Objectives: The purpose of this study was to determine the mechanism by which 60 degrees C sauna treatment improves cardiac function in patients with chronic heart failure (CHF).
Background: We have previously reported that repeated 60 degrees C sauna treatment improves hemodynamic data and clinical symptoms in patients with CHF. We hypothesized that the sauna restores endothelial function and then improves cardiac function.
Methods: Twenty patients (62 plus minus 15 years) in New York Heart Association (NYHA) functional class II or III CHF were treated in a dry sauna at 60 degrees C for 15 min and then kept on bed rest with a blanket for 30 min, daily for two weeks. Ten patients with CHF, matched for age, gender and NYHA functional class, were placed on a bed in a temperature-controlled (24 degrees C) room for 45 min as the nontreated group. Using high-resolution ultrasound, we measured the diameter of the brachial artery at rest and during reactive hyperemia (percent flow-mediated dilation, %FMD: endothelium-dependent dilation), as well as after sublingual administration of nitroglycerin (%NTG: endothelium-independent dilation). Cardiac function was evaluated by measuring the concentrations of plasma brain natriuretic peptide (BNP).
Results: Clinical symptoms were improved in 17 of 20 patients after two weeks of sauna therapy. The %FMD after two-week sauna treatment significantly increased from the baseline value, whereas the %NTG-induced dilation did not. Concentrations of BNP after the two-week sauna treatment decreased significantly. In addition, there was a significant correlation between the change in %FMD and the percent improvement in BNP concentrations in the sauna-treated group. In contrast, none of the variables changed at the two-week interval in the nontreated group.
Conclusions: Repeated sauna treatment improves vascular endothelial function, resulting in an improvement in cardiac function and clinical symptoms.