Determinants of exercise limitation in contemporary paediatric Fontan patients with an extra cardiac conduit

Abstract

Background: Although various determinants of exercise limitation in Fontan patients have been studied, most research has been performed in patients who underwent different surgical procedures with differing haemodynamic characteristics. The aim of the current study was to evaluate non-invasively measured cardiovascular parameters and their influence on exercise performance in paediatric Fontan patients with an extracardiac conduit and moderate-good systolic ventricular function. Methods: Fontan patients, between 8 and 18 years of age, with moderate to good systolic ventricular function and an extracardiac conduit were included. Exercise performance and cardiovascular assessment, comprising echocardiography, aortic stiffness measurement and ambulatory measurement of cardiac autonomous nervous activity were performed on the same day. Healthy subjects served as controls. Results: Thirty-six Fontan patients (age 14.0 years) and thirty-five healthy subjects (age 12.8 years) were included. Compared to controls, Fontan patients had reduced diastolic ventricular function and increased arterial stiffness. No differences were found in heart rate (HR) and cardiac parasympathetic nervous activity. In Fontan patients, maximal as well as submaximal exercise capacity was impaired, with the percentage of predicted capacity ranging between 54 and 72%. Chronotropic competence, however, was good with a peak HR of 174 (94% of predicted). Lower maximal and submaximal exercise capacity was correlated with a higher HR at rest, higher pulse wave velocity of the aorta and a lower ratio of early and late diastolic flow velocity. Conclusion: Contemporary paediatric Fontan patients have an impaired exercise capacity with preserved chronotropic competence. Exercise performance correlates with heart rate at rest, diastolic function and aortic stiffness.Abbreviations: ANS, Autonomic nervous system; E/A, Ratio between pulse wave Doppler peak early and late diastolic velocities; E/E', Ratio between pulse wave Doppler peak early and tissue Doppler peak early diastolic velocities; HR, heart rate; LF:HF ratio, ratio of low to high frequency power; OUES, Oxygen uptake efficiency slope; PEP, Pre-ejection period; PWVao, Aortic pulse wave velocity; VE/VCO 2 slope, Respiratory minute to CO 2 production slope; VO 2 peak, Peak oxygen uptake..

Exercise Intolerance, Benefits, and Prescription for People Living With a Fontan Circulation: The Fontan Fitness Intervention Trial (F-FIT)—Rationale and Design

“…Vascular dysfunction (increased arterial stiffness and endothelial dysfunction) is associated with worse aerobic exercise capacity (76)(77)(78). This is likely related to impaired skeletal oxygenation and muscle blood flow rather than the contribution of endothelial dysfunction to increased systemic vascular resistance (elevated afterload) in the setting of limited preload reserve (41,79).…”

Adequate exercise response at artificial altitude in Fontan patients

“…This is in line with the findings by Claessen et al and Hedlund et al, who also demonstrated regular HR response and speculated that reduced HR peak in Fontan patients might be an expression of a physiological reaction to maintain SV and Qc within the context of Frank–Starling mechanism, because of reduced preload ( 35 , 36 ). In addition, due to the numerous operations, many Fontan patients have a lack of responsiveness to modulation by the autonomic nervous system and an impaired sinus node function, both with the consequence of a limited HR variability and HR reserve ( 13 , 37 , 38 ). Here, similar to previous studies, Fontan patients showed significantly lower HR peak compared to controls, but these values were measured at significant lower P peak ( 39 ).…”

Exercise Capacity and Training Programs in Paediatric Fontan Patients: A Systematic Review

“…Multiple studies reported significantly lower VO 2peak , 17,18,[21][22][23][24] VO 2 at anaerobic threshold, 17,23,25 and O 2 pulse 17,21 relative to healthy individuals. Although reductions in both maximal and submaximal exercise capacity have been reported, 26 submaximal exercise parameters are typically less reduced than those for maximal exercise. 27 Cardiac response.…”

“…Reported values for the mean peak heart rate ranged from 142.2 AE 24.8 bpm 17 to 173.5 AE 16.0 bpm 26 (Table 1). Multiple studies reported that, compared with healthy controls, paediatric Fontan patients demonstrated significantly diminished peak stroke volume, 26 peak heart rate, 17,18,21,24,28 maximal heart rate, 23,29,30 heart rate gradient, 17 maximal heart rate response, 28,31 maximal stroke index, 23 stroke index response, 23 O 2 pulse, 30 and exercising O 2 saturation. 17 Two studies reported significantly decreased submaximal heart rate response, 28,31 and it was suggested by Banks et al 28 that paediatric Fontan patients may experience enhanced submaximal exercise efficiency relative to healthy individuals.…”