Table 1.

Clinical features of ToF

Cyanosis (may be gradual onset and increasing in severity or with age)

Hypoxia/low Spo2 with little or no response to oxygen therapy

Heart murmurs (pansystolic and ejection systolic)

Spelling episode: agitated, distressed, and profound cyanosis

Arrhythmias (particularly supraventricular or ventricular)

Associated features of other genetic abnormalities

Features of late presentation can include poor exercise tolerance, clubbing, polycythaemia, neurodevelopmental delay, failure to thrive, heart failure, recurrent respiratory tract infections, and cerebral abscess and stroke.