Congenital coarctation of the aorta

Congenital coarctation of the aortaEssentials of Diagnosis

  • Infants may have severe heart failure; children are usually asymptomatic.
  • Absent or weak femoral pulses.
  • Systolic pressure higher in upper extremities than in lower extremities; diastolic pressures are similar.
  • Harsh systolic murmur heard in the back.

General Considerations

Coarctation of the aorta accounting for 5–8% of congenital cardiovascular anomalies. It occurs two to five times more frequently in males. Ninety-eight percent of all aortic coarctations are located at or near the aortic isthmus. Coarctation occurs in three general contexts: as an isolated lesion; with an ventricular septal defect; with associated more severe intracardiac anomalies. Even isolated coarctation has variable morphology and may present as hypoplasia of the isthmus. Types of associated anomalies include patent foramen ovale and ductus arteriosus, and Shone’s syndrome. As a rule, the incidence of associated lesions is inversely proportionate to the age at presentation. Associated anomalies occur in over 70% of neonates and in as few as 10–15% of older children. Theories attempting to explain the embryology and etiology of coarctation describe the effects of decreased flow through the aorta secondary to more proximal left-sided obstruction and the effects of ductal closure. No single theory offers an adequate explanation for the spectrum of coarctation morphology.

The general pathophysiology is distal arch–proximal thoracic aortic obstruction. This leads to systolic and diastolic hypertension in the proximal aorta. Eventually, collateral vessels develop to maintain distal perfusion. In the neonate, distal flow can be maintained by a patent ductus arteriosus. Causes of death include congestive heart failure, endocarditis, aortic rupture, and intracranial hemorrhage.

Clinical Findings

The hemodynamic consequences of coarctation of the aorta depend on the rate of closure of the ductus, the severity of obstruction, the development of collaterals. There appear to be two distinct clinical presentations: patients who present in early infancy and those who present in later childhood. Infants with coarctation may have congestive heart failure and sudden cardiovascular collapse with ductal closure, necessitating maintenance of ductal patency with prostaglandin E1.

Many older children with coarctation are asymptomatic and well-developed. Complaints of headache, pains in the calves when running, or frequent nosebleeds are common. Most of these children have hypertension in the upper extremities, and many have electrocardiographic evidence of left ventricular hypertrophy. The classic findings of notched ribs (secondary to enlarged intercostals vessels, seen in children over 4 years of age) or the “reversed 3” sign are seen less frequently in the modern era of earlier diagnosis. When the disorder is suspected, echocardiography is sufficient to confirm the diagnosis. Magnetic resonance imaging is another useful modality.

Treatment

With modern techniques and the risk of deleterious consequences of hypertension increasing with age, most surgeons advocate correction soon after confirmation of the diagnosis. In the seriously ill neonate, administration of prostaglandin, mechanical ventilation, administration of bicarbonate and inotropes, and restoration of adequate organ perfusion are critical aspects of management prior to surgical correction. Options for coarctation repair include the following:

  • resection with end-to-end anastomosis;
  • extended resection with primary anastomosis;
  • various versions of subclavian flap aortoplasty with or without concomitant extended resection;
  • patch aortoplasty with polytetrafluoroethylene (Gore-Tex) or Dacron;
  • resection and interposition graft;
  • percutaneous balloon dilation.

Most doctors agree that no single technique is optimal for all types of coarctation repair. General principles to consider for first-time repair include resection of the stenotic region and ductal tissue, adequate mobilization to avoid undue tension on suture lines, an attempt to avoid prosthetic material, maintenance of growth potential, and good post-repair patency with no residual pressure gradient across the repair. The superiority of staged repair versus a single-stage repair via a sternotomy (bypass, coarctation repair, septal defect closure) continues to be debated; however, there may be a trend toward single-stage repair.

Extended resection via primary repair via a left thoracotomy is a preferred approach in neonates and accommodates various degrees of arch hypoplasia. Extended mobilization of both the descending aorta proximal to the innominate artery is critical to the success of this technique.

For the young child and a more discrete isolated coarctation, excision with primary repair is a reasonable approach. For the adolescent in whom adequate mobilization may be more difficult, particularly in a reoperative situation, resection with an interposition graft or patch aortoplasty are alternatives.

The experience with balloon angioplasty continues to evolve. With careful patient selection and advanced interventional experience, good results can be obtained. At present, it remains a more selectively applied approach. It continues, however, to be the preferred option for recoarctation (gradient greater than or equal to 20 mm Hg). In most cases, aortography and balloon angioplasty can be performed effectively, thereby eliminating the need for reoperation.

Prognosis

Mortality is variable and depends on associated anomalies. In general, operative and 2- to 5-year survival is well over 95% but may be as low as 40–50% with an associated severe anomaly. Recurrent coarctation occurs in 5–20% of patients, usually in the first year after repair, and depends on the degree of arch hypoplasia and the technique of repair. Potential complications or morbidity include hemorrhage, damage to the laryngeal nerve, Horner’s syndrome, chylothorax, paraplegia (rare), and various complications related to sacrifice of the subclavian artery (uncommon in young acyanotic patients). Postoperative hypertension is another recognized morbidity. Paradoxic hypertension occurs immediately postoperatively and is often transient. A second phase may evolve days after surgery and may persist. Persistent hypertension is believed to be less common if repair is performed early in life. These forms of postoperative hypertension are believed related to changes in sympathetic tone, baroreceptor sensitivity, and the renin-aldosterone system. Pressure should be monitored, and hypertension should be appropriately treated. There is a recognized risk of postoperative mesenteric vasculitis that may be minimized with good blood pressure control.

Leave a Reply

Your email address will not be published. Required fields are marked *