Abstract 1929: Beta-Adrenergic Blockade Improves Exercise Tolerance and Prevents Ventricular Remodeling in Patients with Transposition of the Great Arteries and Symptomatic Systemic Right Ventricular Dysfunction
Background: Systemic right ventricular (RV) dysfunction is a common late problem in patients with transposition of the great arteries (TGA). Several studies have demonstrated the benefit of beta-adrenergic blockade (BB) on mortality, left ventricular remodeling and symptoms in adults with acquired heart failure. The effect of BB has never been adequately studied in adult patients with systemic RV dysfunction due to TGA. We tested the hypothesis that BB improves exercise tolerance and systemic RV function in adult patients with TGA and heart failure.
Methods: We retrospectively studied 79 patients (age 31 ± 9 years, 33 female; 19 L-TGA; 60 D-TGA, 27 ± 5 years after atrial switch operation). Forty-four patients received BB (24 on Carvedilol, mean daily dose 30 mg; 20 on Metoprolol CR/XL, mean daily dose 48 mg). Right ventricular end-diastolic area, ejection fraction, and degree of systemic tricuspid regurgitation were evaluated by echocardiography.
Results: At a mean follow-up of 4 months, patients treated with BB had a significant improvement in NYHA functional class (64% improved 1 class, 8% improved 2 classes, and 28% were unchanged; P < 0.0001). In contrast, 20% of untreated patients had deterioration in NYHA functional class at the end of the follow-up period. A subgroup analysis revealed that only patients with cardiac pacemakers (12 D-TGA, 5 L-TGA) had significant improvement in exercise tolerance after BB compared to patients without cardiac pacemakers (P = 0.0001; mean BB dose in patients with pacemakers 36 mg vs. 27 mg in patients without pacemakers, P = NS). During a mean follow-up of 10 ± 7 months, there were no statistically significant differences in systemic RV echocardiographic indices including RV-end diastolic area (37.8 vs. 37.7 cm2), ejection fraction (35.4 vs. 37.4%), and degree of tricuspid insufficiency before and after treatment with BB. Interestingly, there was a significant increase in RV end-diastolic area (38.6 vs. 42.0 cm2, P = 0.002) in patients untreated with BB followed over the same period.
Conclusions: Beta-adrenergic blockade exerts a beneficial effect on exercise tolerance and systemic right ventricular remodeling in patients with TGA and symptomatic systemic right ventricular dysfunction.