Cardiovascular Journal of Africa: Vol 29 No 4 (July/August 2018)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 29, No 4, July/August 2018

252

AFRICA

Review Article

The challenge in diagnosing coarctation of the aorta

Julien IE Hoffman

Abstract

Critical coarctation of the aorta in neonates is a common

cause of shock and death. It may be the most difficult of all

forms of critical congenital heart disease to diagnose because

the obstruction from the coarctation does not appear until

several days after birth (and after discharge from the hospi-

tal), and because there are no characteristic murmurs. Some

of these patients may be detected by neonatal screening by

pulse oximetry, but only a minority is so diagnosed. Older

patients are usually asymptomatic but, although clinical diag-

nosis is easy, they are frequently undiagnosed.

Keywords:

patent ductus arteriosus, left ventricular failure, pulse

oximetry, balloon dilatation, stent

Submitted 14/7/17, accepted 19/11/17

Published online 11/12/17

Cardiovasc J Afr

2018;

: 252–255

www.cvja.co.za

DOI: 10.5830/CVJA-2017-053

Coarctation of the aorta is a congenital lesion that occurs in 2.5

to four per 10 000 live births.

1,2

With a total world population

of 7.5

and an annual crude birth rate of about 1.365

, each year about 340 000 to 550 000 children are born with

coarctation of the aorta. The anomaly is usually sporadic and is

more frequent in males.

Most coarctations fall into one of two groups: critical

coarctation of the aorta that causes symptoms within two

months of birth and if untreated causes death, and asymptomatic

coarctation of the aorta that presents later, usually with

hypertension in the upper limbs. Critical coarctation of the aorta

accounts for about 60% of all coarctations.

Pathological anatomy

Anatomically a coarctation of the aorta is a shelf of tissue

extending from the postero-lateral aortic wall towards the ductus

arteriosus (Fig. 1). The shelf is near the patent ductus arteriosus,

sometimes above or below it, and is better termed juxtaductal. A

sling of ductus muscle passes around the shelf, and more ductus

muscle extends into the aortic wall above and below the shelf.

This is important, because unlike most other smooth muscle,

ductus smooth muscle tends to contract when exposed to high

oxygen concentrations.

The arch is often hypoplastic and when present, an associated

intracardiac shunt should be suspected. Most commonly this

is an isolated ventricular septal defect, but almost any form

of complex congenital heart disease can be associated. About

50 to 70% of the patients have a bicuspid aortic valve. The left

subclavian artery is often hypoplastic, and in approximately 5%

of these patients arises distal to the shelf.

Developmental physiology

In the foetus, the patency of the ductus arteriosus depends on

a balance between constrictors and dilators. Constriction is due

mainly to an increased sensitivity of ductus smooth muscle to

calcium

but also to endothelin. By contrast, the ductus smooth

muscle is relaxed by vasodilator prostaglandins (mainly PGE

)

that are produced in the ductus wall and also circulate from

the placenta.

The PGE

increases intracellular concentrations

of cAMP, which decreases calcium sensitivity. Nitric oxide and

Department of Pediatrics, University of California, San

Francisco, CA, USA

Julien IE Hoffman, MD,

jiehoffman@gmail.com

LCA

PDA

LSA

Ductus

sling

Hypoplastic

arch

Asc aorta

Fig. 1.

Basic anatomy of coarctation of the aorta.Asc: ascend-

ing; IA: innominate artery; LCA: left carotid artery; LSA:

left subclavian artery; PA: main pulmonary artery;

PDA: patent ductus arteriosus.