Diffuse myocardial fibrosis in the systemic right ventricle of patients late after Mustard or Senning surgery: an equilibrium contrast cardiovascular magnetic resonance study

Aims After atrial redirection surgery (MustardSenning operations) for transposition of the great arteries (TGA), the systemic right ventricle (RV) suffers from late systolic failure with high morbidity and mortality. Mechanisms of late RV failure are poorly characterized. We hypothesized that diffuse interstitial expansion representing diffuse fibrosis is greater in systemic RVs of patients following Mustard-Senning surgery and that it would be associated with other markers of heart failure and disease severity. Methods and results We used equilibrium contrast cardiovascular magnetic resonance (CMR) imaging to quantify extracellular volume (ECV) in the septum and RV free wall of 14 adults presenting to a specialist clinic late after surgery for TGA (8 Mustard, 6 female, median age 33). These were compared with 14 age-and sex-matched healthy volunteers. Patients were assessed with a standardized CMR protocol, NT-brain natriuretic peptide (NT-proBNP), and cardiopulmonary exercise (CPEX) testing. The mean septal ECV was significantly higher in patients than controls (0.254 +/- 0.036 vs. 0.230 +/- 0.032; P = 0.03). NT-proBNP positively related to septal ECV (P = 0.04; r = -0.55). The chronotropic index (CI) during CPEX testing negatively related to the ECV (P = 0.04; r = -0.58). No relationship was seen with other CMR or CPEX parameters. R.V free wall ECV was difficult to measure (heavy trabeculation, sternal wires, blood pool in regions of interest) with high and poor inter-observer reproducibility: this analysis was abandoned. Conclusion Septal interstitial expansion is seen in adults late after atrial redirection surgery for TGA. It correlates well with NT-proBNP and CI and may have a role in the development of RV systolic impairment. Measuring interstitial expansion in the RV free wall is difficult using this methodology.