Letter by Canaud et al Regarding Article, “Retrograde Ascending Aortic Dissection During or After Thoracic Aortic Stent Graft Placement: Insight From the European Registry on Endovascular Aortic Repair Complications”
To the Editor:
We read with great interest the article by Eggebrecht and coworkers.1 They concluded that the majority of retrograde ascending aortic dissection cases were associated with the use of proximal bare spring stent grafts. The authors report that this decision is strengthened by evidence of stent graft–induced injury at surgery or necropsy in half of the patients. However, we have several comments.
First, it is difficult to draw conclusions from a retrospective registry. Second, it is essential to know the ratio of thoracic stent graft with proximal bare spring to stent graft without proximal bare spring used among the 4750 thoracic endovascular aortic repair procedures. Currently, thoracic stent grafts most frequently used in Europe have a proximal bare or covered stent. Thoracic stent grafts without bare springs account for a limited proportion of the stent grafts used, and therefore it seems logical that they are involved in a lower number of retrograde ascending aortic dissection cases. This lack of a control group of patients with thoracic endovascular aortic repair who did not develop retrograde ascending aortic dissection after the procedure does not allow any identification of risk factors predisposing toward this complication.
Third, intramural stress is involved as a major factor leading to retrograde aortic dissection. Intramural stress increases exponentially with oversizing.2 However, in this study, stent graft oversizing appears as a less likely factor leading to retrograde aortic dissection.
Fourth, the occurrence of a retrograde ascending aortic dissection is not specific to endovascular repair. It has occurred in patients after surgical repair of a thoracic aneurysm or in follow-up of medically treated type B dissection.3 Fifth, it is difficult to determine the true incidence of retrograde ascending aortic dissection because among the 72 major referral centers with significant thoracic endovascular aortic repair experience contacted, only 28 centers participated.
In summary, although this study provides an interesting addition to the literature, the statistical analysis provided therein should be interpreted with caution. However, we very much agree on the importance of this specific area of research and believe that specially designed studies may be able to clarify the risk factors of retrograde ascending aortic dissection after thoracic endovascular aortic repair.
Eggebrecht H, Thompson M, Rousseau H, Czerny M, Lönn L, Mehta RH, Erbel R; on behalf of the European Registry on Endovascular Aortic Repair Complications. Retrograde ascending aortic dissection during or after thoracic aortic stent graft placement: insight from the European Registry on Endovascular Aortic Repair Complications. Circulation. 2009; 15: 120: S276–S281.