Thoracic Aortic Aneurysm

DRG Category:	237
Mean LOS:	10 days
Description:	SURGICAL: Major Cardiovascular Procedures With Major CC
DRG Category:	299
Mean LOS:	5.8 days
Description:	MEDICAL: Peripheral Vascular Disorders With Major CC

A thoracic aortic aneurysm is an abnormal widening of the aorta between the aortic valve and the diaphragm. An aneurysm is defined as dilation of the aorta that is more than 50% of its normal diameter for a given segment. A diameter of greater than 3.5 cm is generally considered dilated for the thoracic aorta, whereas greater than 4.5 cm would be considered aneurysmal.

Thoracic aneurysms account for approximately 25% of all aneurysms, and approximately 25% of people with thoracic aneurysms also have abdominal aneurysms. Although aneurysms may be located on the ascending, transverse (aortic arch), or descending part of the aorta or may involve the entire thoracic aorta, they commonly develop between the origin of the left subclavian artery and the diaphragm.

Aneurysm formation is caused by a weakening of the medial layer of the aorta, which stretches outward, causing an outpouching of the aortic wall. Thoracic aortic aneurysms take four forms: fusiform, saccular, dissecting, and false aneurysms (Table 1). Dissection of the aorta can occur with or without an aneurysm but is most often associated with the presence of a preexisting aneurysm. Thoracic aortic aneurysms may lead to serious or fatal complications if they are left untreated. For example, a thoracic dissecting aneurysm may rupture into the pericardium, resulting in cardiac tamponade, hemorrhagic shock, and cardiac arrest.

Forms of Thoracic Aortic Aneurysm

Table 1. Forms of Thoracic Aortic Aneurysm
TYPE	DESCRIPTION
Fusiform	Spindle-shaped bulge that encompasses the entire circumference of the aorta
Saccular	Unilateral pouchlike bulge with a narrow neck, most frequently at a bifurcation that involves only a portion of the vessel circumference
Dissecting	Hemorrhagic separation of the medial and intimal layers, creating a false lumen
False	Pulsating hematoma that results from a rupture of the aorta, secondary to trauma

Causes

The single most important cause is atherosclerosis. The atherosclerotic process damages the arterial wall by weakening the medial muscle layer and distending the lumen. Destruction of the medial layer allows the artery to increase in size circumferentially (a fusiform shape), or the artery develops a saccular outpouching at the weakened area. Tobacco use is also related to aneurysm formation, but the underlying explanation for this relationship is unknown. Other factors that contribute include Marfan’s syndrome (hereditary musculoskeletal disorder), Ehlers-Danlos syndrome (an inherited disorder of elastic connective tissue), coarctation of the aorta, fungal infections (mycotic aneurysms) of the aortic arch, a bicuspid aortic valve, aortitis, and trauma (external, blunt trauma or iatrogenic trauma that occurs during invasive diagnostic procedures).

Genetic considerations

Loci for isolated thoracic aortic aneurysm have been mapped to chromosomes 16, 11, 5, and 3. Thoracic aortic aneurysms and dissections are mainly associated with medial necrosis in which there is degeneration of elastic fibers, a loss of smooth muscle cells, and an accumulation of basophilic ground substance. Medial necrosis and thoracic aortic aneurysm/dissection are known to occur in certain heritable connective tissue diseases such as Marfan’s syndrome and vascular (type IV) Ehlers-Danlos syndrome. Medial necrosis has also been seen to cluster in families in the absence of a clearly identifiable syndrome.

Gender, ethnic/racial, and life span considerations

The most common thoracic aortic aneurysm is an ascending aortic aneurysm, which is usually seen in hypertensive men under age 60. A descending aortic aneurysm is most common in elderly hypertensive men or younger patients with a history of traumatic chest injury. Some experts report that at least 3% to 4% of people older than 65 have aortic aneurysms. The incidence of thoracic aortic aneurysm is higher in men than in women by a ratio of 3:1 and is more common in people with European ancestry than in other populations.

Global health considerations

The global incidence of thoracic aortic aneurysm is similar to that in the United States, where the incidence is approximately 6 cases per 100,000 individuals.

Assessment

History

Establish a history of atherosclerosis, hypertension, hypercholesteremia, smoking, obesity, diabetes, and familial tendencies. Elicit a history of pain, including a description and location (Table 2). Establish a history of pulmonary symptoms, such as wheezing, coughing, hemoptysis, dyspnea, or stridor, which may be caused by a descending thoracic aortic aneurysm that compresses the tracheobronchial tree. Ask if the patient has had difficulties swallowing, hoarseness, dyspnea, or dry cough, all of which may be caused by a transverse arch thoracic aortic aneurysm.

Characteristic Signs and Symptoms of Thoracic Aortic Aneurysms

Table 2. Characteristic Signs and Symptoms of Thoracic Aortic Aneurysms
LOCATION OF ANEURYSM	LOCATION OF PAIN	TYPE OF PAIN
Ascending aorta	Substernal chest pain (reminiscent of angina), extending to the neck, shoulders, lower back, or abdomen but not generally to the jaw or arms; more severe on right side	Severe, boring, ripping
Transverse arch of aorta	Neck pain radiating to the shoulders	Sudden, sharp tearing
Descending aorta	Back and shoulder pain radiating to the chest	Sharp, tearing

Physical examination

The most common symptom is severe chest, neck, and/or back pain. The physical examination of a patient with a thoracic aortic aneurysm does not reveal the presence of the aneurysm itself. Certain physical findings, however, should raise your level of suspicion. Complete a neurological examination to determine the adequacy of tissue perfusion. Take the patient’s blood pressure in both arms because an ascending thoracic aortic aneurysm may cause a contralateral (opposite side) difference. Take both the patient’s right carotid and left radial pulses and note any differences. Auscultate for pericardial friction rub and aortic valve insufficiency murmur, indicating the extension of an ascending aortic aneurysm proximally into the aortic valve. Note any signs of bradycardia.

Psychosocial

Assess the patient’s and significant others’ understanding of the implications of the condition. Assess the ability of the patient and significant others to cope with a sudden life-threatening illness, a prolonged hospitalization, and the role changes that a sudden illness requires. Assess the patient’s level of anxiety about the illness, potential surgery, and complications.

Diagnostic highlights

General Comments: Because this condition causes no symptoms, it is often diagnosed through routine physical examinations or chest x-rays.

Test	Normal Result	Abnormality With Condition	Explanation
Computed tomography scan	Negative study	Locates outpouching within the aortic wall	Assesses size and location of aneurysm
Chest x-ray	Negative study	May show widened mediastinum or enlarged calcified aortic shadow; traumatic aneurysm may be associated with skeletal fractures	Assesses size and location of aneurysm

Other Tests: Electrocardiogram, magnetic resonance imaging, transthoracic echocardiography with Doppler color flow mapping, transesophageal echocardiography, aortic angiography

Primary nursing diagnosis

Diagnosis

Potential for altered tissue perfusion (cerebral, peripheral, cardiopulmonary, gastrointestinal, renal) related to fluid volume deficit and hemorrhage

Outcomes

Cardiac pump effectiveness; Circulation status; Tissue perfusion: Cerebral, Peripheral, Cardiopulmonary, Gastrointestinal, Renal; Vital sign status; Fluid balance; Cognitive status

Interventions

Circulatory care; Cardiac care; Airway management; Fluid monitoring; Medication management and administration; Intravenous insertion and therapy; Neurological monitoring; Oxygen therapy; Emergency care; Laboratory data interpretation; Surveillance

Planning and implementation

Collaborative

A thoracic aortic aneurysm that is 4 cm in size or less may be treated with oral antihypertensives or a beta-blocking agent to control hypertension. Frequent diagnostic testing (every 6 months) is necessary to determine the size of the aneurysm. A thoracic aortic aneurysm that is 5 cm or greater in diameter is usually treated surgically. Other indications for surgical intervention include dissection, intractable pain, and an unstable aneurysm (one that is changing size). The primary complication for thoracic aortic aneurysms is dissection. Monitor the patient for any changes in the quality of peripheral pulses; changes in vital signs; changes in the level of consciousness; and onset of sudden, severe, ripping, or tearing pain in the chest, neck, back, or shoulders. A ruptured thoracic aortic aneurysm requires immediate surgical intervention.

Preoperatively, assess the patient’s peripheral pulses, taking care to compare one side with the other. Take the patient’s blood pressure measurement in both arms and auscultate for an aortic insufficiency murmur to establish a baseline for postoperative comparison. Also, administer large volumes of intravenous fluids and blood products to maintain circulation until surgery is performed. Surgical procedures vary, depending on the location of the aneurysm. An ascending arch aneurysm may be replaced with an interposition graft, a composite valved conduit, or a supracoronary graft with separate aortic valve replacement. A transverse arch aneurysm is usually repaired with anastomoses and reconstructions. A graft is used to repair descending thoracic and thoracoabdominal aneurysms. Postoperatively, monitor cardiopulmonary states, especially for patients with congestive heart failure (CHF), because beta-blocking agents may worsen CHF. If the patient has hypercholesteremia that cannot be controlled with diet, a cholesterol-lowering agent may be prescribed by the physician.

Pharmacologic highlights

Medication or Drug Class	Dosage	Description	Rationale
Antihypertensives	Varies by drug	Beta blockers: Esmolol, labetalol, metoprolol, propranolol	Reduce blood pressure so that hypertension does not stress graft suture lines
Nitroprusside	0.5–10 mcg/kg/min, titrated to reduce blood pressure IV	Antihypertensive	Reduces blood pressure in acute or critical situations
Morphine	1–10 mg IV	Opioid analgesic	Relieves surgical pain
Fentanyl	50–100 mcg IV	Opioid analgesic	Relieves surgical pain

Other Drugs: Diuretics

Independent

Focus on maintaining adequate circulation, preventing complications, and implementing patient education. For the nonsurgical patient, patient teaching includes information about low-fat, low-cholesterol diets to prevent progression of the atherosclerotic process and to treat hypercholesteremia. Urge the patient to stop smoking cigarettes and provide information about smoking cessation.

For the surgical patient, focus on maintaining adequate circulation preoperatively and postoperatively, preventing complications, and patient teaching. Preoperative care of the elective surgical patient is the same as for any patient who undergoes general anesthesia. Postoperatively, care is similar to that of a patient who undergoes any chest surgery. Provide aggressive pulmonary hygiene every 1 to 2 hours to prevent pulmonary complications. Assist with range-of-motion exercises to limit the effects of immobility. Provide emotional support for the patient and significant others.

Evidence-Based Practice and Health Policy

Gopaldas, R.R., Huh, J., Dao, T.K., LeMaire, S.A., Chu, D., Bakaeen, F.G., & Coselli, J.S. (2010). Superior nationwide outcomes of endovascular versus open repair for isolated descending thoracic aortic aneurysm in 11,669 patients. The Journal of Thoracic and Cardiovascular Surgery, 140(5), 1001–1010.

Investigators conducted a study among a sample of 11,669 patients to compare the effectiveness of the standard open aortic repair to thoracic endovascular aneurysm repair (TEVAR), which was introduced in 2005 to treat descending thoracic aortic aneurysms. Open aortic repair was used to treat 78% of the patients in this sample, and TEVAR was used to treat the other 22% of patients.
Although in-hospital mortality rates were the same in both the open aortic repair and TEVAR groups (2.3%), TEVAR was associated with a shorter length of hospital stay by 1.3 days (p < 0.001) and a 60% reduced risk of complications (95% CI, 0.26 to 0.58; p < 0.001). However, a greater proportion of patients who underwent TEVAR experienced subsequent deep vein thrombosis (2% versus 0.4%; p < 0.001).
Compared to patients who were treated with an open aortic repair, patients who underwent TEVAR were four times more likely experience a routine discharge to home without any home health care as opposed to a skilled nursing or intermediate care facility or with home healthcare referrals (95% CI, 3.48 to 4.63; p < 0.001).

Documentation guidelines

Physical findings: Vital signs, pain (location, onset, severity), heart sounds, urine output, healing of incision
Assessment of circulation: Blood pressure in both arms, quality of peripheral pulses in all extremities, capillary blanch test
Response to acute, life-threatening illness: Anxiety, fear, coping
Response to surgery: Incision, wound healing, wound drainage, signs of complications

Discharge and home healthcare guidelines

The nonsurgical patient is discharged to the home setting. The surgical patient is usually discharged to the home setting if a support system can be identified. An extended-care facility may be required for a short time if a support system is not in place for the patient at the time of discharge. Be sure the patient understands all medications prescribed, including dosage, route, action, and side effects. Provide patients and their families with information about a low-fat, low-cholesterol diet (reduced calorie if obese). Be sure the patient understands the importance of controlling blood pressure and blood cholesterol levels in the prevention of progression of the atherosclerotic process.

Provide patients who smoke and their families with information about how to stop smoking. Be sure the patient understands that smoking is a risk factor for hypertension and atherosclerosis. Make sure the nonsurgical patient with a thoracic aortic aneurysm understands the necessity for follow-up examinations at regular intervals to determine the size of the aneurysm and the rate of enlargement. The surgical patient is restricted from activity for 6 to 12 weeks postoperatively. Teach the patient to restrict activities by avoiding heavy lifting, pushing or pulling strenuously, and straining. Give the surgical patient specific instructions for wound care. Teach the patient to examine the incision site for signs of infection and to report any to the physician.