Pulse wave velocity

Pulse wave velocity measures how fast the pressure wave from each heartbeat travels down the aorta, and so how stiff that artery has become. It predicts heart attacks and strokes beyond the usual risk factors, and pulse pressure, the gap between your two blood-pressure numbers, is a free rough version of it. But the measurement is soft, and the one trial of treating to a stiffness target settled nothing.

Measure it if you are curious, but act on blood pressure, fitness and the other risk factors whatever the result. No trial shows that treating to a stiffness number helps.

What it measures

Young, elastic arteries absorb each heartbeat's surge and slow the pressure wave. Stiff, aged arteries carry it fast, and the wave bounces back to the heart while it is still pumping rather than between beats, raising the pressure the heart works against and reducing blood flow to the heart muscle itself. Carotid-femoral pulse wave velocity, measured between the neck and the groin, reads that stiffness directly.

What it predicts

Pooling individual data on 17,635 people, each step of one standard deviation up in aortic pulse wave velocity carried roughly 30% higher risk of a heart attack, stroke or similar event after allowing for the usual risk factors, and adding the measurement improved risk prediction for people at intermediate risk in some subgroups.^[1] The signal is strongest in middle age and fades after 70, when almost every aorta is stiff. It predicts better than age alone and is the closest routine measure of how old an artery behaves.

Why it is a soft number

The neck-to-groin route overestimates true aortic stiffness, and simply estimating the distance between the two pulse points a different way can move a reading by more than 3 m/s. That is why the same review stops short of calling it a clinical standard.^[2]

Pulse pressure: the free version

Pulse pressure is systolic minus diastolic: a reading of 120/80 has a pulse pressure of 40. A widening gap in midlife and beyond, with the top number rising and the bottom one falling, is the visible sign of stiffening arteries. Pooling 14 cohorts covering 510,456 people from the general population, every extra 10 mm Hg of pulse pressure came with about 13% higher cardiovascular mortality and about 9% higher death from any cause.^[3] Among older people with hypertension in treatment trials, the same 10 mm Hg tracked with nearly 20% more cardiovascular deaths even after allowing for average pressure.^[4] Both findings are observational: they show an association, not that narrowing pulse pressure would help.

The one treatment trial was inconclusive

Only one randomised trial has tested treating high blood pressure to a stiffness target rather than a blood-pressure target. It assigned 536 higher-risk patients to stiffness-guided or guideline-directed care and, after a median of four years, found no difference in cardiovascular events that could be told apart from chance. It recorded only 41 events and enrolled roughly a third of the patients it had planned, so the result is compatible with a large benefit and a large harm alike.^[5]

What to do

Treat a high result as a nudge, not a diagnosis. The levers for stiff arteries are the same as for everything else: blood pressure control, aerobic fitness (VO₂ max, Zone 2) and Mediterranean-pattern eating.
Don't compare readings taken by different methods or clinics; method alone can shift the number by more than 3 m/s.