Supravalvar mitral ring (SVMR) is a rare cause of congenital mitral stenosis. It can occur in isolation but often coexists with other cardiac anomalies, such as a ventricular septal defect or left-sided obstructive lesions. Conversely, a complete atrioventricular septal defect (AVSD) is a much more common anomaly. An AVSD may be associated with other major cardiac defects, such as tetralogy of Fallot, transposition of the great arteries, or double-outlet right ventricle. The authors describe what they believe is the first case of SVMR and complete AVSD occurring together; the SVMR was diagnosed by two-dimensional echocardiography, and its morphology could be more accurately delineate using three-dimensional echocardiography.
Case Presentation
An 8-month-old infant was referred to our institution from the Dominican Republic for the surgical management of congenital heart disease. He was born at term following an uneventful pregnancy. At 3 months of age, a workup for failure to thrive resulted in the diagnosis of a ventricular septal defect and mitral stenosis. Despite maximal medical therapy, he continued to have poor weight gain, leading to his referral for surgery.
On our evaluation, the infant was small for his age although in no apparent distress. On auscultation, the first heart sound was normal, while the second heart sound was single and accentuated. A grade II/VI holosystolic murmur and a grade II/IV rumbling middiastolic murmur were appreciated at the apex. The remainder of the examination results were normal. Electrocardiography showed sinus rhythm with right-axis deviation and right ventricular hypertrophy. Chest roentgenography demonstrated cardiomegaly and increased perihilar interstitial lung markings bilaterally.
Two-dimensional echocardiography showed a complete atrioventricular septal defect (AVSD) with a small ostium primum atrial septal defect, a common atrioventricular valve with moderate regurgitation, and a large-inlet ventricular septal defect. The atrioventricular valve regurgitation originated from the zone of coaptation between the left-sided components of the superior and inferior bridging leaflets. A linear density consistent with a supravalvar mitral ring (SVMR) ∗
∗ We recognize that there is not a “true” mitral valve in a complete AVSD and that the stenosing ring in this case is actually situated above the left-sided component of the common atrioventricular valve. The term “supravalvar mitral ring” was chosen because of its familiarity to most cardiologists and surgeons.
was seen just above the left-sided portion of the common atrioventricular valve ( Video 1 ). Doppler interrogation across the ring from the apical 4-chamber view revealed a mean diastolic pressure gradient of 22 mm Hg. The left atrium was dilated, and the right ventricle was hypertrophied. Normal biventricular systolic function was present. The aortic valve appeared normal, and there was no evidence of an associated coarctation of the aorta.To further delineate the morphology of the SVMR, real time three-dimensional (3D) echocardiographic imaging was performed from the subcostal location using a high-frequency matrix array probe (X7-2 probe, Philips iE33 ultrasound system; Philips Medical Systems, Andover, MA). As viewed from the left atrium, the supravalvar ring appeared as a circumferential diaphragm with a very small central orifice ( Video 2 A). The ring was attached to the atrial wall just superior to the left-sided component of the common atrioventricular valve. As viewed from the left ventricle through the common atrioventricular valve, the close proximity of the ring to the valve was appreciated ( Video 2 B).
At surgery, a right atriotomy incision was made, and inspection of the intracardiac anatomy confirmed the presence of a small ostium primum atrial septal defect and a large-inlet ventricular septal defect. A vertical incision was made in the atrial septum, revealing a very tight and thick SVMR, exactly as predicted by 3D echocardiography ( Figure 1 ). The supravalvar ring was located just inferior to the ostium primum atrial septal defect. The ring was widely excised, and the atrioventricular defect was repaired. Pathology of the ring showed fibroelastic tissue. The postoperative course was uncomplicated. Echocardiography performed prior to discharge revealed an excellent repair, with no residual supravalvar obstruction.
