Assessment of working skeletal muscle oxygenation in patients with chronic heart failure

Patients with chronic heart failure (CHF) are frequently limited by muscle fatigue resulting from impaired skeletal muscle blood flow. Accordingly, we assessed working skeletal muscle oxygenation in such patients using near-infrared (NIR) spectroscopy. Nine normal subjects (mean age 52 years) and 12 patients with CHF (mean age 60 years) were studied. NIR spectroscopy was used to monitor relative changes in oxygenated hemoglobin (Hb) and myoglobin (Mb) (oxy Hb/Mb), deoxygenated Hb and Mb (deoxy Hb/Mb), and total (oxy + deoxy) Hb and Mb (total Hb/Mb) contents in the vastus lateralis muscle at rest, during warm-up (0 W, 30 cycles/min to 3 min), incremental maximal supine bicycle exercise (ramp protocal, 15 W/min, 50 cycles/min), and recovery. At peak exercise the patients exhibited reduced heart rate, systolic blood pressure, peak exercise oxygen consumption (VO2; 15 ± 3.0 ml/kg.min vs 32 ± 8.5 ml/kg/min), workload (99 ± 23.4 W vs 183 ± 68.4 W) as compared with the normal subjects. The respiratory quotient was comparable in both groups. In the normal subjects, oxy Hb/Mb was increased from the warm-up period to the early phase of exercise, followed by a progressive decrease to peak exercise. In the recovery phase, oxy Hb/Mb was increased abruptly. For these patients, change in oxy Hb/Mb followed a pattern similar to that seen in normal subjects, and oxy Hb/Mb was decreased earlier in contrast to that in the normal subjects. There was a significant difference in the change of oxy Hb/Mb during warm-up, early phase exercise, and recovery between the two groups. Changes in deoxy Hb/Mb and oxy Hb/Mb were inversely proportionate in both groups. In the recovery phase, the change in totla Hb/Mb was smaller than that in the normal subjects. These data suggest that oxygen delivery to working skeletal muscle is impaired throughout exercise and a reactive hyperemic response to strenuous exercise is blunted in patients with CHF.