Case: A 63-year-old woman with a long history of hypertension faints after experiencing the sudden onset of severe chest pain that radiates to her back. She is rushed to the ED. Upon arrival she is agitated and demands immediate relief. Her HR is 110 bpm and BP is 90/50 mmHg. Jugular veins are distended. An intraarterial catheter shows significant variation of systolic blood pressure related to the respiratory cycle. Chest x-ray shows significant widening of the mediastinum. What is the most likely cause of the patient’s syncopal episode?

Let’s break it down: 

Long history of hypertension (HTN) - higher risk of stroke, myocardial infarction (MI), heart failure, aortic dissection.

Severe chest pain radiating to the back - what internal blood vessel is retroperitoneal? why, did someone say, aorta? Add in the HTN, and you’ve got (most likely) an aortic dissection!

But the question isn’t asking what happened to the patient, they’re asking why she had a syncopal episode. Her BP is low, which we call hypotension in the medical world. Let’s look at the other info. Physical exam shows jugular venous distention, or JVD. “Variation of systolic blood pressure related to respiratory cycle” - a lot of words for the medical term pulsus paradoxus. Okay, but WTF is this “pulsus paradoxus” shit?

Normally when you breathe in, the pressure in the chest cavity becomes negative in order for air to go in, like a vacuum. The same is also true for the right side of the heart. During inspiration, more blood gets sucked into the right heart, causing the volume of the right heart to become larger. Since the heart has a limited amount of space, the extra filling of the right squishes the left side of the heart slightly, which means less blood gets pumped out to the systemic circulation. So, normally when you breathe in, your systolic blood pressure will drop a little, around 10 mmHg. But pulsus paradoxus is when there is MORE than a 10 mmHg drop in systolic BP with inspiration. Oooohhh…

Now we have: aortic dissection + hypotension + JVD + pulsus paradoxus. Together this equals cardiac tamponade, one of the most dangerous consequences of aortic dissection. (Hypotension, JVD, and muffled heart sounds are classically known as Beck’s Triad, which is associated with tamponade.) Aortic dissection (tear in the inner wall of the aorta causing blood to go in and separate the layers) can rupture into the pericardial sac around the heart, causing blood to accumulate in the sac and put pressure on the heart. The heart doesn’t like other things squeezing it, because it limits the amount of blood that can go into the heart. And when you decrease the amount that goes into the heart (preload), you automatically decrease the amount that goes out of the heart (cardiac output) - which is a bad thing. Syncope, or fainting, can be caused by decreased blood flow to the brain.

Hope you’ve enjoyed this moment of medical knowledge, brought to you by USMLEWorld Qbank. Now back to your regular scheduled programming of emo landscape pictures and random pictures from the imgur gallery.