Protecting the aortic root in Marfan Syndrome: a better operation with lower risks?
This week in London’s Royal Brompton Hospital, the surgeon John Pepper has successfully performed the fifth of a new operation, an Exostent for the Marfan aorta. This innovative procedure has the potential to change the life of the many people afflicted with this inherited connective tissue disorder, which is the basis of the Marfan syndrome. If left to nature, two thirds of these people die young, of aortic dissection. When we surgeons intervene to pre-empt this disaster, it is done by replacing the aortic root, usually along with the aortic valve. This is a risky undertaking and even if it goes perfectly, leaves the patient with all the ongoing risks of a surgically implanted cardiovascular device. These risks are (1) device failure (2) infection (in the form of lethal endocarditis), (3) arterial thromboembolism (with its potential for devastating stroke) and (4) anticoagulation. The last two are linked - one risk added to prevent the other; the whole exercise is a balance of rather serious risks. But there is now a better way. We can spare the aorta and the valve with an ingenious operation, devised by the engineer Tal Golesworthy. It was performed first on his own aorta (The Lancet 2004). Joe Treasure, a writer who divides his life between England and California, has borrowed Chaucer’s style and honoured the achievement in verse:
A surgeon came, and with him, for the aid
Of sufferers, brought the tackle of his trade,
His forceps, knife and lancet, and a saw
For opening the chest. His smock he wore,
For he that morning from the brink of death
Had pulled one such, and since had scarce drawn breath.
An engineer, whose working days were spent
On figuring and hairsbreadth measurement
And instruments of intricate design,
Having a notion that one might confine
The swelling artery with an armlet strong
But pliant, with the surgeon rode along.
A sufferer, lean-faced and long of limb,
Was in their company, with eyesight dim
For that his eye did flicker to and fro.
His father, a tall narrow man also,
Too soon, in spite of his physician’s art,
Had died with this affliction of the heart.
Joe Treasure adopts Chaucer’s device of a prologue in which he introduces the characters – a surgeon, an engineer and a “sufferer”. The characters in Canterbury Tales met at the Tabard Inn in Southwark. They are on a pilgrimage, a special kind of journey that brings a diverse group of people together in a common purpose. Theirs was to the shrine of Thomas à Becket in Canterbury; the Haj to Mecca is a larger scale contemporary example. As they converge on the place of pilgrimage the tales they tell are informed by the varied experiences of their lives. The story I tell here is of individuals brought together by a single objective: to find a solution better than total root replacement for people whose lives are threatened by aortic dilatation due to Marfan syndrome.
For twenty years I had been working with the problem of surgery for Marfan syndrome. I learned the Bentall operation in its original form; a porous vascular graft was preclotted and joined to a Star Edwards valve during surgery and the composite used to replace the aortic root and valve. My teacher and mentor Donald Ross took me through my first root replacement in 1982 and in 1984 I went, as a pilgrim, to learn from Denton Cooley and the late Stanley Crawford at the shrine of aortic surgery in Houston, Texas. I adopted new methods and welcomed the nonporous grafts and the factory produced composite grafts as they became available. The best I could add personally was to make my surgery as safe as possible and to time replacement to preserve the natural aorta and valve for as long as was safe. I worked with Steve Gallivan, a London University mathematician to time surgery, seeking the nadir of risk - but it was still, for all our calculations, an exercise in brinkmanship. We deferred surgery until the risk of waiting longer was greater than the risk of operating, as best we could estimate either.
Chaucer’s pilgrims met in 1387 close to where Guy’s Hospital stands (we still have a Tabard House within the campus) to set out on their journey to Canterbury. My journey with Tal Golesworthy began at St George’s Hospital, London, at the meeting of the Marfan Association in 2000. As the invited surgeon lecturer, I explained to the assembled “suffers” the rationale behind the annual echo measurement and the timing of root replacement. Tal Golesworthy, a member of the Marfan Association (and also an engineer in design and development) rose to question me. He quickly exposed my complete ignorance of CAD and RP (computer aided design and rapid prototyping, as I was later to learn). The concept is disarmingly simple. The digital output of MRI or CT imaging is used to sculpt, outside the body, an exact replica of the individual’s aorta. On that is made a jacket that fits it to the millimetre. And then John Pepper positions the external support around the aorta: the result as shown on before and after MRI scans are stunning.
The USA surgeon Francis Robicsek proposed wrapping aneurysms years ago. The wraps were fashioned on the operating table from the stiff and non compliant material of cut-up vascular grafts, but what we have now is a perfect engineered external support. We call it an Exostent. It is a much lower risk operation than root replacement, both at the time of surgery and in the long term. No tissue is lost or destroyed. No bridges are burnt in terms of subsequent surgery. Natural blood, endothelial and valve interfaces are preserved. Because it is a low risk pre-emptive operation it can be performed early and the sufferers are spared years of hospital visits for echo measurement, medical brinkmanship and the anticipatory anxiety that goes with it. Can Exostent really be that good? We cannot be sure after five cases and a maximum 18 months follow up but we certainly hope so. It is so much better than anything we could do before.