Statistics from Altmetric.com
Q1: What is your diagnosis in both the cases?
Dissecting thoracic aortic aneurysm (type A) in case 1 and dissecting thoracic aortic aneurysm (type B) in case 2.
The clinical features which support the diagnosis are the acute crushing pain in the chest radiating to the back and the absent pulses in the upper limbs in case 1. The previous history of an abdominal aortic aneurysm and a large unfolded thoracic aorta on chestx ray without ECG changes of a myocardial infarction should arouse suspicion of a dissecting thoracic aneurysm in case 2.
Box 1: Classification of dissecting thoracic aneurysms
Type A: all dissections in volving the ascending aorta.
Type B: all dissections not involving the ascending aorta.
Type I: originates in the ascending aorta and propogates at least to aortic arch and often beyond.
Type II: originates in and confined to ascending aorta.
Q2: What investigations would you order to obtain a correct diagnosis?
The diagnosis is made most accurately by aortography or computed tomography of the chest. Cross sectional and transoesophageal echocardiography support the diagnosis. In the cases presented here, figure 1 shows dissection flap in a type A aneurysm (arrow), with differential enhancement rates; figure 2 shows dissection flap in a type B aneurysm (arrow).
Q3: How are the two cases managed in clinical practice?
An early diagnosis is crucial. Intensive care units are the ideal place to manage these cases. While type A dissections (acute and chronic) benefit from operative intervention, conservative treatment in the form of controlling blood pressure is usually sufficient for type B dissections (acute and chronic). It is imperative that these patients are followed up on discharge and good control of blood pressure is maintained.
Dissecting thoracic aneurysms can often be mistaken clinically for myocardial infarction, and treatment with thrombolytic agents such as streptokinase can have disastrous consequences and even lead to death. A high index of suspicion is necessary to avoid missing the diagnosis. Clinical symptoms to bear in mind are acute crushing pain in the anterior chest which often radiates to the back and lower abdomen, worsening with each heart beat. Discrepancy in blood pressure between the two arms, or absent pulses in the upper limbs, should also draw suspicion to the condition. Less common presentations include stroke, syncope, or paraplegia as described by Cohen.1 Dissecting aneurysms have now been classified as types 1 and 2 (also called type A), which involve an intimal tear in the ascending aorta within a few centimetres of the aortic valve, and type 3 (also called type B), which involves an intimal tear in the descending aorta distal to the left subclavian artery. The classification is outlined in box 1. The diagnosis is usually made by aortography or computed tomography of the chest, preferably with contrast. Cross sectional echocardiography and transoesophageal echocardiography (TOE) support the diagnosis. With newer advances in technology, magnetic resonance imaging, spiral computed tomography, and electron beam computed tomography (EBCT) will become the procedures of choice in the diagnosis of this condition.
A meta-analysis by Gysi et al of 40 years of experience with thoracic aortic dissections has shown that operative intervention is usually beneficial in both acute and chronic type A dissections. Furthermore, the analysis concluded that acute and chronic type B dissections usually benefited from conservative treatment, especially control of blood pressure.2 Surgical intervention may, however, be necessary for complicated cases. The overall prognosis remains poor if untreated, with 20% dying within 24 hours, 60% in two weeks, and 90% by 12 months. Follow up of these patients involves strict control of blood pressure, as discussed by Wheat.3
Dissecting thoracic aortic aneurysms can be easily missed unless a high index of suspicion is maintained.
Patients presenting with atypical chest or abdomen pain should be carefully examined for discrepancies in blood pressure in the upper limbs.
Computed tomography of the chest or an aortogram are the best investigations to diagnose the condition.
Management is best carried out in an intensive care unit.
Surgical intervention is needed in type A dissections.
Case 1: type A dissecting thoracic aortic aneurysm; case 2: type B dissecting thoracic aortic aneurysm.