Int J Environ Res Public Health 2021 Mar 1;18(5):2384. Microvascular Dysfunction in Peripheral Artery Disease: Is Heat Therapy a Viable Treatment? Cody P Anderson 1 2, Elizabeth J Pekas 1, Song-Young Park 1 Affiliations
1 School of Health and Kinesiology, University of Nebraska at Omaha, Omaha, NE 68182, USA.
2 Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE 68182, USA.
Abstract Peripheral artery disease (PAD) is characterized by the development of atherosclerotic plaques in the lower-body conduit arteries. PAD is commonly accompanied by microvascular disease, which may result in poor wound healing, plantar ulcer development, and subsequent limb amputation. Understanding the mechanisms underlying the development of plantar ulcers is a critical step in the development of adequate treatment options for patients with PAD. Skin is classified into two major components: glabrous and non-glabrous. These skin types have unique microcirculation characteristics, making it important to differentiate between the two when investigating mechanisms for plantar ulcer development in PAD. There is evidence for a microcirculation compensatory mechanism in PAD. This is evident by the maintenance of basal microcirculation perfusion and capillary filling pressure despite a reduced pressure differential beyond an occlusion in non-critical limb ischemia PAD. The major mechanism for this compensatory system seems to be progressive vasodilation of the arterial network below an occlusion. Recently, heat therapies have emerged as novel treatment options for attenuating the progression of PAD. Heat therapies are capable of stimulating the cardiovascular system, which may lead to beneficial adaptations that may ultimately reduce fatigue during walking in PAD. Early work in this area has shown that full-body heating is capable of generating an acute cardiovascular response, similar to exercise, which has been suggested as the most efficient treatment modality and may generate adaptations with chronic exposure. Heat therapies may emerge as a conservative treatment option capable of attenuating the progression of PAD and ultimately impeding the development of plantar ulcers. Keywords: atherosclerosis; endothelial dysfunction; microcirculation; peripheral vascular disease.
Figure 3. A proposed mechanism for how heat therapy may attenuate the progressive ischemia that is characteristic of peripheral artery disease (PAD). Heat therapy may generate beneficial arterial adaptations, leading to improved arterial function and reduced tissue ischemia.
Table 2. Characteristics of the heat therapy studies in patients with peripheral artery disease (PAD) and chronic hindlimb ischemia murine models. The asterisk (*) indicates animal studies. (VEGF—vascular endothelial growth factor; SBP— systolic blood pressure; DBP—diastolic blood pressure; RHR—resting heart rate; PWV—pulse wave velocity; EDT-1—endothelin-1; PBV—popliteal blood velocity; 6MWD—6 minute walk distance; maxPBF—maximum popliteal artery blood flow; maxBC—maximum blood conductance; antPF—antegrade popliteal flow; HR—heart rate).