Coarctation of the aorta typically consists of a discrete, diaphragm-like ridge extending into the aortic lumen just distal to the left subclavian artery at the site of the aortic ductal attachment (the ligamentum arteriosum) (Figure 4). This condition results in hypertension in the arms. Less commonly, the coarctation is immediately proximal to the left subclavian artery, in which case a difference in arterial pressure is noted between the arms. Extensive collateral arterial circulation to the distal body through the internal thoracic, intercostal, subclavian, and scapular arteries frequently develops in patients with aortic coarctation. The condition, which is two to five times as frequent in men and boys as in women and girls, may occur in conjunction with gonadal dysgenesis (e.g., Turner's syndrome), bicuspid aortic valve, ventricular septal defect, patent ductus arteriosus, mitral stenosis or regurgitation, or aneurysms of the circle of Willis.11,56
On physical examination, the systolic arterial pressure is higher in the arms than in the legs, but the diastolic pressures are similar; therefore, a widened pulse pressure is present in the arms. The femoral arterial pulses are weak and delayed. A systolic thrill may be palpable in the suprasternal notch, and left ventricular enlargement may be noted. A systolic ejection click (due to a bicuspid aortic valve) is frequently present, and the second heart sound is accentuated. A harsh systolic ejection murmur may be identified along the left sternal border and in the back, particularly over the coarctation. A systolic murmur, caused by flow through collateral vessels, may be heard in the back. In about 30 percent of patients with aortic coarctation, a systolic murmur indicating an associated bicuspid aortic valve is audible at the base.
The electrocardiogram usually shows left ventricular hypertrophy. On the chest radiograph, increased collateral flow through the intercostal arteries causes notching of the posterior third of the third through eighth ribs; such notching is usually symmetric. Notching is not seen in the anterior ribs, since the anterior intercostal arteries are not located in costal grooves. The coarctation may be visible as an indentation of the aorta, and one may see prestenotic and poststenotic dilatation of the aorta, producing the "reversed E" or "3" sign. The coarctation may be visualized echocardiographically, and Doppler examination makes possible an estimate of the transcoarctation pressure gradient. Computed tomography, magnetic resonance imaging, and contrast aortography provide precise anatomical information regarding the location and length of the coarctation; in addition, aortography permits the visualization of the collateral circulation.
Most adults with aortic coarctation are asymptomatic. The diagnosis is made during routine physical examination, when systemic arterial hypertension is observed in the arms, with diminished or absent femoral arterial pulses. When symptoms are present, they are usually those of hypertension: headache, epistaxis, dizziness, and palpitations. Occasionally, diminished blood flow to the legs causes claudication. Patients sometimes seek medical attention because they have symptoms of heart failure or aortic dissection. Women with coarctation are at particularly high risk for aortic dissection during pregnancy.
Complications of aortic coarctation include hypertension, left ventricular failure, aortic dissection, premature coronary artery disease, infective endocarditis, and cerebrovascular accidents (due to the rupture of an intracerebral aneurysm). Two thirds of patients over the age of 40 years who have uncorrected aortic coarctation have symptoms of heart failure. Three fourths die by the age of 50, and 90 percent by the age of 60.11,57
Surgical repair should be considered for patients with a transcoarctation pressure gradient of more than 30 mm Hg. Although balloon dilatation is a therapeutic alternative, the procedure is associated with a higher incidence of subsequent aortic aneurysm and recurrent coarctation than surgical repair.58 Postoperative complications include residual or recurrent hypertension, recurrent coarctation, and the possible sequelae of a bicuspid aortic valve.59 The incidence of persistent or recurrent hypertension, as well as the survival rate, is influenced by the patient's age at the time of surgery. Among patients who undergo surgery during childhood, 90 percent are normotensive 5 years later, 50 percent are normotensive 20 years later, and 25 percent are normotensive 25 years later.11 In contrast, among those who undergo surgery after the age of 40 years, half have persistent hypertension, and many of those with a normal resting blood pressure after successful repair have a hypertensive response to exercise.
Similarly, survival after repair of aortic coarctation is also influenced by the age of the patient at the time of surgery. After surgical repair during childhood, 89 percent of patients are alive 15 years later and 83 percent are alive 25 years later. When repair of coarctation is performed when the patient is between the ages of 20 and 40 years, the 25-year survival is 75 percent. When repair is performed in patients more than 40 years old, the 15-year survival is only 50 percent.11,60