Aortic Dissection (cardiac view)
- Aortic dissection is a tear in the inner wall of the aorta, so blood burrows into the wall and splits it into a true channel and a false one.
- On a cardiac CT you're hunting for the intimal flap: a thin line floating inside the aorta that shouldn't be there.
- The reason it sits on a cardiac page is that ascending (type A) dissection can dump blood around the heart — pericardial effusion, tamponade, or a torn aortic valve — and that's what kills people fast.
- ECG-gated technique matters: an ungated scan can blur the aortic root and fake a flap that isn't there (or hide one that is).
- If you see blood around the heart plus an aortic flap, that's a surgical emergency until proven otherwise. Phone first, finish the report later.
The aorta is basically a garden hose that has to survive the pressure of a fire hydrant, every second, for eighty years. It's built in layers, like a rolled-up newspaper. A dissection is what happens when the innermost layer tears and high-pressure blood pries those layers apart from the inside. Suddenly the "hose" has two channels: the original one, and a brand-new fake one carved into the wall itself.
That alone is bad. But on a cardiac study, the thing that makes me sit up straight isn't the aorta — it's what the dissection does to the heart sitting right next to it.
Why this lives on a cardiac page
The aortic root is screwed directly onto the top of the heart. So when the tear involves the ascending aorta (the part closest to the heart — this is "type A"), the trouble doesn't stay in the pipe. It spills toward the heart in three classic ways:
- Pericardial effusion / tamponade — blood weeps into the sac around the heart and squeezes it like a hand around a water balloon.
- Aortic valve disruption — the flap pries the valve open so it leaks (acute aortic regurgitation).
- Coronary involvement — the tear can peel into a coronary artery's origin, starving the heart muscle and mimicking a plain heart attack.
A type A dissection with blood in the pericardium is one of the true "minutes matter" findings in all of radiology. Untreated ascending dissection carries a steep early mortality, climbing with every hour. If you spot it, you call the surgeon while the patient is still on the table — you do not save it for the end of the worklist.
The finding: that thin line that shouldn't be there
The money sign is the intimal flap — the peeled-up inner layer, seen on contrast-enhanced CT as a thin curved line sitting inside the bright lumen, dividing it into two. One side is the true lumen (the original pipe) and the other is the false lumen (the new space inside the wall).
The true lumen is usually the smaller, rounder one that connects continuously to the normal aorta; the false lumen is often larger and may fill or enhance more slowly. You don't have to nail which is which to raise the alarm — but you do have to see the flap.
How not to miss it (and how not to invent it)
Here's the trap unique to the heart. The aortic root flips around with every heartbeat, so on an ungated scan it smears across the image — and that motion blur can paint a fake gray line right where you'd expect a flap. I have absolutely pointed at "a flap!" that turned out to be the aorta wiggling for the camera.
Pulsation (motion) artifact at the aortic root is the great pretender. The fix is technique: an ECG-gated acquisition freezes the heartbeat. A real flap stays put across reconstructed phases and curves smoothly; a motion ghost typically appears in a predictable orientation, doesn't respect the lumen, and melts away on a gated or repeat view. When in doubt, ask whether the study was gated.
This is where the scan technique earns its keep — the same ECG-gating you'd use for a coronary CTA is exactly what de-blurs the root and lets you trust the line you're seeing.
Before you even chase the flap, glance at the pericardium and the pleural spaces. A high-density (fresh-blood) effusion next to a wide aortic root is a screaming clue, and sometimes it's easier to see than the tear itself.
The cardiac fallout, at a glance
| Complication | What it does | Why you care on the cardiac read |
|---|---|---|
| Pericardial effusion / tamponade | Blood fills the pericardial sac and compresses the heart | Direct cause of death; look for it every time |
| Acute aortic regurgitation | Flap distorts the valve, so it leaks backward | Sudden heart failure; root looks dilated |
| Coronary extension | Tear peels into a coronary origin | Mimics a routine heart attack, but the fix is surgery, not a stent |
The one thing to walk away with
On a cardiac CT, "aortic dissection" isn't just a line in a pipe — it's a heart problem wearing an aorta costume. Find the flap, then immediately interrogate the pericardium, the valve, and the coronary origins, because that's what turns a wall tear into a code. The full classification scheme (Stanford and DeBakey) and the broader workup live over on the dedicated aortic dissection page; the related blood-around-the-heart picture is covered under pericardial disease. For this page, remember the reflex: flap plus fluid around the heart equals phone call.