Normally the left side of the heart carries oxygenated blood to the rest of the body. Patients who have atrial septal defects or ventricular septal defects or patent ductus arteriosus have an open pathway between the right and left sides of the heart.
Since normally the left side is more powerful the pressure inside it is higher. Hence the flow of blood takes place from left to right, with oxygenated blood going to the right side through the defect then to the pulmonary arteries then back again to the left heart.
However, if this recycling of blood carries on for some time it creates a load on the right side of the heart and the pulmonary artery. One result of this continuing load is it leads to thickening of the wall pulmonary arterioles (small branches of the pulmonary artery). This leads to an increased backward pressure on the right side. When the pressure in the right side of the heart exceeds the pressure of the left side the blood shunting through the defects mentioned above reverses direction. The result is disastrous as the blood in the right side is de-oxygenated (hasn't passed through the lungs yet). Thus, instead of the left side carrying oxygenated blood to the rest of the body it now carries de-oxygenated blood.
The patient turns blue (cyanosis) as the tissues contain deoxygenated blood; the red blood counts are highly elevated (polycythemia) as the body tries to compensate the lack of oxygenated blood by increasing blood production.
Paradoxical embolism may occur in a patients with ASD, VSD, PDA. Symptoms in adult life consist of shortness of breath, chest pain, syncope, and coughing blood. Other signs include clubbing of the fingers and toes.
- Doppler ultrasound can diagnose the direction of the shunt
- Cardiac catheterization.
In all patients, the degree to which pulmonary vascular resistance is elevated before operation is a critical factor determining prognosis. Surgery is useful only in mild cases of pulmonary hypertension. However, if a moderate to severe increase in pulmonary vascular resistance exists preoperatively, either no change or a progression of pulmonary vascular disease is common postoperatively.
Heart lung transplantation
Heart lung transplantation may offer the only cure.