Peripheral limitations of maximal aerobic capacity in patients with chronic heart failure

Conclusions  Exercise intolerance in patients with CHF is related to chronic changes in structure and function of the heart and vessels, which lead to reduction of cardiac output reserve and hypoperfusion of skeletal muscle during exercise. Chronic neurohormonal activation, endothelial dysfunction, and deconditioning may contribute to the abnormalities of skeletal muscle blood flow, function, and metabolism in patients with CHF. A combination of pharmacologic (neurohormonal blockade) and nonpharmacologic therapy (physical training) may provide the optimal regimen to improve functional capacity in patients with CHF. Therapies that increase skeletal muscle perfusion are associated with concomitant increases in peak aerobic capacity. The Xe-133 clearance method for measurement of skeletal muscle blood flow is the only noninvasive technique that allows measurement of blood flow during maximal treadmill or bicycle exercise. If skeletal muscle blood flow measurements are performed in accordance with the fundamental principles of the technique, with recognition of the method limitations and appropriate controls for sources of experimental error, the Xe-133 technique appears to be a useful tool for measurement of skeletal muscle blood flow in clinical investigations. Measurement of skeletal muscle blood flow with PET and O-15—labeled water is a promising tool for investigation of heterogeneity of blood flow within the skeletal muscle circulation, although the need for arterial blood sampling limits its application for serial measurements in response to therapy.