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Eur J Cardiothorac Surg 2008;34:600-604. doi:10.1016/j.ejcts.2008.05.038
Copyright © 2008, European Association for Cardio-thoracic Surgery. Published by Elsevier. All rights reserved.
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Distal aortic surgery following arch replacement with a frozen elephant trunk

Maximilian A. Pichlmaiera,*, Omke E. Teebkena, Nawid Khaladja, Jürgen Weidemannb, Michael Galanskib, Axel Havericha

a Department of Cardiac, Thoracic, Transplantation and Vascular Surgery, Hannover Medical School, Carl-Neuberg-Strasse, D-30625 Hannover, Germany
b Department of Radiology, Hannover Medical School, Carl-Neuberg-Strasse, D-30625 Hannover, Germany

Received 20 December 2007; received in revised form 12 May 2008; accepted 20 May 2008.

* Corresponding author. Tel.: +49 511 532 3453; fax: +49 511 532 8158. (Email: pichlmaier.maximilian{at}mh-hannover.de).


   Abstract
Top
 Abstract
1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 References
 
Objective: The frozen elephant trunk technique allows the repair of concomitant aortic arch and proximal descending aortic pathology in a single stage by using a hybrid prosthesis consisting of a vascular graft with a distal stented end. There are patients, however, who will require a second distal operation despite this new technique due to progression of their aortic disease. It has been unclear whether the presence of the stented segment of the hybrid prosthesis results in unexpected technical difficulties or possibly advantages for further vascular reconstruction. Methods: Six patients out of our initial cohort of 39 treated with a hybrid prosthesis from 2001 through 2006 have since required an additional distal aortic reconstruction. Two received endoluminal stent grafts, four had extensive open replacements. Results: There was no 30-day mortality, one patient died on day 133 having been discharged from hospital of an unrelated MRSA septicaemia. Complete thrombosis of the proximally covered aneurysm or the false lumen had occurred in all patients so that the replacements reached from the end of the stented portion of the hybrid prosthesis to the desired distal level. The operative approach proved to be facilitated by the hybrid prosthesis in terms of the necessary exposure and operative trauma. Postoperative recovery was uneventful as related to the hybrid prosthesis with few pulmonary complications and at least comparable to contemporary results for second stage elephant trunk procedures. Conclusions: The distal operative replacement of the aorta following a frozen elephant operation is safe and technically feasible. Early experience suggests that there is an advantage as compared to the conventional elephant technique in terms of intraoperative handling and postoperative recovery.

Key Words: Endovascular procedures/stents • Reoperation • Aortic arch • Aortic operation


   1. Introduction
Top
 Abstract
 1. Introduction
2. Materials and methods
 3. Results
 4. Discussion
 References
 
The frozen elephant trunk is adapted from the classical elephant trunk technique first described by Borst et al. in 1983 [1] and allows the single stage repair of co-existing aortic arch and proximal descending aortic pathology [2–4]. A hybrid vascular graft consisting of a conventional tube graft with an endovascular stent graft at the distal end is used to achieve an endovascular blood tight seal in the descending aorta which cannot easily be accessed directly from an anterior approach [4]. In the conventional elephant trunk operation, the perigraft space around the elephant trunk remains perfused, thereby allowing for further aneurysmatic dilatation of this aortic segment [5–8]. A second operation is inevitably required, either in the form of a traditional operative replacement or alternatively an endoluminal exclusion of the diseased descending aorta [5]. In contrast, the hybrid prosthesis is designed to exclude the perigraft space in the descending aorta leading to thrombosis and ideally aneurysm shrinkage. The results with conventional stent grafting confirm this concept [9,10]. Similarly, early experience and results with the hybrid prosthesis show successful exclusion of the proximal descending aortic aneurysm or stabilisation of a dissected aortic segment and have been described previously [4].

There are, however, patients who will require a second distal operation despite the use of the hybrid prosthesis usually due to progression of their primary aortic pathology. Here we describe our experience with 6 patients out of our cohort of 39 initially treated with the hybrid prosthesis who have now had such second stage operations.


   2. Materials and methods
Top
 Abstract
 1. Introduction
 2. Materials and methods
3. Results
 4. Discussion
 References
 
All patients from the initial cohort of 39 who have since required a second intervention on their aorta following the implantation of a hybrid prosthesis (Chavan–Haverich-endograft, Curative GmbH, Dresden, Germany) were included in this analysis. The primary use of the hybrid prosthesis and the analysis of follow-up data had been approved of by the local institutional review board [2] and the need for a second operation was reported to the former accordingly. Patients gave informed consent to the evaluation of their data for research purposes. The indication for a second stage operation was, in all cases, enlargement of the aorta distal to the stented segment of the hybrid prosthesis beyond 6 cm in transverse diameter.

2.1 Endografting
Patients were treated interventionally using Medtronic Talent endovascular grafts if the anatomy was suitable (two of six patients). The latter procedures were performed under general anaesthesia in the angio suite. Monitoring included ECG, right radial artery pressure and central venous pressure. Access to the arterial system was via a small transverse inguinal skin incision and a transverse arteriotomy following the application of 5000 i.E. of heparin and clamping the common femoral artery. A 5 Fr sheath was introduced via the arteriotomy and fixed with tourniquets. Using a hydrophilic guide wire (Terumo) the arch was entered retrogradely and the wire exchanged for an Amplatz guide wire over a pigtail catheter following angiographic verification (Philips Integris) of the position of catheter in the arch. The sheath was removed and the Medtronic Talent devices were deployed after positioning under fluoroscopic observation in left anterior oblique (LAO) projection once the systolic blood pressure had been lowered to around 60–70 mmHg to avoid dislocation during deployment (approx. 2 min). The stents were moulded to the distal stent portion of the hybrid prosthesis with a minimum overlap of two stent rows and the aortic wall using a standard Medtronic Reliant balloon while haemostasis was achieved with the tourniquet. Arteriotomy and wound closure were performed in standard fashion. The patients were extubated on the table if body temperature permitted this and monitored on the intensive care unit thereafter.

2.2 Open surgery
All patients operated on conventionally received a spinal catheter for cerebrospinal fluid (CSF) drainage the day prior to surgery. Aortic replacement was carried out through a typical thoracoabdominal approach with radial detachment of the diaphragm and strict retroperitoneal dissection. Distal circulatory support was achieved by femoro-femoral bypass and individual catheterisation of the visceral and renal arteries as required. Moderate hypothermia down to 32 °C was tolerated. Systolic right radial artery pressure of 130 mmHg was maintained insuring adequate coronary and cerebral perfusion. Distal perfusion pressures were aimed at 40–70 mmHg with a desired flow of 2.5–3.5 l/min. Staged replacement of the aorta was performed in the typical fashion from above down reattaching between 2 and 6 intercostals in inlay technique dependent on backflow. Preference was given to the arteries arising just above and to a lesser degree below the area where the aorta passes through the diaphragm. The visceral and renal arteries were reattached in various arrangements ranging from moderately large islands to individual anastomoses. Standard vascular grafts (Boston, Haemashield Platinum and Braun Unigraft) were implanted. The CSF pressure was kept below 20 mmHg aiming for 10 mmHg by draining generously during and for 48 h following the operation. The postoperative regimen included the maintenance of anaesthesia for the initial six postoperative hours and weaning from the respirator starting thereafter according to pulmonary function. Bronchoscopy was performed generously on postoperative day one, if the conventional chest X-ray suggested more than the expected loss of transparency on the left side or the gas exchange was poor. Further treatment was according to the in house protocol with direct transfer from ICU to the normal ward and discharge preferably home or else to a rehabilitation unit if the patients still required care or it was their wish.


   3. Results
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
4. Discussion
 References
 
3.1 Patients and indications
Six patients (18%) out of our previously reported cohort of 39 (33 long term survivors) treated with a hybrid prosthesis [2] have now had a second stage distal aortic replacement at a median age of 55 years (two females) between 23 days and 46 months after the arch replacement with the hybrid prosthesis. For reference, the characteristics of the initial cohort are shown in Table 1 . The overall long-term survival is 80% after a median follow-up of 50.9 months (21–81 months). The indication for the second operation was progressive distal aneurismal change secondary to mega-aortic syndrome in one and chronic dissection (1 type B, 3 type A) in the other five cases (Table 2 ). In two cases there were descending aortic aneurysms and in four cases type II thoracoabdominal aneurysms (TAAA).


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  		Table 1 Baseline data of the original patient cohort with a hybrid prosthesis including long-term survival beyond the second stage aortic replacements of this series.
 

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  		Table 2 Indications for first and second stage operations and time intervals between these.
 
The length of the stented portion of the initial hybrid prosthesis was 9–12 cm (3 or 4 sets of struts) and the extent of descending aortic coverage varied from 10 to 18 cm depending on the extent of original descending aortic disease. Complete thrombosis of the proximally covered aneurysm or the false lumen had occurred in all these patients so that the replacement was always from the end of the stented portion of the graft to the desired distal level. Fig. 1 demonstrates the progressive thrombosis and eventual obliteration of the false lumen after repair of an acute type A dissection with the hybrid prosthesis. Distal to the stented portion of the hybrid prosthesis however, enlargement of the persistently pressurised dissected aorta occasionally occurred (Fig. 2 ).


Figure 1
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  		Fig. 1. Progressive thrombosis and shrinkage of the false lumen following arch replacement with a hybrid prosthesis in type A dissection. False lumen thrombosis occurs due to the loss of proximal inflow and the stent progressively expands into the space re-establishing the original aortic (true) lumen with a simultaneous shrinkage of the overall outside diameter.

 

Figure 2
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  		Fig. 2. Progression of disease following the frozen elephant implantation involving the rest of the aorta (left) and result of the second stage aortic replacement (right). Thrombosis of the false lumen had occurred due to cessation of proximal inflow into the false lumen.

 
3.2 Stents
Two patients received stent grafts to extend the coverage of the descending aorta. Here the disease process was limited to above the coeliac axis and therefore amenable to conventional endoluminal treatment (Fig. 3 ). One of these patients had shown a distal type 1 endoleak in the first postoperative CT scan following the arch replacement with the hybrid prosthesis (Fig. 3).


Figure 3
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  		Fig. 3. The progression of disease (left) is limited to the supra coeliac aorta and therefore amenable to interventional treatment (right). The ectatic brachiocephalic trunk was not repaired during the primary arch replacement and the diameter has remained unchanged during follow-up.

 
3.3 Open replacement
The operative approach in the remaining four patients proved to be comparatively straight forward through either the 7th or 8th intercostal space without the necessity to resection any ribs. For clamping of the stented aorta proximally, it was occasionally necessary to use two clamps to achieve a competent seal. On inspection of the clamped section of the stent from inside there was no evidence of damage to the fabric or the struts by the clamps. The anastomosis proved to be technically comparatively simple where neither slipping of the graft inside the aorta nor tearing of the aortic wall was observed. Fig. 4 demonstrates the typical appearance of the aortic wall at the end of the stent. Thus, the stented portion of the graft was always found to be firmly grown in and the new tube graft was sized to the stent which had, in most cases, not quite reached its designed full expansion. The aortic wall itself tended to be thickened and with some macroscopic inflammatory appearance as compared to the usual finding in primary aortic aneurysm surgery or abdominal conversion surgery following endovascular stent placement.


Figure 4
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  		Fig. 4. The proximal anastomosis is created directly between the new tube graft and the descending aorta at the end of the stented portion of the hybrid prosthesis.

 
The tube graft was anastomosed directly to the end of the stent graft together with the surrounding aortic wall using 3/0 or 2/0 running Prolene sutures as seen in Fig. 4.

The aorta was replaced from the hybrid prosthesis to below the renal arteries in one, to the aortic bifurcation in one and to the bifurcation of the common iliac arteries on both sides in the remaining two cases. Table 3 shows the details of the operations in terms of duration, bypass time, lowest rectal temperature and substitution of blood required.


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  		Table 3 Details of the operative procedures
 
3.4 Outcome
All six patients survived the second operation and were discharged from hospital. One patient died 4 months (133 days) after the second operation having developed multiorgan failure secondary to a MRSA septicaemia after making a very good recovery from a difficult postoperative course including a partial paralysis of the legs and temporary renal failure. Postmortem examination revealed an intact thoracoabdominal graft without evidence for a graft infection.

Table 4 summarises the postoperative details, such as ventilation time, hospital stay and requirement for dialysis in our patients.


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  		Table 4 Postoperative details
 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
References
 
The concept of the hybrid prosthesis aims to complete the traditional elephant trunk technique otherwise performed as two-stage procedure in one single step. Despite this intention, however, there are and will always be patients in whom a second therapeutic measure is required for remaining or new distal disease. The operation may thus be considered a second stage elephant procedure in the traditional sense as far as the indication is concerned. However there are unique technical differences. Here we report the first six cases of such second stage operations in our experience with patients having been treated with the hybrid prosthesis previously. Retrospectively, two of the patients were to be expected to proceed to a further operation judged from their initial CT scans. In one case the landing zone was clearly within a partially thrombosed aneurysm. The fact, that all false lumens had thrombosed and most outside diameters shrunk within the stented aortic segment, must be attributed to depressurisation of the aneurysm sacks and exclusion of antegrade inflow into false lumens and has been published previously for the cohort of patients with hybrid prostheses [2]. An interesting aspect to the discussion of interventional treatment of dissections arises here as definite exclusion of the false lumen and the primary entry proximally did not, in our cases, prevent the distal progression of disease. Thus the prophylactic value of isolated proximal stent implantation in type B dissections may again be questioned.

The operative results and parameters are, apart from the loss of one patient on day 133 (intermediate term mortality 16%) and the paraplegia in the same patient (paraplegia rate 16%), comparable to the literature for extensive vascular surgery on the thoracoabdominal aorta [11] and compare well with our own experience [12]. In representative contemporary series from large volume centres reporting specifically on second stage aortic surgery following a conventional elephant trunk mortality is 4–10% and paraplegia rate 0–4% [8,13–15]. The so-called adjuncts applied include distal perfusion, organ perfusion and CSF drainage and are thus identical to our strategy. The ranges given for perfusion time (20–269 min) and aortic clamp time (10–162 min) again embrace our data. In all these series the proportion of type II aneurysms was less than 50% and usually less than one third making the results not strictly comparable to our series in favour of the latter (67% type II TAAA). The present series is however too small to hold for a detailed direct comparison to these series.

The first advantage of the hybrid prosthesis in the setting of a distal operation is the much reduced extent of necessary proximal access. Thus, rib resections or access via two intercostal spaces was not required nor was extensive handling of the left lung necessary resulting in a much reduced effect of the operation on postoperative pulmonary function. A reduced requirement of postoperative bronchoscopies as compared to expectation was thus observed. The comparatively caudal approach through the 7th or 8th intercostal space facilitated distal reconstruction. The end of the hybrid prosthesis is easily palpated through the aortic wall and thus an appropriate clamping level may be identified even in a dissected aorta. Clamping is performed without further surgical exposure of the prosthesis as there is no folding or kinking of the graft as seen with the conventional elephant trunk. Clamping itself did not result in any appreciable damage of the stented portion of the hybrid prosthesis. There is also no need to further deal with the stented segment of the aorta above as would be required if there is still a perfused false lumen or an only partially thrombosed aneurysm after a traditional insertion of an elephant trunk. The latter additionally tends to be shorter than the hybrid prosthesis and often retracted. Creating the anastomosis between the stented hybrid prosthesis and a vascular graft was technically uneventful.

Despite the extensive replacements, we did not observe any new injuries to the vagus, phrenic or recurrent laryngeal nerves. Furthermore, there was little pulmonary haemorrhage and thus postoperative respiratory deficit in this small series. Two patients required temporary dialysis but their filtration rate had recovered almost completely by the time of discharge.

This experience of reoperations in patients having received a hybrid prosthesis shows in the eyes of the authors, that for one, in these patients the operations have at most an equivalent risk compared to the situation where none or a traditional elephant trunk has been inserted previously. Secondly, there are a number of features that clearly simplify the second operation from which the patients are likely to benefit. The latter is suggestive but cannot be proven on the basis of this small series and time will have to prove the overall superiority of the frozen elephant trunk over the conventional elephant trunk. Furthermore the position of novel techniques such as branched endografts with respect to conventional surgery in such cases will have to be defined. Nevertheless, our own practice has changed in as far as we see the indication for the use of the hybrid prosthesis more liberally and will opt for it even if a healthy non-thrombosed segment of descending aorta cannot be reached with the stented portion of the graft.


   Footnotes
 
{star} The project was funded by the departmental research funds.


   References
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 References
 

  1. Borst HG, Walterbusch G, Schaps D. Extensive aortic replacement using "elephant trunk" prosthesis. Thorac Cardiovasc Surg 1983;31:37-40.[Medline]
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  3. Chavan A, Karck M, Hagl C, Winterhalter M, Baus S, Galanski M, Haverich A. Hybrid endograft for one-step treatment of multisegment disease of the thoracic aorta. J Vasc Interv Radiol 2005;16:823-829.[Medline]
  4. Pichlmaier MA, Teebken OE, Baraki H, Haverich A. The frozen elephant trunk technique. MMCTS 2007. doi: 10.1510/mmcts.2006.001990.[Abstract/Free Full Text]
  5. Borst HG, Frank G, Schaps D. Treatment of extensive aortic aneurysms by a new multiple-stage approach. J Thorac Cardiovasc Surg 1988;95:11-13.[Abstract]
  6. Estrera AL, Miller III CC, Porat EE, Huynh TT, Winnerkvist A, Safi HJ. Staged repair of extensive aortic aneurysms. Ann Thorac Surg 2002;74:S1803-S1805.[Abstract/Free Full Text]
  7. Kouchoukos NT, Mauney MC, Masetti P, Castner CF. Single-stage repair of extensive thoracic aortic aneurysms: experience with the arch-first technique and bilateral anterior thoracotomy. J Thorac Cardiovasc Surg 2004;128:669-676.[Abstract/Free Full Text]
  8. Safi HJ, Miller III CC, Estrera AL, Huynh TT, Porat EE, Allen BS, Sheinbaum R. Staged repair of extensive aortic aneurysms: long-term experience with the elephant trunk technique. Ann Surg 2004;240:677-684.[Medline]
  9. Chavan A, Lotz J, Oelert F, Galanski M, Haverich A, Karck M. Endoluminal treatment of aortic dissection. Eur Radiol 2003;13:2521-2534.[CrossRef][Medline]
  10. Yamazaki I, Imoto K, Suzuki S, Ichikawa Y, Karube N, Manabe T, Noishiki Y, Kondo J, Takanashi Y. Midterm results of stent-graft repair for thoracic aortic aneurysms: computed tomographic evaluation. Artif Organs 2001;25:223-227.[CrossRef][Medline]
  11. Jacobs MJ, Mommertz G, Koeppel TA, Langer S, Nijenhuis RJ, Mess WH, Schurink GW. Surgical repair of thoracoabdominal aortic aneurysms. J Cardiovasc Surg (Torino) 2007;48:49-58.[Medline]
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  13. Azizzadeh A, Miller III CC, Huynh TT, Estrera AL, Porat EE, Safi HJ. Surgical repair of extensive aortic aneurysms. Perspect Vasc Surg Endovasc Ther 2005;17:217-223.[Abstract/Free Full Text]
  14. LeMaire SA, Carter SA, Coselli JS. The elephant trunk technique for staged repair of complex aneurysms of the entire thoracic aorta. Ann Thorac Surg 2006;81:1561-1569.[Abstract/Free Full Text]
  15. Svensson LG, Kim KH, Blackstone EH, Alster JM, McCarthy PM, Greenberg RK, Sabik JF, D’Agostino RS, Lytle BW, Cosgrove DM. Elephant trunk procedure: newer indications and uses. Ann Thorac Surg 2004;78:109-116.[Abstract/Free Full Text]



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