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A 42-year-old man presented to the emergency department after the sudden onset of left hand numbness and tingling, dysarthria, and right-sided temporal region pain that began 30 minutes previously. On his way to the hospital, the patient had developed bilateral flank pain. He denied any significant medical history or history of similar symptoms and stated he had been in his usual state of health until the sudden onset of symptoms that brought him to the emergency department. He denied taking any medications and had no history of stroke, head trauma, recent bleeding, chest pain, back pain, palpitations, fevers, or chills. On direct questioning, he admitted to methamphetamine use. He usually administered methamphetamine intravenously; his most recent use was 2 days before presentation. He denied any history of sexually transmitted diseases. He stated that he regularly lifted weights but had not had any neck strains.
The patient was afebrile and had a blood pressure of 120/76 mm Hg and a regular heart rate of 102 beats/min. Neurologic examination showed minimal left hand clumsiness, mild left lower facial weakness, and minimal dysarthria; fundi appeared normal. Cardiac examination revealed no murmurs, rubs, or gallops. Findings on chest examination were normal, with the exception of mild costovertebral angle tenderness. Findings on abdominal, testicular, and extremity examinations were normal.
The incidence of aortic dissection, an uncommon but potentially catastrophic entity, is approximately 2.6 to 3.5 per 100,000 person-years.1 If the dissection is not treated, mortality rates during the first 24 to 48 hours are as high as 1% to 2% per hour2; therefore, early and accurate diagnosis and treatment are crucial for survival. The peak incidence of aortic dissection is in the sixth and seventh decade of life, with men affected twice as often as women.3
The pathophysiology of aortic dissection involves weakening of any of the 3 contiguous tissue layers of the aortic wall: intima, media, and adventitia. Weakening of these layers usually leads to a tear in the intima that permits entry of blood between the intima and adventitia. Driven by persistent intraluminal pressure, the dissection process extends a variable length along the aortic wall. The blood-filled space between the dissected layers of the aortic wall becomes the false lumen.
Aortic dissections are classified by whether they originate in the ascending aorta, within centimeters of the aortic valve, or in the descending aorta, just distal to the origin of the left subclavian artery. Three major classification systems are used to define the location and extent of aortic involvement: DeBakey types I, II, and III; Stanford types A and B; and the anatomic categories proximal and distal. DeBakey types I and II involve the ascending aorta and are grouped together for simplicity with Stanford type A and the anatomic category proximal. DeBakey type III involves the descending aorta and is grouped with Stanford type B and the anatomic category distal. Most intimal tears occur in the ascending aorta.
According to the International Registry of Acute Aortic Dissection (IRAD),4 the most important predisposing factors for acute aortic dissection are systemic hypertension (72%) and atherosclerosis (31%). However, these factors were less important in young patients; IRAD analysis showed that only 34% of patients younger than 40 years had a history of hypertension and only 1% had a history of atherosclerosis. Our patient was found to be normotensive on presentation, as were most of the younger patients in the IRAD analysis. Interestingly, our patient was an admitted methamphetamine user, and an association between methamphetamine use and aortic dissection has been documented by 1 case report series.5 The median age in that series was 39.5 years, with blood pressures ranging from the normotensive to hypertensive range on initial presentation. Other predisposing factors found in the IRAD analysis included pre-existing aortic aneurysm, vasculitis, bicuspid aortic valve, coronary artery bypass grafting, Turner syndrome, cardiac catheterization, previous aortic valve replacement, disorders of collagen, and trauma.
The clinical manifestations of acute aortic dissection are diverse. Although the IRAD analysis revealed that chest pain was the single most common presenting symptom, occurring in 72.7% of patients,4 other presenting symptoms included cerebrovascular accident, heart failure, syncope, pulse deficit, aortic regurgitation, and shock/tamponade. In one study, painless acute aortic dissection accounted for 6.4% of all presentations and was associated with a less favorable outcome than painful acute aortic dissection.6 The initial aortic tear and subsequent extension of a false lumen along the aorta can occlude blood flow from the true lumen of the aorta into any of the arteries that originate from the aorta. Depending on which arteries become occluded, patients can present with a variety of clinical sequelae, including acute myocardial infarction (coronary artery dissection), syncope, hemiplegia (carotid artery occlusion), anuria/flank pain (renal artery flow disruption), paraplegia or quadriplegia (occlusion of vessels feeding the anterior spinal artery), and death.7
Diagnosis of aortic dissection is primarily made on the basis of history and physical examination findings. Chest radiography classically shows a widened mediastinum. However, the IRAD analysis showed no findings of widened mediastinum or abnormal aortic contour in 21.3% of patients presenting with acute aortic dissection. The imaging modalities of choice in diagnosis of acute aortic dissection are CT and TEE. Both modalities have a sensitivity and specificity greater than 90%. More readily available in most emergency departments, CT is completed quickly. Readily available in many larger centers, TEE can be completed quickly at the bedside, which makes it ideal for evaluating unstable patients.
When all modalities are available, CT should be considered first in the evaluation of suspected aortic dissection in light of its accuracy, safety, speed, and convenience. When CT identifies a type A dissection, the patient may be taken directly to the operating room, where TEE can be performed to assess the anatomy and competence of the aortic valve without delaying emergent surgery. Patients with uncomplicated type B dissections may be managed medically. According to IRAD data, type B dissections have a 10% in-hospital mortality rate with medical management alone and a 60% to 80% 5-year survival rate.
Patients with type A dissections require urgent surgery to avoid death as a consequence of intrapericardial rupture, cardiac tamponade, or myocardial infarction. IRAD data showed mortality rates as high as 1% to 2% per hour after symptom onset if the dissection was left untreated.2 The objective of surgical therapy for aortic dissection is to dissect the damaged segment, excise the intimal tear, and obliterate the entry into the false lumen. The procedure is performed primarily via median sternotomy. Repair involves dissection from inside the aorta to determine the extent of the damage to the intima and media and to remove the damaged segments.8 The aortic wall is rebuilt and continuity of the aorta is re-established by placement of a Dacron prosthetic sleeve graft between the ends of the aorta.
Our case is a perfect illustration of how an acute aortic dissection can present clinically in a nonspecific manner. The unifying diagnosis of acute aortic dissection explained the patient's transient neurologic symptoms, head pain, and costovertebral angle tenderness with renal insufficiency. Misdiagnosis of an acute aortic dissection as unstable angina, myocardial infarction, or an acute nonhemorrhagic stroke can lead to disastrous iatrogenic consequences should the patient receive therapy with either intravenous heparin or fibrinolytic agents. Clinicians must be aware of the varied presentations of an acute aortic dissection and have a high index of suspicion for prompt evaluation of this potentially fatal clinical entity.
The authors wish to thank Dr Krishnaswamy Chandrasekaran for his review of the vascular content of this article.
See end of article for correct answers to questions.
Correct answers: 1. e, 2. a, 3. e, 4. d, 5. b