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Carotid Commentary complications techniques training ultrasound vascular lab

Mind the size of your patch or you’ll make an aneurysm

The patient is a man in his 80’s who presented with left sided weakness and dysarthria. Over 25 years before, he had undergone a carotid endarterectomy after a stroke, and had remained stroke free since. Per protocol, he received systemic thrombolysis and underwent CT angiography which revealed a right sided patch pseudoaneurysm.

Patch pseudoaneurysm with irregularities in lumenal wall of mural thrombus in right carotid bulb

This was seen dramatically on carotid duplex below.

Mural thrombus at carotid bifurcation compresses the right IJ vein

He stabilized and regained much of his function on the left arm and leg, while having a residual paresthesia of the left leg. His dysarthria resolved. His left carotid system was affected by a severe stenosis confirmed on MRA.

Duplex confirmed a tight stenosis of the left ICA with biphasic flows in the ECA.

MRI confirmed a right hemispheric infarction and operation was planned.

Right sided embolic stroke in MCA distribution

One of the great thing about working in a group ours is that we can bounce ideas off of each other and the consensus was for repair of the right carotid aneurysm. No mention was made of stent grafting which would have meant sacrificing the external carotid artery. I feel that the ECA provides some degree of long term insurance much like a good profunda femoral artery does for the common femoral. Shunting was considered a good idea because of the contralateral severe disease.

For me, the technical issue was the size mismatch between the common carotid artery which was around 8mm and the internal carotid which was about 4mm. Sizing for the CCA would leave a step down in lumen size that would result in increased velocities in the smaller ICA, potentially resulting in shear/turbulence/injury. Re-implanting the ECA on a 7mm PTFE graft would draw off some of that flow, but then you might end up with accumulation of mural thrombus on the graft beyond the ECA takeoff -the original problem to begin with. Looking on the shelf, I saw a 4-7mm tapered PTFE graft which was appropriately sized on both ends and would avoid the mentioned issues.

The aneurysm remained thankfully intact during its dissection

The aneurysm remained thankfully intact during its dissection, but to make sure I had control, the CCA at the base of the neck was controlled much as in a TCAR. The next step was in finding the ICA over the hump of the aneurysm and getting a vessel loop doubly around it. The ECA was easily found and controlled. I left the aneurysm alone to avoid perturbing the clot until I had the ICA clamped.

To perform the graft implantation while on shunt, I did the old trick of placing the shunt through the graft. The carotids were clamped and the aneurysm opened. The shunt was inserted into the ICA and CCA and shunt flow started. The ICA anastomosis was done first and the fit was perfect.

Stretch and unstretch, the 4mm end was tapered for the anastomosis on the ICA

The second anastomosis was end to side ECA to graft. The last anastomosis was the proximal to the CCA and it was completed loosely to allow the shunt to be removed then closed after flushing.

After completing the repair, the aneurysm was explored by my chief resident Dr. Shashank Sharma, who will continue his training in vascular surgery at Houston Methodist next year, and the patch was retrieved. It was sterile.

The patch, retrieved floating in the lateral part of the pseudoaneurysm, appears to have been cut from its original configuration

Back in the 90’s, when I was a resident at Roosevelt Hospital in New York,  I scrubbed in on a carotid operation. Dr. Eric Moore, among the first generation of general surgeons to train in a vascular surgery fellowship, was operating. The patient was billed as having a rare carotid aneurysm but in fact had a patch pseudoaneurysm. What was lost on me at the time as we dissected out the dilated bloated artery and replaced it with a graft was the complication was a consequence of the choices made at the carotid endarterectomy done years past. The aneurysm would not have been possible if a saphenous vein patch hadn’t been placed. After resecting the aneurysmal carotid artery, we cut it open. It was lined with the yellow and green mush outside a layer of hard brown laminate thrombus, a kind of AAA in miniature. Dr. Moore muttered, “we should write this up,” and I thought about it briefly, but couldn’t get excited. Now a quarter century later, I am interested because it is poorly studied. 

When you open an artery, you eventually have to close it (figure1).

A longitudinal arteriotomy

If the arteriotomy is in a transverse orientation, you can simply close it because all the sutures can be placed in the axis of flow. This is an important concept when sewing anastomoses -the sutures at the heel and toe need to be placed aligned with the longitudinal axis of the artery. This may shorten the artery but never narrows it. Any suture placed with a bite length of x with an angle θ away from the direction of flow narrows the artery by 2x(sine(θ)). The problem with primary closure, particularly of a small artery is that it narrows the vessel, decreasing the circumference by x, the length of the bite.

Primary closure narrows the artery…unless the adventitia stretches after endarterectomy.

You can sometimes get away with it because after endarterectomy, the adventitia may stretch and accomodate the bites without loss of circumference. To avoid this, since time immemorial, we have been taught that a patch should be applied.

Appropriately sized patch prevents narrowing, but also prevents excess widening

If the suture’s bite is 1mm on both patch and arterial wall, to have no effect on the artery in terms of narrowing or excessively widening the vesssel, the patch theoretically needs to be no wider than 2mm. For the purposes of handling, a wider patch is desired, so let’s say the ideal patch should about 5mm wide. Unfortunately, the precut carotid patches, both bovine pericardium and Dacron, are in the box pre-cut up to 8mm in width. A slim 5mm patch is available in Dacron but who sews in Dacron patches?

Is 8mm too wide? In some patients I believe it is.

Sometimes, the precut patch that is 8mm wide is too big, adding up to 50% to the circumference on a small artery, therefore 50% to the diameter, making the artery aneurysmal. If you see this, you should correct it.

When an 8mm wide patch is sewn on to an ICA at the carotid bifurcation which is 6mm wide, about 6mm is added to the circumference, which results in adding 2mm to the diameter, or 33%. 133% is close to the 150% which is the definition of an aneurysm. There are animal models of aortic aneurysm which involve sewing on a large bovine pericardial patch. While reading carotid ultrasounds, it is not uncommon to come across patient’s after carotid endarterectomy whose patched segments are lined with thrombus, the identifying marker of an aneurysm (picture below).

Patient post carotid endarterectomy over a decade ago now has clot lining a carotid patch aneurysm

The image above is a late presentation in a patient who is asymptomatic of stroke -am observing for now as I have just performed an eversion endarterectomy on the other side. Reading many ultrasounds, on occasion, I will see thrombus-like material accumulating on a patched artery early. And every once in a while, you come across an awkward, oversized patch such as this:

This patch is oversized but also ends where the left ICA makes a sharp turn, something you see more often on the left than on the right. This CT was taken after the patient had a postop TIA and may have formed emboli in the cul-de-sac created by the patch. DAPT was started.

I am not advocating primary closure. It is well established that primary closure of carotid arteries is associated with increased rates of stroke and restenosis in multiple studies and meta-analyses (ref 1), but there are surgeons who still close primarily.

Dr. Matthew Menard (ref 2) et alia found, along with the primary finding greenlighting bovine pericardial patch for the rest of us, that patch pseudoaneurysms are exceedingly rare. I do wonder if each of the ultrasounds were checked for the development of mural thrombus in the followup period. And what do you do about it?

Technically speaking, I advocate developing a sense of beauty when looking at the final product of an endarterectomy. I am not advocating trimming the patch all the time, but I frequently do, but rather to purposely tailor the repair well to recreate the sizes and dimensions that the body originally intended to have.

Patch angioplasty, using bovine pericardium, full width accommodated from about the time the Menard paper came out, taken on an iPhone 3.

Or you can do an eversion endarterectomy and avoid the problem entirely. 

Postop 1 month post eversion endarterectomy duplex above shows a normal ICA with very little evidence I was ever there

References

  1. Counsell C, Salinas R, Warlow C, Naylor R. Patch angioplasty versus primary closure for carotid endarterectomy. Cochrane Database Syst Rev. 2000;(2):CD000160. doi: 10.1002/14651858.CD000160. Update in: Cochrane Database Syst Rev. 2004;(2):CD000160. PMID: 10796309.
  2. Ho KJ, Nguyen LL, Menard MT. Intermediate-term outcome of carotid endarterectomy with bovine pericardial patch closure compared with Dacron patch and primary closure. J Vasc Surg. 2012 Mar;55(3):708-14. doi: 10.1016/j.jvs.2011.10.007. Epub 2012 Jan 4. PMID: 22226180.

By Docpark

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