A pediatric patient with tetralogy of Fallot may have paroxysmal hypercyanotic attacks with hypoxia.


Synonym: blue spell, "tet" (for tetralogy) spell, hypoxic spell


Triggers may include:

(1) crying

(2) waking up in the morning


Clinical features:

(1) hyperpnea (rapid or labored breathing) and/or gasping respirations

(2) restlessness

(3) cyanosis

(4) syncope


Laboratory features:

(1) metabolic acidosis

(2) reduced PaO2, often < 40 mm Hg



(1) weakness and exhaustion

(2) seizures

(3) unconsciousness

(4) occasionally death


Tet spells tend to occur in the pediatric age group, being absent in adolescents and adults.


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