Frozen elephant trunk in acute type A aortic dissection: surgical techniques and the extracorporeal circuit management

Abstract

Acute type A aortic dissection (ATAAD) is a challenging clinical condition with immediate and late complications. Frozen elephant trunk (FET) has been offered as a solution for it promises to address the late complications—false lumen thrombosis and aortic remodelling. Here, we describe the implantation of the FET in ATAAD with the surgical technique and extracorporeal circuit management. A 54-year-old male presented with retrograde type A aortic dissection with an entry point distal to the left subclavian artery. He underwent FET using Thoraflex™ hybrid vascular prosthesis (Vascutek, Inchinnan, Scotland). Three-month follow-up showed a complete obliteration of the false lumen in the descending thoracic aorta. FET in ATAAD is a valid option in the hands of experienced surgeons, while patient selection still remains the key in this surgery.

Introduction

Acute type A aortic dissection (ATAAD) still remains a challenge to the cardiac surgeons. Among the several controversies surrounding the management of ATAAD, the most discussed topic is the management of aortic arch. Frozen elephant trunk (FET) seems to offer a solution for the shortcomings of “limited-approach” repair in ATAAD—false lumen thrombosis and aortic remodelling. The short-term results seem promising, and the long-term results are emerging in support of FET in ATAAD. We report a case of FET in ATAAD, surgical techniques, and the extracorporeal circuit management. To our best of knowledge, this is the first report in India.

Case report

A 54-year-old male presented to a peripheral hospital with lower limb and abdominal pain. Ultrasound abdomen was performed which showed thrombus in the infrarenal abdominal aorta. A misdiagnosis of acute limb ischemia was made and he was planned for embolectomy. A computer tomography (CT) aortogram was performed later which revealed an ATAAD, and the patient was referred to our center. CT aortogram was reviewed. It was evident that the patient had a retrograde type A aortic dissection, with an entry point 1 cm distal to the left subclavian artery (LSA) (Fig. 1). Echocardiogram showed a dissection flap in the ascending aorta, trivial aortic regurgitation, and good left ventricular function. He was planned for emergency FET surgery.

Fig. 1.

Preoperative and postoperative CT aortogram. a Coronal section of the ascending aorta in arterial phase showing no entry point. Axial (b) and oblique (c) sections of the aortic arch showing the entry point with dye leakage into the false lumen (blue arrow). The left subclavian artery is marked in green arrow. b Postoperative image depicting the complete obliteration of the false lumen in the descending thoracic aorta

Extracorporeal circuit

Cardiopulmonary bypass was set up as shown in Fig. 2, with four venous lines (dual-stage right atrial cannula, two cardiotomies, one left ventricular vent) and two arterial pumps. The main arterial pump was connected to the right axillary artery/common carotid artery (A1) and a Y-line was added for future lower body perfusion (A2). A Y-line was taken from the recirculation tube, one of which was used for cardioplegia and another to a second arterial pump. This was connected to the future antegrade cerebral perfusion line (A3).

Fig. 2.

Extracorporeal circuit management: The sequence of clamping the arterial line at different stages of the operation is represented. “X” represents that the tubing is clamped. Red colour represents flow through the arterial line. Pink colour represents “no flow” through the arterial line

Surgical technique

Through the right femoral artery, a stiff guidewire (Lunderquist®, Cook Medicals) was stationed in the ascending aorta with the help of fluoroscopy and transesophageal echocardiogram after administration of 1 mg/kg of heparin. Care was taken that the guidewire was positioned in the true lumen. The proximal right axillary artery was involved in the dissection in this patient and hence, left common carotid artery (LCCA) was used for arterial inflow using a 7-mm vascular tube graft. The right atrium was used for venous drainage. The patient was cooled to 24 °C. Aortic cross-clamp was applied and myocardium was protected with cold Custodial® cardioplegia (histidine-tryptophan-ketoglutarate solution). During cooling, the proximal aorta was prepared with a strip of Teflon inside and outside the aorta. Additionally, a Teflon patch was also placed between the dissected layers. The LSA was ligated at the origin. At 24 °C, aortic cross-clamp was removed and bilateral selective antegrade cerebral perfusion was initiated at a flow rate of 10 to 15 ml/kg/min—arterial inflow in the LCCA (A1) and through the separate antegrade cannula into the innominate artery (A3). The aortic arch was transected at zone 2 (between LCCA and LSA). The three supra-aortic branch vessels are dissected and isolated individually. The true and false lumen of the distal aortic arch were approximated with four 4–0 pledgeted polypropylene sutures inside and a strip of Teflon outside the aorta. Using the stiff guidewire, the Thoraflex™ hybrid vascular prosthesis (Vascutek, Inchinnan, Scotland) was guided into the descending thoracic aorta and the graft was released. The collar of the prosthesis was sutured to the aorta in zone 2. After deairing, the lower body perfusion was re-established with the side branch in the hybrid prosthesis through A2. The LSA was reimplanted to the prosthesis. The hybrid prosthesis was then anastomosed to the proximal aorta and aortic cross-clamp was removed. The LCCA and innominate artery were anastomosed to the hybrid prosthesis. The patient was gradually weaned off bypass. He was extubated on postoperative day 1 and discharged on the 7th postoperative day. Follow-up CT aortogram at 3 months showed a completed obliteration of the false lumen in the thoracic aorta (Fig. 1).

Discussion

ATAAD is a disease known to have a calamitous impact on a patient’s life, if not intervened. A few surgeons advocate a “limited resection” approach to reduce operative and postoperative morbidity and mortality, while others, who advocate an aggressive approach, argue for a late freedom from reintervention due to distal aneurysm formation. In ATAAD, by addressing the tear in the ascending aorta, aortic arch, and the proximal descending thoracic aorta (DTA), the late downstream complications can be addressed. FET seems to address all the above three in a single sitting. The procedure induces positive aortic remodelling, eliminates residual dissection in the arch, improves perfusion of the true lumen, and reduces malperfusion, making it an attractive option in ATAAD. Furthermore, it reduces the late risk of aortic rupture and aneurysm formation. With FET in ATAAD, the exclusion of the false lumen is achieved in 90% of the patients and there is an 85% freedom from reintervention downstream at 8 years [1]. Long-term evidence is still needed to demonstrate a survival benefit in patients undergoing aggressive management of aortic arch in ATAAD. In chronic aortic dissection and degenerative aneurysm, FET is less curative, but provides a less complicated secondary intervention [1].

Recently, there is an increased usage of FET in ATAAD by many centers across the world. The overall in-hospital mortality is 10%, postoperative stroke is 4.8%, and spinal cord injury is 4.3% [2]. A recent analysis from the ARCH Registry database showed that FET for ATAAD does not appear to increase the risk of paraplegia in appropriately selected patients at experienced centers [3]. Though the results look encouraging, these are reports from high-volume aortic surgery centers. The major concern of the FET is the incidence of spinal cord ischemia, which is practically zero in patients undergoing limited resection for ATAAD. FET is a highly demanding and time-consuming surgery, with strategies to preserve organs and necessitates experience in aortic surgery.

The quality of the aorta in ATAAD is not the same as in degenerative aneurysm and chronic aortic dissection. The difficulties encountered in using FET in ATAAD include:

• (i)Quality of tissue in ATAAD is sub-optimum and is fragile.
• (ii)Tissue holding capacity of the acutely dissected aorta is weak.
• (iii)Longer periods of extracorporeal circulation, circulatory arrest, myocardial ischemia, and antegrade cerebral perfusion in an acutely ill patient.
• (iv)Steep learning curve.

Earlier, we have published our initial experience with FET in patients with chronic aortic dissection [4]. To the best of our knowledge, this is the first report of FET in ATAAD in our country. The senior author (BVV) has implanted the first FET in 2012. Since then, 23 patients have undergone FET procedures and we have been cautious in adopting FET to ATAAD. Though a strict algorithm cannot be formed on indication, based on our experience, the authors recommend FET to be performed by surgeons experienced in aortic surgery. We strongly discourage surgeons who have less experience with total arch replacement from using a FET in ATAAD. Further FET in ATAAD is not advisable in patients who are hemodynamically unstable or critically ill. FET is the treatment of choice in patients with retrograde type A aortic dissection patients.

It is well documented that ATAAD can present as myocardial infarction, acute abdomen, limb ischemia, or stroke. It has to be emphasized again that the physician should have a strong suspicion of ATAAD in patients presenting with these symptoms. A wrong diagnosis can absorb a lot of “golden hours”, which can even be fatal to the patients.

Conclusion

FET in ATAAD can be safely performed in our country on well-selected patients by experienced centers. FET has a steep learning curve, especially in ATAAD. The long-term results of the procedure need further large study.

Funding

Nil.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

Not applicable.

Statement of Human and Animal rights

Not applicable

Informed consent

Informed consent has been taken from the patient to publish this case report.