The BNP concentrations and exercise capacity assessment with cardiopulmonary stress test in cyanotic adult patients with congenital heart diseases

Cyanosis is observed in patients with complex congenital heart disease (CHD) and pulmonary hypertension, heart failure represents an important clinical problem in such patients. The aim of this study was to evaluate the exercise capacity in patients with cyanotic CHDs using cardiopulmonary exercise test, measuring serum BNP levels as well as to seek correlation between BNP levels and cardiopulmonary exercise test parameters and identify the effects of blood oxygen desaturation and pulmonary hypertension on these indices.The study group consisted of 53 patients (21 males) at the mean age of 39.4 ± 14.3 years, of whom 19 were operated on at the mean age of 9.6 ± 8.6 years. Mean blood oxygen saturation (SO2) in patients was 81.2 ± 6.2%. Twenty four patients presented with Eisenmenger syndrome, 16 - univentricular hearts, 4 - transposition of the great arteries, 6 - Fallot's tetralogy, and 3 - Ebstein anomaly. The control group comprised 32 healthy individuals (16 males) at the mean age of 40.7 ± 9.9 years. Cardiopulmonary stress test showed significantly lower exercise capacity in patients with cyanosis than in controls: maximal oxygen uptake (VO2max) 15.5 ± 4.9 vs. 31.6 ± 7.1 ml/kg/min (p = 0.00001), maximum heart rate at peak exercise (HR max): 139.5 ± 22.5 bpm vs. 176.6 ± 12.1 (p = 0.0001), VE/VCO2 slope: 46.4 ± 10.1 vs. 27.3 ± 2.9 (p = 0.00001), forced vital capacity FVC: 3.1 ± 1.1 l vs. 4.4 ± 0.8 l (p = 0.00001). Subjects with the evidence of pulmonary hypertension (PH+) had lower exercise capacity than those without (PH-): VO2max: 17.2 ± 4.2 vs. 12.8 ± 4.8 ml/kg/min (p = 0.002), VE/VCO2: 43.7 ± 11.1 vs. 50.9 ± 6.4 (p = 0.01), FVC: 3.46 ± 1.05 l vs. 2.37 ± 0.91 l (p = 0.0002). Plasma BNP levels in the study group were higher than in controls: 122.4 ± 106.7 vs. 21.1 ± 20.2 pg/ml p = 0.00001 and did not differ between PH+ and PH− groups (115.7 ± 99.0 vs. 127.9 ± 114.1 pg/ml p = 0.78). Negative correlations between BNP levels and VO2max (r = − 0.389, p = 0.006), FVC (r = − 0.395 p = 0.005), FEV1 (r = − 0.386 p = 0.006), SO2 (r = − 0.445 p = 0.00001), and positive correlation between BNP level and VE/VCO2 (r = 0.369 p = 0.009) were found.