Lower baroreflex sensitivity during muscle metaboreflex activation in children and adolescents with the Fontan circulation and single ventricle physiology

Abstract

Individuals with the Fontan circulation and single ventricle physiology have elevated sympathetic nerve activity at rest and during muscle metaboreflex activation that is consistent with autonomic dysfunction. Adults with the Fontan circulation also show reduced baroreflex sensitivity (BRS); however, there is limited understanding of BRS in children or adolescents with the Fontan circulation. In healthy adults, BRS decreases with increased sympathetic nerve activity during isometric handgrip exercise, but not during isolated muscle metaboreflex activation. The effect of handgrip exercise and muscle metaboreflex activation on BRS in children and adolescents with the Fontan circulation is currently unknown.PURPOSEWe tested the hypothesis that BRS is lower at rest and less responsive during handgrip exercise and post‐exercise circulatory occlusion (PECO) in children/adolescents with the Fontan circulation compared to healthy controls.METHODSEight children/adolescents with the Fontan circulation (12 ± 2 yrs; 3 males) and 8 healthy controls (13 ± 4 yrs; 5 males) were studied. Continuous heart rate (ECG) and non‐invasive blood pressure (Finometer® MIDI) were recorded during 3‐min of resting baseline, 2‐min of isometric handgrip exercise at 30% of maximal voluntary contraction, and 3‐min of PECO. Continuous heart rate, systolic blood pressure, and diastolic blood pressure signals were analyzed using the BRS Analysis software (Nevrokard, Slovenia, 2018) to yield average BRS values during rest, handgrip, and PECO for each group. Differences between groups and across conditions were assessed using two‐way repeated measures (2 × 3, group × condition) ANOVA. P<0.05 was considered significant.RESULTSThere was a significant group × condition interaction for BRS (P<0.001). BRS was lower in children/adolescents with the Fontan circulation vs. healthy controls at rest (13 ± 8 vs. 38 ± 10 ms/mmHg; P<0.001) and during PECO (18 ± 17 vs. 37 ± 18 ms/mmHg; P=0.044), but not during handgrip (13 ± 10 vs. 14 ± 6 ms/mmHg; P=0.843). BRS in children/adolescents with the Fontan circulation did not change across conditions (P=0.188).CONCLUSIONOur findings suggest that BRS is lower at rest and has a blunted response during sympatho‐excitation in children/adolescents with the Fontan circulation compared to healthy controls. Collectively, our findings indicate potential autonomic dysfunction in children/adolescents with the Fontan circulation.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.