Descending Thoracic Aortic Dissections

doi:10.1016/j.suc.2007.08.003

Surgical Clinics of North America

Volume 87, Issue 5, October 2007, Pages 1047-1086

https://doi.org/10.1016/j.suc.2007.08.003 Get rights and content

Type B dissection has traditionally been managed medically if uncomplicated and surgically if associated with complications. This practice has resulted in most centers reporting significant morbidity and mortality if open repair is required. In the setting of malperfusion, operative repair has been conjoined with fenestration or visceral stenting to improve outcomes. Endovascular stent grafts seem to offer an attractive alternative in the acute complicated type B dissection, with reduced mortality and morbidity, particularly paralysis, compared with open repair. It is reasonable to consider endovascular stent grafts as another tool in managing dissection, but to recognize that open surgical repair still plays an important role, and that the data that define indications and outcomes are still emerging.

Section snippets

Pathophysiology

The principle pathologic mechanism of aortic dissection is a tear in the aortic intima, usually transverse but not completely circumferential, which results in separation between the intimal and medial layers of the aortic wall. Although this usually occurs in pathologic settings (connective tissue disease, atherosclerotic ulcer, and so forth) it can occur in histologically normal aortas also. The most common underlying risk factors for distal dissection are hypertension in conjunction with

Classification

In 1965 DeBakey and colleagues [22] proposed an anatomic classification that is based on the origin and the extent of the dissection (Table 1). Dailey and associates proposed a method based on the inherent different outcomes and operative issues that combined ascending aortic dissections, regardless of origin, as Stanford type A (DeBakey types I and II) and those that originate in and are limited to the descending thoracic aorta (with or without abdominal aortic involvement, DeBakey types IIIa

Presentation

The classic presenting symptom of aortic dissection is abrupt onset of chest pain [6], [25]. With distal dissections the pain is located in the back and characterized in half of cases as tearing but in two thirds additionally as sharp and in approximately one fifth as migratory [6]. In 43% of cases the pain primarily involved or included the abdominal area, raising suspicion of mesenteric ischemia [6]. Unfortunately, if the nature and quality of the pain is not specifically sought after, the

Natural history/medical management

The mortality associated with acute uncomplicated distal aortic dissection managed medically is as low as 10.7%. This figure increases to 31% (or higher) if complications arise that require surgical intervention, particularly during the acute phase [6], [24].

Estrera and colleagues [27] followed 159 consecutive patients, admitted between January 2001 and April 2006, who had acute type B dissection, all initially managed medically. Median time to obtain a systolic blood pressure less than 140 mm

Indications for intervention

There are four indications for acute intervention: rupture, aortic expansion (>5.0 cm), critical vessel malperfusion, and intractable pain. Many authors argue that an aortic diameter in the involved segment of greater than 40 or 45 mm is a reasonable indication for intervention, at least with stent grafts, because of the risk for later aneurysmal development, progressive dissection, or death [8], [36], [41], [51]. Intractable hypertension has been also used as an indication, although as

Operative repair of type B dissection

In contrast to the primacy of open surgical therapy for dissection involving the ascending aorta, the role of open surgery in type B aortic dissection has for years been less well-defined. Enthusiasm for surgical approaches to descending dissection has had peaks and valleys, and with a few notable exceptions, most centers have adopted a protocol of intensive anti-impulse therapy for acute type B dissection [62], [63], [64]. Surgical treatment has for the most part been reserved for complicated

Endovascular management

The recognized difficulties in operative management of acute dissections have led to an increased interest in endovascular approaches, including stent grafting. The enthusiasm was stimulated by the Stanford group's initial report in 1999 [115]. It has been further invigorated by encouraging data in the atherosclerotic aneurysm population, particularly with reduced incidence of spinal cord injury, although how well this translates to the dissection population is still open to question [116].

The endovascular procedure

Although probably more comfortable to perform under general anesthesia, especially if very precise imaging is required, endovascular stent grafting for type B dissection has been performed under spinal, epidural, or even local anesthesia [41].

Vascular access can be a major issue. Occasionally a completely percutaneous approach can be used, but this requires confidence in the integrity of the femoral artery, and our bias has been to use this method less frequently than in the setting of

Retrograde dissection

Retrograde dissection, converting a type B case into an acute type A, has been described with virtually all devices, although initially there was a sense that bare metal proximal extension had a higher risk for this [55], [120], [136], [137], [138], [139]. The reported incidence, in larger series of dissection cases, is roughly 0.5% to 3%, but has been reported in as many as 10% [36], [41], [125], [127], [140], [141]. In addition, because most dissections require extension into the arch to

Related conditions

Intramural hematoma (IMH) and penetrating aortic (or atheromatous) ulcer (PAU) complete, with dissection, the triad of acute aortic syndromes [151], [152], [153]. There are some distinct differences between IMH and PAU, however, notably that (1) PAU tends to occur more often in older patients who have extensive calcification, and (2) whereas PAU can be associated with dissection, either often exists alone [151], [154]. Although PAU and IMH probably share cellular processes (such as apoptosis

Combined procedures

There has been increasing interest in performing hybrid operations for the management of atherosclerotic aneurysms, including arch or visceral debranching accompanied by sequential or simultaneous endovascular stent grafting of the diseased aorta, which can be done in some cases without cardiopulmonary bypass [44], [181]. These approaches are being extended to dissection also. In acute type A dissection, which extends into the descending aorta, because of the concern of persistent false lumen

Future development

As is the case with atherosclerotic aneurysmal disease and traumatic rupture, there is ongoing development of medical, surgical, and endovascular therapies for type B dissection. Aggressive β-blockade has been shown to retard aortic root dilation in the case of Marfan disease, and may well have the same benefit in the thoracoabdominal aorta [187]. Understanding the genetic basis for connective tissue disorders, including how variations may predispose to specific complications, may permit better

Summary

Type B dissection represents an acute aortic syndrome, along with PAU and IMH. The cause predominantly involves atherosclerosis and hypertension, but in a significant proportion also involves connective tissue disorders. In the acute setting and in uncomplicated patients, medical management with blood pressure control is the standard of care. Complicated dissection, manifested predominantly by malperfusion syndromes followed by rupture, requires a complication-specific approach. Acute surgical