Perspective:

This interesting and novel study offered many clinically important positive results that warrant further investigation and validation. The authors state that Waon therapy improves exercise tolerance in HF by improving endothelial function, as evidenced by improvements in FMD and CD34⁺ count. Unfortunately, several study limitations exist. The HF population of study at baseline is poorly described (systolic vs. diastolic heart failure), and neither echo nor hemodynamic criteria were required to meet the HF definition. Further, lack of a control group and lack of blinding has the potential to bias several of the endpoint measures, including that of echocardiographic data, NYHA class assessment, and FMD. Lack of a control group also makes interpretation of functional capacity difficult, as patient ‘learning curve’ on repeat testing is well documented. Overall, this study as designed does not provide strong evidence supporting sauna therapy, but the pilot data are interesting and should be further investigated.