2 The procedure
2.1.1 Marfan syndrome is a genetic connective tissue disorder typically associated with long limbs, lens dislocation and aortic root dilatation.
2.1.2 In patients with Marfan syndrome the proximal aorta progressively dilates and is prone to dissection and rupture. Conventional management involves preventative surgery to replace the ascending aorta with a prosthetic graft. The aortic valve may also be replaced, or the native valve reimplanted.
2.2.1 The aim of external aortic root support in Marfan syndrome is to prevent enlargement and subsequent dissection or rupture, without the need for graft replacement and aortic valve surgery.
2.2.2 Magnetic resonance imaging (MRI) is used to map the precise anatomy of the patient's aorta. Computer-aided design is used to make a bespoke external polymer mesh support.
2.2.3 The mesh support is sutured into place around the aorta via a median sternotomy. Cardiopulmonary bypass is usually not needed.
Sections 2.3 and 2.4 describe efficacy and safety outcomes from the published literature that the Committee considered as part of the evidence about this procedure. For more detailed information on the evidence, see the overview, available at www.nice.org.uk/guidance/IP/885/overview
2.3.1 In a case series of 20 patients with a median follow-up of 20 months, post‑operative changes in aortic root diameter (assessed by MRI) were reported in 16 patients, ranging from a decrease of 6 mm to an increase of 3 mm, with the median change being a decrease in diameter of 1 mm.
2.3.2 The case series of 20 patients reported that cardiopulmonary bypass was used for 20 minutes only in the first patient treated with external aortic root support. Among the comparator group of 7 patients treated by aortic root replacement, the average bypass time was 149 minutes (range 139–243 minutes).
2.3.3 In the case series of 20 patients, all were alive and well (not otherwise described) at the time of the last follow-up (median 20 months).
2.3.4 The operation was completed as planned in 95% (19/20) of patients in the case series of 20 patients.
2.3.5 The case series of 20 patients compared operative characteristics with those of 7 patients treated by aortic root replacement with a prosthetic graft. The median operation times were 148 minutes (range 125–415 minutes) and 374 minutes (range 240–493 minutes) respectively.
2.3.6 The Specialist Advisers listed key efficacy outcomes as avoidance of cardiopulmonary bypass, reduced bleeding, prevention of ascending aortic rupture or dissection, and prevention of ascending aortic enlargement. They noted that there is uncertainty about whether the procedure will prevent aortic dissection in the long term, and whether it will prevent deterioration of the aortic valve.
2.4.1 In the case series of 20 patients, 1 had a post-operative cardiac arrest with ventricular fibrillation. The circulation was restored after removing the anterior closing suture on the aortic root support. The authors observed that the location of one of the coronary origins might have been misinterpreted on the MRI scan. The patient made a good recovery.
2.4.2 Among the first 10 patients in the case series of 20 patients, 2 had transient atrial fibrillation after the procedure.
2.4.3 The Specialist Advisers considered theoretical adverse events to include infection, haemorrhage, migration of the mesh support and possible constriction of the coronary arteries. They listed an additional theoretical possibility of thinning of the aortic wall inside the external support.
2.5.1 The Committee noted that this procedure has the potential for more rapid recovery than aortic replacement surgery, and that treatment may confer psychological benefits and improve quality of life. Commentary from several patients reported a positive effect on their emotional health and wellbeing, stating that the procedure had given them peace of mind.
2.5.2 However, the Committee noted that this is a preventative procedure for a condition with an unpredictable natural history, in terms of the progress and extent of aortic dilatation and the occurrence of aortic dissection. Uncertainties about these long-term outcomes underlie the recommendation for further research.