PURPOSE: Heart failure (HF) patients’ are limited in their ability to manage a thermal load during exercise secondary to impaired skin blood flow (SkBF). Folic acid has been shown to improve vascular function and accompanying changes in SkBF in healthy older individuals and in those with metabolic and cardiovascular disease. Therefore, we examined the effect of folic acid on vascular function, and SkBF responses during exercise in 10 HF patients and 10 age-matched healthy controls (CON) similar in body size during exercise at a fixed rate of metabolic heat production (Hprod) in a 30°C environment.

METHODS: Rectal temperature (Trec) and cutaneous vascular conductance (CVC) were measured during 60min of cycle ergometry before (pre) and after (post) a 6 week intervention period where participants ingested 5mg of folic acid, once daily. At these time points (pre- and post-folic acid), vascular function was assessed using flow-mediated dilation (FMD).

RESULTS: Hprod was maintained at the same level for HF (pre: 332±46; post: 337±51W, p=0.84) and CON (pre: 323±31; post: 317±40W, p=0.72), and no differences were observed between groups in both exercise trials (p>0.05). Trec increased to a similar extent for HF (pre: 0.76±0.22°C; post: 0.70±0.11°C, p=0.63) and CON (pre: 0.55±0.27; post: 0.45±0.25°C, p=0.84); however, the rise in Trec was consistently higher in HF during both exercise trials (p<0.05). Similarly, CVC increased to a similar extent for HF (pre: 0.89±0.43; post: 0.83±0.45au/mmHg, p=0.80) and CON (pre: 2.01±0.79; post: 2.03±0.72au/mmHg, p=0.73), but the rise in CVC was consistently lower in HF during both exercise trials (p<0.05). Furthermore, folic acid improved FMD in HF (pre: 3.72±1.16; post: 5.88±1.29, p<0.01); however, no difference was observed in CON (pre-: 5.47±1.98; post: 6.50±2.49%, p=0.20).

CONCLUSIONS: Collectively, these findings demonstrate that folic acid supplementation does not serve to enhance SkBF responses and attenuate the rise in core temperature during exercise at a fixed Hprod in HF patients. However, folic acid improved vascular function to a greater extent in HF than CON.