Thoracic endovascular aneurysm repair for uncomplicated type B dissection

Abstract

The “landscape” of type B dissection (TBD) management has changed dramatically over the past 30 years. The acceptance of medical therapy as the cornerstone of treatment was borne of prohibitive morbidity when open surgical resection and grafting of the aortic entry tear was attempted. Unlike type A dissection wherein rupture of the ascending aortic entry tear is the principle cause of early death, early mortality in type B dissections often relates to malperfusion syndromes.1Cambria R.P. Brewster D.C. Gertler J. Moncure A.C. Gusberg R. Tilson M.D. et al.Vascular complications associated with spontaneous aortic dissection.J Vasc Surg. 1988; 7: 199-209Abstract Full Text Full Text PDF PubMed Scopus (409) Google Scholar In turn, it has been well-documented that early mortality in TBD is three-fold increase in such patients designated as “complicated” TBD.2Hagan P.G. Nienaber C.A. Isselbacher E.M. Bruckman D. Karavite D.J. Russman P.L. et al.The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease.JAMA. 2000; 283: 897-903Crossref PubMed Scopus (2673) Google Scholar There is consensus that such patients who harbor immediately life-threatening complications are optimally managed with thoracic endovascular aneurysm repair (TEVAR) to seal the aortic entry tear, promote aortic remodeling, and reverse, at least, “dynamic” aortic branch compromise. Accordingly, the initial commercial availability of a TEVAR device (2005) both ushered in a new era in TBD management and, related to their endovascular capabilities, enabled vascular surgeons to manage TBD. Indeed, the recent “blanket” Food and Drug Administration approval for TEVAR in TBD was based on data from studies concentrating on patients with complicated TBD.3Cambria R.P. Conrad M.F. Matsumoto A.H. Fillinger M.F. Pochettino A. Carvalho S. et al.Multicenter clinical trial of the conformable stent graft for the treatment of acute, complicated type B dissection.J Vasc Surg. 2015; 62: 271-278Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar What then of patients with uncomplicated TBD (uTBD) wherein the focus is typically on the principle late complication of the disease viz aneurysmal dilatation of the outer wall of the false lumen? Both the earlier and current literature validates the fact that this is a common problem in survivors of a TBD. DeBakey4DeBakey M.E. McCollum C.H. Crawford E.S. Morris G.C. Howell J. Noon G.P. et al.Dissection and dissecting aneurysms of the aorta: twenty-year follow-up of five hundred twenty-seven patients treated surgically.Surgery. 1982; 92: 1118-1134PubMed Google Scholar in a series of over 500 patients initially treated surgically documented that 30% of late deaths were due to interval aneurysm rupture.4DeBakey M.E. McCollum C.H. Crawford E.S. Morris G.C. Howell J. Noon G.P. et al.Dissection and dissecting aneurysms of the aorta: twenty-year follow-up of five hundred twenty-seven patients treated surgically.Surgery. 1982; 92: 1118-1134PubMed Google Scholar In a recent natural history study of patients with uTBD from our hospital, 30% of patients came to a late intervention (essentially all for aneurysm formation) at a mean follow-up interval of just 4.5 years after their acute presentation.5Durham C.A. Cambria R.P. Wang L.J. Ergul E.A. Aranson N.J. Patel V.I. et al.The natural history of medically managed acute type B aortic dissection.J Vasc Surg. 2015; 61: 1192-1199Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar Furthermore, our data are consistent with that from the International Registry of Acute Aortic Dissection investigators,6Fattori R. Montgomery D. Lovato L. Kische S. Di Eusanio M. Ince H. et al.Survival after endovascular therapy in patients with type B aortic dissection: a report from the International Registry of Acute Aortic Dissection (IRAD).JACC Cardiovasc Interv. 2013; 6: 876-882Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar and late results of the Investigation of Stent Grafts in Patients with Type B Aortic Dissection (INSTEAD) trial7Nienaber C.A. Kische S. Rousseau H. Eggebrecht H. Rehders T.C. Kundt G. et al.Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial.Circ Cardiovasc Interv. 2013; 6: 407-416Crossref PubMed Scopus (678) Google Scholar demonstrating superior and statistically significant improved late survival in patients with TBD who undergo surgery (of any type) as contrasted with those treated with medical therapy alone. These developments then lead to the important clinical question of which patients with uTBD should be offered TEVAR to promote aortic remodeling and, thus, abrogate the need for later repair of often extensive aneurysms of chronic dissection etiology. Even though such aneurysms are often of thoracoabdominal extent, it is not logical to adopt a “wait and see for interval TEVAR” strategy because open repair will frequently be required for such lesions; indeed that has been our experience.5Durham C.A. Cambria R.P. Wang L.J. Ergul E.A. Aranson N.J. Patel V.I. et al.The natural history of medically managed acute type B aortic dissection.J Vasc Surg. 2015; 61: 1192-1199Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar Few prospective data are available as to the worth of early TEVAR in uTBD. INSTEAD-1 related unclear data in this regard, likely related to the selection of all-cause 1-year mortality as the principle endpoint. Yet, the follow-up INSTEAD publication detailed significant favorable later outcomes (all-cause mortality) for the TEVAR vs medically treated patients wherein the survival curves began to separate after 2 years.7Nienaber C.A. Kische S. Rousseau H. Eggebrecht H. Rehders T.C. Kundt G. et al.Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial.Circ Cardiovasc Interv. 2013; 6: 407-416Crossref PubMed Scopus (678) Google Scholar This phenomenon was confirmed by our own series and a recent International Registry of Acute Aortic Dissection study where the survival advantage of intervention over medical therapy became evident after 2 years of follow-up.5Durham C.A. Cambria R.P. Wang L.J. Ergul E.A. Aranson N.J. Patel V.I. et al.The natural history of medically managed acute type B aortic dissection.J Vasc Surg. 2015; 61: 1192-1199Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar, 6Fattori R. Montgomery D. Lovato L. Kische S. Di Eusanio M. Ince H. et al.Survival after endovascular therapy in patients with type B aortic dissection: a report from the International Registry of Acute Aortic Dissection (IRAD).JACC Cardiovasc Interv. 2013; 6: 876-882Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar In addition, studies that focus on aortic anatomic end points at least strongly imply a positive impact of TEVAR on late aneurysm formation.8Conrad M.F. Crawford R.S. Kwolek C.J. Brewster D.C. Brady T.J. Cambria R.P. Aortic remodeling after endovascular repair of acute complicated type B aortic dissection.J Vasc Surg. 2009; 50: 510-517Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar, 9Brunkwall J. Kasprzak P. Verhoeven E. Heijmen R. Taylor P. the ADSORB TrialistsEndovascular repair of acute uncomplicated aortic type B dissection promotes aortic remodelling: 1 year results of the ADSORB Trial.Euro J Vasc Endo Surg. 2014; 48: 285-291Abstract Full Text Full Text PDF PubMed Scopus (231) Google Scholar In this issue of the Journal, Ray et al10Ray H.M. Durham C.A. Ocazionez D. Charlton-Ouw K.M. Estrera A.L. Miller C.C. et al.Predictors of intervention and mortality in patients with uncomplicated acute type B aortic dissection.J Vasc Surgery. 2016; 64: 1560-1568Google Scholar from Houston present an important study focused on the subsequent need for intervention and all-cause mortality of patients with uTBD. Their principle findings indicate an overall aortic diameter ≥44 mm and a false lumen diameter >22 mm (measured in the proximal descending aorta) were significant predictions of later interventions and increased mortality. In patients with these anatomic features, there was a 30% need for later intervention at 5 years after index presentation. Interestingly, this figure is quite similar to our own data in a natural history study of TBD.5Durham C.A. Cambria R.P. Wang L.J. Ergul E.A. Aranson N.J. Patel V.I. et al.The natural history of medically managed acute type B aortic dissection.J Vasc Surg. 2015; 61: 1192-1199Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar Some elements of the Houston data, as acknowledged by the authors, emphasized the problems with retrospective studies. Although the Houston group has managed a large number of patients with TBD over the past 15 years, their Figure 1 indicates that one-half of these patients have been considered “complicated,” an incidence of uTBD at variance with the bulk of the literature.6Fattori R. Montgomery D. Lovato L. Kische S. Di Eusanio M. Ince H. et al.Survival after endovascular therapy in patients with type B aortic dissection: a report from the International Registry of Acute Aortic Dissection (IRAD).JACC Cardiovasc Interv. 2013; 6: 876-882Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar, 11Lauterbach S.R. Cambria R.P. Brewster D.C. Gertler J.P. Lamuraglia G.M. Isselbacher E.M. et al.Contemporary management of aortic branch compromise resulting from acute aortic dissection.J Vasc Surg. 2001; 33: 1185-1192Abstract Full Text PDF PubMed Scopus (157) Google Scholar This may also reflect referral bias. One-half of their patients with uTBD were lost to adequate imaging follow-up at a mean of 3.7 years. Finally, a study end point of all-cause vs aortic-related mortality may lack precision if the goal is to focus on dissection related events in a cohort averaging 60 years of age; similar to many studies, that of Ray et al noted that older patients had decreased survival. Irrespective of such limitations, the Houston data verifies the intuitively logical proposition that dilated aortas are more likely to develop, and require interval treatment for, aneurysm of chronic dissection etiology. It was a pleasure for us to read the report of Ray et al; in a series of prior publications in the Journal and in a follow-up study about to be presented at the New England Society for Vascular Surgery, we found that medical therapy will fail in some 60% of patients at just 4 years of follow-up.5Durham C.A. Cambria R.P. Wang L.J. Ergul E.A. Aranson N.J. Patel V.I. et al.The natural history of medically managed acute type B aortic dissection.J Vasc Surg. 2015; 61: 1192-1199Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar Only 50% of patients will be free of interval aortic expansion (which averages an impressive 12 mm/y) at 5 years of follow-up,12Durham C.A. Aranson N.J. Ergul E. Wang L.J. Patel V.I. Cambria R.P. et al.Aneurysmal degeneration of the thoracoabdominal aorta after medical management of type B aortic dissections.J Vasc Surg. 2015; 62: 900-906Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar and the identical anatomic features reported by Ray et al predict a 2-fold increase in the need for interval intervention. While these are exciting times in the application of TEVAR for patients with TBD, the data on which patients with uTBD are best managed with early TEVAR should hardly be considered definitive. It is known that TEVAR for complicated TBD reduced mortality in such patients from 30% to 10%2Hagan P.G. Nienaber C.A. Isselbacher E.M. Bruckman D. Karavite D.J. Russman P.L. et al.The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease.JAMA. 2000; 283: 897-903Crossref PubMed Scopus (2673) Google Scholar, 3Cambria R.P. Conrad M.F. Matsumoto A.H. Fillinger M.F. Pochettino A. Carvalho S. et al.Multicenter clinical trial of the conformable stent graft for the treatment of acute, complicated type B dissection.J Vasc Surg. 2015; 62: 271-278Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar; this is, of course, a very different consideration from patients with uTBD wherein early TEVAR is essentially a prophylactic intervention that, in itself, can never be a risk-free procedure in a cohort of patients with very acceptable 1-year survival with medical therapy alone.13Estrera A.L. Miller C.C. Safi H.J. Goodrick J.S. Keyhani A. Porat E.E. et al.Outcomes of medical management of acute type B aortic dissection.Circulation. 2006; 114: I384-I389PubMed Google Scholar Doubtless a spectrum of clinical and anatomic variables will be defined in ongoing and future studies already being formulated. In a first of its kind combined Food and Drug Administration/Society for Vascular Surgery-Vascular Quality Initiative and industry-sponsored prospective registry study to examine real world practice of TEVAR in TBD, 400 patients will be followed for 5 years after TEVAR. This study has recently completed enrollment and includes patients treated for the spectrum of type B dissection in the post approval era. A consortium of vascular specialists and thought leaders is also about to submit a proposal to the National Institutes of Health for a randomized study of TEVAR vs medical therapy for uTBD. Evidence-based guidelines for applying early TEVAR in patients with TBD are not currently available. It is logical to consider such therapy in younger patients with anatomy suitable for TEVAR given extant natural history data of uTBD. Additional data to inform such clinical decision making is anticipated in the foreseeable future.