Low-intensity dynamic handgrip exercise produced comparable blood flow kinetics in Fontan patients and healthy controls (tau 22 vs 23 s, P=0.702), despite lower steady-state blood flow.
Cross-Sectional (n=31)
Does low-intensity dynamic handgrip exercise alter peripheral blood flow kinetics in patients with a Fontan circulation compared to healthy controls?
In patients with a Fontan circulation, peripheral blood flow kinetics during low-intensity exercise are comparable to healthy controls, but the amplitude of blood flow increase is lower, indicating differences in vascular control.
Absolute Event Rate: 22% vs 23%
p-value: p=0.702
Fontan circulation (FTN) is associated with exercise intolerance, but the contribution of peripheral blood flow to this limitation is unclear. This study aimed to determine whether peripheral blood flow kinetics are altered in response to low-intensity dynamic handgrip exercise. It was hypothesized that patients with FTN would exhibit slowed blood flow kinetics. To test this hypothesis, FTN (9M/9F, 16 ± 4 years of age) and similar age- and sex-matched healthy controls (CTL, 7M/6F, 17 ± 4 years of age, P=0.614) completed three bouts of dynamic handgrip exercise for 5 min at 20% of maximal voluntary contraction (FTN: 10 ± 4 kg vs CTL: 18 ± 7 kg, P< 0.001). Brachial artery diameter and blood flow velocity were continuously recorded using Doppler ultrasound (Vivid i, GE Medical Systems), analyzed offline (Cardiovascular Suite 4.3.0, Quipu, Italy), and used to calculate blood flow. Second-by-second blood flow from each bout were time-aligned and averaged to obtain a single response profile for each participant. Subsequently, blood flow data was further averaged into 5-s bins and the first 3 min of the exercise were modelled using monoexponential curve fitting (OriginLab, OriginPro 2024b). FTN and CTL had similar baseline blood flow (FTN: 24 ± 11 mL/min vs CTL: 27 ± 14 mL/min, P=0.553). The amplitude increase in blood flow was lower in FTN (14 ± 7 mL/min) vs CTL (25 ± 16 mL/min, P=0.014), owing to the lower absolute exercise intensity. Accordingly, steady-state exercise blood flow was also lower in FTN (38 ± 11 mL/min) vs CTL (53 ± 25 mL/min, P=0.031). The time delay for the increase in blood flow was comparable between FTN (0.03 ± 0.36 s) and CTL (-0.05 ± 0.26 s, P=0.507). The blood flow time constant, tau, was also comparable between FTN (22 ± 8 s) and CTL (23 ± 11 s, P=0.702), as was the mean response time (time delay + tau, FTN: 22 ± 8 s vs CTL: 24 ± 10 s, P=0.560). During the exercise transient, FTN showed a 7% smaller reduction in vessel diameter and a 33% lower increase in blood velocity than CTL. These data indicate that the kinetics of blood flow are comparable between FTN and CTL, but that the control of blood flow differs. Funding: Saskatchewan Centre for Patient Oriented Research, Canadian Institute of Health Research, Scottish Rite Charitable Foundation of Canada, Heart and Stroke Foundation of Canada) This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Harder et al. (2026) conducted a cross-sectional in Fontan circulation (n=31). Low-intensity dynamic handgrip exercise vs. Healthy controls was evaluated on Blood flow time constant (tau) (p=0.702). Low-intensity dynamic handgrip exercise produced comparable blood flow kinetics in Fontan patients and healthy controls (tau 22 vs 23 s, P=0.702), despite lower steady-state blood flow.