Exercise Skeletal Muscle Blood Flow Is Related to Peripheral Microvascular Stiffness in Idiopathic Dilated Cardiomyopathy

Abstract

Peripheral microvascular function plays an important role in congestive heart failure (CHF). Decreased exercise blood flow and microvascular dysfunction have been described in CHF and both factors are regarded as parameters that might influence exercise capacity in these patients. Whether these factors are related to or can be characterized in clinical severity of CHF has not been elucidated in this population. Skeletal muscle blood flow (SMBF) was measured continuously noninvasively, by means of the local isotope washout technique using 133Xenon, in musculus tibialis anterior during graded maximal supine bicycle exercise. The distensibility in skeletal muscle was measured in a papaverine-relaxed vascular bed using 99mTc-pertechnetate. The investigation included 20 patients with moderate CHF (NYHA II), 11 patients with severe CHF (NYHA III, IV) due to idiopathic dilated cardiomyopathy (IDCM), and 31 age-matched healthy subjects. The maximal SMBF level was significantly lower in severe CHF (3.6 ± 2.5 (ml · (100 g · min)−1)) compared with moderate CHF (8.6 ± 5.1 (ml · (100 g · min)−1); P < 0.005) and controls (11.0 ± 4.1 (ml · (100 g · min)−1); P < 0.0001), but similar between moderate CHF and controls. Distensibility in skeletal muscle was decreased in severe CHF (12 ± 8%) compared with controls (44 ± 17%; P < 0.0001 vs severe CHF) and decreased with increasing severity of CHF (moderate CHF, 23 ± 14%; P < 0.0005 vs controls). In CHF patients, a relationship was demonstrated between skeletal muscle distensibility and the maximal SMBF (P < 0.0001; r = 0.70). Moreover, maximal SMBF correlated directly to exercise time (P < 0.005; r = 0.54). Patients with CHF have reduced exercise SMBF, which may be a limiting factor for the reduced maximal exercise capacity. Moreover, microvascular distensibility in skeletal muscle is reduced and correlates to maximal exercise SMBF. Furthermore, maximal SMBF correlates to exercise time. This implies that increased skeletal muscle microvascular stiffness may contribute to the reduced blood flow during exercise and SMBF may partly limit exercise performance in CHF patients due to IDCM.