A modified total arch replacement combined with a stented elephant trunk implantation for acute type A dissection under deep hypothermic circulatory arrest and selective antegrade cerebral perfusion

Acute type A dissection that conjointly involves the ascending aorta, aortic arch, and descending aorta remains a challenge for surgeons and results in high morbidity and mortality [1],[2]. Several surgical approaches have been introduced [3]-[8], but the optimal approach for patients with acute type A dissection involving the aortic arch is still open to discussion.

Recently in our institute, patients with acute type A dissection involving the aortic arch have undergone total replacement of the ascending aorta and aortic arch combined with transaortic stented elephant trunk implantation. Cardiopulmonary bypass (CPB) and selective antegrade cerebral perfusion (SACP) were achieved by cannulation of the right axillary artery, Deep hypothermic circulatory arrest (DHCA) was adopted. In this study, we report our experience with this procedure and evaluate the most efficacious management strategy for this lethal condition.

As one of the most catastrophic cardiovascular diseases, acute type A dissection has unfavorable clinical outcomes. Tsai et al. [1] reported that patients that undergo this procedure have an overall 32.5% in-hospital mortality rate and Weigang et al. [2] reported a 15.9% postoperative 30-day mortality rate in this patient population. Normally, emergency surgery is required and can significantly reduce mortality. In this study, we report our clinical experience with modified total arch replacement combined with stented elephant trunk implantation for acute type A aortic dissection.

Many procedures have been developed for the treatment of acute type A dissection. These include a conservative strategy with a simple replacement of the ascending aorta and hemiarch to a more aggressive one with a total aortic replacement. To improve late surgical outcomes, extended aortic replacement has been recommended for initial surgical treatment of acute type A dissection, and is not associated with higher morbidity and mortality [7],[10].

Spielvogel et al. [11],[12] have reported their experience with the use of a trifurcated graft and have shown that this procedure reduced the hypothermic circulatory arrest time to about 30 minutes. However, the graft used in the Spielvogel study was handmade, incorporating a different-diameter graft that increased the anastomotic stoma. It should be noted that most patients included in their study had an aneurysm and chronic dissection.

Since the introduction of the elephant trunk technique by Borst et al. [13] in 1983, several complications have been reported. Specifically, the soft graft located in the descending aorta was easy occluded and kinked, the recurrent laryngeal nerve was damaged, and it was very difficult to insert the soft graft into the true lumen [14]. In 1996, Kato et al. [3] described a partially stented graft, but this approach has also resulted in many complications that were reported in later studies [15]-[17]. Sun et al. [7] introduced their version of a modified elephant trunk procedure and showed that it had satisfactory clinical outcomes, making the Sun procedure (total arch replacement with stented elephant trunk implantation) a promising “standard” procedure for patients with acute type A dissection. Sun et al. [7] selectively perfused the brain via the right axillary artery, but the lower body was not perfused during DHCA. In their study, the rate of postoperative spinal cord injury was outstanding (2.1%), but they did not measure the low-body circulatory arrest time. Additionally, the strategy used for total arch replacement in the Sun et al. [7] study varied.

As a result of the problems stated above, we modified our surgical procedure using a four-branched graft concomitant with a stented elephant trunk, which handled better intraoperatively and produced medium term outcomes.

In terms of intraoperative handling, implantation of the stented elephant trunk in a bound and compressed state into the true lumen of a directly visible distal aorta is relatively straightforward. After the stented graft was implanted, the true lumen was expanded, substantiating the anastomosis to the distal end of prosthetic graft, thereby reducing the circulatory arrest time. The entire length of the elephant trunk was sustained by a stent, and the radial force exerted by the stented graft to the fragile aortic wall was uniform, avoiding the possible distortion of the prosthetic graft; in contrast to the segment of a prosthetic graft without a stent. The radial force was relatively low, minimizing the injury to the aortic wall. It is crucial that this procedure enlarges the true lumen, promotes thrombosis of the false lumen, and contributes to the shrinkage of the aorta. Thrombosis of the false lumen presented in most patients and enlargement of the true lumen and shrinkage of the entire aorta was seen in some patients.

Both CPB and SACP were performed using right axillary artery cannulation. Once the stented elephant trunk was successfully deployed and anastomosed with the distal end of the prosthetic graft, the perfusion of the lower body resumed. Song et al. [18] examined intermittent lower body perfusion with effective end-organ protection but they did not determine suitable flow and they performed the operative procedure under moderate hypothermia. In the ENREF_17 study, Luehr et al. [19] estimated a 120-minute ischemic tolerance of the spinal cord under deep hypothermia (20°C). The mean time of DHCA in our study was 18.5 ± 8.4 minutes, and the rate of spinal cord injury was 2.3% as a result of the administration of methylprednisolone during the surgical procedure, consistent with previous studies [7],[18]. Therefore, we believe that our DHCA strategy was safe. Moreover, the cannulation of the femoral artery may cause further damage and lower extremity complications. In our hospital, the femoral artery is used as an alternative approach in cases where the cannulation of the right axillary artery is difficult.

Since it was introduced in the late 20th century [20]-[22], profound hypothermia circulatory arrest and selective cerebral perfusion have provided favorable neuroprotection and clinical outcomes. As a result, they have been widely accepted as the standard strategy for transverse arch surgery. Clinicians are increasing body temperatures during this surgery to mitigate the systemic inflammatory response, avoid coagulation dysfunction and avoid the adverse effects associated with profound hypothermia and shortened CPB. The safest time for circulatory arrest of the spinal cord and end-organs (especially at a higher temperature) is still under debate. However, lower-body circulatory arrest is inevitably more dangerous when performed during a high body temperature. Leontyev et al. [23] recommended a more pronounced hypothermia, particularly when the operation was complex with a prolonged expected circulatory arrest time. Some investigators believe that profound hypothermia causes coagulation dysfunction and thereby, serious postoperative bleeding. However, the danger is possibly overestimated. According to a report by Milewski et al. [24], the rate of revision for bleeding was not higher in patients with profound hypothermia (3.8%) compared to those that had been placed in deep hypothermia (4.3%). However, Svensson et al. [25] reported a higher risk of coagulation dysfunction and end-organ failure associated with lower-body circulatory arrest under a higher temperature.

In this study, we modified the more common sequence of brachiocephalic artery anastomosis to the prosthetic graft such that anastomosis began with the left common carotid artery, and moved to the proximal aortic stump, innominate artery, and left subclavian artery. The SACP ceased when anastomosis to the left common carotid artery was completed, the flow was gradually returned to normal and rewarming began. Once anastomosis of the proximal aortic stump was complete, the myocardium was reperfused. In the present study, the duration of CPB and myocardium ischemia was relatively shortened: 186.3 ± 45.2 and 102.6 ± 28.1 minutes, respectively.

Despite our important observations, limited conclusions can be drawn from the present study because it was an observational and retrospective study and other surgical methods were not compared. The outcomes only represent the experience of a few skilled surgeons in a single center.

In this report, we describe a modified anastomotic procedure in which the total arch was replaced with a four-branched prosthetic graft combined with an implanted stented elephant trunk under deep hypothermic circulatory arrest and selective antegrade cerebral perfusion. In our center, this modified procedure produced satisfactory clinical outcomes for the patients with acute type A dissection and was recommended as a safe and effective alternative treatment.