CONGENITAL HEART DISEASE

Broken baby hearts

Congenital heart disease is when a baby is born with an anatomical irregularity of the heart or Aorta. These are a big deal, because they are both (a) common and (b) deadly. Most congenital heart diseases occur sometime between weeks 3 and 8 of development, as the heart organ is being created. They affect 1% of births. I’ve listed some risk factors below. There are many different kinds of congenital heart problems, so to make it simpler we often break it down to left vs right shunts. A shunt just means that the blood has taken a shortcut. 

In left to right shunts, blood moves from the left side of the heart to the right. Well oxygenated blood from the left heart re-enters the pulmonary circulation, which is a bit redundant because that blood is already pumped full of oxygen. Cardiac output drops a bit, which can cause fatigue. 

In right to left shunts, blood moves from the right side of the heart to the left. Poorly oxygenated venous blood skips past the lungs, and is sent through the Aorta to the body. This causes cyanosis.

VSD

Hole between the ventricles

VSD is the most common congenital heart disease. It usually occurs at the top of the septum (closer to the atria), since the wall tapers down into a thin membrane at the top. Small membranous VSDs are clinically insignificant, and most kids will outgrow them. Larger VSDs will involve the muscular portion of the wall, and these can cause failure to thrive in an infant. Big VSDs will require surgery. Interestingly, the smaller defects often cause louder murmurs! The murmur sounds similar to Aortic stenosis.

Paradoxical Emboli

Emboli can cross VSDs and ASDs. They’re called paradoxical emboli when they do. The classic example is a DVT that becomes a stroke. 

Eisenmenger Syndrome

Imagine a kid has a VSD. Blood is moving into his right heart from the left side. Over time, as blood fills up the R side of the heart, pulmonary hypertension will develop. That raises the pressure inside the RV. Eventually, the pressure in the RV becomes bigger than the pressure in the LV, and flow reverses (now it’s R to L). Flow reversal is called Eisenmenger Syndrome, and is associated with a few typical findings. They get right ventricular hypertrophy (since it’s pumping against pulmonary hypertension), cyanosis and finger clubbing. 

ASD

Atrial Septal Defect

An ASD is a hole connecting the atria. They are present in fetuses, but close shut when we take our first breaths. In adults, they are both common and benign. Unbeknownst to them, many adults have silent ASDs. On auscultation they cause fixed splitting of S2. They can also cause paradoxical emboli. But otherwise they aren’t too big of a deal.

PDA

Patent Ductus Arteriosus

Fetuses have two special connections between their arteries and veins. The first is the ASD (see above). The second is called the Ductus Arteriosus. It’s kept open by Prostaglandin E1 (supplied by mom). A few weeks after delivery, the prostaglandin supply dries up, and the DA closes and turns into the Ligamentum Arteriosum. But sometimes it remains open, which is called a PDA. If you want to get rid of the PDA, you can do so easily by blocking prostaglandin with the NSAID Indomethacin.

The PDA isn’t subject to systole and diastole, as blood is always flowing through the PDA. That constant flow results in a constant murmur (with a “machine-like” quality). It sounds a bit like “WOOSH-kkkkthhhhhhh-WOOSH-kkkkthhhhhhh.”

In some babies with other heart defects, the PDA strategically remains open. It can be a good thing! For example, in Coarctation of the Aorta the PDA often stays open to provide some blood flow distal to the coarctation.

TETRALOGY OF FALLOT

Highest of yields

Tetralogy of Fallot is the most common cyanotic congenital heart disease. The symptomology depends on the severity (of the Pulmonic Stenosis specifically). During embryological development, there is an “anterosuperior deviation of the infundibular septum” that causes all of the problems. Severe cases will involve blue babies. In milder cases, the child will only become symptomatic (cyanosis) during exercise. For a baby, its only exercise is feeding (each feed is the equivalent of an adult running 10 miles). These episodes are called “Tet Spells,” and the child quickly figures out that squatting down relieves the symptoms (by raising afterload and the LV pressure). On a chest XR, you can spot ToF’s characteristic boot-shaped heart.   

TRANSPOSITION OF THE GREAT VESSELS

The ol’ switcheroo

Transposition of the Great Vessels is when the Aorta emerges from the RV, and the Pulmonary Trunk emerges from the LV. It results in two discrete loops, and none of the systemic circulation gets oxygenated! The only connections between the loops is a PDA and ASD. A cardiothoracic surgeon can enlarge / create an ASD or VSD to add more connections. But this disease is pretty deadly. 

TRUNCUS ARTERIOSUS

Two become one

If the beginning of the Aorta fuses with the beginning of the Pulmonary Trunk, then Truncus Arteriosus is taking place. Not much else to say. 

TRICUSPID ATRESIA

Tricuspid Atresia - Tricuspid stenosis leads to an ASD and the withering away of the RV. Also low yield.

COARCTATION OF THE AORTA

A kink in the garden hose

Coarctation of the Aorta is a fancy way of saying a narrowing of the early Aorta. It can occur in infants and adults. 

The infant form results in leg cyanosis and wimpy femoral pulses. The PDA keeps them alive.

The adult form results in HYPERtensive arms + HYPOtensive legs. Instead of the PDA, anastomosis via the Intercostal arteries keep their legs perfused (results in rib notching on CXR).