Left cardiac obstruction (without shunt)
Obstructions, i.e., constrictions of the flow path at various levels can also occur on the left side of the heart. Pure obstructions result in a massive supplementary load on the cardiac muscle because it must pump against elevated resistance. Partially, there are compensatory shunts without which survival would not be possible.
Aortic stenoses occur relatively frequently and comprise 7% of congenital cardiac abnormalities. These are obstructions of the left ventricular outflow tract, i.e., the aortic valve and the ascending aorta.
In all its forms constriction of the left ventricular outflow tract gives rise to pressurestress of the left ventricle with compensation by a left ventricular hypertonia.
Aortic insufficiency is seldom found in newborns and is mainly a consequence of an operative intervention, e.g., from the balloon dilatation of an aortic stenosis.
Aortic isthmus stenosis (coarctatio aortae)
The region of the distal aortic arch near the ductus arteriosus inlet is called the aortic isthmus. A coarctation is a stenosis in the aortic isthmus region and it is encountered with a frequency of ca. 6% of all congenital cardiac abnormalities. Often dispersed ductus tissue, which contracts after birth, is found in sections of a stenosized wall.
Interrupted aortic arch
While with aortic isthmus stenoses the continuity of the aortic arch is preserved, this is lost when the aortic arch is interrupted - a segment of the aortic arch is missing. This abnormality is relatively seldom, however.
Hypoplastic left cardiac syndrome
In the hypoplastic left heart syndrome, which comprises only 2% of all cardiac abnormalities, one finds a poorly developed (hypoplastic) left ventricle that is often only a few millimeters thick. The aortic and mitral valves are constricted (stenotic) or completely closed (atretic). Only the right ventricle functions normally and supplies the circulation system with blood. The arterial blood from the left atrium gets into the right atrium and ventricle via the foramen ovale that is kept open. The aorta ascendens that mostly ends blind at the valve is filled retrograde by the blood of the ductus arteriosus. In this way the coronary arteries that leave the proximal part of the aorta ascendens can also be supplied with blood.