USE OF AORTIC ARCH BRANCHED GRAFT IN THE TREATMENT OF AORTIC ARCH ANEURYSM OR AORTIC DISSECTION

Teruhisa Kazui, M.D., Katsushi Yamashita, M.D., Noaki Washiyama, M.D., Hitoshi Terada, M.D., Abul Hasan Muhammad Bashar MBBS. First Department of Surgery, Hamamatsu University School of Medecine, Shizuoka, Japan.

Introduction

It has been recognized that an appropriate selection of both the cerebral protection method during aortic arch exclusion, and the operative technique of aortic arch reconstruction have substantial influence on the surgical outcome of aortic arch aneurysm. The methods of cerebral protection during aortic arch repair currently used are profound hypothermic circulatory arrest (HCA) with or without retrograde cerebral perfusion (RCP), and antegrade selective cerebral perfusion (SCP). Each of the cerebral protection methods has its own advantages and disadvantages, and is selected mainly on surgeon’s preference and experience as well as the expected duration of cerebral protection to be required, and the underlying disease. The operative technique used for aortic arch repair are the hemiarch or partial arch replacement and total arch replacement. As for the latter, there are two techniques; one is the en-bloc repair or island technique in which the arch vessels are reconstructed in an island fashion, and the other is the separated graft technique, which uses an aortic arch branched graft. We report below our clinical experience with the use of a new aortic arch branched graft (InterGard Aortic Arch, InterVascular, la Ciotat, France) (Fig. 1) in the treatment of aortic arch aneurysm with the aid of SCP.

Case History

A 73-year-old Japanese male was referred to our hospital for the surgical treatment of an enlarging aortic arch aneurysm. His thoracic aneurysm was incidentally discovered when he had been receiving treatment for pulmonary emphysema 4 years ago.

Digital substraction angiogram taken on admission showed remarkable enlargement of the thoracic aorta extending from the ascending to the mid descending aortic segment (Fig. 2).

CT scan revealed that the maximum diameter of the aneurysm was 7 cm (Fig. 3).

The operation was performed through a median sternotomy with an extension of the incision to the left supraclavicular region.

The details of the moderate hypothermic cardiopulmonary bypass (CPB) and SCP has been described previously (§ 1, 2). The patient was placed on the CPB by cannulating the ascending aorta and right atrium (Fig. 4).

The patient was then cooled down to a rectal temperature of 22° C, and systemic circulation was arrested. The ascending aorta and the aortic arch were incised.

Both innominate (IA) and left common carotid arteries (LCCA) were cannulated and perfused at a rate of 10ml/kg/min using a single roller pump separate from the systemic circulation. The left subclavian artery (LSA) was kept clamped during SCP.

The details of the total arch replacement using aortic arch branched graft has also been described previously (Fig. 5) (§ 2). The distal side of the arch graft with four limbs was sutured to the descending aorta 7 cm distal to the origin of the LSA (Fig. 5C).

The proximal arch graft was cross-clamped and antegrade systemic perfusion from the fourth graft limb was started (Fig. 5 D). The third limb was sutured to the LSA (Fig. 5 E), and rewarming by CPB was started. The proximal side of the arch graft was sutured to the ascending aorta and coronary circulation was started (Fig. 5 E). The 1 st and 2 nd limbs of the graft were anastomosed to the IA and LCCA respectively (Fig. 5 F, G). Once the extracorporeal circulation was terminated, the fourth graft limb used for an antegrade systemic perfusion was resected (Fig. 5 H).

Total pump time was 166 minutes, SCP time was 94 minutes, and systemic circulatory arrest time during open distal anastomosis was 55 minutes. The patient had an uneventful postoperative course.

Figure 5. Schema of the separated graft technique using aortic arch 4 branched graft

Discussion

Special care should be taken to avoid cerebral embolic events while treating aortic arch aneurysms (§ 3). As the arterial cannulation site for instituting CPB in case of atherosclerotic arch aneurysm, we now prefer the ascending aorta. Before cannulating the ascending aorta, epiaortic echo scanning is routinely performed to determine an atherosclerotic plaque-free site for the cannulation. If the ascending aorta is not suitable, our next site of choice is the right axillary artery.

Our previous experimental study indicated that SCP was the safest method for arch reconstruction procedures that require a cerebral protection time of 90 minutes (§ 4), and was physiologically superior to HCA and RCP because it supplies sufficient oxygenated blood to the brain in an antegrade fashion and therefore, can be used to protect the brain for an unlimited duration. Therefore, we have exclusively used SCP in the case of complicated total arch replacement for both atherosclerotic aneurysm and acute aortic dissection which usually require a brain protection time of approximately 60-90 minutes in our hand.

A suggested drawback of SCP is the risk of cerebral infarction due to dislodgment of debris during insertion of the perfusion cannula. However, this complication can be avoided by direct insertion of the cannula through the arteriectomy site. Another disadvantage of SCP is the risk associated with the cannulation of arch vessels that are involved in the dissection. However, in acute cases, the true lumen can be distinguished from the false lumen and direct cannulation of the true lumen from the arteriectomy site is not difficult.

As for aortic arch repair, total arch replacement could reduce the incidence of stroke because, in this technique, the ascending aorta and aortic arch, in which clots and atheroma are often present even in the absence of aneurysms, are completely resected. Moreover, the separated graft technique has several advantages when compared with the en-bloc repair technique; 1. Artherosclerotic lesions that frequently develop near the origin of the arch vessels are excluded, 2. Anastomosis can be performed at the intact site of the arch vessels where dissection has not extended, and 3. Bleeding at the site of the arch vessel anastomosis can be readily controlled.

The main role of the fourth branch attached to the middle portion of the aortic arch graft is that it provides the route for antegrade systemic perfusion after completion of distal graft anastomosis under circulatory arrest. This can prevent embolism that may otherwise occur due to retrograde perfusion through the femoral artery and organ malperfusion due to perfusion of the false lumen in the case of acute aortic dissection. There in turn can reduce the incidence of postoperative neurological dysfunction. The separated graft technique can also be safely applied to select cases of acute aortic dissection (§ 5).

A special characteristic of the InterGard Aortic Arch Branched Graft as compared with other commercially available grafts is the anatomically correct angle of its branches (approximately 60°) that allows an easy suturing to the host vessels and prevents kinking of the branches (Fig. 6) The in-hospital mortality of total arch replacement using aortic arch branched graft in the 120 patients operated on over the last four years at our institution was 2.5%, and postoperative temporary and permanent neurological dysfunctions were 2.5% and 2.5%, respectively.

In conclusion, the separated graft technique with the aid of SCP could reduce mortality and morbidity in operations for aortic arch aneurysms including acute dissection, and could improve late results.

References

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3.		Kazui T,Washiyama N,Bashar AHM,Terada H,Yamashita K,Takinami M. Improved results of atherosclerotic arch aneurysm operations with a refined technique. J Thorac Cardiovasc Surg 2001;121:491-499.
4.		Sakurada T,Kazui T,Tanaka H.Komatsu S.Comparative experimental study on cerebral protection during aortic arch reconstruction. Ann Thorac Surg 1996;61:1348-1354.
5.		Kazui T,Washiyama N,Bashar AHM,Terada H,Yamashita K,Takinami M, Tamiya Y.Extended total arch replacement for acute type A aortic dissection: Experience with seventy patients. J Thorac Cardiovasc Surg 2000;119:558-565.

(PN 20125/1)