Abstract 17826: Long-term Survivors With Transposition of the Great Arteries After Arterial Switch Operation Show No Signs of Adverse Myocardial Remodeling

Abstract

Background: The arterial switch operation (ASO) for transposition of the great arteries (TGA) involves coronary translocation. The altered coronary geometry may lead to subclinical myocardial ischemia, which may result in myocardial scarring and diffuse myocardial fibrosis. We hypothesized that myocardial fibrosis is present late after ASO, despite excellent functional outcomes of the ASO in most patients. Methods: 30 pediatric TGA patients after ASO were prospectively studied by cardiac magnetic resonance imaging (CMR). Late gadolinium enhancement (LGE) was used to detect discrete myocardial scarring. Native T1 relaxation times and extracellular volumes (ECVs) at the mid-ventricular short-axis level of the left ventricle (LV) were used to quantify diffuse myocardial fibrosis. The midventricular short-axis slice was divided into 6 segments. Patients were compared to 21 healthy controls. Results: Mean ages at ASO and at CMR were 6.3±5.2 days and 15.4±2.9 years, respectively. Mean age of controls at CMR was 14.1±2.6 years. TGA patients showed preserved LV ejection fraction (57±5% vs. 59±4% in controls, p=0.08) and similar indexed LV mass (54±10g/m2 vs. 49±9%, p=0.12). LV end-diastolic and end-systolic volumes were mildly increased (104±20ml/m2 vs. 89±11ml/m2, p=0.01 and 46±13ml/m2 vs. 36±6ml/m2, p<0.01, respectively). None of the TGA patients demonstrated evidence of localized myocardial scarring by LGE. Native T1 times and ECV values for all 6 LV segments were not significantly different to controls. There was no association between global T1 times or global ECV and LV volumes and ejection fraction. Furthermore, native T1 and ECV were not associated with bypass and cross-clamp times at the time of the ASO, or with coronary artery patterns. Conclusions: Adolescent TGA patients late after ASO have preserved systolic LV function. There is no evidence of myocardial scarring or fibrosis. Our results suggest excellent long-term myocardial and cardiac health after the ASO, paralleling the encouraging clinical outcomes with this procedure.