Dr Gilhooly's discussion on valves
by Arlene Pellar Hubbard on Wednesday, September 7, 2011 at 11:59am
Dealing with Valves in CCSVI
Treatment of CCSVI has developed rapidly in the past 2 years with over 75 centres worldwide now offering differing forms of angioplasty procedures. Some centres are very research orientated with a steady flow of good quality research adding to the body of evidence supporting CCSVI as a real entity worthy of intervention.
The draft NICE guidelines in the UK has endorsed this approach and has encouraged further investigation of CCSVI in MS in the UK. We are pleased to have contributed to this process by direct conversations with the NICE committee and providing patient evidence of the effectiveness of this treatment.The excellent safety data from our clinic in Edinburgh is quoted in the draft guidance as well as the studies from Bulgaria and Poland.
It has become clear that one of the main issues with CCSVI is venous hypertension; raised pressure within the venous system of the brain. This increased pressure is transmitted to the deep veins in the white matter of the brain and in time affects the integrity of the tight junctions of the blood brain barrier.
Venous hypertension develops principally because of intraluminal abnormalities such as abnormal membranes, webs and most commonly abnormal jugular valves. A secondary effect of the decreased flow caused by an intraluminal abnormality is the development of collateral veins where the smaller veins enlarge due to increased blood flow. This in turn reduces further the flow in the jugular veins and can lead to stenosis or narrowing of the jugular veins. The presence of stenosis is usually an indicator of intraluminal abnormalities but venous hypertension can still exist in the absence of stenosis.
Treating the valves and other intraluminal abnormalities is therefore a central issue in the treatment of CCSVI and one that all the treatment centres in the world are dealing with. A balance has to be struck however, between aggressively treating the valves with high pressure balloons to reduce venous hypertension, and the possibility of vein damage. Excessive pressure could cause scarring and possibly further venous problems.
We recently discussed this issue with some of the world's leading experts on CCSVI.
Dr Salvatore Sclafani from New York pointed out that the veins are totally dependent on the venous blood for their nutrients and therefore this flow should not be disrupted for any significant period of time. Overenthusiastic and aggressive use of balloon catheters to disrupt valves could be damaging to the veins in the long term if the oxygen supply is reduced by the very procedure which is aimed at restoring normal flow. Current practice in the UK is similar to other centres where the valves and other intraluminal obstructions are treated with a combination of balloons, cutting wires, cutting balloons and particularly double balloons.
Dr Ivo Petrov in Bulgaria has performed over 1300 CCSVI procedures and was closely associated with the development of CCSVI in the UK. His practice is similar to that in the UK when dealing with valves but feels that although current treatment options are bringing good results, that further technical advancements will continue to improve the procedure.
The use of stents in the neck veins has been one solution to this problem but it has become clear that this approach is associated with increased complications. Professor Simka in Katowice has reported that the use of stents in his unit has dropped from 50% of patients to only 5%.
Professor Paulo Zamboni has obviously given this area much thought and has filed a patent for a device called a valvulotome. He feels this will be the most effective way of dealing with abnormal valves without damaging the vessel wall but on further questioning it became clear that there is no suitable valvulotomes available at present which are the right size for use in the jugular veins. This type of device is designed to permanently damage the valves without damaging the surrounding veins. It has been used in cardiology to remove the valves of the saphenous veins used in cardiac grafting.
There has been much discussion about the use of valvulotomes between some of the world's leading endovascular CCSVI surgeons including Professor Paulo Zamboni, Mr Donald Reid and Mr Ted Diethrich of Arizona. The current devices are designed to damage normal valves where the cusps are in the expected positions. In CCSVI we face the problem of abnormal valve cusps which will require a different design. Another consideration is the use of these devices in the neck veins could increase the risks in what is a very safe intervention. The anatomy of the jugular veins is such that the left jugular has a marked twist immediately after the valve, which could increase the risk of vein damage with the use of a valvulotome. The right jugular is usually straight which would make this form of treatment potentially less hazardous. Given the nature of the venous system where the drainage is shared bilaterally in the venous sinuses, it begged the question, would treatment of only the right jugular produce a reduction in venous hypertension? We sought the opinion of a Professor of flow mechanics who did extensive calculations on flow and pressure before concluding that he thought that it would improve venous hypertension.
The valves in the jugular veins are not essential with over 20% of the population having no valves in these veins. It is thought that permanent disruption of the valves using balloons alone is not possible at present and that over aggressive high pressure ballooning may risk venous damage.
The future of CCSVI treatment may well involve the development of a new device such as a valvulotome which can safely disrupt the jugular valves and so reduce venous hypertension over a long period of time. We are working with our International colleagues over the development of this.
In the meantime, the encouragement of new research by NICE brings the prospect of angioplasty treatment on the NHS closer to reality. We would encourage all our patients to comment on the current draft guidance from NICE before the end of the public consultation period on 21st September 2011. You can see these on http://guidance.nice.org.uk/IP/891/DraftGuidance