Guenette JA, Ramsook AH, Dhillon SS, Puyat JH, Riahi M, Opotowsky AR, Grewal J.
Am J Physiol Heart Circ Physiol. 2019 Feb 1;316(2):H335-H344. doi: 10.1152/ajpheart.00322.2018. Epub 2018 Nov 2.
Take Home Points:
Compared to controls, patients with Fontan circulation have:
- restrictive ventilatory impairment,
- higher ventilatory requirement for the same amount of work rate, and
- higher sensory response to exercise (breathing and legs discomfort) at a given work rate.
Commentary from Dr. M.C. Leong (Kuala Lumpur), section editor of ACHD Journal Watch: The reduced exercise capacity in patients with Fontan circulation is largely thought to be driven by the inability of the heart to increase preload to match the increase of cardiac output. Though not systemically studied before, pulmonary function abnormalities during exercise may also be a contributing factor to reduced exercise capacity. This study aimed to describe the ventilatory and sensory response during exercise in adults with Fontan circulation.
This is a case control study involving 17 patients with Fontan circulation and 17 matched controls. The authors found that patients with Fontan had lower values for most pulmonary function measurements (Table 3). They had a lower total lung capacity but at the same time, a normal FEV1/FVC ratio, suggesting an inherent restrictive ventilatory defect. They also had significantly higher breathing frequency, end-inspiratory lung volume, ventilator inefficiency (high VE/VCO2) and dyspnea. In terms of sensory response, patients with Fontan achieved a breathing discomfort and legs discomfort scores similar to controls at a much lower work rate (Figure 5). There was no difference in the qualitative descriptors of dyspnea and the dyspnea intensity rating.
The authors noted that patients in the Fontan group had other confounding factors such as poorer ventricular function, atrio-ventricular valve regurgitation and beta-blocker use which may affect exercise capacity and the sensory response of these patients.