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Interact CardioVasc Thorac Surg 2009;9:562-564. doi:10.1510/icvts.2009.207985 © 2009 European Association of Cardio-Thoracic Surgery
Total aortic arch stenting – hemodynamical impact of carotid artery perfusionDepartment of Cardiovascular Surgery, University Hospital CHUV, Rue du Bugnon 46, CH-1011 Lausanne, Switzerland Received 7 April 2009; received in revised form 20 May 2009; accepted 25 May 2009
*Corresponding author. Tel.: +41 276038507; fax: +41 276034669 (after the 30.05.2009 fax: +41 213142278).
The aim of this experimental study is to evaluate the feasibility and the outcome of total endovascular stent implantation in the aortic arch. Indications for this operation-technique would be acute or chronic dissection of the aortic arch (non-A–non-B dissection) or type B dissection with retrograde extension. Four pigs were canulated via the distal abdominal aorta and a retrograde placement of a Djumbodis® arch stent (4–9 cm) was controlled by using intravascular ultrasound and intracardiac ultrasound by the inferior cava vein and under radioscopic control. Cerebral perfusion, by using a flow meter placed on one prepared carotid artery, were controlled before, immediate post-procedural (<1 min), and in the early follow-up after aortic arch stent implantation. During the implantation process, especially during balloon inflation and deflation, mean carotid perfusion decreases slightly. A reactive increase of carotid perfusion after stent placements indicates transitory cerebral hypo-perfusion. Non-covered aortic arch stent implantation is technically feasible and could be a potential treatment option in otherwise inoperable arch dissections. The time required for balloon inflation and deflation causes an important risk of cerebral ischemia. The latter can be reduced by transaxillary perfusion.
Key Words: Aortic arch dissection; Total endovascular procedures; Non-covered aortic arch stent; Cerebral perfusion
Endovascular approaches for vascular pathologies of the thoracic aorta are nowadays standard procedures. In the last years, even the aortic arch became an endovascular treatment target. Avoiding open surgical repair, by using a total endovascular approach for complex aortic arch pathologies, seems to be an elegant method. This technique redundantizes cardiopulmonary bypass, deep hypothermia and circulatory arrest and could, therefore, probably reduce morbidity and mortality [1–4]. The aim of this experimental study is to evaluate the feasibility of total endovascular, non-covered stent deployment in the aortic arch and its specific impact to cerebral perfusion.
All procedures in this study were realized in accordance with current ethic guidelines. Four pigs were canulated via the distal abdominal aorta. Localisation of the aortic arch and retrograde placement of a Djumbodis® stent (4–9 cm) were controlled, by using intravascular (IVUS Boston Scientific), intracardiac ultrasound (AcuNav Siemens) and under radioscopic control. Cerebral perfusion, via a flow meter placed on one prepared carotid artery, was measured before, immediate post-procedural (<1 min) and in early follow-up after stent deployment. Trans-apical stent application via the left ventricle was realised post mortem in two other pigs. Finally, stent positioning was evaluated at necropsy of all pigs (Fig. 1a).
During balloon inflation (mean 50±8.7 s, range 40–55 s) – deflation time (mean 70±13.2 s, range 55–80 s), the carotid perfusion decreases slightly. The following reactive increase of carotid perfusion (blood flow before 353± 285 ml/min, range 150–680 ml/min, after stent deployment 885±120 ml/min, range 800–970 ml/min) indicates transitory cerebral hypo-perfusion (Table 1). One pig died due to hemorrhagic shock from bleeding of abdominal aortic access. A trans-apical approach via the left ventricle for the aortic arch is feasible and seems to be easier in the animal model. The deployment of two (from six) implanted devices was not correct. We observed a kinking of the stent and subsequent intimae lesion of the proximal right brachiocephalic trunk (Fig. 1b) and an incomplete stent deployment.
In the past two decades endovascular surgery has played an important role in the treatment of acute, chronic diseases and redo surgery of the great thoracic vessels, with satisfactory results [1, 5]. Today, also pathologies of the aortic arch will be treated surgically by less invasive techniques. Hybrid antegrade repair, so-called ‘Frozen elephant trunk technique’ is one endovascular application form to implant endoprothesis in aortic arch pathologies [6, 7]. Using the Djumbodis® stent for this technique is an alternative and results are available [8–10]. Transposition of supra-aortic vessels to create sufficient ‘proximal landing zones’ and covered endovascular stent implantation of the distal aortic arch is a treatment option in aneurysmal malformations and type B dissections [2, 11]. Complete endovascular arch covering, after de-branching of supra-aortic vessels, has already been successfully performed [2, 11, 12]. However, this still remains a complex technique, with suture lines in atherosclerotic vessels, anastomosis of the ascending aorta, extracorporeal circulation and consequentially, an elevated risk for complications (bleeding, neurological damage). Advantages of endovascular surgery may only partially be used. A total endovascular treatment of the aortic arch could be the answer to the above-mentioned problems. In this experimental study, we implanted the ‘Djumbodis® stent’ in the aortic arch. The device consists of a non-covered stent, fixed on a trans-luminal balloon catheter, therefore, resulting in the main advantages:
Potential indications could be the total endovascular treatment of non-A non-B dissections or high type B dissections. Clinically applied and established endovascular techniques for aortic arch dissections are still complex procedures and probably inappropriate in emergency situations. A simple endovascular technique remains necessary, avoiding open surgical interventions and, therefore, reducing morbidity and mortality in otherwise inoperable patients. Stent positioning can be controlled satisfactorily. Technical problems consist of, besides creating an available design of a self-adapting device (problems of kinking, insufficient arch covering), in stent expansion. Balloon inflation interrupts cerebral blood flow and thereby inflation–deflation time becomes an important parameter to determine the feasibility of the procedure. Pre- and post-procedural carotid blood flow showed a reactive increase of cerebral perfusion, probably post-cerebral ischemia. In two pigs we found insufficient stent deployment. Kinking and subsequent intimae lesion of the proximal right brachiocephalic trunk (Fig. 1b) and an incomplete deployment of another stent were probably due to an inappropriate choice of the animal model. The smaller ascending aorta and the arch create an obvious size mismatch. The narrow angle between the ascending and descending aorta prevents, that a segmented stent form follows the curve of the arch in pigs easily. Therefore, result limitations in comparison to a clinical application in adult humans. Selection of an adequate animal model and further preclinical studies are mandatory. The design of non-covered stents must be improved to receive an optimal adaptation to the aortic arch, respecting the outflow of the supra-aortic vessels. Furthermore, the feasibility of this total endovascular technique depends on the balloon inflation and deflation time. Basic concept to collimate the false to the right lumen in dissections of the aortic arch would be a stent application under pressure. Reduction of stent deployment time should be a target of future development of applicable, pressurising, non-covered aortic arch stents.
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Abstract
1. Introduction