External aortic root support: NICE guidance.

Interventional Procedure Guidance 394 from NICE concerns external aortic root support. The work of NICE is rightly regarded world wide as setting the standard in healthcare evaluation, and is to be welcomed by all who desire their practice to be underpinned by evidence, in the best interests of patients. The guidance sets out the evidence to date, and the steps which ‘clinicians wishing to undertake external aortic root support in Marfan’s syndrome should take’ in terms of governance, patient information, audit and clinical review. The ‘external stent’ (the term used in the patients’ version ‘Understanding NICE guidance’) is an alternative to ‘conventional management’ which ‘involves preventive surgery to replace the ascending aorta with a prosthetic graft. The aortic valve may also be replaced, or the native valve reimplanted.’ The new procedure completely conserves the valve and blood/endothelial interface. Images of the patient’s own aorta are the source of data for computer aided design. A replica of the aorta is used as a former on which an external support is manufactured prior to surgery (figure 1). At operation, performed without the need to open the aorta or to use bypass or myocardial ischaemia, the pliable support is placed around the aorta from the aortoventricular junction, extending beyond the brachiocephalic artery. Appropriately sized openings are fashioned to allow for the exit of the coronary arteries. The technical details have been described along with postoperative MRI confirmation of unaltered morphology and function of the aortic valve (figure 2). Where does external aortic root support, and the guidance concerning it, fit into present practice? For people with known or suspected Marfan syndrome, echo imaging of the aortic root is routine. The aortic root in people with the Marfan phenotype has a characteristic morphology. Once that appearance is seen, current advice is that the patient should be monitored with interval echo measurements, with a view eventually to intervening with surgery. The purpose of surgery is to prevent the more common (type A) form of aortic dissection, prevalent in those with Marfan syndrome, in which a transverse intimal tear within the sinuses of Valsalva is associated with propagation of dissection in the aortic media. This has devastating consequences: the aorta may rupture into the pericardium; or the dissection may obstruct blood flow in one or a series of arterial branches resulting in cerebral, spinal cord, renal and/or other visceral ischaemia. Although familiar to cardiac specialists, dissection is easily missed in the emergency situation. Given its devastating consequences, there are compelling reasons to prevent it. Bentall, of the Hammersmith Hospital, is credited with performing the first operation replacing the aortic root and reconnecting the coronary arteries. Total root replacement was at the outset a high risk operation. During the 1980s, surgery was progressively made safer by refinement of technique and materials, the availability of factory made valved aortic graftsdand practice, practice, practice. The most reliable form of surgery included insertion of a mechanical valve, with subsequent lifelong anticoagulation, starting in the teens or twenties in many cases. Conserving the native aortic valve to avoid these hazards re-set the learning curve, and once more surgery became technically challenging. With more practice in the hands of highly skilled superspecialist surgeons, the perioperative risks have again become low. Re-operation for failure of the native valve is a legacy. 8 The trade-off of the hazards of anticoagulation and bleeding versus tissue valve failure, true of all aortic valve surgery, is a particular concern in patients with Marfan syndrome. Their inherited fibrillin deficiency remains: further lifesaving aortic surgery, and surgery on the spine and other parts of the body, may be called for during the hoped-for normal lifetime with the disease.