Aortic dissection has a myriad of clinical presentations and is for certain a diagnostic challenge. According to the relevant literature, in cases of AAD the most common symptom by far is chest pain, which is usually sharp and sometimes reported as tearing or ripping, while often radiating to the back or the abdomen [4, 6]. In our case series, the acute onset of severe chest pain was the most common initial complain and in 36% of patients it was the only symptom. Chest pain was usually accompanied by back pain, paralysis of lower or upper extremities, symptoms of congestive heart failure or syncope. Less common manifestations included symptoms of congestive heart failure, syncope, lower extremity ischemia and anuria without chest pain.
In our study the correct diagnosis of AAD was straightforward in 69% of patients, making 15 patients who were later found to have suffered an AD (31%) initially misdiagnosed. Our findings are in agreement with data from large series where up to 30% of patients with AAD, were initially given a different diagnosis [7]. According to Spittell et al in 17 patients (28%) the diagnosis of AAD was not made until post-mortem examination [8].
In the present study, twelve patients were initially diagnosed with acute myocardial infarction. According to large series, confusion of AAD with acute coronary syndrome may occur in up to 45% of cases [1, 9, 10]. Examination of cardiac troponin contributed to the correct diagnosis in only one patient of the twelve that were tested. According to Liang et al, results of CPK-MB and cardiac troponin could not discriminate between AAD and MI in a total of 33 patients who suffered from AAD, and this fact contributed to the misdiagnosis in more than half the cases [9]. Hansen et al underlined that the confusion of AAD with acute coronary syndrome not only does delay correct diagnosis but may prove lethal for the patient due to initiation of treatment with antithrombotic agents [1]. Kawano et al also reported a case of a patient who died of AAD while treated for MI [11]. Among the other clinical examinations that might be helpful in distinguishing MI from AAD, D-dimers is a valuable test. However, because it is highly elevated in both acute PE and acute AAD [12] we did not use it as first line test in the ER.
Although pain is the most common presenting symptom in AAD, painless acute aortic dissection may occur in approximately 5% of patients [13, 14]. Syncope occurred in 8% of patients with no accompanying pain. Thus, AAD should be considered in the differential diagnosis of syncope, even in the absence of pain. Acute aortic dissection is associated with neurological sequella in as many as one third of patients [3, 15, 16]. Painless AAD presenting as hemiplegia or paresis is a rare phenomenon, occurring in 2% to 8% of patients [3, 17, 18]. Data from 1,805 patients with aortic dissection showed that 4.2% of patients presented with acute paraplegia or paraparesis [3]. Donovan et al reported a case of a 77-year-old patient who presented with paraplegia, with no chest or back pain and was diagnosed with pneumonia and paraplegia. In this case chest CT was performed on hospital day 4, and revealed a type A dissecting aneurysm extending from the aortic valve leaflets to the take off the renal arteries [19].
Regarding the imaging studies used in our series, most patients had multiple imaging studies performed. Chest X-ray had a specificity of 41% in our series. Widened mediastinum in a chest X-ray is a common finding in 60% to 90% of cases of suspected AD [7], while according to Earnest et al up to 20% of chest X-rays may be negative in patients with AAD [20]. Similarly, in 464 patients enrolled in the IRAD study, chest X-ray revealed no mediastinal widening or abnormality in aortic contour in 21.3% of patients [6].
Various imaging modalities such as conventional angiography, helical computed tomography (CT), magnetic resonance imaging (MRI), transthoracic echocardiography and transesophageal echocardiography (TEE) are available to evaluate patients with suspected aortic dissection. In the IRAD, the first diagnostic test used was computed tomography in 61% [6]. According to Sommer et al, CT, MRI, and TEE are equally reliable for the diagnosis of aortic dissection. CT of the thoracic aorta is currently the imaging study of choice for the evaluation of patients with suspected AAD, with its sensitivity and specificity reaching 100% [21]. In our unit the first diagnostic test was CT in 76% of cases, with sensitivity and specificity of 100%. However CT failed to define the exact type of AAD in 13 of 37 cases (35%) and further diagnostic investigation was needed. This was due to the fact that aortic valve insufficiency is difficult to depict using CT [4].
Magnetic resonance imaging (MRI) was not the first choice of imaging modality in our Unit, because despite its high sensitivity and specificity (mean value 95%) and accuracy in confirming aortic dissection for high risk patients [4, 22], MRI has certain limitation. These are time delay, restricted ability to monitor patient during imaging [23] and inability to be performed in hemodynamically unstable patients [2]. For the above reasons we use CT as a first line imaging test. On the other hand MRI is favoured for the assessment of chronic dissection [2]
Coronary angiography was performed in 22 patients and was diagnostic in 21 of them (specificity 95,45%). Coronary angiography is time consuming and so, it can not be performed to hemodynamically unstable patients. More importantly the diagnostic accuracy of this examination is limited [24]. According to the European study, sensitivity and sensitivity of coronary angiography for the diagnosis of AAD are 88% and 94% respectively [25]. Transthoracic echocardiography managed to establish the diagnosis of AAD in only 50% of patients.
Although aortic dissection is an old disease, misdiagnosis still remains an unresolved problem as was shown in our study. The diverse manifestations of the disease together with certain limitations in imaging studies contribute to this high rate of misguided diagnosis. However due to clinical awareness and vigilance and high degree of suspicion the correct diagnosis was promptly established in all cases and all patients were submitted to the appropriate therapy. The mortality rate associated with thoracic aortic dissection is high and has recently been reported to increase by 1% to 1.4% per hour when a patient remains untreated, leading to a 68% mortality rate in the first 48 hours [2, 6]. Therefore, prompt and accurate diagnosis and treatment decisions between surgical and conservative intervention are mandatory for reducing mortality among patients with clinically suspected thoracic aortic dissection [26].
Our study is certainly limited by its retrospective nature and the lack of a uniform approach to all cases as many were initially not considered AAD and were evaluated and assessed in a different manner.
