Evaluation of Exercise Capacity with Cardiopulmonary Exercise Testing and Type B Natriuretic Peptide Concentrations in Adult Patients with Patent Atrial Septal Defect

Abstract

Adults with patent atrial septal defect (ASD) usually find their exercise capacity satisfactory, and therefore hesitate to accept proposed surgical treatment of the heart disease. The aim of our study was to evaluate both the exercise capacity, using the cardio-pulmonary stress test, and brain natriuretic peptide (BNP) levels in asymptomatic adults with ASD. Thirty-six patients with patent secundum type ASD (aged mean 44.7 ± 8.2 years) were studied. The control group consisted of 25 healthy subjects at the mean age of 45.6 ± 6.1 years. Echocardiography and CPST were performed and BNP levels measured in all subjects. Oxygen uptake (VO_{2 max}) was lower in ASD patients than in controls (22.1 ± 5.6 vs. 30.0 ± 6.8 ml/kg/min, p = 0.00001); the VE/VO₂ slope was elevated in ASD patients compared with healthy subjects (31.3 ± 6.6 vs. 26.9 ± 3.3, p = 0.001), and exceeded 34 in 5 patients. VO_{2 max} showed a negative correlation with the pulmonary to systemic flow ratio Qp:Qs (r = –0.46, p = 0.004), and a positive correlation was found between the VE/VO₂ slope and Qp:Qs (r = 0.32, p = 0.05). BNP levels were higher in the ASD group than in the controls (60.6 ± 49.9 vs. 32.6 ± 24.5 pg/ml, p = 0.02). BNP correlated positively with RV diameter and Qp:Qs (r = 0.38 and 0.39 respectively, p = 0.03) and negatively with maximum VO₂ (r = –0.5, p = 0.004) and VO₂% (r = –0.32, p = 0.07). Conclusions: Although most adult patients with ASD perceive their exercise capacity as satisfactory, objective assessment reveals that in fact it is significantly decreased. BNP levels are increased comparing to healthy individuals. Decreased exercise capacity and increased BNP levels seem to result from right ventricular volume overload.