Exercise skeletal muscle blood flow is related to peripheral microvascularstiffness in idiopathic dilated cardiomyopathy

Peripheral microvascular function plays an important role in congestive hea rt failure (CHF). Decreased exercise blood now and microvascular dysfunctio n have been described in CHF and both factors are regarded as parameters th at might influence exercise capacity in these patients. Whether these facto rs are related to or can be characterized in clinical severity of CHF has n ot been elucidated in this population. Skeletal muscle blood now (SMBF) was measured continuously noninvasively, by means of the local isotope washout technique using (133)Xenon, in musculus tibialis anterior during graded ma ximal supine bicycle exercise. The distensibility in skeletal muscle was me asured in a papaverine-relaxed vascular bed using Tc-99m-pertechnetate. The investigation included 20 patients with moderate CHF (NYHA II), II patient s with severe CHF (NYHA III, IV) due to idiopathic dilated cardiomyopathy ( IDCM), and 31 age-matched healthy subjects. The maximal SMBF level was sign ificantly lower in severe CHF (3.6 +/- 2.5 (ml . (100 g . min)(-1))) compar ed with moderate CHF (8.6 +/- 5.1 (ml . (100 g min)(-1)); P < 0.005) and co ntrols(11.0 +/- 4.1 (ml . (100 g . min)(-1)); P < 0.0001), but similar betw een moderate CHF and controls. Distensibility in skeletal muscle was decrea sed in severe CHF (12 +/- 8%) compared with controls (44 +/- 17%; P < 0.000 1 vs severe CHF) and decreased with increasing severity of CHF (moderate CH F, 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 exerci se 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 c orrelates to maximal exercise SMBF. Furthermore, maximal SMBF correlates to exercise time. This implies that increased skeletal muscle microvascular s tiffness may contribute to the reduced blood flow during exercise and SMBF may partly limit exercise performance in CHF patients due to IDCM. (C) 1999 Academic Press.