Coarctation of aorta

Coarctation of aorta

Coarctation of aorta is a narrowing in the proximal descending aorta. It can be a discrete narrowing or a tubular one. Usual site is opposite the erstwhile ductus arteriosus and it is thought to be due to an extension of the process of natural closure of the ductus to the aorta. The usual location is post subclavian though it can be before the origin of the left subclavian. When a patent ductus arteriosus is associated with coarctation of aorta in a child, the coarctation can be easily missed as the lower limb pulses may not be feeble as in isolated coarctation. This is because the ductal ampulla opposite the ductus reduces the narrowing of the aorta. In a neonate with severe coarctation, symptoms may start with the spontaneous closure of the ductus.

The important physical findings of coarctation are the delayed femoral pulses (brachiofemoral or radio-femoral delay) and the collateral pulsations in the region of the scapula. Systolic or continuous murmur may be heard at over the site of the coarctation at the back. Findings of associated bicuspid valve with aortic stenosis or regurgitation may also be noted.

Electrocardiogram may show left ventricular hypertrophy due to the hypertension or associated aortic stenosis. X-ray chest shows the characteristic rib notching of the lower borders of 3rd to 8th ribs due to the erosion by the tortuous posterior intercostal arteries. The notching is not seen in small children. It becomes more prominent as age increases and the sclerosis at the edge of the notch makes it quite visible. Rib notching is not seen in the upper intercostal spaces as both the posterior and anterior intercostal arteries arise from the high pressure zone proximal to the coarctation, while in the lower spaces, the posterior intercostal arteries arise from the low pressure zone below the coarctation. Unilateral rib notching occurs in pre subclavian coarctation, on the right side only as both anterior and posterior intercostal arteries will be in the low pressure zone in this case. Collateral pulsations may be felt posteriorly in the region of the scapula.

The natural history of unrepaired coarctation of aorta is poor and is characterised by aneurysm formation / dissection of the aorta, hypertension, heart failure and premature coronary artery disease. Even individuals whose coarctation has been repaired are more prone for hypertension and coronary artery disease.

The important methods of repair are by patch aortoplasty, either resection and anastomosis or subclavian flap angioplasty. Alternatively, a bypass graft can be used to bypass the obstruction.

Interventional treatment in the form of balloon dilatation and stenting are becoming increasingly common.