Coarctation of the Aorta

More than 50% of infants with a coarctation of the aorta become symptomatic during the first month of life. Associated cardiac anomalies accompany this lesion in more than 75% of patients. In neonates, infusion of prostaglandin E₁ prevents or reverses constriction of the ductal tissue. An open ductus improves lower body perfusion by allowing right-to-left shunting into the descending aorta. By relaxing the aortic end of the ductus, prostaglandin E₁ often results in a larger lumen at the coarctation site. Surgery can then be safely delayed until the left ventricular function, which is often poor, improves and any signs of low cardiac output syndrome, such as renal insufficiency, resolve. Older children may present with upper-body hypertension and/or signs and symptoms of decreased lower-extremity perfusion.

INCISION

In patients with an isolated aortic coarctation, the involved area can be adequately exposed through a fourth intercostal left posterolateral thoracotomy. For any patient undergoing coarctation repair through a thoracotomy, it is paramount in the morning of the operation to rule out fever and also to allow the patient to cool passively during the anesthetic preparation; mild hypothermia may mitigate the risk of spinal cord injury during the operation. Infants with associated lesions may be better served with a complete repair on cardiopulmonary bypass through a median sternotomy using a period of deep hypothermia to resect or augment the coarcted segment. Even in infants with no other cardiac anomalies, the aortic arch may be hypoplastic. These patients should undergo patch augmentation of the entire arch and proximal descending aorta under deep hypothermia (see Chapter 29).

SURGICAL ANATOMY

A coarctation of the aorta affects the junction of the aortic arch, descending aorta, and ductus arteriosus in more than 98% of patients. It can, however, occur anywhere along the course of the aorta.

The left vagus nerve enters the thoracic cavity from the root of the neck between the left subclavian and left common carotid arteries, crosses the aortic arch, and continues downward anteromedial to the descending aorta, traversing the ligamentum arteriosum. The recurrent laryngeal nerve has its origin in the vagus nerve, curves around the ligamentum arteriosum, and continues back upward into the neck (Fig. 15.1). There may be poststenotic dilation just distal to the coarctation. In older patients, the poststenotic dilation may be more pronounced and there may be extensive enlargement of collateral vessels about the shoulder and back muscles. This may include the intercostal arteries, whose walls may be paper thin and friable.

EXPOSURE OF THE COARCTATION

The left lung is retracted inferiorly and anteriorly, often with placement of a so-called “Kirklin tent” to help in exposure. The parietal pleura is divided longitudinally over the left subclavian artery and descending thoracic aorta across the coarctation segment. The pleural edges are then suspended (Fig. 15.1). The left subclavian artery, aortic arch distal to the left carotid artery, and the descending aorta are mobilized from the root of the neck to a distance well below the coarctation. Vessel loops may be passed around the aorta and the subclavian artery to facilitate exposure (Fig. 15.2).

Protection of the Vagus and Recurrent Laryngeal Nerves

The left vagus nerve and its recurrent laryngeal branch may be injured during mobilization.

Enlarged Intercostal Arteries

The intercostal arteries are usually enlarged. They have extremely thin walls and can cause troublesome bleeding if traumatized.

Bleeding from Aortic Branches

Bronchial arteries may occasionally arise from the posterior surface of the aorta and the left subclavian artery. They can be inadvertently torn during mobilization and dissection.

FIG. 15.1 Surgical anatomy of a coarctation of the aorta.

COARCTECTOMY

Whenever possible, a coarctectomy is the procedure of choice. It entails removal of stenosed or hypoplastic segments of the aorta and of abnormal ductal tissue in neonates. Appropriate clamps are selected, usually a straight vascular clamp for the descending aorta and a curved clamp to be placed across the left subclavian artery and distal arch. The descending aorta is clamped first and then the proximal clamp is applied. The ductus arteriosus or ligamentum arteriosum is ligated or clipped on the pulmonary artery side and divided to give the aorta additional mobility. The coarcted segment is excised, with attention paid toward making the proximal aortotomy on a bevel to increase the anastomotic surface, and the two clamps are now carefully maneuvered to bring the aortic ends together. The anastomosis is accomplished with a running Prolene suture (Fig. 15.3). The distal clamp and then the proximal clamp are removed, and the anastomosis is inspected for hemostasis as well as the absence of constriction or torsion.

FIG. 15.2 Exposure of a coarctation.

Use of Approximator

A combination of straight and spoon-shaped atraumatic clamps with an approximator is useful. This allows the clamps to remain immobile while the aortic ends are being sutured together without tension. The operative field is not obscured by the assistant’s hands, which is especially important in neonates. Alternatively, the assistant surgeon has the critical responsibility of holding the two ends of the aorta together so that a satisfactory anastomosis can be completed.

Placement of Clamps

The clamps should be positioned far enough away from the excision lines to provide adequate aortic cuffs for suturing. The aortic wall is elastic and will retract after each end is transected. At least 5 mm in neonates or 1 cm in older children is required to secure a satisfactory anastomosis.

Residual Coarctation

Inadequate resection of a coarctation may leave the patient with residual disease (Fig. 15.4).

Preserving the Maximal Diameter of the Lumen

The aortic anastomosis should incorporate the widest lumen of the aorta to prevent any local constriction. The
proximal opening can be enlarged, if necessary, to conform with the poststenotic dilation of the lower aortic segment (Fig. 15.5).

FIG. 15.3 Technique for a coarctectomy.

Intercostal Arteries

The first set of intercostal arteries is often located close to the distal extent of the coartation. They can usually be preserved and temporarily occluded with small bulldog clamps during the resection and anastomosis. The distal aortic clamp is placed below the first intercostal vessels (Fig. 15.5). However, if their division is required for full mobilization to perform and extended end-to-end anastomosis, this should be pursued.