Hypercyanotic episodes are characterized by paroxysms of hyperpnea, prolonged crying, intense cyanosis, and decreased intensity of the murmur of pulmonic stenosis.
It is secondary to infundibular spasm and/or decreased SVR with increased right-to-left shunting at the VSD, resulting in diminished pulmonary blood flow. Treatment consists of oxygen to reduce the hypoxia, propranolol to decrease the infundibular spasm. Presentation depends on degree of pulmonary stenosis. If severe then lung blood flow is reduced & cyanosis is observed as a neonate. If it is less severe as the degree of pulmonary stenosis increases with age it presents later in infancy. Clubbing develops by around 6 months of age.


If left untreated, may result in syncope, seizure, stroke, or death