Atlas of pathophysiology, 2 Edition

Part II - Disorders

Cardiovascular disorders

Aortic Aneurysm

A thoracic aortic aneurysm is an abnormal widening of the ascending, transverse, or descending part of the aorta. Aneurysm of the ascending aorta is the most common type and has the highest mortality. An abdominal aneurysm generally occurs in the aorta between the renal arteries and the iliac branches.

Causes

Aneurysms commonly result from atherosclerosis, which weakens the aortic wall and gradually distends the lumen. Other causes include:

·   age and family history

·   fungal infection (mycotic aneurysms) of the aortic arch and descending segments

·   bicuspid aortic valve

·   congenital disorders, such as coarctation of the aorta or Marfan syndrome

·   inflammatory disorders

·   trauma

·   syphilis

·   hypertension (in dissecting aneurysm).

Age Alert

Ascending aortic aneurysms, the most common type, are usually seen in hypertensive men under age 60. Descending aortic aneurysms, usually found just below the origin of the subclavian artery, are most common in elderly men with hypertension. They may also occur in younger patients after traumatic chest injury or, less commonly, after infection.

Pathophysiology

First, degenerative changes create a focal weakness in the muscular layer of the aorta (tunica media), allowing the inner layer (tunica intima) and outer layer (tunica adventitia) to stretch outward. The outward bulge is the aneurysm. The pressure of blood pulsing through the aorta progressively weakens the vessel walls and enlarges the aneurysm. As the vessel dilates, wall tension increases. This increases arterial pressure and dilates the aneurysm further.

Aneurysms may be dissecting, a hemorrhagic separation in the aortic wall, usually within the medial layer; saccular, an outpouching of the arterial wall; or fusiform, a spindle-shaped enlargement encompassing the entire aortic circumference.

A false aneurysm occurs when the entire wall is injured, with blood contained in the surrounding tissue. A sac eventually forms and communicates with an artery or the heart.

Signs and symptoms

Ascending aneurysm

·   Pain, the most common symptom of thoracic aortic aneurysm

·   Bradycardia

·   Murmur of aortic insufficiency

·   Pericardial friction rub (caused by a hemopericardium)

·   Unequal intensities of the right carotid and left radial pulses

·   Difference in blood pressure between the right and left arms

·   Jugular vein distention

Descending aneurysm

·   Pain, usually starting suddenly between the shoulder blades; may radiate to the chest

·   Hoarseness

·   Dyspnea and stridor

·   Dysphagia

·   Dry cough

Abdominal aneurysm

Although abdominal aneurysms usually don't produce symptoms, most are evident as a pulsating mass in the periumbilical area. Other signs include:

·   systolic bruit over the aorta

·   tenderness on deep palpation

·   lumbar pain that radiates to the flank and groin.

Clinical Tip

Pain caused by a dissecting aortic aneurysm:

·   may be described as “ripping” or “tearing”

·   commonly radiates to the anterior chest, neck, back, or abdomen

·   usually has an abrupt onset.

Diagnostic test results

·   Echocardiography shows the aneurysm and its size.

·   Anteroposterior and lateral abdominal X-rays show aortic calcifications present in abdominal aortic aneurysms; posteroanterior and oblique chest X-rays will show widening of the aorta and mediastinum in thoracic aortic aneurysms.

·   Computed tomography scan shows the effects on nearby organs.

·   Aortography shows the size and location of the aneurysm.

·   Complete blood count reveals decreased hemoglobin levels.

Treatment

A dissecting aortic aneurysm is an emergency that requires prompt surgery and stabilizing measures. Treatment includes:

·   antihypertensives such as nitroprusside

·   negative inotropic agents to decrease force of contractility

·   beta-adrenergic blockers

·   oxygen for respiratory distress

·   opioids for pain

·   I.V. fluids

·   possibly, whole blood transfusions.

P.39

TYPES OF AORTIC ANEURYSMS

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