Diffuse and Focal Myocardial Fibrosis Late after Norwood Procedure

Introduction: The modification of placing the shunt from the right ventricle to the pulmonary arteries, also known as Sano procedure, for hypoplastic left heart syndrome (HLHS) has been associated with improved postoperative hemodynamics and outcome but at the cost of a ventriculotomy that may have detrimental long-term sequelae. The conventional modified Blalock-Taussig shunt (MBT) avoids any incision into the ventricle. However, the diastolic run-off of the MBT can cause hemodynamic instability and unpredictable coronary steal phenomenon.

This study analyses cardiovascular magnetic resonance (CMR) measurements of myocardial extracellular volume fraction (ECV) and late gadolinium enhancement (LGE) in the systemic right ventricle late after the Norwood procedure (≥9 years). This analysis should determine the frequency, location, and patterns of myocardial fibrosis and evaluate the relationship between diffuse myocardial fibrosis and ventricular performance in patients with Sano procedure or MBT procedure.

Methods: A total of 13 patients with HLHS, all with total cavopulmonary connection (TCPC) were evaluated prospectively by CMR. The entire cohort was divided into 2 groups: 9 patients with Sano Shunt (age median: 11 years, range: 9–13 years) and 4 patients with MBT (age median: 13.5 years; range: 13–14 years). The native T1 times (T1) and ECV in the free wall of the right ventricle (RVAW) away from scar, in the interventricular septum (IVS) and in the myocardium bordering the LGE area in patients after Sano shunt were compared with corresponding segments of MBT hearts and correlated with hemodynamic parameters.

Results: RV ejection fraction and RV size did not differ between groups. LGE was present in 9 (100%) of the Sano shunt patients (at ventriculotomy site) and in 1 (25%) of the MBT patient (one papillary muscle). Median ECV was not significantly different between groups. There was no correlation between ECV and right ventricular volumes or ejection fraction.

Conclusion: In this patient cohort late after completion of TCPC, focal myocardial fibrosis (LGE) was common only at ventriculotomy site and was not associated with adverse ventricular mechanics. Myocardial extracellular volume does not differ depending on the surgical technique (Sano/MBT).

No conflict of interest has been declared by the author(s).