Small unrepaired atrial septal defects display impaired exercise capacity compared with healthy peers

Abstract

Objective: Adult patients with small, unrepaired atrial septal defects have an increased risk of pneumonia, atrial fibrillation, and stroke. Furthermore, they have higher late mortality than the background population. The functional capacity is unknown in these patients. Therefore, our objective was to determine exercise capacity in adult patients diagnosed with an unrepaired atrial septal defect compared to healthy controls.

Design: A cross-sectional study.

Patients: Adult patients with small, unrepaired atrial septal defects, aged 18-65, diagnosed between 1953 and 2011.

Interventions: Cardiopulmonary exercise test was performed using an incremental bicycle test and gas exchange was measured using breath-by-breath technique.

Outcome measures: Primary outcome was peak oxygen uptake, secondary outcome was maximal workload and ventilatory anaerobic threshold.

Results: We included 32 patients previously diagnosed with a small, unrepaired atrial septal defect and 16 healthy, age- and gender-matched controls (age 36.3 ± 13 years). Patients were divided into two groups based on whether the atrial septal defect was open (age 36.3 ± 11 years) or spontaneously closed (age 36.8 ± 14 years) since time of diagnosis. No differences in demographic characteristics or weekly exercise levels were found. Both patient groups reached lower peak oxygen uptake (open: 31.7 ± 11 mL/kg/min; spontaneously closed: 29.7 ± 6.9 mL/kg/min) compared with controls (42.6 ± 6.1 mL/kg/min; P = .0001). Workload (open: 2.6 ± 1.0 watt/kg; spontaneously closed: 2.5 ± 0.6 watt/kg) and aerobic capacity (open: 21.4 ± 8.7 mL/kg/min; spontaneously closed: 22.5 ± 6.5 mL/kg/min) was also poorer in patients compared to controls (workload: 3.5 ± 0.5 watt/kg; P = .0006, aerobic capacity: 31.3 ± 6.8 mL/kg/min; P = .0007).

Conclusion: Adult patients with a diagnosis of small, unrepaired atrial septal defect have significantly impaired exercise capacity when compared to healthy controls. The impairment was present even if, by the time of assessment, the defect had closed spontaneously. The pathophysiological mechanisms behind the impaired exercise capacity demonstrated in these patients remain unexplained and will be a target for future work.

Keywords: cardiopulmonary exercise test; exercise capacity; grown-up with congenital heart disease (GUCH); simple lesions; small atrial septal defect.