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The modification of placing the shunt from the right ventricle to the pulmonary arteries, also known as Sano procedure, has allegedly improved results over the short term in surgical palliation of hypoplastic left heart syndrome with the Norwood procedure. With this in mind, we reviewed autopsied specimens from neonates and children who did not survive after either a classic arterio-pulmonary shunt, or the modified procedure with the shunt placed from the right ventricle to the pulmonary arteries, so as to evaluate the pathological substrates of the remodelling of the systemic right ventricle, assessing any differences induced by the 2 techniques.
We obtained the hearts from 11 patients with neonatal diagnosis of hypoplastic left heart syndrome who died after the first or second stages of the Norwood sequence of operations, comparing them with 6 normal hearts matched for age and weight. Macroscopic, microscopic and morphometric analysis were performed on each specimen, evaluating the diameter of the myocytes, extracellular matrix remodelling in terms of fibrosis and type of collagen, and vascularization in terms of capillary density.
Hypertrophy of the myocytes was significantly increased in the hearts from patients having either a classic arterio-pulmonary or the ventriculo-pulmonary modification of the shunt compared to controls (p < 0.05). Myocardial fibrosis was increased in those having a shunt placed from the right ventricle to the pulmonary arteries when compared to the other 2 groups. The ratio of collagen I to collagen III was similar in those undergoing a classic arterio-pulmonary shunt compared to controls (0.94), but was lower in those having a shunt placed from the right ventricle to the pulmonary arteries (0.61), with an increase in collagen type III. The density of capillaries was lower in those who had undergone a classic arterial shunt when compared to the others.
We have shown greater remodelling of the ventricular myocardial extracellular matrix in patients having a shunt from the right ventricle to the pulmonary arteries when compared to those having a classic arterio-pulmonary shunt, with this remodelling progressing even after the neonatal period. This may influence a later suboptimal ventricular performance.