Which statement best describes a cyanotic spell associated with tetralogy of Fallot?

Which statement best describes a cyanotic spell associated with tetralogy of Fallot?

• A. Coarctation of the aorta
• B. Pulmonary stenosis
• C. Cyanotic spell related to tetralogy of Fallot
• D. Ventricular septal defect

Answer: (C)

The main idea here is tet spells in tetralogy of Fallot. A tet spell is a sudden episode of worsening cyanosis caused by an abrupt increase in right-to-left shunting across the ventricular septal defect, driven by dynamic obstruction of the right ventricular outflow tract (pulmonary stenosis). This reduced pulmonary blood flow forces more desaturated blood to pass into the systemic circulation, producing the characteristic cyanosis during the spell. Choosing the statement that describes a cyanotic spell as related to tetralogy of Fallot best captures the phenomenon, because the spell is a recognized complication of TOF itself—linking the episodic cyanosis to the condition as a whole. While pulmonary stenosis is a key factor in the mechanism, identifying the spell as TOF-related ties together the physiology of the defect, rather than listing a single component. The other options point to individual anomalies that can be present with TOF but do not describe the episodic cyanosis that defines a tet spell.

The main idea here is tet spells in tetralogy of Fallot. A tet spell is a sudden episode of worsening cyanosis caused by an abrupt increase in right-to-left shunting across the ventricular septal defect, driven by dynamic obstruction of the right ventricular outflow tract (pulmonary stenosis). This reduced pulmonary blood flow forces more desaturated blood to pass into the systemic circulation, producing the characteristic cyanosis during the spell.

Choosing the statement that describes a cyanotic spell as related to tetralogy of Fallot best captures the phenomenon, because the spell is a recognized complication of TOF itself—linking the episodic cyanosis to the condition as a whole. While pulmonary stenosis is a key factor in the mechanism, identifying the spell as TOF-related ties together the physiology of the defect, rather than listing a single component. The other options point to individual anomalies that can be present with TOF but do not describe the episodic cyanosis that defines a tet spell.