Rhythmic handgrip exercise failed to increase brachial artery diameter in Fontan patients (3.08 to 3.10 mm) compared to healthy controls (3.25 to 3.34 mm; interaction P=0.012).
Cross-Sectional (n=31)
Does acute rhythmic handgrip exercise elicit attenuated brachial artery endothelium-dependent vasodilation in individuals with Fontan circulation compared to healthy controls?
Individuals with Fontan circulation exhibit attenuated exercise-induced flow-mediated dilation and forearm vasodilation, suggesting underlying conduit artery and microvascular dysfunction.
p-value: p=0.012
Background: Reactive hyperemia-induced brachial artery flow-mediated dilation (FMD) is attenuated in individuals with Fontan circulation. However, it is unknown whether exercise-induced FMD is attenuated in this population. Hypothesis: It was hypothesized that individuals with Fontan circulation exhibit attenuated brachial artery endothelium-dependent vasodilation during steady-state acute exercise. Methods: Individuals with Fontan circulation (n=18, 9 F; 16±4 yrs; 23±5 kg/m 2 ) and similar age and sex healthy control participants (n=13, 7 F; 17±4 yrs; 22±5 kg/m 2 ) performed 3 bouts of acute exercise that each involved a 1 minute rest period followed by 5 minutes of rhythmic handgrip exercise (2:2 duty cycle) at 20% of maximum voluntary contraction. Participants performed handgrip exercise using a dynamometer and the brachial artery diameter and velocity were recorded using high resolution duplex ultrasonography while blood pressure was measured using finger photoplethysmography. Diameter, velocity, and blood pressure were used to compute antegrade shear rate, retrograde shear rate, mean shear rate, and oscillatory shear index as well as forearm vascular conductance. Data from the 3 bouts of handgrip were averaged to yield a single profile. Furthermore, data during the final 30 seconds of rest and steady-state exercise were each averaged and analyzed using a 2 × 2 ANOVA (group; Fontan and control × condition; rest and exercise). Results: The data revealed brachial artery diameter increased significantly in healthy controls, but not in individuals with Fontan circulation (control: 3.25±0.47 to 3.34±0.43 mm vs. Fontan: 3.08±0.35 to 3.10±0.35 mm, interaction, p=0.012). Antegrade (controls: 161±53 to 280±115 s-1 vs. Fontan: 210±68 to 283±85 s-1, condition, p< 0.001) and mean shear rate (controls: 71±30 to 132±54 s-1 vs. Fontan: 79±39 to 122±48 s-1, condition, p< 0.001) increased from rest to exercise, but did not differ between groups (group, p=0.363). Retrograde shear rate (controls: -19±16 to -16±13 s-1 vs. Fontan: -51±29 to -40±24 s-1 condition, p=0.002) and oscillatory shear index (controls: 0.11±0.09 to 0.05±0.04 a.u. vs. Fontan: 0.20±0.10 to 0.13±0.09 a.u. condition, p< 0.001) decreased from rest to exercise, and were greater in individuals with Fontan circulation than healthy control participants (group, p=0.008). Forearm vascular conductance increased from rest to exercise in both groups (controls: 0.4±0.2 to 0.8±0.3 vs. Fontan: 0.3±0.1 to 0.5±0.1, interaction, p=0.004); however, it was greater in controls than individuals with Fontan circulation during exercise (p< 0.001). Conclusion and significance: Exercise-induced FMD and vasodilation of the forearm vasculature is attenuated in individuals with Fontan circulation, implicating both conduit artery and microvascular dysfunction in the pathophysiology of disease. 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.
Khan et al. (Fri,) conducted a cross-sectional in Fontan circulation (n=31). Rhythmic handgrip exercise vs. Healthy controls was evaluated on Brachial artery diameter change from rest to exercise (p=0.012). Rhythmic handgrip exercise failed to increase brachial artery diameter in Fontan patients (3.08 to 3.10 mm) compared to healthy controls (3.25 to 3.34 mm; interaction P=0.012).