Aortopulmonary Window

Resistance sets the shunt, not the hole - The window is unrestrictive, so the ratio of pulmonary to systemic vascular resistance decides how much output goes to the lungs. High FiO2 and hyperventilation both drop PVR and flood the lungs at the expense of systemic perfusion. Use the lowest FiO2 that keeps saturation acceptable and let PaCO2 sit at the upper end rather than ventilating it down.

Diastolic runoff comes out of the coronaries - Aortic blood runs off into the pulmonary artery during diastole, which is why systemic diastolic pressure is low and the pulses are bounding over a hyperdynamic precordium. That same diastolic pressure is what fills the coronaries, so guard it.

Do not wait for a continuous murmur - The connection is usually too large to generate a pressure gradient, so the classic continuous murmur is often absent and color Doppler shows no high-velocity jet. What you hear instead is a mitral rumble from the volume load. The diagnosis is made on 2D echo images of the communication, with CT when the echo windows are inadequate.

Find the second lesion before you induce - Half of these children have another defect. With an interrupted aortic arch the neonate presents in shock as the ductus constricts, meaning systemic flow is duct-dependent and prostaglandin is what is holding it open. Echo should also document the coronary origins, and with tetralogy the exam adds a pulmonary ejection murmur and click.

They arrive on heart failure therapy - Expect diuretics such as furosemide and chlorothiazide plus digoxin, sometimes with ACE inhibition for afterload reduction. None of it alters the natural history. Check electrolytes and volume status, and approach afterload reduction cautiously because renal perfusion can be abnormal.

Late presentation is a different disease - A restrictive window can surface in older childhood or adult life with cyanosis and clubbing from Eisenmenger physiology. That patient needs catheter-measured pulmonary vascular resistance and vasodilator reactivity testing before anyone discusses closure, and in the room, any fall in SVR deepens the right-to-left flow and the hypoxemia.

Timing is not negotiable - The window does not restrict or become less significant over time, and irreversible pulmonary vascular disease is the clock. Surgical patch closure early in infancy gives an excellent long-term prognosis; small restrictive defects can be sutured, ligated, or device-closed at catheterization.

Know the residua on a repaired patient - Branch pulmonary artery stenosis is the common one, with residual window flow and rarely aortic stenosis behind it, and balloon angioplasty is used cautiously because aggressive dilation could re-open the window. Hoarseness or choking with feeds after repair points at recurrent laryngeal nerve injury — that changes both your airway assessment and the aspiration risk on the next anesthetic.

An aortopulmonary window is a direct side-to-side communication between the ascending aorta and the main pulmonary artery, with a normally formed aortic valve, pulmonary valve and right ventricular outflow tract — that last point is what separates it from truncus arteriosus. It arises when the aortopulmonary septum fails to complete its division of the common arterial trunk, and it accounts for well under 0.5% of congenital heart defects.

Roughly half occur alongside another lesion, most often an interrupted aortic arch, but also coarctation, transposition of the great arteries, tetralogy of Fallot, ventricular septal defect and coronary anomalies. The defect is usually large and unrestrictive — fewer than 10% restrict flow — so as pulmonary vascular resistance falls over the first weeks of life a torrential left-to-right shunt develops, producing pulmonary over-circulation, congestive failure, and if left alone, irreversible pulmonary vascular obstructive disease.