Characteristics of exercise intolerance in different subgroups of pulmonary arterial hypertension associated with congenital heart disease

Background: Exercise intolerance is a major manifestation of pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD). We aimed to investigate the characteristics of exercise intolerance in different subgroups of PAH-CHD. Methods: We retrospectively enrolled 171 adult patients with PAH-CHD and 30 age and sex-matched healthy subjects and performed cardiopulmonary exercise testing. Gas exchange parameters, including peak oxygen uptake (peak VO2), anaerobic threshold, and the slope of ventilatory equivalent for carbon dioxide (VE/VCO2 slope), were recorded. Results: The median age of patients at enrollment was 27.8 years, and 131 (76.6%) were female. Peak VO2 was reduced in patients compared to healthy controls (median, 14.8 ml/kg/min versus 26.9 ml/kg/min, p < 0.001). Of all 171 patients, 60 (35.1%) had Eisenmenger syndrome, 35 (20.5%) had PAH associated with systemic-to-pulmonary shunts (PAH-SP), 39 (22.8%) had PAH with small defects (PAH-SD), and 37 (21.6%) had PAH after cardiac defect correction (PAH-CD). Patients with Eisenmenger syndrome had the lowest peak VO2 (p = 0.003) and the highest VE/VCO2 slope (p = 0.012), compared with other patients, representing the worst exercise capacity and ventilatory efficiency. Patients with PAH-SP had the best exercise capacity among the four groups, indicated by the highest peak VO2 (p = 0.003) compared with other patients. Peak VO2 was negatively correlated with pulmonary vascular resistance (r =-0.411, p < 0.001). Conclusions: Exercise capacity was severely reduced in patients with PAH-CHD. Among the four subgroups, patients with Eisenmenger syndrome had the worst exercise capacity and ventilatory efficiency.

Automated summary

This study investigated the characteristics of exercise intolerance in patients with pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD), and found that exercise capacity was severely reduced in these patients. Among the different subgroups of PAH-CHD, patients with Eisenmenger syndrome had the worst exercise capacity and ventilatory efficiency, while patients with PAH associated with systemic-to-pulmonary shunts had the best exercise capacity.