Optimal management of acute aortic dissection

Bilateral superior cervical ganglionectomy attenuates the progression of β-aminopropionitrile-induced aortic dissection in rats

AIMS

Aortic dissection (AD) represents one of the most common aortic emergencies with high incidence of morbidity and mortality. Clinical studies have shown that the increased excitability of the sympathetic nerve may be associated with the formation of AD. In this study, we examined the effects of bilateral superior cervical sympathectomy (SCGx) on the progression of β-aminopropionitrile (BAPN)-induced AD in rats.

MAIN METHODS

Sprague-Dawley rats were randomly divided into three groups, including BAPN, BAPN+SCGx and control groups. For terminal measurements, the mean arterial pressure (MAP) and heart rate (HR) were monitored and the basal sympathetic nerve activity (SNA) was assessed through recording the variation in arterial pressure in response to hexamethonium application. Pathological changes in the aortic wall were observed by histological staining. Matrix metalloproteinase-2 (MMP-2) and MMP-9 concentrations within the aortic wall were analyzed by western blot.

KEY FINDINGS

The results show that BAPN administration could elevate SNA and cause the formation of AD in rats with a high incidence (67.7%), while SCGx treatment inhibited the elevation of SNA and significantly reduced the incidence (20%). SCGx may suppress the formation of BAPN-induced AD via restraining the rise of HR and reducing the MMP-9 concentration in aortic wall.

SIGNIFICANCE

These results indicate that surgical techniques such as sympathetic nerve block may be a potentially useful therapy for the prevention of AD.

Acute aortic emergencies--part 2: aortic dissections

Patients with aortic disease are some of the highest acuity patients that emergency clinicians encounter. Dissection is the most common aortic catastrophe and involves separation of the aortic layers in a longitudinal fashion leading to diminished perfusion and systemic ischemia. Characteristics of pain, branch vessel involvement, and incidence lead to an understanding of patient presentation, morbidity, and mortality. Diagnosis, selection of diagnostic studies, the degree of preoperative ischemia, and risk of operative mortality can be accomplished using validated clinical decision tools. Emergency interventions are guided by the type of dissection according to the Stanford classification system. Medical management includes pain control and anti-impulse, antihypertensive therapy through vasodilatation and blockage of the sympathetic β-response. The patient may then be evaluated for open surgical intervention, aortic fenestration, endovascularly placed stent grafts, or a combination possibly in a staged approach. Morbidity includes rupture, stroke, paraplegia, acute renal failure, bowel ischemia, and peripheral ischemia.

Ischemic stroke with left hemiparesis or shock should be evaluated by computed tomography for aortic dissection

An 82-year-old woman with consciousness disturbance, left hemeparesis, and dysarthria was discovered at home by her family and was transported to a hospital. On arrival, she remained in a sleepy and disorientated and shock state. She complained of nausea but no chest or back pain. She obtained stable circulation after infusion. Her chest roentgen results showed widening of the mediastinum and the existence of a separation of the intimal calcification from the outer aortic soft tissue border, thus suggesting a Stanford A–type aortic dissection. Her head computed tomography depicted no signs of cerebral infarction. Because she did not complain of any pain, the possibility of acute phase aortic dissection was rejected. A permissive hypertensive therapy was initiated. Next day, she suddenly died. We diagnosed that she had died of a Stanford A–type aortic dissection based on the following facts: (1) patients presenting with stroke due to a Stanford A–type aortic dissection tend to have left hemiparesis because of malcirculation of the innominate artery and (2) a patient presenting with stroke by aortic dissection may have hypotension, which is unusual in standard stoke cases. Ischemic stroke induced by aortic dissection is not common among the patients with aortic dissection. However, given the high morbidity and mortality after misdiagnosis of aortic dissection, patients with ischemic stroke with left hemiparesis or shock should be evaluated by enhanced truncal computed tomography.