Purpose: This study was conducted to determine the association between the characteristics of calf muscle hemoglobin oxygen saturation (StO(2)) and exercise performance in patients with intermittent claudication.
Methods: The study comprised 39 patients with peripheral arterial disease limited by intermittent claudication. Patients were characterized on calf muscle StO(2) before, during, and after a graded treadmill test, as well as on demographic and cardiovascular risk factors, ankle-brachial index (ABI), ischemic window, initial claudication distance (ICD), and absolute claudication distance (ACD).
Results: Calf muscle StO(2) decreased 72%, from 55% +/- 18% (mean +/- SD) saturation at rest to the minimum value of 17% +/- 19% saturation attained 459 +/- 380 seconds after the initiation of exercise. After exercise, recovery half-time of calf muscle StO(2) was attained at 129 +/- 98 seconds, whereas full recovery to the resting value was reached at 225 +/- 140 seconds. After adjusting for sex, race, and grouping according to the initial decline constant in calf muscle StO(2) during exercise, the exercise time to minimum calf muscle StO(2) was correlated with the ischemic window (r = -0.493, P = .002), ICD (r = 0.339, P = .043), and ACD (r = 0.680, P < .001). After treadmill exercise, the recovery half-time of calf muscle StO(2) was correlated with the ischemic window (r = 0.531, P < .001), ICD (r = -0.598, P < .001), and ACD (r = -0.491, P = .003).
Conclusion: In patients limited by intermittent claudication, shorter ICD and ACD values are associated with reaching a minimum value in calf muscle StO(2) sooner during treadmill exercise and with having a delayed recovery in calf muscle StO(2) after exercise.