Explain the PS In VCD in Cyanotic Heart Disease ?

These are peculiar to this group only. It occurs in young infants (usually after two months and rarely after two years), It consists of rapid and deep breathing (Hyperpnoea), worsening of cyanosis, and decrease or disappearance of heart murmur. Any event such as crying, defecation, or increased physical activity that suddenly lowers the systemic venous resistance (SVR) may initiate the spell by establishing a vicious cycle of hypoxic spells. The sudden onset of tachycardia or hypovolemia can also cause the spells.

Acyanotic /'Pink' TOF: Depending on severity of RVOT obstruction, the magnitude and the direction of the VSD shunt vary. With mild stenosis PS a small to moderate, left to right VSD shunt is present. The systolic pressures are equal in Right Ventricle (RV), Left Ventricle (LV) and Aorta due to large unrestrictive VSD. The PA pressure is slightly elevated and has a moderate pressure gradient between the PA and RV. The heart size and pulmonary vascularise is slight to moderately increased.
Differential Diagnosis
1) Fallot's tetrology.
2) Transposition of great arteries with I&D and PS.
3) Tricuspid Atresia with VSD and PS.
4) Single ventricle / Very large VSD, acting as single chamber with PS.
5) Double Outlet Right ventricle (both Aorta and Pulmonary artery wising from right ventricle) with PS
6) Corrected Transposition of Great arteries with VSD and PS.