Peripheral Artery Disease Symptomatology and Ischemia
Data on simultaneous hemodynamic calf changes and pain rating estimation while walking are very interesting, showing that the decrease of near infrared spectroscopy (NIRS) is preceding calf pain occurrence. We confirmed this finding using transcutaneous exercise oximetry (another noninvasive technique) in isolated proximal (buttocks) and isolated distal (calves) claudication. One notable difference is that we found in both proximal and distal ischemia that pain disappears whereas hemodynamic parameters are not normalized (Fouasson-Chailloux et al., 2017). Our observation corroborates the concept of reduced walking ability of the forthcoming second walking period if walking is started at pain disappearance (Gernigon et al., 2015). One possible explanation for the difference between these two results is the overshoot of NIRS signal from baseline, resulting in calf NIRS reaching resting value very early in the recovery period. This overshoot is probably reflecting the systemic increase in oxygen content observed in most PAD subjects during walking exercise (Ouedraogo et al., 2011), thus “overestimating” hemodynamic recovery. In future studies, it may be informative to study NIRS changes at the limb level relative to NIRS changes in a nonactive area that could reflect the systemic changes in oxygen content of blood during exercise.
The study of Schorr et al. (2017) is a great step for the better understanding of symptom to ischemia relationship in claudication. Nevertheless, we strongly recommend the use of recent questionnaires to fit to the American Heart Association recommendation (Gerhard-Herman et al., 2017) and as previously underlined in one of the author's paper (Schorr & Treat-Jacobson, 2013) and to decrease the risk of diagnostic erring in patients experiencing noncalf or noncramp pain. Using these questionnaires, other criteria common to the Rose and more recent definitions of claudication (pain absent at rest, occurring at exercise, and resolving at exercise cessation within 10 minutes) can be used to define “vascular-type” and “nonvascular-type” claudication as previously suggested (McDermott et al., 2009).