In the case of aortic dissection:
Because of the variations in severity and the wide variety of potential clinical manifestations, the diagnosis of acute aortic dissection can be challenging. Only 3 out of every 100,000 patients who present to an emergency department with acute chest, back, or abdominal pain are eventually diagnosed with aortic dissection. Not surprisingly, diagnostic delays are common; delays beyond 24 hours after hospitalization occur in up to 39% of cases (Fig. below).
Algorithm used to facilitate decisions regarding treatment of acute aortic dissection. CT = computed tomography; MRA = magnetic resonance angiography; TEE = transesophageal echocardiography.
Mortality rates for operative repair of an aortic arch aneurysm have been significantly reduced intraoperatively by:
Like the operations themselves, perfusion strategies used during proximal aortic surgery depend on the extent of the repair. Aneurysms that are isolated to the ascending segment can be replaced by using standard cardiopulmonary bypass and distal ascending aortic clamping. This provides constant perfusion of the brain and other vital organs during the repair. Aneurysms involving the transverse aortic arch, however, cannot be clamped during the repair, which necessitates the temporary withdrawal of cardiopulmonary bypass support; this is called circulatory arrest. To protect the brain and other vital organs during the circulatory arrest period, hypothermia must be initiated before pump flow is stopped. However, hypothermia is not without risk, and coagulopathy is associated with deep levels of hypothermia (below 20°C), which have been traditionally used in open arch repair. Recently, more moderate levels of hypothermia (often between 22°C and 24°C) have been introduced that appear to decrease risks associated with deep hypothermia while still providing sufficient brain protection.
According to the Crawford classification scheme, surgical repair of thoracoabdominal aortic aneurysms with repairs beginning near the left subclavian artery but extending distally into the infrarenal abdominal aorta, often reaching the aortic bifurcation is classified as:
Extent I thoracoabdominal aortic aneurysm repairs involve most of the descending thoracic aorta, usually beginning near the left subclavian artery, and extend down to the suprarenal abdominal aorta. Extent II repairs also begin near the left subclavian artery but extend distally into the infrarenal abdominal aorta, and they often reach the aortic bifurcation. Extent III repairs extend from the lower descending thoracic aorta (below the sixth rib) and into the abdomen. Extent IV repairs begin at the diaphragmatic hiatus and often involve the entire abdominal aorta.
Treatment of descending aortic dissection by nonoperative, pharmacologic management:
Nonoperative, pharmacologic management of acute descending aortic dissection results in lower morbidity and mortality rates than traditional surgical treatment does. The most common causes of death during nonoperative treatment are aortic rupture and end-organ malperfusion. Therefore, patients are continually reassessed for new complications. At least two serial CT scans-usually obtained on day 2 or 3 and on day 8 or 9 of treatment-are compared with the initial scan to rule out significant aortic expansion. Once the patient's condition has been stabilized, pharmacologic management is gradually shifted from intravenous to oral medications. Oral therapy, which usually includes a beta antagonist, is initiated when systolic pressure is consistently between 100 and 110 mm Hg and the neurologic, renal, and cardiovascular systems are stable. Many patients can be discharged after their blood pressure is well controlled with oral agents and after serial CT scans confirm the absence of aortic expansion. Long-term pharmacologic therapy is important for patients with chronic aortic dissection. Beta blockers remain the drugs of choice. In a 20-year followup study, DeBakey and colleagues found that inadequate blood pressure control was associated with late aneurysm formation. Aneurysms developed in only 17% of patients with "good" blood pressure control, compared with 45% of patients with "poor" control.
Which of the following is the most typical presenting symptom in a patient with an aortic dissection?
The onset of dissection often is associated with severe chest or back pain, classically described as tearing, that migrates distally as the dissection progresses along the length of the aorta. The location of the pain often indicates which aortic segments are involved. Pain in the anterior chest suggests involvement of the ascending aorta, whereas pain in the back and abdomen generally indicates involvement of the descending and thoracoabdominal aorta.
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