Cyanotic heart defect pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-In-Chief: Keri Shafer, M.D. [2], Atif Mohammad, M.D.; Kalsang Dolma, M.B.B.S.[3]
Overview
Pathophysiology
Tetrology of Fallot
The obstruction of right ventricular outflow in Tetralogy of Fallot causes blood to shunt or flow from the right to left side of heart through the ventricular septal defect. This causes right ventricular hypertrophy and eventual right sided heart failure. There is flow of deoxygenated venous blood from the right side of the heart to the systemic circulation resulting in cyanosis.
Total Anomalous Pulmonary Venous Connection
In this condition,the right side of heart is receiving blood both from pulmonary and systemic circulation. There is a mixing of oxygenated pulmonary venous blood with deoxygenated blood from systemic circulation. The mixing of blood could occur at three levels i.e. supracardiac, infracardiac and cardiac. In the former two the mixing occurs outside the heart and in latter inside the heart (right atrium)
Hypoplastic Left Heart Syndrome
In patients with hypoplastic left heart syndrome, the left side of the heart is unable to send enough blood to the body. As a result, the right side of the heart must maintain the circulation for both the lungs and the body. The right ventricle can support the circulation to both the lungs and the body for a while, but this extra workload eventually causes the right side of the heart to fail.
Transpostion of Great Arteries
The pulmonary and systemic circulations function in parallel, rather than in series. Oxygenated pulmonary venous blood returns to the left atrium and left ventricle but is recirculated to the pulmonary vascular bed and deoxygenated systemic venous blood returns into right atrium and ventricle which is subsequently pumped back into systemic circulation.
Truncus Arteriosus
In truncus arteriosus, the pulmonary arteries are connected to the aorta. A decrease in PVR at birth causes a left to right shunt with evidence of congestive heart failure. These patients have a very high incidence of pulmonary hypertension and vascular disease.
Tricuspid Atresia
In tricuspid atresia, there is no continuity between the right atrium and right ventricle. Blood from superior vena cava and inferior vena cava is forced across intra atrial connection into the left heart. As a consequence, oxygen saturation in the left atrial blood is diminished.