Assessment of biventricular functional reserve and NT-proBNP levels in patients with RV volume overload after repair of tetralogy of Fallot at young age
Purpose: To assess biventricular functional reserve (FR), NT-proBNP levels and exercise performance, in relation to right ventricular volume in patients with pulmonary regurgitation (PR) after repair of tetralogy of Fallot (TOF) at young age. Methods: In 53 TOF patients (maximum age at repair 2.0 years, interval since repair 15 (5) years) without residual lesions except PR, biventricular FR (derived from magnetic resonance imaging with dobutamine stress), NT-proBNP levels, maximal workload, and peak oxygen uptake were assessed. Results: Mean right ventricular end-diastolic volume was 140(38) ml/m2. Median pulmonary regurgitant fraction was 37% (range 0-57%). Biventricular systolic stress response was normal: mean (SD) ESV decreased (ΔRVESV - 17(8) ml/m2, ΔLVESV - 11(5)), SV increased (ΔRVSV + 12(9) ml/m2, ΔLVSV + 9(6)), FR was positive in all (RV-FR + 11(5)%, LV-FR + 13(6)). No serious adverse effects to dobutamine were encountered. NT-proBNP was increased in 2 patients. Median level was 10 pmol/L (range 2-42). NT-proBNP correlated with PR-percentage but not with right ventricular size. High-risk levels of NT-proBNP indicated a smaller RV-FR and a smaller decrease of biventricular ESV. Mean (SEM) VO2maxwas 96(3)%, mean Workloadmax89(2)% of predicted. Conclusion: At mid to long term follow-up overall NT-proBNP levels are normal and biventricular functional reserve and exercise tolerance are well preserved in TOF repaired at young age, irrespective of RV volume. This questions the validity of isolated PR or RV volume criteria for pulmonary valve replacement in this group. Low-dose dobutamine stress testing is well tolerated and may be a useful additional tool for clinical decision making.