Surgical strategies and outcomes in patients with supra-annular mitral ring: a single-institution experience.

OBJECTIVE: Supra-annular mitral ring (SMR) is a rare developmental abnormality of the supra-valvular area of the mitral valve, which produces a variable degree of obstruction to left ventricular (LV) filling. Management of SMR remains an important therapeutic challenge. SMR constitutes a small but inadequately described subset that has a relatively good outcome with appropriate management.

METHODS: Between 1983 and 2009, 27 patients with SMR underwent surgical treatment directed to the stenosing SMR. The demographic and clinical features, diagnostic modalities and the surgical management were studied retrospectively. Of these, 92% of patients had associated SMR with other congenital heart disease. The membranous component of the SMR was completely excised in all patients.

RESULTS: There were no early deaths; however, there were five late deaths. The 20-year survival rate was 82%. By univariate analysis, young age (<1 year; p=0.02) and Shone's anomaly (p<0.001) were risk factors for late mortality. The median follow-up duration was 6.5 years (range: 3 months to 20 years). Three patients required re-operation for recurrent LV outflow tract (OT) obstruction (all with Shone's anomaly), resection of sub-aortic membrane (n=2) and the Ross-Konno procedure (n=1). Additionally, one patient required MV replacement. Freedom from re-operation for LV outflow and/or inflow obstruction was 88% at 20 years. At latest follow-up, only two patients had peak trans-mitral gradients >5 mmHg related to supra-valvular obstruction.

CONCLUSION: SMR is an uncommon lesion, which can be safely and effectively managed by surgical resection. While co-existent mitral valvular lesions are usual, they are not typically severe in degree, as evidenced by the generally benign postoperative outcome following resection of SMR.