The impact of hypovolaemic shock on the aortic diameter in a porcine model.

OBJECTIVES: To investigate the impact of hypovolaemic shock on the aortic diameter in a porcine model, and to determine the implications for the endovascular management of hypovolaemic patients with traumatic thoracic aortic injury (TTAI). MATERIALS AND METHODS: The circulating blood volume of seven Yorkshire pigs was gradually lowered in 10% increments. At 40% volume loss, an endograft was deployed in the descending thoracic aorta, followed by gradual fluid resuscitation. Potential changes in aortic diameter during the experiment were recorded using intravascular ultrasound (IVUS). RESULTS: The aortic diameter decreased significantly at all evaluated levels during blood loss. The ascending aortic diameter decreased on average with 38% after 40% blood loss (range 24-62%, p = 0.018), the descending thoracic aorta with 32% (range 18-52%, p = 0.018) and the abdominal aorta with 28% (range 15-39%, p = 0.018). The aortic diameters regained their initial size during fluid resuscitation. CONCLUSION: The aortic diameter significantly decreases during blood loss in this porcine model. If these changes take place in hypovolaemic TTAI patients as well, it may have implications for thoracic endovascular aortic repair (TEVAR). Increased oversizing of the endograft, or additional computed tomography (CT) or IVUS imaging after fluid resuscitation for more adequate aortic measurements, may be needed in TTAI patients with considerable blood loss.

Oversizing of aortic stent grafts for abdominal aneurysm repair: a systematic review of the benefits and risks.

OBJECTIVE: Sizing of aortic endografts is an essential step in successful endovascular treatment of aortic pathology, although consensus regarding the optimal sizing strategy is lacking. Some proximal oversizing is necessary to obtain a seal between the stent graft and the aortic wall and to prevent the graft from migrating, but excessive oversizing might influence the results negatively. In this systematic review, we investigated the current literature to obtain an overview of the risks and benefits of oversizing and to determine the optimal degree of oversizing of stent grafts used for endovascular abdominal aortic aneurysm repair. METHODS: PUBMED, EMBASE and Cochrane Library databases were searched for articles related to the impact of proximal endograft oversizing on complications after endovascular aneurysm repair. After in- and exclusion, 23 relevant articles reporting on 8415 patients remained for analysis and critical appraisal. RESULTS: Most studies that investigated neck dilatation are flawed by poor methodology. No clear relationship between proximal oversizing and neck dilatation relative to the first post-operative scan was found. None of the studies described a positive relationship between the degree of oversizing and the incidence of endoleaks. On the contrary, oversizing up to 25% seems to decrease the risk of proximal endoleaks. There are conflicting data regarding the risk of graft migration when oversizing by more than 30%. CONCLUSIONS: Based on the best available evidence, the current standard of 10-20% oversizing regime appears to be relatively safe and preferable. Oversizing >30% might negatively impact the outcome after EVAR. Studies of higher quality are needed to further assess the relationship between proximal oversizing and the incidence of complications, particularly regarding the impact on aneurysm neck dilatation.

Aneurysm rupture after EVAR: can the ultimate failure be predicted?

OBJECTIVES: To provide insight into the causes and timing of AAA rupture after EVAR. DESIGN: Original data regarding AAA ruptures following EVAR were collected from MEDLINE and EMBASE databases. Data were extracted systematically and patient and procedural characteristics were analyzed. RESULTS: 270 patients with AAA ruptures after EVAR were identified. Causes of rupture included endoleaks (in 160: type IA 57, type IB 31, type II 23, type III 26, type IV 0, endotension 9, unspecified 14), graft migration 41, graft disconnection 11 and infection 6. Most of the described AAA ruptures occurred within 2-3 years after EVAR. Mean initial AAA diameter was relatively large (65 mm). No abnormalities were present in 41 patients during follow-up before rupture. Structural graft failure was described in 96 and a fatal course in 119 patients. CONCLUSIONS: Focus of surveillance on the first 2-3 years after EVAR may possibly reduce the AAA rupture rate, especially in patients with increased risk of early rupture (relatively large initial AAA diameter or presence of endoleak or graft migration). Better stent-graft durability and longevity is required to further reduce the AAA rupture risk after EVAR. Complete prevention will however remain challenging since AAA rupture may occur even if no predisposing abnormalities are present.