Valve Disease Detail (AS/AR/MR/MS)
- A heart valve has exactly two ways to fail: it won't open all the way (stenosis) or it won't close all the way (regurgitation). That's the whole vocabulary.
- Stenosis is a clogged doorway — pressure builds behind it. Regurgitation is a door that won't latch — blood sloshes backward and the upstream chamber stretches to hold the extra.
- Echocardiography is the workhorse. Cardiac MRI steps in to settle arguments — especially to actually measure leaky valves and to size the chambers.
- The four big ones to know cold: aortic stenosis (AS), aortic regurgitation (AR), mitral regurgitation (MR), and mitral stenosis (MS).
Think of the heart as a four-room house where the doors only swing one way. Each door (valve) has one job: open wide when blood needs through, then slam shut so nothing leaks back. When a door misbehaves, it misbehaves in one of two boringly predictable ways — and once you internalize those two patterns, all of valve disease stops being a memorization slog and starts being common sense.
The only two failure modes
Stenosis is the stuck door. It won't open all the way, so blood has to be forced through a smaller hole. The chamber pumping into it has to crank up the pressure, like trying to push a crowd through a turnstile during a fire drill. Over time that chamber gets thick and muscular from the constant strain.
Regurgitation (also called insufficiency) is the leaky door. It won't fully close, so every time the chamber pumps, some blood squirts back where it came from. The upstream chamber now has to handle its normal load plus the returning leak, so it stretches and dilates to hold the extra volume.
Two words, two pictures: stenosis means pressure and thick walls; regurgitation means volume and big roomy chambers. Hold onto that and the rest is detail.
Stenosis = pressure overload = the chamber gets thick (hypertrophy). Regurgitation = volume overload = the chamber gets big (dilatation). Almost everything downstream follows from those two sentences.
Aortic stenosis (AS): the calcified turnstile
The aortic valve is the front door out of the left ventricle (LV) into the aorta — the body's main exit. When it stiffens and calcifies (often just wear-and-tear with age, sometimes a congenitally bicuspid valve that wore out early), the LV has to generate brutal pressure to shove blood past it. The LV wall thickens in response.
On imaging, you'll see a heavily calcified valve that barely opens, and a thick-walled LV. Echo measures how fast blood jets through the narrowed opening — faster jet, tighter valve. The classic trio of symptoms (chest pain, fainting, heart failure) shows up late, and once it does, this is a serious diagnosis.
Aortic regurgitation (AR): the door that won't latch
Same door, opposite problem. The aortic valve won't seal, so during the heart's relaxation phase, blood that was just ejected into the aorta dribbles back into the LV. The LV now fills from two directions and copes by getting large and dilated over time. Causes range from a worn valve to a dilated aortic root stretching the leaflets apart (think of a screen door frame warping so the door no longer meets the jamb).
This is where cardiac MRI earns its keep: it can directly quantify how much blood leaks backward (the regurgitant fraction) using phase-contrast flow imaging — basically a radar gun for blood — and precisely measure the LV size that echo sometimes only estimates.
The recurring theme: echo first, MRI to referee. Echocardiography is fast, bedside, and excellent. Cardiac MRI comes in when the echo is technically limited, the numbers don't add up, or you need a rock-solid measurement of chamber volumes and regurgitant fraction before someone operates.
Mitral regurgitation (MR): the upstream backsplash
The mitral valve sits between the left atrium (LA) and LV. When it leaks, every LV squeeze sends some blood backward into the LA instead of forward to the body. The LA dilates to absorb the backsplash, and that pressure can eventually back up into the lungs. If you've read about pulmonary edema, this is one of its cardiac sources — the upstream traffic jam reaches the lungs.
MR has many flavors (a floppy prolapsing leaflet, a ruptured supporting cord, a stretched-out valve from a dilated heart), and sorting out the mechanism matters because it changes the repair. MRI and echo together map both the severity of the leak and the shape of the chambers behind it.
Mitral stenosis (MS): the narrow upstream doorway
Mitral stenosis narrows the LA-to-LV doorway, so the LA struggles to empty and pressure backs up — again, toward the lungs. Worldwide, the dominant cause is old rheumatic heart disease, which scars and fuses the leaflets over years. The hallmark you'll hear described is a valve with thickened, fused tips that domes open like a tent instead of swinging freely.
Don't reflexively blame a big left atrium on mitral stenosis — a leaky mitral valve (MR) enlarges the LA too. The distinction is the mechanism at the valve: a narrowed, doming, often calcified opening points toward stenosis, while a valve that simply fails to coapt points toward regurgitation. Severity and cause both change management, so name the mechanism, not just the dilated chamber.
Putting it together
| Valve lesion | Failure mode | Upstream chamber | What it does | Common cause |
|---|---|---|---|---|
| Aortic stenosis (AS) | Won't open | Left ventricle | Thickens (pressure) | Age-related calcification, bicuspid valve |
| Aortic regurgitation (AR) | Won't close | Left ventricle | Dilates (volume) | Worn valve, dilated aortic root |
| Mitral regurgitation (MR) | Won't close | Left atrium | Dilates (volume) | Prolapse, chordal rupture, dilated LV |
| Mitral stenosis (MS) | Won't open | Left atrium | Dilates + high pressure | Rheumatic disease |
When you read a valve study, answer three questions in order: which valve, which failure mode (stenosis or regurgitation), and how severe. If you can say "moderate-to-severe aortic stenosis with a thick left ventricle," you've already told the clinician what they most need to know.
If you remember nothing else: two failure modes, two consequences. Stuck doors build pressure and thick walls; leaky doors build volume and big chambers. Everything else — the calcium, the jets, the dilated atrium, the lungs getting wet — is just that one idea echoing downstream. For the chambers and views these valves live in, it's worth a quick detour through cardiac anatomy and planes.