Cardiovascular autonomic modulation during passive heating protocols: a systematic review

Abstract

Objective: To conduct a systematic review about the possible effects of passive heating protocols on cardiovascular autonomic control in healthy individuals. Approach: The studies were obtained from MEDLINE (PubMed), LILACS (BVS), EUROPE PMC (PMC) and SCOPUS databases, simultaneously. Studies were considered eligible if they employed passive heating protocols and investigated the cardiovascular autonomic control by spontaneous methods, such as heart rate variability (HRV), systolic blood pressure variability (SBPV) and baroreflex sensitivity (BRS), in healthy adults. The revised Cochrane risk-of-bias tool (RoB-2) was used to assess the risk of bias in each study. Main results: Twenty-seven studies were included in the qualitative synthesis. Whole-body heating protocols caused a reduction in cardiac vagal modulation in fourteen studies, and two studies reported both increased sympathetic modulation and vagal withdrawal. Contrariwise, local heating protocols and sauna bathing seem to increase cardiac vagal modulation. A reduction of BRS was reported in most of the studies that used whole-body heating protocols. However, heating effects on BRS remain controversial due to methodological differences among baroreflex analysis and heating protocols. Significance: Whole-body heat stress may increase sympathetic and reduce vagal modulation to the heart in healthy adults. On the other hand, local heating therapy and sauna bathing seem to increase cardiac vagal modulation, opposing sympathetic modulation. Nonetheless, further studies should investigate acute and chronic effects of thermal therapy on cardiovascular autonomic control.

Orthostatic Stress and Baroreflex Sensitivity: A Window into Autonomic Dysfunction in Lone Paroxysmal Atrial Fibrillation

“…One of the main determinants of baroreceptor function is the activity of the autonomic nervous system (ANS), which, upon postural baroreceptor unloading, elicits adjustments in sympathetic and parasympathetic outflow to the cardiovascular system, increasing both the heart rate and vasoconstriction [ 38 , 39 , 40 , 41 ]. Our previous study suggested the presence of ANS disturbances in cardiovascular regulation in patients with PAF, as evidenced by diminished heart rate variability during HUT [ 30 ] together with the delay in the baroreflex activation immediately after tilting up, as shown in Figure 2 .…”