Type A aortic dissection should be managed with urgent aortic repair, whereas type B aortic dissection is generally managed medically in the absence of complications. Thus the majority of patients who are managed medically will have type B acute aortic dissection. Nevertheless, in some instances patients with type A aortic dissection have contraindications to surgery (progressive cancer, end-stage COPD, subacute stroke), in which case medical therapy is indicated as an alternative.
Patients should be admitted to a cardiac intensive care unit for ongoing medical therapy and hemodynamic monitoring. The initial pharmacologic therapy described above is continued through the initial intensive care unit stay. However, even on the first hospital day, oral medications can be started and the doses titrated upward, with the goal of gradually transitioning from the intravenous medications to all oral ones over a period several days. Beta blockers are again the mainstay of therapy, but the majority of patients will require the addition of several oral antihypertensive medications before they can fully wean off the intravenous ones. Typically, an angiotensin converting enzyme inhibitor is added next, followed by a calcium-channel antagonist and/or a thiazide diuretic. Alpha blockers or other vasodilators may also be required. Most patients will require two to five different oral medications to achieve stable blood pressure and heart rate targets.
In addition to pharmacologic therapy of dp/dt and hypertension, patients need to be closely monitored for any evidence extension of the aortic dissection process or the development of any new complications of the existing dissection. Among those with type B aortic dissection, retrograde extension could result in involvement of the ascending aorta, thus transforming it into an acute type A aortic dissection that would require urgent aortic repair. Evidence of retrograde extension includes the onset of new chest or neck pain, the onset of hypotension or shock, a new blood pressure differential between the two arms, the appearance of a new diastolic murmur of aortic insufficiency or a pericardial rub, or new electrocardiographic evidence of pericarditis or acute myocardial infarction. Complications of the existing type B aortic dissection that would merit consideration of aortic repair include compromise of arterial flow to vital organs or extremities, leaking or rupture of dissected aorta, or a rapidly expanding aortic aneurysm.
Frank mesenteric ischemia may present as abdominal pain out of proportion to findings on physical examination, progressing to bloody diarrhea, acidosis, and hypotension. However, in its early stages the presentation of mesenteric ischemia may be more subtler, with symptoms of postprandial abdominal pain ("abdominal angina") or perhaps just nausea or anorexia. Because bowel infarction may occur before the symptoms and signs of mesenteric ischemia are fully manifest, it is essential that all care providers be aware of and vigilant for the earliest warning symptoms so that intervention can be performed in a timely fashion6. Renal ischemia or infarction may present with flank pain (renal infarction) but more often is manifest only by acute renal insufficiency and a drop in urine output. Lower extremity arterial compromise may result in a cold, pulseless, and/or painful limb. Therefore, patients with acute aortic dissection should be monitored for renal function and urine output and should have femoral and pedal pulses checked on a daily basis.
In the past, it was advocated that recurrent pain was an indication for surgical repair of a type B aortic dissection. However, most no longer believe this to be the case. In a retrospective study by Januzzi et al. of 53 patients with acute type B aortic dissection, 34 (64%) had one or more episodes of recurrent pain7. Repeat imaging studies were performed in 31 of these 34 patients (91%), and there was no change in the mean aortic diameter compared with presentation, nor was there any radiographic evidence of extension of the dissection, impending or active rupture, or branch arterial compromise. Among the 34 patients with recurrent pain, there was only one death and one who required surgery, whereas among the 19 patients without recurrent pain, there were three deaths and two others who required surgery. Therefore, recurrent pain predicted neither radiographic complications nor adverse outcomes and, thus, in and of itself, appears not to be an indication for surgical intervention.
A significant proportion of patients with type B aortic dissection develop severe or refractory hypertension during their stay in the intensive care unit, even if they did not have such significant hypertension on presentation. Many care providers assume that worsening hypertension is likely a manifestation of acute renal artery compromise and order a renal artery MRA or CTA. However, typically there is no objective evidence of renal ischemia. In another retrospective study by Januzzi et al.8 of 53 patients with acute type B aortic dissection, 34 (64%) had what was termed refractory hypertension, which was defined as a requirement for four or more concurrent adequately dosed antihypertensive agents to achieve an arterial pressure of 040/80 mmHg. When compared with the 19 study patients who did not have refractory hypertension, those with refractory hypertension had no greater incidence of renal artery compromise; in fact, if anything, there was a trend toward a lower incidence of renal artery compromise among the refractory hypertension group (12% vs. 32%; p = 0.06). There was no difference between the two groups in the frequency of acute renal failure or adverse events (death, vascular surgery, extension of dissection, or aneurysm expansion). Therefore, in the absence of compelling evidence of renal ischemia, such as rise in creatinine or a decline in urine output, one should manage the refractory hypertension with appropriate medications, but routine imaging of the renal arteries is not necessary.
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