Congenital Heart Disorders – Disorders with Obstruction to Blood Flow
Disorders with Obstruction to Blood Flow
Obstruction to the blood flow in the heart may be caused by narrowing of vessels or valves. As a result, the pressure before the narrowed part increased while it decreases after the narrowed area. This prevents the heart from reaching the lungs for oxygenation or the rest of the body. Disorders under this category include pulmonary stenosis, aortic stenosis and coarction of aorta. These heart diseases can cause back-pressure of the heart thereby overwhelming it.
The word stenosis means narrowing of a specific part. Pulmonary stenosis is the narrowing of the pulmonary valve or the pulmonary artery itself distal to the valve. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. A pulmonary valve is a flap of tissue that opens with pressure to allow blood to enter the pulmonary circulation. Inability of the right ventricle to evacuate blood to the pulmonary artery would result to right ventricular hypertrophy.
Some infants with pulmonary stenosis may be asymptomatic or have mild signs of right –sided heart failure. Severe narrowing of the pulmonary artery may cause the following manifestations:
- Typical systolic ejection murmur (grade IV or V crescendo-decrescendo quality) – loudest at the upper left sternal border
- Thrill at the upper left sternal border
Oxygenated blood is pumped from the left ventricle to the aorta. Presence of a stricture or stenosed aortic valve prevents blood from flowing to the systemic circulation. The heart’s inability to evacuate blood in the left ventricle results to increased pressure and hypertrophy of the left ventricle. If the left ventricle’s pressure becomes acute, pressure in the left atrium increases that would result to back-pressure in the pulmonary veins and possible pulmonary edema.
Most infants are asymptomatic however generally they present the following physical manifestation:
- Typical murmur (rough systolic sound at the second right interspace)
- Thrill at the suprasternal notch
For severe cases
- Decreased cardiac output
- Poor sucking ability
- Chest pain similar to angina (when the child is active)
The narrowing of the lumen of aorta is a congenital heart failure called coarction of aorta. There are two types of this disorder:
- Preductal – coarction is present between the subclavian artery and the ductus arteriosus
- Postductal – coarction is present distal to the ductus arteriosus
Difficulty of the blood to enter the systemic circulation through narrowed aorta result to increase the blood pressure before (proximal) the coarction and decreased distal to it.
- Absence of palpable femoral pulses
- Elevated blood pressure in the upper part of the body and decreased BP in the lower extremities.
- Leg pain on exertion
- Exceptional irritability
images from marvistavet.com, heart-valve-surgery.com, nlm.nih.gov