Aortic dissection: Clinical sciences

Aortic dissection occurs often due to long-standing untreated high blood pressure, when blood tears through the intimal layer of the aortic wall and bleeds into the muscular layer, creating an intraluminal flap and a double lumen, which means that there is a true and a false lumen of the aorta.

Acutely, blood will flow into the false lumen because there’s less resistance, which can lead to obstruction of the true lumen, resulting in malperfusion of end-organs, such as the brain, bowel, or kidneys.

In addition, as blood accumulates in the false lumen with no way out, it may clot leading to the formation of thrombi. Lastly, as blood keeps flowing into the false lumen, the shear stress on the aortic wall can cause the tear to expand, or in the worst cases even lead to aortic rupture, causing mortality from cardiac tamponade or internal hemorrhage.According to the Stanford classification, aortic dissection is either classified as Type A, which always involves the ascending aorta with or without involving the descending aorta; and Type B, which only involves the descending aorta.

Let’s first look at an unstable case. When approaching a patient who presents with signs and symptoms suggestive of an acute aortic dissection, your first step is to do an ABCDE assessment in order to determine if the patient is unstable or stable.

If the patient is unstable, you need to stabilize their airway, breathing, and circulation first. This means that you should secure their airway, obtain IV access, and begin fluid resuscitation while continuously monitoring their vital signs, especially their blood pressure and heart rate.

Next, take a focused history and physical exam. Patients with unstable aortic dissections typically report an acute and severe “tearing” or “ripping” chest pain, and since the aorta is mostly a retroperitoneal organ, the pain can radiate to the back.

In fact, the location of the pain depends on which area of the aorta is affected, and sometimes the pain can evolve and migrate as the dissection expands.

If the ascending aorta is involved, your patient will typically report acute onset of severe chest pain and upper back pain.

If the descending aorta is involved, the pain can radiate to the upper, mid, and lower back. Lastly, in addition to pain, patients may also report diaphoresis or syncope.

On physical exam, you’ll typically note tachycardia and hypotension. Additional findings may depend on the areas impacted by the dissection.

For example, if the dissection is more proximal, it may reach and involve the aortic valve, so you could hear a murmur from aortic regurgitation, and you may also see signs of cardiac tamponade, like jugular venous distension.

Other findings may depend on the area of the body that’s not getting adequate blood supply. For example, if the aortic arch or spinal arteries are involved, your patient may develop neurologic defects like limb paresthesia or paraplegia.

There may also be asymmetric pulses or blood pressure measurements between extremities, which can cause acute limb ischemia.

Lastly, if the renal arteries are involved, your patient may develop anuria. Your next step in an unstable patient is to obtain a transesophageal echocardiogram, or TEE for short, to help confirm diagnosis, since these patients may not be stable enough for other types of imaging like a CT angiogram, or CTA for short.

TEE might show a double lumen, with the true lumen and a false lumen in the dissected portion, and an intraluminal flap between them.

The TEE may also show a thrombus in the false lumen. Finally, the most severe cases may even reveal an aortic rupture, and if the ascending aorta is involved, you may see cardiac tamponade.

These TEE findings indicate an aortic dissection, and because this patient is unstable, they’ll typically need emergent surgical repair regardless of the Stanford classification.

Here’s a clinical pearl! Patients with type A aortic dissections are almost always hemodynamically unstable, while patients with type B dissections can become unstable, but are most often stable at presentation.So now, let’s go all the way back and shift our focus to stable patients.

In a stable patient, your first step is to perform a focused history and physical exam. Stable patients will often have a similar history as unstable patients, again presenting with ​​acute, severe “ripping” or “tearing” chest or back pain, as well as diaphoresis, and syncope.

In contrast to unstable patients though, a physical exam here typically reveals severe hypertension. As before, you can also expect to find asymmetric pulse or blood pressures between extremities, as well as additional findings that depend on the area of the body that’s not getting adequate blood supply.

Next, you should order labs, including CBC, CMP, and lactate, as well as blood type and crossmatching in case your patient needs transfusion.

You should also obtain a CTA to confirm the presence of an aortic dissection and get an idea about its location and extent.

If the patient has severe contrast allergy or significant renal impairment, you can order an MR angiogram, or MRA, instead.Okay, now let’s talk about possible imaging findings.

First of all, you could see a normal aortic diameter with a single lumen and no evidence of dissection. In this case, consider an alternative diagnosis.Alright, let’s go back to imaging.

Next, the CTA or MRA might show an intraluminal flap and double lumen involving the ascending aorta only, or both the ascending and descending aorta.

If this is the case, you can confirm your diagnosis of a Stanford type A aortic dissection. This is a surgical emergency, so your next step is to obtain an emergent surgical consultation to evaluate for immediate surgical repair.

Alright, let’s go back to imaging one last time! If the CTA or MRA shows an intraluminal flap and double lumen in the descending aorta only, you can make your diagnosis of a Stanford type B aortic dissection.

The management of these dissections depends on the presence or absence of complications, so your next step is to assess for complications including uncontrolled pain; rapid tear expansion; aortic rupture; or signs of end-organ malperfusion, such as focal neurologic deficits, abdominal pain, renal insufficiency, or labs revealing elevated serum creatinine or lactate levels.

In uncomplicated cases, start medical therapy for aggressive blood pressure control with IV beta-blockers or calcium channel blockers.

Lowering the blood pressure will help reduce the shear stress on the aortic wall and hopefully prevent the aortic dissection from expanding!

On the flip side, if your patient presents with complications, or if at any point their presentation becomes complicated, you must call for an urgent surgical consultation for endovascular repair.Alright, as a quick recap… Aortic dissections are defined as the tearing of the aortic wall creating an intraluminal flap and a double lumen, typically associated with long-standing uncontrolled hypertension.

First, perform an ABCDE assessment to determine if they’re unstable or stable. If unstable, stabilize airway, breathing, and circulation, then evaluate with a TEE to confirm the diagnosis, and send them for emergent surgical repair.

When it comes to stable patients, they need either a CTA or MRA to confirm the diagnosis. Type A dissections need emergent surgical consultation for surgical repair.

On the other hand, for type B dissections, check for complications; uncomplicated cases can be treated with medical therapy for aggressive blood pressure control with IV beta-blockers or calcium channel blockers, while complicated cases need urgent surgical consultation