Peripheral adaptations in congestive heart failure: a review.
In congestive heart failure, peripheral adaptive mechanisms play a significant and largely underestimated role. In acute heart failure, sympathetic-mediated peripheral vasoconstriction together with chronotropic and inotropic actions serves to maintain perfusion pressure and blood supply to the vital organs. In chronic heart failure, activation of the renin-angiotensin system increases peripheral vascular resistance and arterial tone and decreases arterial compliance and vasodilator capacity. Endothelium-mediated, flow-dependent vasodilation is reduced as a consequence of reduced blood flow. Deconditioning renders the blood vessels incapable of dilating in response to increased flow. Simultaneously, reduced blood flow and inactivity are induced by deconditioning, with functional and structural consequences within the skeletal muscle. Exercise performance is limited by reduced overall blood flow, reduced conductance of the feeding arteries, elevated tone of the resistance vessels, reduced vasodilator capacity, impaired dissipation of heat from the working muscle, and functional and structural changes of the skeletal muscle due to underperfusion and inactivity. The adaptive mechanisms operate at different time scales. Under therapeutic intervention, their reversibility also follows different time constants. Restoration of the vasodilator capacity of the large arteries and of the abnormalities of skeletal muscle in heart failure requires time. Vasodilation with reduced pre- and/or afterload will retard progression of the superimposed ventricular dilation and hypertrophy, and therefore retard the progress of the disease. However, restoration of the peripheral blood flow and of organ function will require time. Restoration of the vascular compliance and of the full amplitude of adaptive flow-dependent vasodilation in the large arteries requires weeks or months. Similarly, restoration of functionally and morphologically altered skeletal muscle can be expected to be reversible over a longer time period.
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Medizinische Universitätsklinik, Freiburg, Federal Republic of Germany.
D001775:Blood Circulation / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001808:Blood Vessels / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans