ArticleMisdiagnosing aortic dissection: A fatal mistake
Section snippets
Incidence
The true incidence of acute aortic dissection is difficult to identify because many patients die before reaching the hospital or prior to correct diagnosis.7 The estimated incidence of aortic dissection is 3 to 4 per 100,000 people per year.8, 9 However, it is thought that for every correct diagnosis, there are 2 undiagnosed cases.2 Many clinicians agree that the incidence is probably higher than expected and will continue to be one of the most lethal cardiovascular disorders.10, 11, 12, 13
Histology
The aorta contains 3 layers. The intima is the innermost layer that is in direct contact with the flow of blood and consists of endothelium and connective tissue. The middle layer, the thicker media, is composed of elastin, collagen, and smooth muscle cells. The outermost layer, the adventitia, is thin and composed of connective tissue, which provides strength and stability as it anchors the vessel to surrounding structures. The blood supply to the aortic media is supplied via the vasa vasorum,
Pathophysiology
Diseases that have weakened the aortic wall predispose the patient to aortic dissection. The distinctive underlying pathology of aortic dissection is medial degeneration, a decrease in aortic wall cohesiveness and an increase in sheer stress. Medial degeneration tends to be more extensive in older adults with chronic hypertension, in cystic medial necrosis associated connective tissue disorders such as Marfan's syndrome and with atherosclerosis causing occlusion and injury of the vasa vasorum.11
Etiology
A number of inherited and acquired conditions are thought to predispose the aorta to dissection, but medial degeneration is common to all dissections. When the diseased aortic wall is exposed to specific stresses, the aorta is at risk for dissection. In summary, all mechanisms weakening the media can lead to higher aortic wall stress, which can result in dissection, aneurysm formation, and rupture. Acute aortic dissection requires a tear in the aortic lumen that is complicated by medial wall
Classification
Aortic dissections may be classified in three ways: according to the anatomical involvement, according to the time of onset and according to the underlying pathology. There are two traditional classification systems for acute aortic dissection that are based on the site of the intimal tear and the extent of the aorta involved in the dissection. DeBakey's classification subdivides the dissection into type I, which is proximal to the arch vessels and may extend the length of the aorta; type II
Clinical Presentation
The primary challenge in managing acute aortic dissection is to correctly diagnose and treat the event as early as possible. Therefore, the need for a high index of clinical suspicion is crucial in potentially improving early survival rate. The diagnosis should be suspected in any patient who has abrupt, sharp chest or back pain, pulse deficits, blood pressure differentials and mediastinal widening on chest radiography.28
Chest pain is the most common presenting symptom and is described as
EKG
The electrocardiogram can help distinguish aortic dissection from acute coronary syndrome where treatment may include anticoagulation but would be contraindicated in aortic dissection. Unfortunately, 20% of patients with type A dissection have EKG changes as a result of dissection involving the coronary arteries, making it impossible to differentiate between the 2 conditions without further tests. A normal EKG may also be seen but should not rule out the possibility of aortic dissection.14, 21,
Additional Laboratory Tests
Laboratory testing is not very helpful when assessing for aortic dissection. Unlike cardiac troponins in Acute Coronary Syndrome (ACS), there are no conclusive tests proven to be specific for dissection, although the smooth muscle myosin heavy chains, D-dimer, and C-reactive protein have shown diagnostic promise. In cases of severe hemorrhage, the hemoglobin and hematocrit measurements may be decreased; and renal compromise may be reflected by an elevated blood urea nitrogen (BUN) and
Prehospital care
Establishing the diagnosis of acute aortic dissection in the prehospital setting is challenging, if not impossible. The typical patient with aortic dissection is a male in his 60s with a history of hypertension who presents with an abrupt onset of chest pain. Most prehospital providers are well trained in the management of patients with ACS including the use of anti-coagulation; however, the consequences of misdiagnosis of aortic dissection with ACS may be disastrous. In the event that the
Surgical and Interventional Therapy
Urgent surgical intervention in type A (type I, II) dissections is required to prevent aortic rupture and related complications associated with the dissection process, such a cardiac tamponade, aortic regurgitation and ischemia to the myocardium, brain, intestine, kidneys and limbs. Resection of the intimal tear and implantation of a composite graft in the ascending aorta and anastamosis of involved aortic branches is performed. The numerous surgical procedures, grafts, glue and aortic
Post-Procedure Nursing Care and Monitoring
Most facilities have specific, standardized protocols for postoperative care. In general, the immediate postoperative nursing interventions in the intensive care unit include continuous monitoring of hemodynamics, vital signs, neurological status, pain level, chest tube drainage, urine output, skin and lab values. Systolic BP should be maintained below 120 mm Hg or as ordered to decrease the risk of bleeding yet ensure adequate renal, cerebral and cardiac perfusion. This maintenance is often
Prognosis
Despite improved diagnostics and therapeutic techniques, the over all in-hospital mortality rate for proximal dissections remains 27% and approximately 10% for patients with distal dissections. The predicting factors for in-hospital mortality include proximal dissection, age 65 or greater and extension of the dissection associated with pain, shock, pulse and neurologic deficits. Approximately one-third of surviving patients will experience redissection, or aortic rupture, or they will require
Case Study 1
Mr. R was a 65-year-old male with a history of hypertension who was preparing for work one morning when he experienced acute onset of substernal chest pain radiating to his back, accompanied by upper extremity numbness. Thankfully, he was able to call 911. Initially, the first responders assumed Mr. R. was having a heart attack; however, the experienced staff in the emergency department quickly realized his presenting symptoms indicated something more ominous. He was drowsy but arousable and
Case Study 2
Patient S. was a 70-year-old female with a history of hypertension and smoking who developed sudden anterior chest pain that was described as ripping in nature and radiating to the back; followed by left lower-leg tingling. The patient thought she was having a heart attack and called 911. When the paramedics completed a quick history and assessment, they assumed the patient was experiencing ACS. Aspirin was administered per protocol, the patient was transported to a local receiving emergency
Conclusion
Aortic dissection remains the most devastating cardiovascular disorder facing the most experienced clinician today. The mortality risk is 1%–3% per hour in untreated patients.1, 11, 14 A high level of clinical suspicion is crucial in the presence of abrupt chest pain, pulse or BP differentials and radiographic mediastinal widening. Aortic dissection is often confused with ACS, leading to delayed diagnosis and inappropriate treatment with fibrinolytics, which contributes to an increased
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The author reports no grant support or other financial assistance for this research.