2025 – PAGE 131 – CARDIOLOGY

COARCTATION OF THE AORTA

(This is NOT A CYANOTIC DEFECT, but its discussion may help you with the upcoming disorders.) Coarc­tation of the aorta can result in congestive heart failure (CHF) symptoms including a gallop, weak pulses from cardiogenic shock, and a “pale” appearance (not cyanotic). Treat with PROSTAGLANDIN (PGE) to keep the ductus arteriosus patent.

PEARLS: Due to the coarctation, there is a blood pressure differential between the RIGHT ARM and RIGHT LEG. There is a lower blood pressure distal to the coarctation, thus the RIGHT LEG’s pulse is weaker than the RIGHT ARM’s.

PREDUCTAL & POSTDUCTAL SATURATION

The topic of preductal saturation versus postductal saturation can get confusing. Basically, O₂ saturations in the RIGHT HAND are considered PREductal. O₂ saturations measured in ANY OTHER EXTREMITY are considered POSTductal.

• PULMONARY HYPERTENSION: There is a RIGHT to LEFT shunt at the PDA as deoxygenated blood is shunted from the PA to Aorta. PREductal O₂ sats will be HIGHER than the POSTductal sats because of the shunted deoxygenated blood.

TRUNCUS ARTERIOSUS (TA)

Instead of two “great arteries,” a single TRUNK comes off of the ventricular chambers to create the truncus arteriosus. There is BIVENTRICULAR hypertrophy on the EKG and cardiomegaly on the chest X-ray. The shunt is bidirectional, and there is a strong association with DiGeorge Syndrome (so obtain a FISH!). TA results in severe CHF and death within months to one year. Cyanosis is only mild.

PEARLS: It’s technically a right to left shunt because the aorta is supposed to carry “red” blood. But, when you are asked about a shunt, read the question very carefully to understand the SITE that is being discussed because a condition can have multiple types of shunts associated with it. For example, in a patient with truncus arteriosus, the shunt at the level of the VSD is a bidirectional shunt with mixing of the blood at the VSD. But, at the level of the aorta (and overall), this is a right-to-left shunt and results in a blue baby.

TRANSPOSITION OF THE GREAT ARTERIES (TGA/TOGA)

The “great arteries” are the AORTA and the PULMONARY ARTERY. In Transposition of the Great Arteries, the LV leads to the PA, and the RV leads to the Aorta. This is the most common cardiac cause for cyanosis on DOL 1, and usually presents within hours. The EKG shows RVH. The two circuits do not connect and are “running in parallel” (see image). Mixing needs to occur in order to support life. Often a VSD is present, but if not, then a septal “defect” needs to be created. To treat, create an ASD to allow mixing (Rashkind procedure, balloon atrial septostomy done in cath lab or at beside in NICU). Mixing at the PDA also helps (though not as much), so create the presence of BOTH (ASD and the PDA) by also giving PGE. The ASD (or existing VSD) allows a RIGHT to LEFT shunt (deoxygenated circuit to oxygenated circuit) to be created. CXR shows an EGG SHAPED and vascular congestion (due to blood flow from the LV to the PA). There is no associated murmur. In the image below, note the circuits running in parallel. Treatment is an ASD (represented by the crossed arrows).

PEARL: If you suspect a cardiac cause for cyanosis on DOL 1, TOGA is probably your answer!