Staged Left Ventricular Recruitment for Biventricular Conversion in the Borderline Left Heart
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The patient was a 16-month-old female with a diagnosis of Shone’s complex, including hypoplasia of the mitral valve, aortic valve, left ventricle, and aortic arch, and a ventricular septal defect. She had previously undergone single ventricle palliation with a Norwood procedure as a neonate and subsequent bidirectional Glenn procedure at the age of four months. Clinically, the patient displayed appropriate weight gain and energy level and no significant cyanosis or work of breathing.
Preoperative transesophageal echocardiogram demonstrated normal sized right heart structures with a right ventricular ejection fraction of 54% and a diminuitive left heart. The left ventricular ejection fraction was measured at 40%, and the left ventricular end diastolic volume index was 11 ml/m2. The mitral valve annulus measured 8.8 x 6.6 mm, with a Z-score of -3.8, and an inflow gradient of 1-2 mm Hg. The aortic valve was hypoplastic, with no regurgitation and only mild flow acceleration, measuring 8 mm, with a Z-score of -2.4. The atrial septum was wide open measuring 1.2 cm, with a minimal gradient measured across the atrial septum. The preoperative clinical parameters obtained by echocardiogram and MRI are summarized in this slide.
After redo sternotomy, aortobicaval cannulation was performed. Cardioplegia was administered and the heart was arrested. A right atriotomy was performed, and the mitral valve was inspected across the open atrial septum. The mitral valve was probed and was able to accommodate a 7.5 mm dilator, but unable to accept an 8 mm dilator. A fenestrated atrial septal defect closure was then performed, leaving a 4-5 mm fenestration, which promotes flow through the mitral valve and encourage left ventricular growth over time. A right ventriculotomy was then performed for placement of the right ventricle to pulmonary artery conduit. Right ventricular muscle was resected to prevent any potential obstruction at the proximal RV-PA conduit. A pulmonary arteriotomy was then performed towards the left of the pulmonary artery bifurcation, creating an opening for the distal RV-PA conduit anastomosis. The RV-PA conduit now perfuses the left pulmonary artery, and the right pulmonary artery flow is supplied by the Glenn anastomosis. A 6 mm ringed Goretex graft was then fashioned, and the distal RV-PA anastomosis was performed. The cross clamp was then removed to allow for reperfusion while the proximal RV-PA conduit anastomosis was performed. There is now augmentation of the pulmonary blood flow, and therefore increased pulmonary venous return to the left heart, promoting left ventricular growth. A left atrial pressure monitoring line was placed through the fenestrated atrial septal defect closure to provide hemodynamic data in the immediate postoperative period.
The postoperative echocardiogram now demonstrated a mean mitral valve inflow gradient of 4-5 mm Hg, secondary to the increased flow across the left heart. Due to the restriction of the atrial septal defect, the gradient across the ASD now measured 7-8 mm Hg. The patient will be followed with serial echocardiograms and cardiac MRI to assess for left ventricular growth and future consideration for completion of the biventricular conversion.