Exercise intolerance in chronic heart failure: mechanisms and therapies. Part I.

Muscular fatigue and dyspnoea on exertion are among the most common symptoms in chronic heart failure; however their origin is still poorly understood. Several studies have shown that cardiac dysfunction alone cannot fully explain their origin, but the contribution of the multiorgan failure present in this syndrome must be highlighted. In this study, divided in two parts (see part II: pp. 643–648), we aimed to summarize the existing evidence and the most controversial aspects of the complex interplay of different factors involved in symptom generation. In this first part of the review, six key factors are revised: the heart, the lung, the skeletal muscle, the hormonal changes, the O2 delivery to the periphery, the endothelium. In the second part, the role of the excitatory reflexes and the cardiac cachexia will be presented, and finally, the potential therapeutic implications are discussed. We believe that a better knowledge of the pathophysiology of this syndrome may contribute to the management of the patients and to the improvement in their stress tolerance and quality of life.