This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Valvular hea diseases, Subject name: Medicine
"Squatting attacks" and polycythemia are features of? 
Select and explain. 
A. Acyanotic hea disease, B. Cyanotic hea disease, C. Eisenmenger syndrome, D. Lutembacher syndrome
B: Cyanotic hea disease
Answer: B: Cyanotic hea disease 
Explanation: In Tetralogy of Fallot, the affected child suddenly becomes increasingly cyanosed, often after feeding or a crying attack and may become apneic and unconscious. These attacks are called Tet spells. Some children characteristically obtain relief by squatting after exeion (this increases the after load to the left hea and decreases the right to left shunting). In older children, Tet spells are uncommon, but cyanosis becomes increasingly apparent, with stunting of growth, digital clubbing and polycythemia.