traditional ergometer cycle exercise. Key words: Chronic heart failure, creatine, exercise capacity, local muscle training, skeletal muscle, knee extensor muscles, quality of life, sympathetic activation.