Congenital supravalvar mitral ring: an underestimated anomaly.

OBJECTIVE: Congenital mitral ring is a rare subtype of congenital mitral stenosis. Our objective is to review the anatomic findings and surgical results of this lesion and to identify early predictors of outcome.

METHODS: Clinical reports, echocardiographic studies, cardiac catheterizations, surgical reports, and follow-up data of all patients with mitral ring diagnosed at the Bambino Gesù Hospital were retrospectively reviewed.

RESULTS: Between January of 1987 and June of 2007, a mitral ring was diagnosed in 25 patients (13 male) with a mean age at diagnosis of 36 months. The ring was identified in a single neonate but seemed to develop and progress during infancy. All but 1 patient had associated cardiac anomalies. We identified 2 distinct subtypes: "intramitral ring" in 18 of 25 patients (72%), associated with complex valve pathology and a worse outcome, and "supramitral ring" in 7 of 25 patients (18%), in whom the mitral apparatus was usually normal and the outcome was better. The ring was surgically removed in 13 of 25 patients (52%) (mean Doppler gradient 15 +/- 4 mm Hg). The gradient decreased in 9 of 13 patients (mean diastolic transmitral gradient <or= 5 mm Hg) and has remained stable during a mean follow-up of 90 months. The mean diastolic gradient remained high (>8 mm Hg) in the other 4 patients, all with intramitral ring. All 4 patients underwent repeat mitral valvuloplasty. There were no operative or late deaths.

CONCLUSION: Two types of congenital mitral ring, with diverse valve pathology and outcome, were identified. Rarely seen in neonates, the ring develops and often progresses during infancy. Recognition is important because surgical results are better than for other forms of congenital mitral stenosis.