The closer to birth that congenital heart defects are simulated, the more valid the model. Unlike obstructive lesions such as pulmonic and aortic stenosis, which can be constructed in utero or in infancy, left-to-right shunts are more difficult to create due to the extreme friability of fetal and neonatal tissue. A method for creating left-to-right shunts in infant pigs using a pleural-sparing transverse sternotomy and direct side-to-side anastomosis between the redundant pulmonary artery and the ascending aorta has been introduced. The pigs developed palpable thrills, systolic and diastolic flow murmurs, and congestive heart failure. The average pulmonary-to-systemic flow ratio by the microsphere technique was 2.1:1 compared to 2.1:1 by oximetry. Left-to-right shunts can be constructed in infant pigs to simulate congenital heart defects.
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