Aortic stenosis: a narrow exit
The aortic valve is the last door blood passes before it leaves the heart for the whole body. In aortic stenosis, the leaflets stiffen and fuse, usually from slow calcium build-up over decades, so the opening shrinks. To keep pushing the same blood through a smaller hole, the left ventricle must generate much higher pressure during systole. It responds the way any muscle does to heavy lifting: its walls thicken. This is left ventricular hypertrophy, and for a long time it works — the heart keeps output normal and the person feels fine.
When the valve finally narrows enough, three classic symptoms appear, often remembered as the triad: chest tightness (angina) because the thick muscle outstrips its blood supply; fainting on exertion because the narrow valve caps how much blood can reach the body when demand rises; and breathlessness as the stiff ventricle and eventually heart failure set in. The faint-on-exertion story is the one to recognise — a fixed, severely narrowed valve simply cannot let extra blood out when you climb stairs.
Aortic regurgitation: a leaky exit
Now flip the failure. In aortic regurgitation, the aortic valve no longer seals during diastole, so a fraction of the blood just ejected into the aorta pours straight back into the left ventricle. The ventricle now has to handle a double load each beat — the normal inflow from the left atrium plus the regurgitant blood. Over time it enlarges and stretches to hold the extra volume, becoming one of the largest hearts in all of cardiology.
This volume load produces a memorable sign you can sometimes feel at the wrist: a wide pulse pressure. Because the ventricle ejects a large stroke volume the systolic pressure rises, and because blood leaks back the diastolic pressure falls — so the pulse pounds up and collapses away, the so-called water-hammer pulse. The body tolerates chronic aortic regurgitation for years; sudden, severe leak (as in infective endocarditis or aortic dissection) is a different, urgent matter because the ventricle has had no time to adapt.
Pulse pressure = systolic − diastolic Normal adult: 120/80 mmHg → 120 − 80 = 40 mmHg (typical) Severe AR: 150/50 mmHg → 150 − 50 = 100 mmHg (wide) Why: a big leak back into the LV means a big stroke volume is ejected (systolic up) and the aorta drains fast in diastole (diastolic down) → a wide, bounding pulse.
Listening for the two patterns
Because the aortic valve is *meant* to be open during systole and shut during diastole, the timing of its murmur tells you instantly which failure you are hearing. Aortic stenosis makes a harsh systolic murmur — blood roaring through the narrow valve while it should be wide open — that often radiates up to the neck. Aortic regurgitation makes a softer diastolic murmur — blood whooshing backward while the valve should be sealed. One valve, two opposite lesions, two opposite times in the cycle.