Guenette JA; Ramsook AH; Dhillon SS; Puyat JH; Riahi M; Opotowsky AR;
Grewal J.

American Journal of Physiology – Heart & Circulatory Physiology.
316(2):H335-H344, 2019 02 01.

Many adults with single-ventricle congenital heart disease who have
undergone a Fontan procedure have abnormal pulmonary function resembling
restrictive lung disease. Whether this contributes to ventilatory
limitations and increased dyspnea has not been comprehensively studied. We
recruited 17 Fontan participants and 17 healthy age- and sex-matched
sedentary controls. All participants underwent complete pulmonary function
testing followed by a symptom-limited incremental cardiopulmonary cycle
exercise test with detailed assessments of dyspnea and operating lung
volumes. Fontan participants and controls were well matched for age, sex,
body mass index, height, and self-reported physical activity levels (all P
> 0.05), although Fontan participants had markedly reduced
cardiorespiratory fitness and peak work rates ( P < 0.001). Fontan
participants had lower values for most pulmonary function measurements
relative to controls with 65% of Fontan participants showing evidence of a
restrictive ventilatory defect. Relative to controls, Fontan participants
had significantly higher breathing frequency, end-inspiratory lung volume
(% total lung capacity), ventilatory inefficiency (high ventilatory
equivalent for CO2), and dyspnea intensity ratings at standardized
absolute submaximal work rates. There were no between-group differences in
qualitative descriptors of dyspnea. The restrictive ventilatory defect in
Fontan participants likely contributes to their increased breathing
frequency and end-inspiratory lung volume during exercise. This abnormal
ventilatory response coupled with greater ventilatory inefficiency may
explain the increased dyspnea intensity ratings in those with a Fontan
circulation. Interventions that enhance the ventilatory response to
exercise in Fontan patients may help optimize exercise rehabilitation
interventions, resulting in improved exercise tolerance and exertional
symptoms.
NEW & NOTEWORTHY This is the first study to comprehensively
characterize both ventilatory and sensory responses to exercise in adults
that have undergone the Fontan procedure. The majority of Fontan
participants had a restrictive ventilatory defect. Compared with
well-matched controls, Fontan participants had increased breathing
frequency, end-inspiratory lung volume, and ventilatory inefficiency.
These abnormal ventilatory responses likely form the mechanistic basis for
the increased dyspnea intensity ratings observed in our Fontan
participants during exercise.