1Division of Cardiology, University Hospital Rostock, Rostock School of Medicine, Ernst-Heydemann-Strasse 6, 18057 Rostock, Germany
2Division of Cardiovascular Surgery, University Hospital Rostock, Rostock School of Medicine, Rostock, Germany
* Corresponding author. Tel: +49 381 494 77 00; fax: +49 381 494 77 02. E-mail address: christoph.nienaber{at}med.uni-rostock.de
This editorial refers to Endovascular stent-graft treatment of aortic dissection: determinants of post-interventional outcome
by H. Eggebrecht et al., on page 489
Eggebrecht and colleagues,1 report their single centre experience with the interventional use of endovascular stent-grafts in the setting of both chronic and acute thoracic aortic dissection, referred to or recruited by a group of cardiologists and followed up for between 1 and 57 months. The group at the West German Heart Centre in Essen confirm the reported feasibility and report a high technical success rate for endovascular stent-grafting in the hands of skilled practitioners,25 associated, however, with an 11% non-fatal periprocedural complication rate.
Interestingly, though not surprisingly, multivariate analysis of their 38 cases revealed only parameters such as advanced age and poor health status due to comorbidities, to be predictors of mortality after successful stent-graft placement, while the mixed bag of accepted indications for stent-graft placement, such as contained rupture, refractory hypertension from renal malperfusion, branch vessel compromise and progressive enlargement of more than 1 cm/year of a patent false lumen,57 were not among those predictive variables with significant impact. The reported results, although derived from a limited number of patients, may shed new light on an ongoing conflict which closely accompanies any new and potentially helpful interventional technology, and in this case endovascular stent-graft placement in aortic pathology. It is almost a decade since aortic stent-grafts were introduced to the clinical arena initially to avoid extensive surgery for both thoracic and abdominal aneurysmal diseases.812 Both feasibility and safety were reported early and consistently and initial enthusiasm may have triggered a spreading, potentially unconsidered use or unthinking preference for endoaortic prosthesis with about 80% mid-term survival compared with the classic surgical treatment option. Yet even today, for the treatment of aortic aneurysm located in the descending thoracic aorta, we have no randomized study to confirm any consistent prognostic benefit with current generations of aortic stent-graft; the only long-term information can be derived from surveying patients treated with first-generation stent-grafts.9,10 Those long-term follow-up results, however, are sobering and show exactly the same observation reported by Eggebrecht and colleagues in dissection;1 that co-morbidity and age are predictors of mortality in patients considered unfit for surgery and subsequently subjected to the presumably low-risk procedure of stent-graft placement. Interestingly, in the medical community lower risk appears to be coupled with the anticipation of a better long-term outcome. But outcome, and this is something we have to learn in aortic disease, is largely not a matter of a less invasive or presumably safer treatment strategy, but is mostly determined by other variables reflecting the general health status of a given patient and his overall life expectancy.10,11 The specific pathology, for example aortic dissection or aortic aneurysm, appears to play a secondary role. In other words, mortality and death rate at long-term follow-up turn out to be variables hard to influence in a sick and old patient subset. Similarly, it was 14 years from the introduction of the stent-graft as an alternative to classic surgery for treatment of abdominal aortic aneurysm, before a randomized study could eventually prove better early outcome with current surgical technology.15
How do those sobering reflections relate to Eggebrecht's work? We believe that any new technology that is appealing and attractive to both practitioners and patients should be monitored by post-marketing registries until data are available from randomized studies comparing it with established strategies. With regard to type B aortic dissection, there is plenty of information on feasibility and safety, and procedural aspects, but little scientifically sound and solid comparison with either medical or surgical treatment.16 Of course randomized studies in certain subsets of patients may be ethically unjustifiable considering the already overwhelming observational evidence that some scenarios of type B dissection with imminent rupture, malperfusion syndrome, or shock are likely to benefit from stent-graft placement instead of surgery. Ironically, those high-risk patient subsets were not identified as likely to benefit with the statistical methodology used in Eggebrecht's paper. It was simply the multi-morbid and old patients who died despite successful stent-graft placement, who were identified, an observation that is indeed not unexpected. Considering this conflicting observation, what may then be the most appropriate reaction to those intriguing findings? The authors suggest better patient selection, but who are the chosen few? Should we avoid using the lower-risk procedure of stent-graft placement in an old and sick person unfit for surgery because he or she is, demographically speaking, already doomed to die and not worth the investment (costs)? Should we redirect and focus our financial resources only to those younger and fitter patients who have a better demographic chance to benefit from an expensive strategy?
This would be wrong in our opinion and would trigger a useless emotional debate and deviate far from our ethical title of best medical care. More than ever we need to reflect on the potential of this promising new therapy on an individual basis, especially as long as scientifically solid randomized studies are unavailable.14 Moreover, we should utilize clinical tools to predict outcomes that are readily available, even for patients with thoracic aortic dissection, and integrate the predictive power of those tools into the individual assessment of a given case.10,11 We will learn that not every technically feasible case should be subjected to stent-graft placement or surgery and that even the most advanced and least invasive strategy may not necessarily impact beneficially on outcomes because confounders such as age and fitness are far more dominant. Just as it was shrewd to test the revolutionary concept of drug-eluting coronary stents initially in simple lesions (documented in FIM, RAVEL, and TAXUS studies), so any randomized testing of the concept of stent-graft placement in aortic dissection should focus first on the relatively simple, stable type B dissection at a reasonable age range up to 75 years and use surrogate parameters rather than mortality to prove a reliable advantage;14 such surrogate parameters could be aortic expansion, aneurysm formation, and long-term complications or the lack of them.
Finally, the sobering information presented in Eggebrecht's analysis may be instrumental in forcing us, that is the interventional cardiovascular community, to better integrate all available predictive information into the management of a given case of dissection, and even import personal experience from a multidisciplinary expert panel, and develop even better scientifically solid predictive algorithms to eventually improve service to our patients by better selection for or against a new treatment strategy.
Footnotes
References
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