Patience Is Required After Late Conversion To Norwood Physiology
Dennis Wells, MD, David S. Winlaw, MD, MBBS.
Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
A term newborn with Type A Interrupted Aortic Arch, ventricular septal defect, and mitral valve dysplasia underwent biventricular repair. Preoperative assessment yielded little concern regarding adequacy of left sided structures with normal mitral and aortic annular sizes and mild left ventricular hypoplasia(end diastolic dimension z-score -3.2). Initial operation appeared successful but suprasystemic right ventricular pressures manifested within days. Escalating inotropes and pulmonary vasodilators failed to prevent low output syndrome. Mitral valve stenosis and the small LV were thought to be the culprit and it is likely that the unrestrictive VSD clouded the preoperative assessment of mitral valve and left ventricle adequacy. Cardiogenic shock led to urgent conversion to Norwood complicated by failure to wean from bypass with moderate mitral regurgitation and right ventricular dysfunction. The mitral valve annulus was reduced but right ventricular failure required initiation of veno-arterial extracorporeal membrane oxygenation(ECMO). After weaning from ECMO, the subsequent weeks were characterized by right ventricular diastolic dysfunction, pulmonary hypertension and hypoxia. Six weeks after the Norwood procedure, the Sano conduit was converted to a 4mm right modified Blalock-Tausig-Thomas shunt to improve pulmonary blood flow. Second stage palliation was delayed due to persistently elevated pulmonary vascular resistance and right ventricular end-diastolic pressures. Superior cavopulmonary connection was achieved at 6 months together with arch augmentation and repair of new pulmonary venous stenosis with subsequent hospital discharge after 282 days. Late conversion to Norwood remains a difficult prospect, with a long period of support required for the RV to adapt to the systemic load.
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