Background: Adult patients with congenital heart disease (CHD) usually find their exercise capacity satisfactory. However, objective evaluation is important for diagnostic and prognostic purposes. The aim of this study was to evaluate exercise capacity using cardiopulmonary exercise tests and measurement of serum B-type natriuretic peptide (BNP) levels in adult patients with CHDs, both in the entire study cohort and in subjects with individual types of cardiac lesions, as well as to verify the relation between BNP level and cardiac performance.
Methods: The study group included 265 patients (136 males; mean age 34.4 ± 11.6 years) 173 of whom were operated on at the mean age of 9.2 ± 7.3 years. They represented the following types of CHD: 72 patients - surgically corrected coarctation of the aorta, 62 - surgically corrected tetralogy of Fallot, 28 - Ebstein anomaly, 26 - patent atrial septal defect, 24 - Eisenmenger syndrome, 20 - uncorrected or palliated complex cyanotic lesions, 11 - corrected transposition of the great arteries (TGA), 14 - TGA after Senning operation, and 8 - common ventricle after Fontana operation. The control group consisted of 39 healthy individuals (17 males) with a mean age of 35.8 ± 9.3 years.
Results: According to NYHA classification, 207 patients were recognized as representing class I symptoms, 47 subjects class II, and 11 class III. Cardiopulmonary exercise revealed significantly reduced exercise capacity in adults with CHD in general, compared to control subjects: maximal oxygen uptake (VO₂max) was 23.3 ± 6.9 vs. 33.6 ± 7.2 mL/kg/min, respectively (p = 0.00001); maximum heart rate at peak exercise (HRmax) -161.1 ± 33.2 vs. 179.6 ± 12.3 bpm (p = 0.00001); respiratory workload (VE/VCO₂slope) - 35.7 ± 9.7 vs. 26.3 ± 3.1 (p = 0.00001); and forced vital capacity (FVC) - 3.8 ± 1.1 vs. 4.6 ± 0.7 L (p = = 0.00003). Various degrees of peak VO₂max reduction were observed across the spectrum of CHD. Patients after repair of aortic coarctation demonstrated the highest VO₂max (26.8 ± 6.6 mL/kg/min), and the lowest was demonstrated by patients with Eisenmenger syndrome (12.8 ± 4.8; ANOVA p = 0.00001). Serum BNP levels in the study group were higher than in the controls: 55.4 ± 67.5 vs. 13.9 ± 13.7 pg/mL, respectively (p = 0.00001). Various degrees of BNP level increase were found across the spectrum of CHD. Patients after repair of aortic coarctation demonstrated the lowest BNP level (24.8 pg/mL), and the highest level was found in patients with cyanotic defects (120.7 pg/mL; ANOVA p = 0.00001). BNP levels across the NYHA classes were as follows: I - 35.7 pg/mL, II - 94.1 pg/mL, and III - 225.6 pg/mL. BNP levels showed negative correlation with VO₂max (r = –0.525, p = 0.0001), FVC (r = = –0.349, p = 0.00001), FEV1 (r = –0.335, p= 0.00001), and positive correlation with VE/VCO₂slope (r = 0.447, p = 0.00001).
Conclusions: The exercise capacity of patients with CHD is, in general, compromised, most strikingly in patients suffering from pulmonary hypertension and cyanosis. Serum BNP levels in these subjects are increased and correlate well with exercise capacity. BNP level is higher in patients with cyanotic CHDs.