DrSclafani answers some questions

[strawberry]

Dr. Sclafani,
...
I read with interest the remark about stents being able to withstand flexion 40,000-50,000 times, and tried to calculate how many times one might turn ones head, cough, chew, etc., in a day. I'm sure that it would be hundreds of times a day, at least. I don't see relying on a stent for decades.

I second this question as a very important one. What happens if a stent fractures? What, if anything, can be done to save the vein? Is replacement of the stented segment impossible? 40-50 thousand neck bendings is indeed not much, Johnson, I can't find the comment you're referring to, and what stents it is based on? Perhaps Dr. Scafani has a feeling about whether steel or nitinol are more durable.

This article is relevant to the question:

http://tinyurl.com/yc8rnfl

It looks at the effects of torsion (bending) and axial (lengthwise) compression on various types of nitinol stents. After a few million cycles (which is a bit more comparable to the remaining lifetime of a person with MS than 50,000) many of the commonly used types had fractured. It does not discuss torsion unfortunately. Together, bending, axial compression, pinching (e.g. by neighboring muscles), and torsion should be the most important forces acting in the neck. If anybody can find material on pinching and torsion in nitinol and steel stents, that would be complementary to the above article, and very useful information for those of us planning to go to Katowice.

Also, if some of the Stanford patients could let us know what types of stents were used in them (cheerleader mentions stents specifically shaped for jugular veins), that would be helpful.

[drsclafani]

he patch was obviously more risky because of the amount of stitches but better in the long term. He had the patch procedure and has done well. So is there a reason why some of these procedures aren't considered for veins. I'm wondering if the tissue is more delicate and stitches won't hold up. I know it is far more invasive but is there another reason that these ideas aren't considered?

Surgeons tell me that operating on veins does not have the success rate of surgery on the heart and the arteries. Perhaps the slower flow, the compressibility, and the compliance all act against these surgeries. My first life was as an interventional radiologist taking care of patients with injuries such as car accidents and gunshot wounds. We always looked pessimistically on vein injuries because the repairs did not stay open like arterial repairs.

[drsclafani]

DrSclafani, so could this suggest that the slow flow venous issue would not necessarily be linked to MS placques but to simply a seperate blood circulation problem - or as an interaction with MS neurologic issue, worsening certain MS symptoms?

Good question, but like most of this there are more good questions than answers. It could be that all of what you say is true

The pathology suggests that CCSVI is related to the development of inflammatory processes in the brain. Perhaps even the autoimmune process is initiated by the venous insufficiency too.

The venous outflow problem may worsen the situation because it may be the culprit behind the cerebral atrophy and diminished blood flow through the brain.

Many a career will be made answering these questions
I wish i were younger

[drsclafani]

My questions is about angiograms. Strictly in terms of acquiring a CCSVI diagnosis, is there any reason that going up through the arteries, and sending dye through the brain and back down the jugular veins, wouldn't be just as effective in finding problems as going up through the veins.

One definitely sees the jugular veins when you do a brain angiogram. However the dye is diluted and the view is not so clear as when desne contrast media is injected. the view in the venogram is much much sharper and more likely to see some of the subtle webs, septum and valves

There are other reasons NOT to try it through the arteriial tree

Going into the high pressure arteries has a greater risk of causing bleeding at the puncture. Also damage to the artery has a distinct but small risk of causing loss of blood flow down the leg.

Also injecting the dye through the arteries into the brain has the added risk of sending debris, arteriosclerotic plaque, blood clot or air up into the brain and that can lead to a transient ischemic attack (TIA) or stroke. We want to avoid that. A little bit of those things going out of the jugular vein is pretty safe.

So I applaud your though process and understanding of the flow dynamics, but stay out of my arteries, thank you very much.

[drsclafani]

I have a question about pressure gradients. I have been told that they are not meaningful if measured over large distances in veins. In particular, if there's a pressure gradient of, say, 3 mmHg over the length of such a collapse (say 3 cm), would you consider this reason to treat such an area?

I really do not think that minor pressure differences are going to make a real difference. After all, the arterial pressure exposed to the brain is more than 100 mm higher than the pressure in the veins. I think it is flow, not pressure related.

[drsclafani]

Genesis (Johnson & Johnson) is "made of stainless steel and has a closed-cell configuration". It seems to have a "superior crimpability, flexibility, and comparable radial strength to the Palmaz iliac stent, and superior crimpability and radial strength and comparable flexibility to the IS LD series."

First of all, deviice manufacturers are no different that pharm. they use whatever selling point they can think of. It is trials that make a difference in deciding this. As i said we are no where near deciding if any stent has superiority over any other in ccsvi.

I prefer nitinol to stanless steel. until endothelialization, those big magnets used in MRI can have effects on ferromagnetic devices. Nitinoll does not. You do get MRIs once and a while dont you.

Also crimpability is a negative anywhere that someone can exert force on them. bankng your neck in the wrong way against something might cause the stent to crimp.

[Cece]

You do get MRIs once and a while dont you.

That we do.

[drsclafani]

What about the use of filters in the Superior Vena Cava (normally employed for embolisms, and such) to "catch" any transient stents? And, would these filters catch fragments of any stents that might fracture?

My question about endothelialization was ultimately answered, but I still wonder if that means that the stent might have to be excised at some point, if the stent was causing untenable contra-indications (nerve pain, callousing, thrombosis, etc.). Is endothelialization a desired process in stenting?

Placing a filter would prevent a rouge stent from going to the heart, but you would end up with a bunch of junk in the superior vena cava and that could lead to clotting of the entire superior vena cava. I would not think that having superior vena caval syndrome on top of ccsvi would not be a pretty picture

stents have risks of thrombus formation until they are incorporated into the wall of the vein. that happens via endothelialization. Takikng a stent out if its endotheialized would not be a pretty picture. the vein would have to be excised.

Stents have a variety of patterns of the metal that make them more or less rigid and able to withstand motion stress. I have seen stents that fracture but continue to do their job.

[Zeureka]

I prefer nitinol to stanless steel. until endothelialization, those big magnets used in MRI can have effects on ferromagnetic devices. Nitinoll does not. You do get MRIs once and a while dont you.

So stainless steel potential interference with MRI - could there be any other issues for MRI?
Found that at airport security checkpoints should however not bring problems.

Guess this already gives part of the answer on interference issue:
http://content.onlinejacc.org/cgi/conte ... /23/2202-a
There have been numerous reports demonstrating almost complete loss of signal with stainless steel stents both ex vivo and in vivo when imaging with magnetic resonance, leading to significant image artefacts and obscuring of the vessel lumen (2–4). These artefacts are most problematic with steady state free precession (SSFP) and gadolinium angiography. Typical metallic stent artifact on MRI causes signal dropout due to magnetic susceptibility and radiofrequency shielding. Magnetic susceptibility scrambles the phases of individual spins leading to signal void, which is almost complete with stainless steel—particularly when compared with other alloys such as nitinol and platinum (2). Radiofrequency shielding refers to current induced in the stent wall that opposes the original magnetic field and leads to reduction in overall signal. This current increases with the resonance frequency, and thus shielding becomes more pronounced with high field strengths used in clinical imaging. Thus, MRI is not equipped to identify in-stent stenosis or aneurysm formation, and indeed lack of signal might give falsely reassuring appearances within the vessel lumen.

[magoo]

My stents are nitinol.

[Rosegirl]

Hi Dr Sclafani

If a scan shows one or more blockages, should a patient be satisfied that blockages must be removed just because blockages aren't ever a good thing? Or should we ask more questions and/or more specific symptom relief be a goal of the procedure?

My doctor is very open to the concept of a CCSVI/MS connection. But he wouldn't offer any prediction about if/how removing a blockage would affect my symptoms.

So is undergoing a procedure doing anything more than satisfying his intellectural curiosity?

[Hope66]

Re: Your statement, "Many a career will be made answering these questions. I wish i were younger."

It comforts me to know that you think that the CCSVI/MS link will become part of the future of MS diagnosis/treatment.

I personally would like to thank you for your involvement at TIMS and with CCSVI/MS in general. Kudos to you.

If you ever find yourself in or near London, Ontario, Canada, please do not hesitate to call on me.

Thank you (thank you thank you)
Hope66

[Vonna]

Hello,
This question comes from a friend who is having technical issues posting.

"Could you possibly pose a question to Dr. Sclafani concerning this hypothetical situation.

What if the IR encounters an IJV valve that has formed a pocket and is ballooning up restricting flow...what is the approach to correct the problem?"

Thanks!

[drsclafani]

What if the IR encounters an IJV valve that has formed a pocket and is ballooning up restricting flow...what is the approach to correct the problem?"

Why do i think this is a known lurker who wants to know how i will treat the second time around. Nice try!

This is an unusual finding that amazed dr zambni when i showed it to him. I wish i had an easy answer, we would not have to do a second procedure if i did!

i think that a stent makes the most sense right now since all the surgeons i offered this vein to, demured with thanks. it is kind of a valve that formed a pocket and that pocket balloons out on ivus to occlude the main lumen. I think we need to permanently compress the valve against the wall.

If i knew how to show pictures here, i would.

sorry madame lurker....we will find out in a few weeks

[drsclafani]

So is undergoing a procedure doing anything more than satisfying his intellectural curiosity?

If you are looking for certainty, you will be disappointed. This is an age of discovery and we just do not have sufficient data and trials to answer this.

we are in a time sort of reminiscent of the age of the automobile. The benefits and the dangers of cars were not apparent at the beginning. Lots of horse and buggies traveled the highways for quite some time. Who could predict 50,000 deaths a year on highways and who would have predicted the freedom they would bring.

Forget his curiosity. what about yours? You are in this together.