Beware! Aortic Dissection
#lessonslearned is a case series submitted by former senior residents describing B-pod cases that taught them the art of medicine
A male in his 30s with a past medical history significant for hypertension presented via EMS with pain all over, anxiety and shortness of breath. The EMTs reported that he had smoked marijuana about 30 minutes before his presentation from his normal supply. At the scene he was noted to be very agitated, diaphoretic and vocal about his pain. He was yelling that he was hurting all over, he was having trouble breathing, and that he wanted to be sedated. He states that he has never had problems like this.
Past Medical/Surgical History: Hypertension
Medications & Allergies: None
Social History: Daily THC use, 1/5 ppd smoker, social drinker
Vital Signs: T 97.7, HR 75, BP 189/83, RR 30, O2 100% on room air
Exam significant for diaphoresis and that he appears anxious with a labile affect and agitation.
The patient arrived complaining of severe diffuse pain. The initial assessment revealed a well-dressed, well-nourished male in acute distress, flailing in bed, unable to assume a comfortable position. He reported pain in his neck, abdomen, and right leg. He had normal strength but the pain in his right leg was so severe that he was unable to bear weight causing him to nearly fall on the nurse in the bathroom. The patient was markedly hypertensive and mildly bradycardic but the remainder of his vitals were within normal limits. The patient’s initial blood work was unremarkable. We were able to initially control his pain and agitation with Dilaudid and Ativan. The patient, however, continued to complain of abdominal pain. Subsequently, a CT abdomen/pelvis with IV and PO contrast was ordered which revealed his aortic dissection. A completion CT scan of the chest demonstrated a Type A aortic dissection extending from his right coronary artery to the right common iliac artery.
A male in his 40s presented with the chief complaint of “unable to walk”. He also complained of vague, intense back pain that started the day before presentation. On exam he was found to have normal vitals with flaccid bilateral lower extremities. The team’s top differential diagnoses were spinal cord lesion versus aortic dissection.
The decision was made to obtain an MRI for spinal cord lesion. The MRI took several hours to complete and when he returned to B-pod he quickly decompensated and went into PEA arrest. The patient was immediately moved to the SRU and ACLS was initiated. Approximately 10 minutes into the code, radiology called to report an acute aortic dissection was picked up on the MRI. The patient was coded for >30min without return of spontaneous circulation.
The patients in case one and two both presented to B-pod complaining of something other than chest pain, had abnormal but stable vital signs initially, and had aortic dissections diagnosed incidentally. Even though aortic dissections are the most common aortic pathology requiring acute surgical intervention, 38% of people who present with this pathology will be missed initially. The incidence of aortic dissections has been reported to be between 2.3 and 4.6 per 100,000 people per year. What makes this disease process even more terrifying is that 22% of patients go undiagnosed until an autopsy is performed. Mortality in patients who go without treatment is 25% in the first 24h and 75% within 2 weeks of the initial dissection. However, patients who receive proper treatment have a greater than 90% survival rate at 1 year. As evidenced by this data, timely diagnosis and treatment of aortic dissection, much like stroke myocardial infarction, is essential.
Aortic dissections occur when a tear in the intimal lining of the vessel allows blood from the lumen to seep into the wall of the vessel causing a separation of the intima and the media. Propagation of this process can lead to vessel occlusion, embolic phenomena, and vessel rupture.
There are 2 systems of classification: the Stanford Classifications and the DeBakey Classification. In the Stanford Classification system dissections are categorized as either Type A or Type B. Type A dissection are defined as those involving the ascending aorta and Stanford Type B dissections are defined as those that start distal to the origin of the subclavian artery. The DeBakey Classification system categorizes dissections into 3 types, which are: Type 1 dissections involve the ascending aorta, aortic arch, and descending aorta; Type 2 involve the ascending aorta; and Type 3 involve the descending aorta. The Standford classification is the more commonly used system. The patient in case one is an example of a Stanford Type A/DeBakey Type 1 because of the ascending aortic involvement. Of note, 60% of dissections involve the ascending aorta.
Aortic dissections classically present with tearing or ripping pain that radiates to the back. However, a description of tearing pain is only 38% sensitive for an acute dissection. The most sensitive complaints were any complaint of pain (90%), severe pain (90%), and sudden onset pain (84%). Patients typically present with hypertension, which most prominent in those with Type B dissections, and usually have pain that is difficult to control, as in case one. No single physical exam finding is sensitive for dissection. Pulse differences and aortic regurgitation murmurs are only present in 19% and 44% of Type A dissections, respectively. These physical exam findings are even less sensitive in Type B dissections. Type A dissections present with stroke like symptoms 20% of the time due to involvement of the carotids.
Most lab markers of acute dissection are non-specific, and the few that show potential are not readily available in most hospitals. D-dimer is the most widely studied marker and may have a place in the diagnosis of dissection. A meta-analysis of D-dimers in acute dissections showed a sensitivity of D-dimer for acute dissection using a cutoff of <500ng/ml is 97% and the negative predictive value is 96%. However, there are older studies showing false negative rates up to 18%. Furthermore, d-dimer cannot screen for intramural hematomas, a subset of aortic dissections in which a hematoma forms within the vessel wall but does not communicate with the lumen. Intramural hematomas are treated with the same urgency as classic dissections. For these reasons d-dimer is not currently recommended as a screening tool for ruling out aortic dissections. Chest x-ray is a good screening tool, as approximately 80% of dissections will show a widened mediastinum. However, this should not be used to rule out dissection for a patient in which there is a high index of suspicion. Ultimately, given the high mortality of a missed aortic dissection, there should be a low threshold to obtain definitive imaging. CT angiogram is the most commonly used diagnostic tool in the emergency department due to availability, however both MRA and TEE are considered to be adequate at identifying dissections.
Management of any aortic dissection acutely is focused on decreased shear forces on the wall of the aorta by lowering both blood pressure and heart rate. B-blockers are the ideal first agent because they address both blood pressure and heart rate. Esmolol is the first line beta-blocker as it is easily titrated. Often, as case one, more than one blood pressure agent is required to obtain the goal blood pressure. It is imperative to have B-blockers on board prior to adding additional antihypertensives to prevent rebound tachycardia. Ideally, the patient’s systolic blood pressure should be under 120mmHg-100mmHg but it can be titrated lower as long as the patient’s mental status is maintained. The goal heart rate should be under 60 bpm. B-blockers are the only medical intervention in acute aortic dissection to show an improvement in mortality.
Patients with type A dissections have a 1- week mortality of 50% when managed medically. However, when rapid surgical intervention is used to treat Type A dissections, mortality at one week decreases to 10-35%. The patient in case one went directly from the Emergency Department to the operating room for surgical repair. Type B dissections tend to better overall, with an in-hospital mortality of around 10%. Indications for surgical repair of Type B dissections include cases that present with end-organ dysfunction such as mesenteric ischemia, renal ischemia or limb ischemia. These complicated Type B dissections traditionally have a higher mortality, between 25-50%, typically attributed to the extent of dissection and not surgery itself. Endovascular repair is currently the surgical intervention of choice. Recent studies show that surgery may improve mortality of these patients to 11%, which is comparable to that of patients who are managed medically.
It is not hard to see why patients who have aortic dissections leave an imprint on their provider’s minds. These patients can present with a variety of chief complaints from leg pain, to syncope, to abdominal pain. They can appear sick or relatively well depending on the location and extent of the dissection at the time of presentation. It is important to remember that there are plenty of historical features, physical exam findings, and screening tests that should heighten the clinician’s suspicion for aortic dissection and prompt the clinician to obtain a definitive test. However, there is no one screening test that can rule out an aortic dissection and the morbidity and mortality of missing this disease process is extremely high. With prompt diagnosis, medical management, and, when appropriate, definitive surgical repair these patients tend to do well overall. In order to do all of the above in an environment such as B-pod, one must have a high clinical index of suspicion and a low threshold to obtain the definitive study in a timely manner.