Coarctation of the Aorta

Anatomy & Physiology

The narrowed aorta is usually in the region of the ductus. When coarctation presents in the neonate it is usually severe and duct dependent. The flow through the ductus is predominantly from right to left and post-ductal saturations may be lower although this is not a reliable feature. The reduced perfusion to the lower body may cause renal failure and predispose to necrotizing enterocolitis.

Presentation in the older age group is often by the presence of upper limb hypertension or reduced femoral pulses found on incidental examination. The duct is almost always closed. There is left ventricular hypertrophy due to the excess pressure needed to drive the blood through the coarctation.

Collaterals (mammary, scapular & intercostal arteries) may become very large and give rise to continuous murmurs.

Presentation

This comprises about 6% of congenital heart disease. It either presents as neonatal collapse or as an infant or older person with absent femoral pulses and upper limb hypertension.

Examination Absent or reduced lower limb pulses Hypertension upper body Hypotension in lower body Murmur between scapulae (continuous in infant type, ejection in neonatal)	Typical Blood Pressures
		Right	Left
	Arm	121/82	116/43
	Leg	64/41	63/39

Investigations

Electrocardiogram

The ECG may be normal or show signs of left ventricular hypertrophy. Neonates with duct dependant disease may also show right ventricular hypertrophy.

Chest X-ray

Cardiomegaly is seen in neonatal disease (far right X-ray) but long standing coarctation may cause rib notching (arrows) due to the collateral circulation.

Echocardiography

Although the coarctation is very posterior it is usually possible to image the area in babies and in all ages the Doppler pattern has a characteristically saw toothed appearance.

Magnetic resonance Imaging

MRI can delineate the anatomy and demonstrate the collateral vessels that reduce the incidence of neurological injury at the time of repair allowing perfusion of the spinal cord when the aorta is clamped. It is especially useful when the condition presents in older children and can improve surgical decision making between a transcatheter or transthoracic approach.

Natural History

Neonatal presentation leads to rapid death without treatment. In the older age group early death from cardiac failure or consequences of hypertension occurs. It is associated with Berry aneurysms and hence intracranial haemorrhage may occur - especially as systemic upper body hypertension is present.

Management

Neonates require resuscitation including prostaglandin to reopen the ductus prior to urgent surgery. Particular attention should be paid to renal function and restoration of acid-base balance. In the older child elective repair is undetaken.

The preferred surgical repair is through a left lateral thoracotomy with excision of the coarctation (taking care to remove all ductal tissue) and direct end to end anastomosis of the aorta.

The subclavian flap repair was commonly used prior to 1990 but sacrifices the subclavian arterial supply to the arm which may then grow poorly. It is still used in long segment coarctations when it is not possible to mobilize the descending aorta sufficiently to directly anastomose the ends.

Such patients are commonly found in exams with absent right brachial pulse & thoracotomy scar!

Balloon angioplasty is becoming an accepted treatment for the primary management of coarctation in the older age group. It is not suitable for neonates as the ductal tissue is not removed and re-constricts the aorta after balloon removal.

The procedure entails putting a catheter in the femoral artery and passing it across the aortic coarctation. A wire is then passed through the catheter into the ascending aorta and the catheter withdrawn leaving the wire in place. A balloon catheter is then "railroaded" over the wire to the coarctation site and inflated for a few seconds. It is then deflated and removed.

The principle complication that can occur is aortic aneurysm formation and this may require a covered stent to protect the aorta from dissection with catastrophic consequences.

Coarctation Angioplasty Animation (file download time 15s)

Hover the mouse over the heart to see the animation

Prognosis

Recurrence occurs in up to 10% of neonatal repairs and is usually dealt with by balloon angioplasty.

The risk of hypertension in teenagers and adults is greater than the normal population - even with a successful repair. Follow up should therefore be lifelong.