AD is a life-threatening emergency accompanied with high mortality rate. It is also associated with hypertension and genetic connective tissue abnormalities that may culminate in medial degeneration, intimal tear and false lumen formation. There are two well-known classifications of AD (Figure 3), the Stanford type A and B , and the DeBakey type I - III . The Stanford type A refers to the dissections which involve the ascending aorta and may extend to the aortic arch and descending aorta. In the contrast, the type B only involve the descending aorta. DeBakey type I refers to the dissections which involves the whole aorta, however, the type II only involve the ascending aorta, and the type III only involves the descending aorta. Type III further subdivided into IIIa and IIIb. IIIa limits to descending thoracic aorta and IIIb extends below diaphragm. Therefore, Stanford type A dissection includes DeBakey types I and II, and Stanford type B includes DeBakey type IIIa and type IIIb. According to the classification mentioned above, our case belongs to Stanford type A dissection or DeBakey type I.
Acute sudden onset of severe pain in the chest, back or abdomen is the typical manifestation of AD. However, 5% to 15% of AD patients present painless [15, 16], but with a wide variety of other symptoms, including syncope, paraplegia, amnesia, dyspnea, nausea, vomiting, Dysphagia, hoarseness, vertigo, and so on. Asymptomatic AD is extremely rare. It has been reported occasionally and was diagnosed by transesophageal echocardiography (TEE) or contrast CT. In our case, the patient is a long-segmental AD patient, but completely asymptomatic, which only showed an exaggerated low DBP and widened PP when measuring routine BP. PP more than 60 mmHg is widened PP. It is an indicator of the structure or function change in heart; and it may be the result of severe anemia, hyperthyroidism, aortic regurgitation and atherosclerotic disease. Widened PP only has been reported as one of signs in AD patients [3, 17], however, we first found that it could be the only complain of AD patients.
The diagnosis of AD is made by a variety of imaging techniques, such as TTE, TEE, CT, CTA and Magnetic resonance imaging(MRI). Due to the shorter acquisition time, wide availability, and high diagnostic accuracy, CT and CTA have been considered as the ideal methods for diagnosis and monitoring of patients with aortic disease. Furthermore, MRI has high accuracy, sensitivity and specificity equal to or superior to CT. TTE, as a routine imaging technique for cardiovascular evaluation, is usually used in AD patient as an initial method. However, the usage of TTE is limited in AD diagnosis because of an inadequate echo window and suboptimal echo quality, especially in obese patients and in those with chronic obstructive pulmonary disease. However, TTE may be the only method which will be used for asymptomatic AD patients, since patients without any symptoms to attract enough attention by clinician. To reduce the risk of miss diagnosis in asymptomatic or painless AD, it is important to pay more attention in aortic root, ascending aorta, aortic arch and descending aorta when take the left parasternal view and suprasternal view of TTE.