Carotid duplex for syncope workup?

[I_love_UMKC]

Had a quick question for the experts out there. If you are working someone up for syncope, why are carotid duplex done? For example, if you have one sided stenosis, how often do you present with syncope rather than other manifestations? Does anyone have any articles (NEJM or other literature) that supports carotid duplex for work-up of syncope?

Specially, in the anterior circulation if you have one sided stenosis, how would you cause syncope? Are Duplex good source to look for posterior circulation stenosis/occlusions too?

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[danielmd06]

Had a quick question for the experts out there. If you are working someone up for syncope, why are carotid duplex done? For example, if you have one sided stenosis, how often do you present with syncope rather than other manifestations? Does anyone have any articles (NEJM or other literature) that supports carotid duplex for work-up of syncope?

Specially, in the anterior circulation if you have one sided stenosis, how would you cause syncope? Are Duplex good source to look for posterior circulation stenosis/occlusions too?

I am no expert on this, but I think I can help you out. Obviously, stroke doesn't present too often with syncope. You typically would be more concerned about seizure from a neurologic standpoint and would thus be interested in regular brain imaging and an EEG for these patients.

But yes, stroke is often tossed into the differential. Ideally, you want to investigate the posterior circulation because syncopal events and/or alterations in consciousness generally indicate brainstem territory via the basilar or vertebrals. Of course, bilateral anterior circulation events can do this, too (whether via azygous ACA or simply bilateral strokes). So an MRA or (better yet) CTA of the head/neck are the imaging modalities of choice (ie would give you a better picture of the posterior circulation than an ultrasound). A carotid duplex would be done if you couldn't get the CTA or MRA for whatever reason or deemed the administration of contrast to be too dangerous given the low suspicion for stroke in a particular case.

I don't know of any specific articles discussing duplex versus the other vascular imaging modalities for syncope, but in broad terms I dug up the following...

I found an article that at least touched on this topic here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2117584/

An article from Circulation (I love this journal) about the workup of syncope (neurologic workup doesn't appear until page 9): http://circ.ahajournals.org/content/113/2/316.full.pdf+html

An article from American Family Physician for the workup of syncope: http://www.aafp.org/afp/2005/1015/p1492.html

 

[typhoonegator]

A unilateral carotid lesion shouldn't cause syncope, although a severely stenosed or totally occluded carotid could make you much more sensitive to variations in BP due to the fact that your whole hemisphere has an increased MTT at baseline.

In many cases the story of a patient's "syncope" is not very clear, so there is a bit of CYA going on in many cases to make sure some sort of TIA or small stroke couldn't be causative of their event.

Also, albeit rare, a TIA from a carotid source could provoke a seizure leading to LOC. But if you really want to be this complete in your workup, you might want to get a brain biopsy for Kuru as well.

In reality, only severe bilateral carotid disease (or VBI, which the standard carotid studies will not evaluate for) should cause anything like true syncope. I've certainly seen cases present this way, but I'm sure it would be hard to justify getting carotid ultrasounds on everyone as a screening test for this rare eventuality.

Agree that CTA/MRA would be more helpful, particularly if there is anything that sounds like VBI in the history. Vert u/s would be OK, particularly if you find reversal of flow or severe dampening, but that still wouldn't tell you if there was a mid-basilar lesion.

 

[HarveyCushing]

A simplistic method that I was taught by one of my neuro attending to work up syncope was:

Pump (tachy/brady-dysrrhythmias, valvular, pump failure)
Pipes (dissections, subclavian steal, Takayasu's)
Fluid (hypovolemia, dehydration, anemia)
Tone (drugs that decrease tone, PD, amyloidosis, GBS, Sjorgen's)
Situation (Vasovagal, cough syncope, micturation syncope, valsalva, deconditioning)
Misc (3rd ventricular colloid cyst, SDH, hyperviscosity)

This list isn't meant to be all inclusive, but the majority will probably be pump, pipes, fluid or tone based. Depending on the HPI, you are most likely going to do a CTA/MRA anyways as daniel and typhoonegator mentioned. I'm not sure a carotid duplex would provide much to the workup. As with most pt workups (and especially with syncope) a good HPI + H&P is vital to determining the ddx and ordering tests that will help you determine the etiology rather than doing a shotgun method and ordering unnecessary tests. If you are out in a rural ED and don't have easy access to a CTA/MRA in the middle of the night, than the carotid duplex might be all you have to work with.

 

[neglect]

There seems to be an inverse correlation between skills/intelligence and the number of tests ordered for syncope.

If you know nothing, then looking at the ICA's or the neck/brain vasculature seems like a good idea. See the "light on stroke" thread. If you know something, then you know that syncope is not a presentation of a neurologic disease. All you need is a history to make vascular imaging useless in the vast, vast majority of cases. The confusion that arises is usually from institutional idiocies and weak over utilizing docs training the incurious.

Much harder to separate syncope out from seizure.

@ DanielMD: that was a review on stroke, not syncope. The circulation review is excellent. In other words, if this is not syncope but either seizure or stroke, then do that workup.

 

[neurologist]

There seems to be an inverse correlation between skills/intelligence and the number of tests ordered for syncope.

If you know something, then you know that syncope is not a presentation of a neurologic disease.

Weeeellllll . . . it could be in the picture for an autonomic neuropathy, which I guess you could argue is a neurologic disease . . ..

But, that being said, yeah, a carotid u/s still isn't gonna buy you much in that case.

All you need is a history to make vascular imaging useless in the vast, vast majority of cases.

History? What's that? How do I order one of those?

Much harder to separate syncope out from seizure.

Usually just when there is only the patient to give the history. When there's a witness to the event, I find it's usually pretty clearly one or the other.

 

[danielmd06]

@ DanielMD: that was a review on stroke, not syncope. The circulation review is excellent. In other words, if this is not syncope but either seizure or stroke, then do that workup.

Yep. I was trying to specifically find an article at least touching on the topic of CTA/MRA versus U/S and just couldn't find one on syncope. As posterior circulation stroke was the ostensible differential that imaging was being meant to rule out, I picked that one.

And yes, "absolument," I'm taking it for granted that this is for seizure or stroke...not plain old syncope.

 

[neglect]

History? What's that? How do I order one of those?

I'm warning you: I'm totally going to steal this one in order to make fun of people, OK?

Usually just when there is only the patient to give the history. When there's a witness to the event, I find it's usually pretty clearly one or the other.

Yeah, but I've encountered a bunch of people who just drop and have no memory of preceding events, and no witness. Then I actually do seizure workups (unless they were also getting lightheaded in separate spells).

 

[95439]

I remember the good ole days when I was a resident and we still had tilt table tests...

 

[ThomasHendricks]

I saw an interesting (to me) case of syncope the other day in the ED - where I am spending the month. Young guy who passed out at the bus stop after walking around in the heat all day, no apparent head trauma, no prodrome aside from nausea and lightheadedness, no pain anywhere currently and was not orthostatic at the time of exam. No medical problems he knows of.

One strange thing about being in the ED is that a nurse sees everyone for triage, and they put in whatever orders they think are necessary. So when I saw him, he had a CT head, EKG, and a BMP. CT was totally normal, pending a read, and BMP just looked like pre-renal with increased BUN/Cr ration. EKG was fine other than some LVH, which in this area is weird not to get. I present to my attending and think this is super easy dehydration. Attending agrees, but we order CBC to be complete, and give him a liter NS. While waiting on the CBC someone, no idea who, does a troponin on him as an i-stat, and it's up. Very strange, and this guy denies any pain or SOB or anything. We re-check it with the main lab, thinking it is false, get a CXR that is stone cold normal, and I leave for the night thinking this case is pretty cut and dry and I have stayed late anyhow and all my other patients are wrapped up.

I come in the next day and look up his results, and his next troponin came back further elevated, and CBC showed H/H of ~6/20. Asked the attending that was on overnight about it, and he said that the guy got irate over something and left refusing any other treatment.

So that was an interesting case, something I thought was pretty straight forward and ended up not really being what I thought. That has happened to me a lot this month.

 

[HarveyCushing]

I saw an interesting (to me) case of syncope the other day in the ED - where I am spending the month. Young guy who passed out at the bus stop after walking around in the heat all day, no apparent head trauma, no prodrome aside from nausea and lightheadedness, no pain anywhere currently and was not orthostatic at the time of exam. No medical problems he knows of.

One strange thing about being in the ED is that a nurse sees everyone for triage, and they put in whatever orders they think are necessary. So when I saw him, he had a CT head, EKG, and a BMP. CT was totally normal, pending a read, and BMP just looked like pre-renal with increased BUN/Cr ration. EKG was fine other than some LVH, which in this area is weird not to get. I present to my attending and think this is super easy dehydration. Attending agrees, but we order CBC to be complete, and give him a liter NS. While waiting on the CBC someone, no idea who, does a troponin on him as an i-stat, and it's up. Very strange, and this guy denies any pain or SOB or anything. We re-check it with the main lab, thinking it is false, get a CXR that is stone cold normal, and I leave for the night thinking this case is pretty cut and dry and I have stayed late anyhow and all my other patients are wrapped up.

I come in the next day and look up his results, and his next troponin came back further elevated, and CBC showed H/H of ~6/20. Asked the attending that was on overnight about it, and he said that the guy got irate over something and left refusing any other treatment.

So that was an interesting case, something I thought was pretty straight forward and ended up not really being what I thought. That has happened to me a lot this month.

That is why I love medicine and more specifically neurology. Will never know everything and will constantly learn. Good stuff