Measurements of calf muscle oxygenation during standing and exercise in patients with primary valvular insufficiency.

Abstract

Despite the established role of the calf muscle pump for preventing chronic venous disorders, hemoglobin flow in the calf muscle is poorly understood. Near-infrared spectroscopy (NIRS) provides continuous noninvasive monitoring of changes in tissue-oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) levels. The purpose of this study was to investigate the changes in calf muscle O2Hb and HHb levels during standing and exercise in patients with primary valvular insufficiency (PVI). Eighty-three limbs in 81 patients with PVI were enrolled. The clinical manifestations of these patients were categorized according to the CEAP (Clinical, Etiologic, Anatomical, and Pathophysiologic) classification, and patients were divided into group I (C1-3S,Ep,As,d,p,Pr) and group II (C4-6S,Ep,As,d,p,Pr). Moreover, to assess the severity of PVI, the revised Venous Clinical Severity Score (VCSS) was employed. NIRS was used to measure changes in the calf muscle O2Hb and HHb levels. On standing, increases in O2Hb and HHb were calculated by subtracting the baseline value from the maximum value (ΔO2Hbst and ΔHHbst). The time elapsed until the maximum increases in O2Hb and HHb concentrations (TO2Hbst, and THHbst) were also measured. During 10 tiptoe movements, the relative change in O2Hb was calculated by subtracting the value measured at the end of exercise from the value measured at the beginning of exercise(ΔO2Hbex). On the other hand, 10 tiptoe movements produced venous expulsion (ΔHHbEex) and a subsequent retention (ΔHHbRex). The oxygenation index (HbD; HbD= O2Hb- HHb) was also calculated at the end of standing and10 tiptoe movements (ΔHbDst and ΔHbDex). Among the 83 limbs evaluated, 48 were classified as group I and 35 as group II. Standing caused increases in the levels of both ΔO2Hbst and ΔHHbst. However, there were nosignificant differences in these increases between the two groups. In contrast, the TO2Hbst was significantly reduced in group II in comparison with group I (55± 29 vs 36± 30 seconds; P= .007). During 10 tiptoe movements, a decrease in O2Hb concentration was observed, and there was no significant difference in ΔO2Hbex between group I and group II. In contrast, the ΔHHbRex was significantly increased in group II compared with group I (6± 7 vs 9± 6 μmol/L; P= .013). Furthermore, falls in ΔHbDex were more pronounced in group II (7± 16 vs-7± 16 μmol/L; P= .001). A statistically significant correlation was found between C of CEAP and the VCSS (r= 0.778; P< .001). Moreover, NIRS-derived TO2Hbst (r=-0.312; P< .01) and ΔHbDex (r=-0.332; P< .01) showed moderate inverse correlationswith C of CEAP. Similarly, NIRS-derived ΔHbDex (r=-0.501; P< .001) had a strong inverse correlation, and ΔHbDst (r=-0.383; P< .001) and TO2Hbst (r=-0.378; P< .001) had moderate inverse correlations with VCSS. Changes in O2Hb and HHb concentrations differ according to CEAP manifestation and VCSS. These data offer new insights into calf muscle hemodynamics at the microcirculation level in patients with PVI.