An expeditious diagnosis of thoracic aortic pathology in the emergency department remains a great challenge, especially its differentiation from acute coronary syndrome (ACS) . Previous studies have suggested that there are many presenting signs and symptoms for TAD/TAA but routine blood work and standard imaging have not been shown to be reliable nor reproducible [10–12]. Potential genetic markers  and biomarkers in rat models  have been proposed; however, there is a need for practical and cost effective tools that can be quickly obtained in the emergency department for the routine screening of patients with acute thoracic complaints. In the present study, we have identified factors that are typically present on admission and routine emergency medical screening.
The study group of 136 patients with thoracic aortic dissection (TAD) or aneurysms (TAA) represented a mere 0.36% of the population presenting with acute chest complaints, highlighting the difficulty in diagnosing this rare entity. It would not have been possible to employ contrast-enhanced CT scans on all such patients, especially in an emergency department that sees more than 100,000 patients per year. Pain characteristics have been shown to be unreliable in a systematic review [2, 15]. The present study shows that the sudden onset in nature was more likely associated with TAA/TAD. This is in concordance with previous report by Klompas et al. . On the other hand, our finding of association with increasing intensity has not been reported in other studies and may explain the evolving nature of thoracic aortic disease. On multivariate analysis, chest pain, head and neck pain, and dizziness were identified to be independently associated with ACS. These all represent easily obtainable factors in routine history taking.
As expected, past medical history for the most part was not a useful tool in differentiating TAA/TAD from ACS, as both share similar comorbidities. For example, having a history of hypertension was not a useful tool in differentiating the two disease processes. However, history of diabetes and myocardial infarction was significantly associated with ACS, both in univariate and multivariate analysis, providing another easily obtainable factor in differentiating TAA/TAD from ACS. In fact, diabetes may have a protective association against the development of aortic disease . Diabetes has been shown to decrease the progression of aortic disease by direct metabolic effects by the decreased secretion of metalloproteinases from these individuals . The decreased production of inflammatory cells caused by hyperglycemia in mice has also been shown to inhibit vascular smooth muscle cell death, thereby thwarting the progression of aortic disease . Diabeteic patients are also more likely to develop ACS because of the proatherosclerotic and proinflammatory states associated with diabetes . Our data is consistent with these findings. Diabetic patients are more likely to experience ACS than TAA/TAD.
On physical exam, we found tachypnea, bradycardia, and lower extremity neurological deficits to be associated with TAD/TAA. Of particular importance, when heart rate was analyzed as a continuous variable, increasing heart rate was independently associated with ACS.
There has been much interest in the identification of useful blood tests to make the diagnosis of TAA/TAD. Elevated plasma D-dimer levels [19–21] and plasma smooth muscle myosin heavy chain protein  have shown some diagnostic promise but are not routinely obtained on initial presentation. A protocol for or obtaining routine plasma D-dimer studies was not used in the present study but has been advocated by others . Plasma D-dimer levels were obtained in only 13 patients in the current study (5 in study group, 8 in control), yet elevated levels showed a trend for significance. D-dimer levels may also be elevated in a large variety of other conditions, including venous thromboembolism (VTE), atrial fibrillation, congestive heart failure, disseminated intravascular coagulation and routine post-operative recovery . Routine analysis on screening may therefore remains controversial. An element of coagulopathy may be a component of thoracic aortic diseases, however, as patients that presented with acute thoracic aortic disease had an elevated initialed normalization ratio (INR) compared to the ACS group. This association between elevated INR and thoracic aortic disease has been reported elsewhere . Elevated BUN was associated with TAD/TAD in univariate analysis, an association that has not been reported. This may represent the physiological changes in blood flow resulting from the acute aortic injury.
It is worthwhile to note that while elevated troponin was associated with ACS in the present study, 9% of TAD/TAA cohort also demonstrated elevated serum troponin levels. Patients have been reported to have acute thoracic aortic dissection with concomitant myocardial infarction and this confusion could result in a catastrophe . Thrombolytic therapy for acute myocardial infarction would be contraindicated in patients with acute thoracic aortic disease. Further confusion may be caused by EKG analysis because it has been reported that 0.1-0.2% of patients with proximal TAD will have ST-elevation myocardial infarctions occur in the setting . Luo reported on six patients with clear electrocardiographic and serological evidence of acute myocardial infarction and concomitant thoracic aortic dissection, underscoring the need to be continuously vigilant for acute thoracic aortic disease, even after the diagnosis of myocardial infarction is confirmed .
When present, the finding of a widened mediastinum was associated with TAD/TAA, as previously reported . Because a widened mediastinum is difficult to interpret on a portable x-ray, a formal standing posterior-anterior chest x-ray for patients presenting with chest pain may be necessary. CT scanning is an effective screening modality  but cannot be utilized for all patients with acute thoracic complaints who present to busy ED’s. Transthoracic echocardiography may also a useful imaging modality for the diagnosis of acute aortic syndromes. Some have reported it to be beneficial for screening  but it should not be used as the sole screening imaging technique .
Limitations of the study include the retrospective nature of the study design. A larger cohort of patients that presented with acute thoracic symptoms but were not found to have acute thoracic aortic dissection or aneurysm would have provided a statistically enhanced database to allow for the development of a risk prediction model. Such modeling would facilitate the use of the findings reported herein. In addition examining the missed diagnosis rate and delay in diagnosis in a prospective fashion using this model would validate the findings from this study.
Screening patients with acute chest pain in the emergency department for thoracic aortic dissection or thoracic aortic aneurysm presents a clinical challenge. In the current study, we identified increasing heart rate, presence of chest pain, head and neck pain, dizziness, diabetes, and history of myocardial infarction to be independently associated with ACS as opposed to TAA/TAD. These represent easily obtainable factors that can be used to screen patients to undergo prompt confirmatory imaging with CT of the chest.