Definition, Etiology, Pathogenesis Top
Coarctation of the aorta refers to a narrowing of the aorta, most frequently at the level of the aortic isthmus, that is, distal to the origin of the left subclavian artery, opposite to the ligamentum arteriosum. Usually collateral circulation develops via the internal thoracic arteries and intercostal arteries. The most common association is the presence of a bicuspid aortic valve. Intracranial aneurysms of the circle of Willis (the most common extracardiac anomaly) occur in 3% to 5% of patients. Turner syndrome is a commonly associated chromosomal abnormality.
Clinical Features Top
1. Symptoms usually develop in the second or third decade of life and are associated with prestenotic hypertension in the aorta. However, there is an inverse relationship between the severity of stenosis and age at which symptoms develop. Other factors that determine severity and age at which symptoms occur are the presence and quality of collateral circulation and presence (or absence) of additional defects. Symptoms include headaches, epistaxis, and disturbances of vision.
2. Signs involve hypertension (blood pressures measured on the upper extremities are >10 mm Hg higher than those measured on the popliteal artery); different blood pressures on both brachial arteries in patients with stenosis including the origin of the left subclavian artery; weak or absent pulse on the femoral arteries; and rarely, intermittent claudication (usually collateral circulation is well developed). A continuous murmur caused by blood flow in the narrowed aorta is audible in the left interscapular area as well as posteriorly. Precordial murmurs caused by a coexisting aortic valve disease (a bicuspid aortic valve) may also be present. The presence of a systolic ejection click with or without a systolic murmur should make one suspect the presence of an associated bicuspid aortic valve. A sustained apical impulse and a fourth heart sound are found in many patients due to the underlying left ventricular (LV) hypertrophy.
3. Complications (may be fatal): Heart failure, aortic rupture or dissection, infection of the aortic wall, intracranial hemorrhage, and complications of rapidly developing coronary artery disease.
Coarctation of the aorta is usually diagnosed in the course of a workup of secondary hypertension or headache and is confirmed by imaging studies.
1. Electrocardiography (ECG): Features of LV hypertrophy. Atrial arrhythmias such as atrial fibrillation can be seen.
2. Chest radiographs: A characteristic indentation of the outline of the aorta (the so-called figure-3 configuration) and erosions (notching) of the lower edges of the ribs by well-developed collateral circulation, dilatation of the left subclavian artery and the ascending aorta.
3. Transthoracic echocardiography is useful in assessing functional consequences, prestenotic and poststenotic pressure differences, and the nature of flow in the abdominal aorta. Frequently, stenosis is not immediately apparent. Assessment of the degree of LV hypertrophy as well as of the systolic and diastolic function are important components of the evaluation. The presence of a congenitally abnormal aortic valve and associated aortic dilatation are also assessed on echocardiography.
4. Traditional aortography or magnetic resonance angiography (MRA): Direct assessment of aortic stenosis, especially when qualifying the patient for surgery. MRA with hemodynamic assessment can be performed in many sites and has replaced conventional cardiac catheterization. Computed tomography angiography (CTA) can also provide anatomic evaluation of the presence and severity of coarctation. Catheterization is performed for evaluation of coronary arteries (preoperatively), in individuals with discrepant data from noninvasive assessment, as well as in those in whom percutaneous therapy is being considered.
Invasive treatment (surgical or percutaneous) in patients with a pressure gradient >20 mm Hg between the right upper extremity and the right lower extremity and blood pressure >140/90 mm Hg, significant LV hypertrophy, or a pathologic blood pressure response to exercise. Systemic hypertension frequently persists after surgery. Annual follow-up visits are recommended to detect possible restenosis as well as local site complications (such as pseudoaneurysms). In patients with an associated bicuspid aortic valve continued surveillance of the valve is recommended.