HEART-FAILURE - AN UPDATE ON PATHOPHYSIOLOGY

Myocardial hypertrophy is an established risk factor for cardiovascular morbidity and mortality. Beyond quantitative and mechanical aspects hypertrophy is associated with alterations in cardiac gene expression, resulting in a more fetal-like myocyte phenotype with a fragile Ca++ homeostasis. Depressed expression of sarcoplasmatic reticulum ATPase is the hallmark of this overload phenotype. Conversely, the gene expression and the activity of sodium calcium exchanger is up-regulated in endstage heart failure. Both alterations contribute to prolonged cytosolic Ca++ transients, disturbed relaxation and, probably, to electrophysiologic instability. Angiotensin II is a growth promoting agent and several lines of circumferential evidence suggest that the local formation of angiotensin II might contribute to the trophic response and phenotype shift, in cardiac overload. The cardiac gene expression of angiotensin converting enzyme and angiotensinogen is increased early after cardiac overload and in patients with severe heart failure. Chronic ACE inhibition suppresses plasma and tissue ACE activity, reduces LV hypertrophy and improves long-term survival. The hallmark of the peripheral adaptation in chronic heart failure is systemic vasoconstriction, associated with neurohumoral activation. Several mechanisms are involved in the impaired peripheral perfusion, including increased sympathetic tone and increased vascular stiffness. Recently, data suggest an important role of the endothelium for perfusion of skeletal muscle in heart failure. Endothelium-dependent dilation of resistance vessels is blunted in patients with severe chronic heart failure. Conceivably, this abnormality may be involved in the impaired reactive hyperemia in patients with chronic heart failure. Moreover, alterations of skeletal muscle emerge in chronic heart failure contributing to reduced exercise performance. Both endothelial dysfunction and alterations of skeletal muscle appear to be reversible with chronic ACE-inhibitor therapy and/or physical training.