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What Is Proven (Evidence Based) Surgical Management of Acute Aortic Dissections?

Aortic dissection is one of many surgical diseases and therapies that do not easily lend themselves to randomized trials or other comparative studies. Through an analysis of the pathology and natural cause of the disease, DeBakey [1] and Shumway [2], among others, proposed surgical treatment of acute type A aortic dissections with the distinct aim to replace the ascending aorta with a vascular graft. This treatment soon became the accepted approach to the treatment of these severely ill patients with their very dismal prognosis. Figures from the International Registry of Acute Aortic Dissections (IRAD), using observational data, have shown the obvious benefit on survival by this surgical approach both in the first [3] and subsequent [4] eras of the database (Fig. 14.1).

Fig. 14.1
figure 1

Survival curves for patients with acute type A aortic dissections (Data from IRAD). (a) The first era of the database, published in 2000 (From Hagan et al. [3]; used with permission). (b) The recent era, published in 2011 (From Trimarchi et al. [4]; used with permission). Surgical treatment confers a survival benefit in all patient groups, maybe except for the very elderly patients

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As the surgical techniques and general management of these patients have improved, a number of other interventional approaches have been proposed, including arch reconstructions [5], surgery for uncomplicated B-dissections [6] and lately reimplantation of the aortic valves in completely resected roots [7] and finally combined stent-grafting of the descending aorta with arch and ascending replacement [5, 8]. In an era of increasing focus on best-evidence treatment, there is an ongoing concern on how to document and investigate the merits of these different surgical treatments for aortic dissections. Use of an open distal anastomosis during reconstruction of the aorta is one of the technical concepts that seems logical and potentially can improve the prognosis for patients with acute type A dissection.

The Open Distal Anastomosis: Why Should Such a Technique Improve Surgical Outcome?

Apart from the limited number of dissections confined to the ascending aorta alone (DeBakey type II morphology, [9]), most type A dissections affect the aorta from the ascending well into the descending aorta. As such, the upper part of the ascending aorta, the prevalent distal landing zone for the implanted graft in most operations, does not mark a logic natural site to truncate the reconstruction. The selection of this landing zone has emerged as a “compromise” between the pressing need to at least reconstruct the aorta within the pericardium (to avoid tamponade, coronary involvement and valve incompetence) and the limited invasiveness desirable in severely ill patients. From a morphological point of view, a more extensive approach including the arch in the reconstruction is logical [10], but there is a prize to pay for an extensively invasive procedure in these patients. Doing a large reconstruction, including the neck vessels and placing the distal landing zone in the descending aorta, puts increasing demand on brain protection and meticulous surgical technique to avoid neurological complications and bleeding problems from large anastomoses in friable tissue.

The thought of including part or the whole of the arch in the surgical resection emerged as deep hypothermia became commonplace [11]. By avoiding a clamp on the ascending aorta during reconstruction, a diagnostic inspection of the arch, arch vessels and proximal descending aorta is possible. In those cases where the primary tear is in the arch, a reconstruction that can remove this tear is possible. It is a general concept that removal of the entry tear can decompress the tension in the false lumen and thus reduce the risk of secondary rupture, dilatation and persistent flow in the false channel of the aortic wall. In addition, constructing the distal anastomosis in an open fashion i.e. with no clamp crowding the site of anastomosis, should make for a more secure and precise anastomosis. This should further reduce one of the most dreaded complications in dissection surgery; a difficult and at times uncontrollable bleeding from the distal anastomosis.

What Is the Documented Status for an Open Distal: Proven Benefit or “Suggestive and Hope-Driven”?

In 2004, we did a systematic survey of the literature addressing whether or not using an open distal no-clamp technique in the surgical treatment of acute type A aortic dissection could translate into an increased survival for the patients [12]. The design of the study was as a systematic literature review using the PubMed database with the search words “aortic dissection” and “treatment”. The important selection criteria for inclusion of studies were a demand for inclusion of more than 20 patients, the study should be performed after 1980, include a follow-up period of more than 1 year and allow a two-group comparison between an open distal and clamped anastomosis [12].

At that time point, no randomized trials had been done. Based on these selection criteria, six papers allowed a comparison between the two techniques (Table 14.1).

Table 14.1 Effect of an open distal technique on surgical outcome
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Of these six studies, one was a patient series and five were case-control studies with historical controls. The outcome is summarized in Table 14.1. A lower mortality was observed in the open-distal group in one of the studies. Importantly, no study had an observational period exceeding 5 years, and there were obvious shortcomings to all studies. For instance, the control groups were overall the eldest, and the open distal anastomoses were mostly done in the contemporary era. Due to the substantial development in surgical and anesthesiological techniques, this put a serious deficiency to the scientific quality of the studies. However, as there was no overall survival benefit to an open distal anastomosis, this historical fact, if anything, put forward the possibility that an open distal anastomosis gives an inferior result masked by the general improvement of treatment in the recent era.

It is obvious that the lack of statistical superiority from using an open distal technique in the various studies could be due to a statistical type-II error related to the low number of patients included in these overall single institutional series. Also, as the follow-up period was limited (mostly short, and not exceeding 5 years), a long term benefit from resecting more extensively the proximal part of the aorta may not appear until an extended observation period is possible. The overall conclusion from this review of the literature, was that the data available for supporting one or the other technique was clearly insufficient. However, as none of the authors could clearly demonstrate a benefit for an open distal anastomosis, the potential statistical difference cannot be substantial, and not approaching the level observed for medical vs surgical treatment for acute type A dissections.

For the purpose of an updated review, we have now done a new literature screening using the same criteria as those used in 2004. The new search again could not find any randomized trials and only two new studies [13, 14] were found based on our selection criteria (see Table 14.2). In this new table, however, we also have included a study by Pugliese and coworkers from 1998 [15]. This study is not assessing the effect of the open distal technique on survival, but the study is an analysis of factors influencing the need for reoperations after the primary surgery for type A dissections.

Table 14.2 Effect of an open distal technique on surgical outcome – update 2013
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In essence, the new search has the same outcome as the 2004 search. There is no discernible difference between the two techniques. Therefore, we are still left with data that says these techniques are reasonably equal in securing patient survival after the primary operation for type A aortic dissection.

Current Recommendation for the Distal Anastomosis

We do not have surveys stating the preferred technique used to reconstruct the distal anastomosis in surgical treatment of acute type A aortic dissections. Thus, based on the documented results alone, the surgeon can decide for him or herself whether or not to clamp the aorta when constructing the distal anastomosis. However, the results obtained from surgery of the arch and related reconstructions are steadily improving [16], and the surgeon thus has more alternatives and liberties when performing such procedures. In the IRAD database, 96 % of procedures for type A aortic dissections are done with an open distal anastomosis [15], and our impression is that this trend is the prevailing one.