Porcine Model of the Arterial Switch Operation: Implications for Unique Strategies in the Management of Hypoplastic Left Ventricles

Abstract

There are no reports on the performance of the arterial switch operation (ASO) in a normal heart with normally related great vessels. The objective of this study was to determine whether the ASO could be performed in a healthy animal model. Cardiopulmonary bypass (CPB) and coronary translocation techniques were used to perform ASO in neonatal piglets or a staged ASO with prior main pulmonary artery (PA) banding. Primary ASO was performed in four neonatal piglets. Coronary translocation was effective with angiograms confirming patency. Piglets could not be weaned from CPB due to right ventricle (RV) dysfunction. To improve RV function for the ASO, nine piglets had PA banding. All survived the procedure. Post-banding RV pressure increased from a mean of 20.3 ± 2.2 mmHg to 36.5 ± 7.3 mmHg (p = 0.007). At 58 ± 1 days post-banding, piglets underwent cardiac MRIs revealing RV hypertrophy, and RV pressure overload with mildly reduced RV function. Catheterization confirmed RV systolic pressures of 84.0 ± 6.7 mmHg with LV systolic pressure 83.3 ± 6.7 mmHg (p = 0.43). The remaining five PA banded piglets underwent ASO at 51 ± 0 days post-banding. Three of five were weaned from bypass with patent coronary arteries and adequate RV function. We were able to successfully perform an arterial switch with documented patent coronary arteries on standard anatomy great vessels in a healthy animal model. To our knowledge this is the first time this procedure has been successfully performed. The model may have implications for studying the failing systemic RV, and may support a novel approach for management of borderline, pulsatile left ventricles.

Keywords: Arterial switch operation; Heart failure; Hypoplastic left heart syndrome; Left ventricle hypoplasia; Porcine model; Right ventricle failure.

Fig. 1

Angiography of translocated coronary arteries in 28-day-old piglet (Group 1) that underwent primary arterial switch operation with atrial septectomy. Both right and left coronary systems are widely patent

Fig. 2

Cardiac MRI of 90-day-old piglet 57 days post-PA banding (Group 2a). Note the RV hypertrophy (a and b) and D-shaped left ventricular cavity (b) indicative of RV pressure overload

Fig. 3

Contrasted-enhanced magnetic resonance angiogram of the pulmonary arterial tree. The banded segment of the main pulmonary artery is visualized in axial (a), three-dimensional (b), coronal (c), and sagittal (d) projections. PA pulmonary artery

Fig. 4

Angiogram of 82-day-old piglet (Group 2b) that had arterial switch operation with atrial septectomy. The animal was successfully weaned from cardiopulmonary bypass, with good RV function and the translocated coronaries are widely patent, indicated by white arrows. Prior PA banding was performed at 31 days of age

Fig. 5

Left atrial contrast injection in after arterial switch in a piglet with prior PA banding. There is limited mixing into the RA with streaming of pulmonary venous blood to the LV/PA

Fig. 6

Right heart angiography following arterial switch in piglets with prior PA banding. Right atrial contrast streams to the aorta with little “washout” from the left atrium

Fig. 7

A more aggressive septectomy that extends inferiorly to the coronary sinus and IVC results in improved mixing after arterial switch in a piglet model with prior PA banding. Contrast fills both the left atrium and right atrium through the septectomy (white arrow) when injected into the left atrium

Fig. 8

a Presents a diagram illustrating hypoplasia of the left ventricle [10]. The great vessels are normally related. The LV is not apex forming, but pulsatile. The aortic valve and mitral valve are hypoplastic but not atretic. There is an atrial septal defect and a patent ductus arteriosus. There is retrograde flow in the aortic arch. b Presents the arterial switch in the setting of LV hypoplasia and normally related great vessels. An extensive atrial septectomy is performed allowing for atrial level mixing and pulmonary venous inflow to the RA-RV-Aorta axis. The LV provides antegrade systolic pulmonary blood flow. The ductus arteriosus has been ligated and divided. The coronary arteries are translocated to the main PA root with coronary button defects filled with patch material in the native aortic root. A pulsatile small LV that could generate a systolic pressure of 25–40 mmHg is inadequate for the systemic output but may support pulmonary blood flow