Introduction
Systemic right ventricular dysfunction is a common occurrence in patients with Transposition of Great Arteries, with an incidence of 32-48% at 15-18 years follow-up, and this only tends to worsen with age.
A few small studies have been inconclusive in demonstrating any benefit from medical therapy in this situation, despite some improvement in the peak oxygen consumption, and increased exercise capacity.
Our study is a prospective, non-randomised case series of patients with TGA, commenced on medical therapy and followed with MRI at 12 months time.

Methods
Patients with complete or congenitally corrected TGA were invited to participate in this study after written informed consent.
13 patients were included, of which 11 were commenced on medical therapy (two patients declined medication and they were included in the control group). A cardiac MRI was performed at the commencement of the study and then repeated after 12 months of follow-up. In the treatment group, six patients were on a combination of ACEI / A2 blocker and beta blockers (Carvedilol in three patients, Bisoprolol in one patient, and Atenolol in two patients). Three patients were on a single ACEI only, and one patient was on angiotensin II receptor blocker alone. Only one patient was on beta blocker alone (Metoprolol).
Statistical analysis was performed using the Wilcoxon test.

Conclusions
Medical therapy in patients with systemic right ventricular dysfunction in TGA may results in an improvement of the right ventricular ejection fraction, mainly by increasing the indexed stroke volume of the systemic right ventricle.