coarctation of the aorta
Coarctation of the aorta is a localized narrowing of the body's main artery, like a kink or pinch in the principal water main supplying a building. The constriction usually sits just past the vessels that branch off to the head and arms, so pressure builds up upstream while everything downstream is starved of flow.
The hallmark is a pressure mismatch: high blood pressure in the arms but weak, delayed pulses in the legs. The heart must push harder to force blood through the narrow segment, and over time small bypass arteries enlarge to carry blood around the obstruction. Severe coarctation can overwhelm a newborn's heart within days, whereas milder cases may surface only as unexplained hypertension in a young adult.
The narrowing is relieved either surgically or by a catheter that balloons the segment open, sometimes with a stent. Untreated, the chronically high upstream pressure strains the heart and arteries and raises the long-term risk of complications.
A teenager evaluated for high blood pressure is found to have arm pressures far exceeding leg pressures, and imaging confirms coarctation of the aorta.
Arm pressure much higher than leg pressure is a key clue to coarctation.
Coarctation is strongly associated with a bicuspid aortic valve, and it occurs more often in conditions such as Turner syndrome; checking arm-versus-leg blood pressures is a simple way to suspect it.