Acyanotic vs Cyanotic Congenital Heart Defects

You separate congenital heart defects into acyanotic and cyanotic. Basically, is the baby (or kid) nice and pink, or is he or she dusky as they like to say. Sometimes the blueishness only happens when they’re working really hard, like feeding and crying (or thinking about the pathophysiological mechanisms of heart disease).

One of the important things to remember is that acyanotic heart defects can switch over if they’re left alone for too long because of pulmonary hypertension caused by the extra flow. This is called Eisenmenger Syndrome.

It’s also important to realize that many of the cyanotic lesions are duct dependent, meaning that as long as the ductus arteriosus is open, they are happy and pink. The problems start in that time 6-24h after delivery when the ductus closes. Thankfully you can keep it open by giving prostaglandin E1.

Need the ductus for systemic circulation:

  • Coarctation of the aorta
  • Critical aortic stenosis
  • Hypoplastic left heart syndrome

Need the ductus for pulmonary circulation:

  • Pulmonary atresia
  • Critical pulmonary stenosis
  • Tricuspid atresia
  • Tetralogy of fallot

Also, I realize that the 5 Ts of cyanotic heart lesions are a pentad of 6 (plus some), but mnemonics can only do so much, and the T thing is just so catchy.

For a more detailed illustration of PDAs, you can check out this doodle!

Special physical exam techniques for cardiac murmurs

Heart murmurs are pretty nifty things to listen to on physical exam. Not only are they discernible somewhat by location, there are lots of special tricks and maneuvers doctors have up their sleeves to figure out exactly what kind of murmur it is.

If you are suspecting aortic regurgitation (AR), you should hear it just below the pulmonic area (where the aortic valve is located). When you get the patient to hold their breath and lean forward the murmur should get louder. Holding their breath makes mitral stenosis (MS) murmur quieter.

Getting a patient to squat from a standing position increases their stroke volume which will make any regurgitation murmur (whether it’s mitral or aortic) louder.

Similar to how laying on the left side will make it easier to feel the apical impulse, this maneuver brings out mitral stenosis (MS).

Finally, getting the patient to do a Valsalva maneuver (bearing down) will decrease left ventricular (LV) outflow and bring out a hypertrophic cardiomyopathy murmur (this finding is almost pathognomonic with HCM)


Patent ductus arteriosus

Normal fetal circulation

The ductus arteriosus is a connection between the aorta and pulmonary artery present in the fetal circulation. Since the pulmonary vascular pressure is higher than the systemic pressure, blood is shunted through the ductus from the right to the left, bypassing the lungs.


When the baby is born, the resistance in the pulmonary vascular falls and more of the blood goes through the lungs. In conjunction with this the fall in the level of circulating prostaglandins causes the contraction of the ductus arteriosus.

Patent ductus arteriosus

In some babies, particularly those born prematurely, the ductus fails to close and the shunt becomes left to right.

This gives you the classic “continuous machine-like murmur

Systolic vs diastolic heart murmurs

The differences between mitral insufficiency (regurgitation) and stenosis and aortic insufficiency and stenosis. It’s important to know where to listen for them and what sort of other findings they go along with. Really aortic insufficiency is the one with all the wonderful findings that all all named after different people.

Systolic vs Diastolic Heart Failure

Left-sided heart failure leads to fluid accumulation in the lungs and has an increased left ventricular end diastolic pressure (LVEDP). The left ventricular end diastolic volume (LVEDV) can either be increased or normal. When it is increased and the end systolic volume is also increased, this indicates systolic dysfunction. When the LVEDV is normal or the ejection fraction is normal, this indicates diastolic dysfunction.

Ejection fraction = Stroke Volume/End Diastolic Volume
Stroke Volume = End Diastolic Volume – End Systolic Volume

Systolic Heart Failure

The inability to expel sufficient blood, has a decreased ejection fraction. You might feel a displaced apical impulse or hear an S3.

Causes: Decreased contractility (ischemia, MI, chronic mitral regurg), Increased afterload (aortic stenosis, hypertensive crisis)

Diastolic Heart Failure

Failure to relax and fill normally, has a normal ejection fraction

Causes: Chronic hypertension, hypertrophic cardiomyopathy, aortic stenosis, coronary disease

Heart sounds


Where S1 and S2 fall in the cardiac cycle and how they correspond with the EKG rhythm. I’ve also included where and why S3 and S4 fall.

S3: dilated ventricle, usually due to heart failure, though it can be normal in children

S4: the sound is caused by blood entering a ventricle with decreased compliance.
A patient with atrial fibrillation can’t have an S4 because there isn’t enough coordinated atrial contraction to force enough blood into the ventricles at once