Monday, May 15, 2017

A neonate with cyanotic heart disease (Case #2)

A 3 day old new born is found to have cyanosis. On examination, a II/IV holosystolic murmur is heard. CXR shows decreased pulmonary vascular markings and cardiomegaly. ECG shows tall P waves and left axis deviation. Diagnosis?

Similar to the case we discussed last time (A neonate with cyanotic heart disease #1), let's narrow our differential.

First, congenital cyanotic heart diseases are few:
1. Tetralogy of Fallot
2. Transposition of the great arteries
3. Truncus arteriosus
4. Pulmonary atresia
5. Total anomalous pulmonary venous return
6. Tricuspid atresia
7. Hypoplastic left heart

Then, the pulmonary vasculature markings differentiation!

Increased pulmonary markings (increased pulmonary blood flow):
1. Transposition of great arteries
2. Total anomalous pulmonary venous return
3. Truncus arteriosus

Decreased pulmonary markings (diminished pulmonary blood flow):
1. Pulmonary atresia or severe stenosis
2. Tetralogy of Fallot
3. Tricuspid atresia
4. Ebstein anomaly

So we have narrowed our differential to 4 conditions. 

What else do we know?

Murmur: Doesn't tell us much.
Cardiomegaly: Doesn't tell us much.

ECG with LAD: What about it?

I want to emphasize that in utero, the right heart pumps blood to the entire body via the patent ductus arterisosus. That is why, newborn babies have a physiologic right ventricular hypertrophy (and therefore, a right axis deviation.)

Which means, left axis deviation in a neonate is abnormal.

Now, let's break it down!

Pulmonary atresia: Pulmonary atresia is characterized by complete obstruction to right ventricular outflow. There is great variation in the morphology of the RV, ranging from a severely hypoplastic small cavity with marked muscular hypertrophy to a large, dilated, thin-walled chamber.  The morphology of the left ventricle (LV) is usually normal in pulmonary atresia. It would not have LAD.

TOF: In TOF, there is no antegrade flow from the right ventricle (RV) to the pulmonary artery. ECG would show RAD, which is normal for the neonate but would not show LAD.

Ebsteins anomaly: Ebstein anomaly is a congenital malformation that is characterized primarily by abnormalities of the tricuspid valve and right ventricle. It would not cause LAD.

Tricuspid atresia: In TV atresia, the only exit of blood from the right atrium is through an interatrial communication. There will be a right atrial enlargement (tall P waves) --> Blood flows from the right atrium to the left atrium and left ventricle --> left ventricular hypertrophy (LAD) and RV hypoplasia.

There, we have our diagnosis!

That's all!
Hope this was helpful :D

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