Mnemonic Monday: Cyanotic Congenital Heart Defects

By Haley Masterson

This mnemonic has been passed around pediatric residency programs for decades but is rarely mentioned in the medical school setting (which is unfortunate, because it works so well).  

The 5 Cyanotic Congenital Heart Defects are as easy as 1, 2, 3, 4, 5.

One big trunk:   Truncus arteriosus.

Two interchanged vessels:  Transposition of the Great Vessels.

ThreeTriscuspid Atresia.

FourTetralogy of Fallot.

Five words:  Total Anomalous Pulmonary Venous Return.


The utility of this mnemonic is in differentiating cyanotic heart lesions from non-cyanotic heart lesions.   There are more non-cyanotic heart lesions than cyanotic, so this mnemonic can help you quickly determine whether a given lesion should be cyanotic or not. This is one of the most important differentiations in congenital heart disease, because a question stem will nearly always mention how the baby appears on physical exam.

It’s helpful to keep in mind that cyanotic heart lesions are a natural result of a right-to-left shunt within the heart (blood that would normally go to the lungs to become oxygenated is instead shunted systemically). 

Some of the more common non-cyanotic heart defects include:  Ventricular Septal Defect (VSD), Atrial Septal Defect (ASD), Atrioventricular Septal Defect (AVSD), and Patent Ductus Arteriosus (PDA).   These non-cyanotic heart defects are a result of a left-to-right shunt, where blood is shunted to the lungs instead of the body – which explains why the baby wouldn’t appear cyanotic on physical exam. 

Keep in mind:  while fetal circulation has higher right-sided pressures (placental) than left-sided pressures (systemic), the left-sided pressures quickly become greater than the right-sided ones as soon as the umbilical cord is cut (due to decrease in resistance from lack of placenta as well as the baby’s first breath).  

Once the right-sided pressures are less than the left-sided pressures, any “hole” in the heart will naturally shunt blood to the area of lower pressure.  This is why ASD, AVSD, VSD, and PDA are all non-cyanotic – all are “holes” shunting blood naturally to the lungs.



  1. 1.    Kumar, Vinay, and Stanley L. Robbins. Robbins Basic Pathology. 8th ed. Philadelphia, PA: Saunders/Elsevier, 2007.
  2. 2.    Le, Tao, and Vikas Bhushan. First Aid for the USMLE Step 1 2010. New York: McGraw-Hill Medical, 2010.

Categories: Mnemonics

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