Frozen elephant trunk (FET) procedure

Complex lesions of the thoracic aorta are traditionally treated in two surgical steps with the elephant trunk technique. The frozen elephant trunk (FET) technique potentially allows treating in a single procedure by combining endovascular treatment with conventional surgery using a hybrid prosthesis. The E-vita Open Plus (Jotec GmbH, Hechingen, Germany) was the first commercially available hybrid graft. It combines surgical graft replacement of the aortic arch with stent-grafting of the descending thoracic aorta using a covered stent. More than 28,000 hybrid prostheses were implanted worldwide until 2014.

Credits: Shrestha et al. European Journal of Cardio-Thoracic Surgery 47 (2015) 759–769 doi:10.1093/ejcts/ezv085

Indications

  • Acute Stanford Type A aortic dissection
  • Post-dissection aneurysmal formation after type A repair
  • Acute Stanford Type B aortic dissection when primary TEVAR is not feasible or the risk of retrograde type A aortic dissection is high
  • Post-dissection aneurysmal formation after chronic type B aortic dissection
  • Thoracic aortic aneurysms
  • Penetrating atherosclerotic ulcers/intramural hematomas
  • Descending or thoracoabdominal aneurysms
  • Other pathologies such as penetrating aortic ulcers

Devices

Initially, home-made devices were used and thereafter companies developed multiple devices for FET without differences in clinical outcomes with regard to the device used:

  • Gianturco Z-stent (Cook®, Inc., Bloomington, USA).
  • Chavan-Haverich Prosthesis (Curative GmbH, Dresden, Germany).
  • E-Vita Open and E-Vita Open Plus® (Jotec® GmbH, Hechingen, Germany).
  • Cronus™ (MicroPort Medical Co., Ltd, Shanghai, China).
  • Thoraflex™ Hybrid Prosthesis (Vascutek®, Terumo®, Inchinnan, Scotland, UK).

E-vita Open Plus vs. Thoraflex

Two devices are widely used in Europe: E-Vita Open and E-Vita Open Plus® (Jotec® GmbH, Hechingen, Germany) and the Thoraflex™ Hybrid Prosthesis (Vascutek®, Terumo®, Inchinnan, Scotland, UK).

The choice is made according to the individual strategy required in the specific case. The main difference is the presence of a quadruple branched Dacron® part with the Vascutek® system compared with a straight Dacron® part with the Jotec® device. The quadruple branched design (Vascutek® prosthesis) enables a more proximal descending aortic anastomosis (between the left common carotid and the left subclavian arteries) since the left subclavian artery can be re-attached to the prosthesis using the most distal branch of the device.

Hypothermic circulatory arrest and cerebral protection strategy

The 2014 ESC guidelines on the diagnosis and treatment of aortic diseases recommend antegrade selective cerebral perfusion during the hypothermic circulatory arrest to reduce the risk of stroke during aortic arch surgery (Class IIa, Level B) with some degree of spinal cord blood supply by antegrade selective cerebral perfusion.

Early complications

  • need for postoperative re-exploration because of bleeding (2.5–30%)
  • stroke (2.5–20%)
  • spinal cord injury (SCI) that includes paraplegia and paraparesis (0–21%, higher than conventional elephant trunk)
  • acute kidney injury (AKI) requiring dialysis (4–34.8%)
  • laryngeal nerve palsy (0–12.8%)
  • In-hospital mortality (30 days—no discharge) (1.8–17.2%)
  • Average reported survival rates at 1, 3 and 5 years are 87, 78 and 68%, respectively

Neurological injury: paraplegia after conventional and frozen ET

  • spinal cord injury (SCI) is one of the most devastating complications after extensive thoracoabdominal aortic surgery, in particular after primary aortic arch repair
  • the incidence rate of permanent or transient ischaemic SCI after cET is 0.4-2.8% while in patients undergoing FET is significantly higher (as high as 21-24%)
  • Possible mechanisms to explain SCI in FET:
    • spinal cord ischaemic times longer than 60 min
    • unstable haemodynamics after cardiopulmonary bypass
    • distal circulatory arrest time longer than 40 min
    • level of the distal landing zone of the stent-graft: the more distally the FET is deployed, the higher the number of occluded intercostal arteries (> T7 = significantly higher incidence of SCI)
    • Thromboembolism to the spinal cord in the presence of severe atherosclerosis at the distal landing zone
    • Distal landing zone of T7 or lower + history of previous abdominal aortic aneurysm repair is the strongest predictor for SCI

References

  • Di Marco L, Pantaleo A, Leone A, Murana G, Di Bartolomeo R, Pacini D. The Frozen Elephant Trunk Technique: European Association for Cardio-Thoracic Surgery Position and Bologna Experience. Korean J Thorac Cardiovasc Surg. 2017;50(1):1-7. doi:10.5090/kjtcs.2017.50.1.1
  • Shrestha M, Bachet J, Bavaria J, Carrel TP, De Paulis R, Di Bartolomeo R et al. Current status and recommendations for use of the frozen elephant trunk technique: a position paper by the Vascular Domain of EACTS. Eur J Cardiothorac Surg 2015;47:759–69.
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