Skeletal muscle microcirculatory abnormalities are associated with exercise intolerance, ventilatory inefficiency, and impaired autonomic control in heart failure

BACKGROUND: Several skeletal muscle abnormalities have been identified in patients with chronic heart failure (CHF), including endothelial dysfunction. We hypothesized that skeletal muscle microcirculation, assessed by near-infrared spectroscopy (NIRS), is impaired in CHF patients and is associated with disease severity. METHODS: Eighty-three stable patients with mild moderate CHF (72 males, mean age 54 +/- 14 years, body mass index 26.7 +/- 3.4 kg/m(2)) and 8 healthy subjects, matched for age, gender and body mass index, underwent NIRS with the vascular occlusion technique and cardiopulmonary exercise testing (CPET) evaluation on the same day. Tissue oxygen saturation (StO(2), %), defined as the percentage of hemoglobin saturation in the microvasculature compartments, was measured in the thenar muscle by NIRS before, during and after 3-minute occlusion of the brachial artery. Measurements included StO(2), oxygen consumption rate (OCR, %/min) and reperfusion rate (RR, %/min). All subjects underwent a symptom-limited CPET on a cycle ergometer. Measurements included VO2 at peak exercise (VO(2)peak, ml/kg/min) and anaerobic threshold (VO(2)AT, ml/kg/min), VE/VCO2 slope, chronotropic reserve (CR, %) and heart rate recovery (HRR1, bpm). RESULTS: CHF patients had significantly lower StO(2) (75 +/- 8.2 vs 80.3 +/- 6, p < 0.05), lower OCR (32.3 +/- 10.4 vs 37.7 +/- 5.5, p < 0.05) and lower RR (10 +/- 2.8 vs 15.7 +/- 6.3, p < 0.05) compared with healthy controls. CHF patients with RR >= 9.5 had a significantly greater VO(2)peak (p < 0.001), VO(2)AT (p < 0.01), CR (p = 0.01) and HRR1 (p = 0.01), and lower VE/VCO2 slope (p = 0.001), compared to those with RR <9.5. In a multivariate analysis, RR was identified as an independent predictor of VO(2)peak, VE/VCO2 slope and HRR1. CONCLUSIONS: Peripheral muscle microcirculation, as assessed by NIRS, is significantly impaired in CHF patients and is associated with disease severity. J Heart Lung Transplant 2011;30:1403-8 (C) 2011 International Society for Heart and Lung Transplantation. All rights reserved.