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Eur J Cardiothorac Surg 1999;15:496-501
© 1999 Elsevier Science NL
a Clinic for Thoracic and Cardiovascular Surgery, University Hospital, CH-3010 Berne, Switzerland
b Department of Radiology, University Hospital, CH-3010 Berne, Switzerland
Received 28 September 1998; received in revised form 23 December 1998; accepted 8 January 1999.
Corresponding author. Tel.: +41-31-632-2375; fax: +41-31-382-0279; e-mail: thierry.carrel@insel.ch
| Abstract |
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Key Words: Aortic dissection Surgical repair Magnetic resonance imaging Morphology of the distal aorta
| Introduction |
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| Methods |
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All patients were interviewed to establish intercurrent problems with their aorta, actual symptoms and medicamentous treatment. MR imaging was performed on a 1.5-T whole body imaging system (VISION, Siemens Medical Systems, Erlangen, Germany). A circularly polarized body coil was used with the subject in the supine position. Three ECG leads were attached to the anterior chest wall over the heart. Cardiac and respiratory motion induced artefacts were reduced or eliminated by the use of acquisitions gated to the R-wave and breath hold imaging. The morphology and function of the heart, aorta and supraaortic branches were evaluated by use of a T1-weighted turbo spin-echo sequence, a T2-weighted inversion recovery turbo spin-echo sequence and a gradient echo cine sequence. First a dark blood (flowing blood dark) half-Fourier T2-weighted turbo spin-echo sequence (matrix=128x256, seven sections per breath hold, section thickness 6 mm) in the coronal plane and then dark blood high resolution single slice, segmented T1-, T2-weighted, and inversion recovery turbo spin-echo sequences (turbo factor 33, matrix=128x256, one section per breath hold, section thickness 5 mm) targeted to specific regions were acquired in the oblique sagittal plane parallel to the aortic arch and perpendicular to the aorta. For functional imaging a bright blood (flowing blood bright) single-slice segmented fast low angle shot (FLASH) sequence (TR=100, TE=4.8 ms, flip angle=20°, nine phase-encoding steps per segment, matrix=128x256, section thickness 6 mm) was applied in the same regions mentioned above. In each patient, the vascular prosthesis (especially the proximal and distal anastomoses) and any segment of the native aorta were evaluated.
Statistical analysis was performed using the StatView Programm (Los Angeles, CA). Comparison between the group was performed with the chi2 test and a P-value of less than 0.05 was considered as statistically significant.
| Results |
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From the 54 patients who underwent radiological follow-up, 38 (70.3%) had some demonstrable blood flow in the distal false channel and 16 patients (29.7%) were found to have complete obliteration of the false lumen. The highest rate of persistent false lumen perfusion (17/20, 85%) frequently associated with the presence of an intimal flap in the aortic arch (13/20, 65%) was observed in patients following closed repair of acute ascending aortic dissection, whereas the lowest rate of such findings was demonstrated in patients who had undergone open distal aortic repair using biologic glue (false lumen perfusion 10/18, 55% and intimal flap in the arch 2/18, 11%). Redo surgery was significantly reduced in the open repair group using GRF glue (1/18, 5.5%) as compared with the Teflon felt repair group (3/16, 18%) and the closed repair group (6/20, 30%) (Table 1). Some interesting findings are presented in Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 .
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| Discussion |
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Long-term follow-up after operated acute type A dissection is usually characterized by complications from persistent blood flow in the distal false lumen [8] [9]. A patent distal false lumen with demonstrable blood flow has been found in as high as 80% of the patients following replacement of the ascending aorta [10]. The mechanisms through which the false channel remains patent may be due to a constant blood flow to one or several major aortic branches that communicate or originate from the false channel, which might be fed by distal entry sites [8]. The major problem inherent to persistent distal false lumen perfusion is increasing dilatation of the false channel with a potential for late aortic rupture.
Svensson found that residual dilatation of the aorta after repair of aortic dissection was a significant risk factor for late aortic rupture and that patients with dilated aorta usually have double lumina without thrombosis [8]. His data did not show that the risk of rupture was greater when a double lumen was present and the aorta was not dilated. In their observation, Erbel et al., showed that complete obliteration of the false lumen is rare in the remaining dissected aorta [11]. The risk of reoperation or rupture was thought to be higher for patients with communication between the true and false lumina or with no thrombus formation in the false lumen [12]. Unfortunately, the majority of studies dealing with persistent false lumen perfusion after repaired type A dissection do not analyze the influence of operative technique on this potentially dangerous finding.
In the present series, a significant reduction of patent distal false channel was observed after open distal repair using GRF-glue when compared with the closed repair technique. In contrast, Barron et al., found that their incidence of persistent distal false lumen was exactly comparable with other series using various open techniques and that neither open repair, GRF-glue nor extension of the repair into the arch contributed to reduce the incidence of persistent distal false lumen [5]. Only few groups were able to demonstrate that surgical intervention reduces the incidence of patent distal false lumen [4] [13]. Antegrade reperfusion following circulatory arrest might improve immediate healing process of the glued aortic layers at the level of the distal anastomosis and also contribute to diminish distal false lumen perfusion.
The advantages of biologic GRF-glue are numerous and have been outlined in several previous reports [14]. The main advantages of glue are the reinforcement of the native aortic tissue and the closure of small tears at the level of the anastomosis with the vascular prosthesis.
The location of the intimal tear in the aortic arch has been considered to be a reason to extend surgery into the aortic arch by many authors [15] [16]. Looking at the results obtained in this series, we believe that repair of the proximal aortic arch by gluing the dissected layers and confection of the distal anastomosis with some extension in the concavity of the aortic arch, followed by antegrade reperfusion through the vascular prosthesis represent an valuable option. In our experience, obliteration of the intimal flap at least at the level of the aortic arch was obtained in more than 80% of the cases, as compared with an incidence of 43% persisting intimal flap in the arch following repair with Teflon felt only and 65% when the closed method was used. This might be due to the fact that re-entries are infrequently localized in the aortic arch, as compared with the proximal descending aorta. Therefore, only few re-interventions were needed on the aortic arch after open distal repair with GRF-glue. At the moment, we are not able to demonstrate any advantage of antegrade rewarming on early or late outcome. However, we strongly believe that this additional refinement might contribute to decrease the incidence of significant morphologic changes at the level of the aortic arch, since the cannula is advanced into the proximal descending aorta.
The incidence of redo-surgery in this series was similar to that reported in previous works [17]. Interestingly, all patients could be operated on a elective schedule (six of them only after the actual MR-scan) and there was no mortality in this small series of complex reoperations.
Magnetic resonance imaging has been recognized recently as the optimal method for follow-up of surgically treated type A acute aortic dissection [18] [19] [20]. In the chronic phase of the disease, sensitivity and specificity have been described as high as 96100%, compared with somewhat lower values for contrast enhanced computed tomography or echocardiography [21] [22]. MRI is superior to CT since it does not require injection of contrast medium or ionizing radiation, it allows multiplane scanning and demonstrates flowing blood. MRI provides excellent information about distal aneurysm formation, pattern of blood flow within the true and the false channels and allows in certain cases to distinguish aortic branch malperfusion.
Our current follow-up protocol includes a basic MRI examination before hospital discharge in every patient and then every 6 months: all patients are referred to our institutional consultation for thoracic aortic disease. Depending on the evolution of the disease in the remnant aorta, the interval between scans may be reduced to 3 months or extended to 1 year.
| Conclusions |
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| Footnotes |
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| Appendix A. Conference discussion |
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Dr Carrel: That's truly correct. This study was a retrospective study comparing three different techniques done during three different time periods. But actually since more than 5 years at my institution, only open distal repair is performed. The group of closed distal repair was the first group done between 1989 and 1990.
As I mentioned, in those 34 patients with open distal repair, some extension in the arch by gluing quite far away (distally) from the site of the anastomosis was performed in a majority and a classical Hemiarch repair was done in 10 of 34. So it probably means that with very good gluing and a limited extension of the anastomosis in the concavity of the arch, you might eliminate a majority of the problem, in the arch at least. But you still see something between 55 and 75% of false lumen perfusion at the level of the proximal segment of the descending aorta, since there you have also the first reentries.
Dr J. Bachet (Suresnes, France): There is, I think, a missing group in your experience, that is, the closed distal anastomosis with the GRF glue. It is indeed in fashion now to perform open anastomosis. But I wonder if this is compulsory in any patients and if we are not trading some complications to others. As a matter of fact, performing the open anastomosis means, in one way or another, to perform arch surgery. Indeed, it means that to protect the brain you have to go down in temperature, you have to make circulatory arrest, and by doing so you are threatening your patient with some possible neurologic trouble.
After more than 210 acute dissections with the GRF glue, I believe (and I know that Stephen Westaby totally disagrees with me) that open anastomosis is not compulsory at all. If the tear is on the ascending aorta, just put on a clamp and replace the ascending aorta after checking the arch.
On the other hand, what I believe is of most importance, is to reperfuse the patient antegradely through the prosthesis and not through the femoral artery when one resumes the cardiopulmonary bypass after the replacement of the aorta has been completed. Can you please comment on that?
Dr Carrel: Starting with the last question, I think this is one of the most important factors, because during the initial experience when we glued the distal anastomosis and reperfused retrogradely, we saw in some cases a subadventitial hematoma caused by a splitting of the fresh-glued layers, and I think that it doesn't make sense to redissect your fresh-glued anastomosis. So that is certainly one of the main issues to prevent any problems at the level of the distal anastomosis.
Concerning the second problem, I do not agree completely with gluing the dissection and closed repair. Usually now we do not clamp the aorta during cooling: there are many reasons for that. We had some experience where we had the impression that the repair was technically perfect but the patient didn't wake up like we were expecting, and probably the cross-clamping during the cooling period was responsible for this. In fact if you don't have any major reentry in the descending aorta or in the arch during retrograde perfusion, you might compromise the true or the false lumen by cross-clamping the cranial portion of the ascending aorta, since the major reentry for unproblematic perfusion might be the primary tear in the ascending aorta, clamping the aorta might really compromise perfusion of the supraaortic branches.
So now we first cool down and then open the aorta without cross-clamping the aorta and always perform the distal repair first and then reinstitute perfusion through the prosthesis, and most recently through the Anteflow (Vaskntek, Sulzer, Winterthur, CH) vascular prosthesis within the already sewn side arm of the prosthetic graft.
Dr A. Moulijn (Antwerp, Belgium): Some time ago we had a similar experience like yours: an acute retrograde dissection appeared after cannulation of the common femoral artery in a patient operated for an aneurysm of the ascending aorta.
However the patient survived, after this event in the following cases we changed towards the cannulation of the subclavian artery by using a 8 mm Dacron artery graft anastomosed end to side the subclavien artery who on his turn was connected with the arterial line of the CPB.
We found it to not be a very demanding procedure and successful in every case.
We think it is a tremendous way of perfusing this patient safely and antegradely.
Mr S. Westaby (Oxford, UK): You looked at all those groups. Was there an increase in operative mortality in the closed over the open patients?
Dr Carrel: Surprisingly, one colleague of our group had published early outcome 3 years before and the comparison of open versus closed repair showed a slightly superior mortality in the open group, a fact that would support the findings of Mr. Bachet. The worst outcome was interpretated as a result of more extensive reconstruction, probably. Presently the comparison is no more valuable because we always perform open repair and closed repair has been abandoned.
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