#hypercyanosis

[medicine-mu]

Tertalogy of fallot

Tet spell : hypercyanosis due to increased oxygen demand > more deoxygenated > baby gets more cyanotic .

The aim of management is to increase SVR and decrease PVR to reverse the shunt from right - left to left-right ( knee chest position , keep the baby calm , give oxygen supplements, sodium bicarbonates for metabolic acidosis , beta blockers , IV fluid )

1. Right ventricular hypertrophy (RVH): Narrowing or blockage of the pulmonary valve or infundibulum causes restriction of blood outflow. This leads to increase in right ventricular work and pressure, leading to right ventricular thickening or hypertrophy.

Ventricular septal defect (VSD):. The oxygen-poor blood in the right ventricle gets mixed with oxygen-rich blood in the left ventricle because of this septal defect. This poorly oxygenated blood is then pumped out of the left ventricle to the rest of the body. Hypoxemia causes cyanosis giving bluish color to the skin, lips, and membranes inside the mouth and nose.

Overriding of the VSD by the aorta: the aortic valve is situated immediately over the VSD also called overriding aorta. It is the main site for outflow of blood from both ventricles.

Right ventricular outflow tract obstruction (pulmonary stenosis): The major issue and most important prognostic factor in tetralogy of Fallot is the degree of pulmonary valve stenosis. If the stenosis is mild, there is low pressure in right ventricle and thus left to right shunt is present, minimal cyanosis occurs, since blood still mostly travels to the lungs. However, if the PS is moderate to severe, right ventricle has very high pressure leading to right to left shunt and a smaller amount of blood reaches the lungs, most is shunted right-to-left through the VSD. It causes significant hypoxemia and cyanosis.