"Squatting attacks" and polycythemia are features of?

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.