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Recognition and Care of Aortic Dissection
EMS crews frequently respond to calls for chest pain where they discover the patient is having an acute myocardial infarction. They may also respond to cerebrovascular accidents where they find the patient suffering acute neurological insult. So what happens when your patient is having chest pain with objective signs of an AMI along with pronounced neurological deficits suggesting an acute stroke?
A dissecting aorta can result in a patient having a heart attack, acute heart failure, or cerebrovascular accident as the result of blocked blood flow to the heart and/or brain.1 Some subjective signs of an aortic dissection can include musculoskeletal pain, chest pain, abdominal pain, neurological deficits, syncope, difficulty swallowing, and shortness of breath.2
The common carotid arteries are located just superior to the aortic arch and divided into the internal and external carotid arteries. The anterior portion of the cerebrum receives its blood supply from the internal carotid arteries. Impairment of cerebral function to the frontal lobe occurs when there is any decrease of blood flow through either of the internal carotid arteries. This lack of blood flow can produce numbness, weakness, or paralysis, generally to the opposing side of the body.3
The DeBakey classification for aortic dissection consists of three different presentations of how the aorta can dissect. A DeBakey type 1 dissection starts in the ascending portion of the aorta, spreading to the arch and sometimes past the arch distally. In type 2 dissections the ascending portion of the aorta is involved. DeBakey type 3 dissections begin in the descending aorta and extend down the vessel wall but can dissect in a reverse fashion back up to the arch of the aorta along with the ascending aorta.
Risk Factors
Females with a history of multiple pregnancies are predisposed to aortic dissection.4 Stressful events like intense exercise, delivery of a child with labor, and profound emotional stress can be contributing factors. Women under 50 who experience myocardial infarction, specifically those without the presence of cardiovascular risk factors, should raise providers’ clinical suspicion for the possibility of a sudden thoracic aortic dissection.4
Connective tissue disorders such as Marfan and Ehlers-Danlos syndromes predispose patients to aortic dissection. Enlargement of the aorta is what makes the patient with Marfan’s syndrome vulnerable. Sarcoidosis is another connective tissue disorder where the collection of cell growth on the lymph nodes can affect the heart, resulting in aortic dissection.4
Elderly patients, specifically those above 85, can present with atypical symptoms in acute myocardial infarction. These can include neurological symptoms like syncope, stroke, and confusion, which may lead the provider to suspect a neurological emergency, not a cardiovascular complication.5
Cocaine use encompasses approximately 25% of patients between the ages of 18–45 years of age who suffer a myocardial infarction and increases their risk for development of aortic dissection.5 These patients are highly susceptible to having these STEMI/CVA presentations.
A history of aortic coarctation as a child can predispose development of ascending or descending thoracic aortic aneurysm or dissection later in life.6 Obtaining a thorough history can reveal invaluable clues for patients who appear to be suffering a cardiovascular or neurological emergency.
The presentation of ascending aortic dissections can mimic acute myocardial infarction; however, it can also result in a true myocardial occlusion from the dissection flap. Aortic dissections can only be repaired with surgical intervention for patients able to undergo it. Pharmacological interventions used in the treatment of myocardial infarction and cerebrovascular accidents (e.g., clot-busters) can cause detrimental outcomes in patients suffering aortic dissections by exacerbating bleeding.6
In the hospital more invasive diagnostic equipment, such as an x-ray, echocardiogram, or CT scan, can be utilized to confirm the presence of an aortic dissection. A chest x-ray can be performed prior to going to the catheterization lab or once the patient has arrived there for angioplasty to detect a widened mediastinum, which would help prevent a misdiagnosis.
Prehospital Management
In the prehospital environment a confirmed diagnosis of acute aortic dissection is nearly impossible; however, some assessment skills can help the provider clue in to the possibility.
If the patient can talk, they may describe a ripping or tearing sensation between their scapulas. If they can’t speak because of reduced cerebral blood flow, subjective assessment tools may not be available. The American Heart Association recommends performing a 12-lead ECG on patients who present with symptoms of a stroke. The patient will likely be hypertensive, particularly in the earlier stages of this emergency, and have a history of hypertension, which is a significant risk factor for myocardial infarction, stroke, and aortic dissection.
If the provider feels aortic dissection is a possibility, they should obtain blood pressures in all four extremities. Blood pressures that are higher in the upper extremities than in the lower increase the likelihood aortic dissection is present. Obtain a 12-lead ECG, but this alone cannot complete the diagnosis. Lead V4R, along with leads V7, V8, and V9, should also be obtained in this situation. ST-segment elevation in leads II, III, aVF, V4R, V7, V8, and V9 proves the presence of a proximal right coronary artery occlusion. Additionally, when the ST-segment elevation continues to evolve globally with serial 12-leads of any suspected STEMI, this should heighten awareness a thoracic dissection is possible. Knowing the anatomy of the aorta, along with its anatomical location to the coronary arteries, can help raise the practitioner’s awareness level that the aorta may be involved and possibly dissecting into one of the coronary arteries.
Reductions in blood pressure and heart rate are crucial elements in the management of acute aortic dissections. Recommendations on the management of blood pressure suggest a range of 100–110 systolic while maintaining the heart rate around 60 bpm to reduce stress on the aorta. Medications that will assist in the management of afterload reduction include sodium nitroprusside.6 Cardene, which is classified as a calcium channel blocker, can also be utilized in this treatment and is indicated for hypertensive emergencies in cases such as aortic dissections and intracranial hemorrhage, where management of blood pressure is crucial.7
Esmolol hydrochloride is a cardioselective blocker of beta-1 receptors. It has a rapid onset but short duration of action, making it a very attractive option for this setting. Blocking beta-adrenergic receptors results in reducing contractile and chronotropic effects on the heart, another benefit in the management of aortic dissections.
Esmolol hydrochloride is meant for short-term use, making it desirable for rapid ventricular rate control when short-acting agents are needed.8 Labetalol is beneficial as well because it provides alpha- and beta-blockade properties. Whatever medication regimen is utilized, attempts to lower the blood pressure should be part of a management strategy so that a reflex tachycardia is not produced from an abrupt decrease. This risk can be reduced by using medications to reduce blood pressure and heart rate in a controlled fashion.
There are other neurological disorders that can produce ST-segment elevation on the 12-lead ECG, such as subarachnoid hemorrhage. Subarachnoid hemorrhage can occur in patients without signs of neurological deficits. The patient may complain of the classic “thunderclap” headache, or sudden onset of the worst headache of their life. Depending on the severity of the bleed, a subarachnoid hemorrhage can produce neurological deficits. This combination of findings can make it difficult for the prehospital provider to distinguish which route of treatment to follow.9
Conclusion
In the prehospital environment responding to a patient suffering from a thoracic aortic dissection is not rare. However, those presenting with signs of acute myocardial infarction coupled with strokelike symptoms may be less frequently encountered. This combination, along with their signs and symptoms and coupled with a thorough assessment, should alert the provider of the real possibility that the patient is not having an acute myocardial infarction or a cerebrovascular accident but that an aortic dissection is the underlying culprit.
References
1. Salameh MJ, Ratchford EV. Aortic dissection. Vasc Med, 2016 Jun; 21(3): 276–80.
2. McLean MM, Bunn J, Wasserman A, Tilney P. A 62-Year-Old Man With Aortic Dissection and Flail Chest. Air Med J, 2018 Sep; 37(5): 272–6.
3. Zarrinkoob L, Ambarki K, Wåhlin A, et al. Blood flow distribution in cerebral arteries. J Cereb Blood Flow Metab, 2015; 35(4): 648–54.
4. Esawy A. Role of MDCT MULTISLICE in coronary artery part 5 (non atherosclerotic coronary abnormalities). Slideshare, www.slideshare.net/ahmedesawy543/role-of-mdc-tin-coronary-artery-part-5-non-atherosclerotic-coronary-abnormalities-dr-ahmed-esawy.
5. Stapczynski JS. The Missed acute Myocardial Infarction in the ED: Strategies to Reduce the Risk for Both the Patient and the Physician. Relias Media, 2009 May 10; www.reliasmedia.com/articles/115516-the-missed-acute-myocardial-infarction-in-the-ed-strategies-to-reduce-the-risk-for-both-the-patient-and-the-physician.
6. Elefteriades JA, Sang A, Kuzmik G, Hornick M. Guilt by association: paradigm for detecting a silent killer (thoracic aortic aneurysm). Open Heart, 2015; 2(1): e000169.
7. Baxter. CARDENE IV prescribing information, www.accessdata.fda.gov/drugsatfda_docs/label/2011/019734s017lbl.pdf.
8. Baxter. BREVIBLOC prescribing information, www.baxterpi.com/pi-pdf/Brevibloc_PI.pdf.
9. Park I, Kim YJ, Ahn S, et al. Subarachnoid hemorrhage mimicking ST-segment elevation myocardial infarction after return of spontaneous circulation. Clin Exp Emerg Med, 2015; 2(4): 260–3.
Sidebar: The DeBakey Classification System for Aortic Dissection
- Type I—Involves both ascending and descending aorta
- Type II—Involves ascending aorta only
- Type III—Involves descending aorta only, commencing after origin of left subclavian artery
Roger L. Layell, FP-C, CCP-C, CCEMT-P, NRP, is a flight and critical care paramedic at Wake Forest Baptist Health AirCare in Winston-Salem, N.C. He has 15 years of experience in the field as a paramedic and 10 of critical care experience in the HEMS environment.
