vascular medicine

Peter Henke, MD, on Optimal Anticoagulation Management After Lower Extremity Bypass Surgery

Amanda Balbi

 

 

In this podcast, Peter Henke, MD, talks about his recent session at the 2021 VEITHsymposium, during which he talked about the research supporting newer direct oral anticoagulation (DOAC) therapies, the future of research, and which patients should receive DOACs after lower extremity bypass surgery.

Additional Resource:

 

Peter Henke, MD, is a vascular surgeon and section head of vascular surgery at the University of Michigan in Ann Arbor.

 

TRANSCRIPT:

Amanda Balbi: Hello and welcome to another installment of Podcasts360—your go-to resource for medical news and clinical updates. I’m your moderator, Amanda Balbi with Consultant360.

Today we’re speaking with Dr Peter Henke, who is a vascular surgeon and section head of vascular surgery at the University of Michigan in Ann Arbor. He will be answering my questions about his recent session at the VEITHsymposium 2021. Let’s listen in.

Can you give us a brief overview of your session and any of the research you will be talking about?

Peter Henke: Yeah. So, I was assigned a topic looking at the optimal use of anticoagulants and/or antiplatelet therapy in patients who have had bypass grafts, either a vein undua type or a prosthetic type. I reviewed the most recent data that applies to those group of patients, as well as described a little bit of our statewide data from our quality collaborative that surveyed the use of DOACs, which are direct oral anticoagulants, in post-bypass patients that was published about a year and a half ago.

Amanda Balbi: Great so, can you give us a little bit more in depth about those patients who might benefit from anticoagulation?

Peter Henke: Yes. For anticoagulation, in the old days so to speak, it was basically the use of warfarin. That, while effective, has bleeding risks that are not insignificant. Most of our patients who require a bypass for limb salvage or for severe claudication are already on aspirin. That's pretty well accepted, and that's an effective and cost-effective medication.

The addition of warfarin in the past, again, was standard for patients who had an at-risk graft. I wouldn't say standard, but many practitioners used warfarin for patients who had an at-risk graft. What I mean by that is patients who may have 1 vessel run off as their only blood flow to their foot, patients who have had prior failed bypasses (the “salvage bypass”), and thirdly, patients who've had prosthetic bypasses that cross below the knee, so they go from the groin/femoral artery down to a tibial vessel or the popliteal artery. Those benefit from being on an anticoagulant such as warfarin.

Now, the more recent data with the use of anticoagulants is the revolution of the DOAcs, or the direct oral anticoagulants, and typically we use Factor 10-α inhibitors such as rivaroxaban, apixaban, edoxaban are the most common ones that are used. Those have generally the same efficacy as warfarin does for preventing pathologic clotting or thrombosis.

But they have a better safety profile. They're also easier for patients, because you don't have to undergo repeated blood draws. You don't have to worry quite as much about what you eat, diet-wise, with leafy vegetables or things that have a lot of vitamin K in them, which would inhibit the warfarin effect. So, it's surveying or putting up best opinion and evidence related to the use of the new oral anticoagulants or the DOACs with aspirin.

Along that same line, there's been a couple very large, well-done randomized controlled trials primarily, initially focused on patients who are at high cardiac risk, coronary heart disease. One of those was called the COMPASS trial, which was assessing the potential benefit of low-dose rivaroxaban with aspirin compared to just aspirin alone. It showed significant benefit with regards to major cardiac events, morbidity, and mortality. 

Then the little more relevant study to this topic, or this session, is the Voyager trial, which was again a multicenter, randomized controlled trial looking at rivaroxaban plus aspirin in patients who've had either an endovascular procedure, which I'm not talking about in this session, and the use of medications around endovascular procedures for PAD. Bypasses made up about 35% of that group, and again showed a benefit in terms of a composite endpoint with morbidity, mortality, and limb loss. Really it showed a decrease significantly in acute limb ischemia, so it seemed to protect from an unexpected or acute graft occlusions—is my read of that paper. 

We're going to go over that data in this session. Then, getting back a little bit to our statewide data that came out prior to the Voyager trial and the use of direct oral anticoagulants. At that point, the majority of vascular surgeons considered its use but didn’t use it. Again, this is about a year and a half ago, so that's the long and short of that aspect of this session with regards to anticoagulation in bypass patients.

Amanda Balbi: Interesting. So where do you think the research is going after all of this new data is coming out?

Peter Henke: I think refinements probably in 2 areas. One is, while the trials I just mentioned looked at aspirin plus a low-dose direct oral anticoagulant, can you use or is it better to use Plavix or a P2Y12 inhibitor, which can be prasugrel or ticagrelor, plus low-dose rivaroxaban. Is that more efficacious? Is it as safe? That's an unanswered question that I think may just have to be answered by using retrospective methods for patients who are put on them. Things such as using the VQI (Vascular Quality Initiative), which is the quality registry across the US that's sponsored by the SPS. So that's one main area.

Who are the patients who need the full-strength direct oral anticoagulant plus an antiplatelet vs just the low dose? Are there certain subgroups that are at a higher risk of clotting, even with low-dose and maybe benefit from that that higher dose of a direct oral anticoagulant, realizing that there are bleeding risks with that as well? So determining that balance too.

Thirdly, the cost of these agents isn’t insignificant, meaning that warfarin is cheap as a pill. Now the cost comes somewhat in the monitoring and the patient time commitment and potential bleeding risks. But the new direct oral anticoagulants are all, of course, still under patent, and they're not cheap. I mean, there are programs that pharmaceutical companies have to help patients pay, but getting that widely disseminated can be a challenge.

So, it's one of these things where these are good agents, but they're not free. They're not cheap, especially if you don't have insurance.

Amanda Balbi: Yeah absolutely. So, what are some of the other challenges that doctors might experience—physicians, specialists, or even general practitioners—might experience when prescribing anticoagulants or managing patients on anticoagulants?

Peter Henke: Certainly, the big aspect of these is the bleeding, clotting tight rope sometimes. Certain patients who are elderly, frail, maybe with renal failure, they are at higher risk of bleeding. So, using any agent that thins blood are higher risk for bleeding as well, but some of those patients have the higher clotting risk, too.

That's one major thing, I think, that needs to be balanced and can be a challenge. One of the upsides of the old-fashion anticoagulation and warfarin is it took a while for agent to be therapeutic as measured by the INR. And so, once you were there, you usually had a couple days of leeway. With these new agents, if they stopped taking them or miss doses, they may clot. We do see that sometimes, where patients who are dependent on these to keep a bypass open—or we think that's what helps keep it open—if they get sick or can't take their medicine or forget, especially with folks in this group generally are on multiple medications that they may lose that effect. 

They don't have as much of a therapeutic buffer with the new agents that you do with the older agents. I mean, you have some. It's not gone by 24 hours, but definitely within 2 days you're losing that effect. So, that's another challenge that I think anyone who prescribes these medications for any condition—atrial fibrillation, coronary heart disease, venous thromboembolism—that's one of the things that needs to be considered.

Amanda Balbi: Absolutely, and hopefully we'll get the research to investigate that a little bit more.

Peter Henke: Yeah, with the electronic health records that are so prevalent now, the databases are generally getting better and better with regard to being able to get granular data of medication use and pairing that with patient outcomes. I mean, it's not the gold standard of a randomized controlled trial, but those are so expensive that that's prohibitive in many cases.

Thinking 2 to 5 years in the future, I think this will be an increased efficiency as of computers. I think a lot of this will be able to be answered, without a separate trial. So, I think that's exciting.

Amanda Balbi: Yeah, for sure. What would you say, if nothing else, that your audience takes away from your session?

Peter Henke: With the data that I show and some of the summative data, it can be confusing for practitioners to know which antiplatelet therapy to use for these patients, which anticoagulant to potentially use, and/or which combination to use. So, I would hope that with what I present, especially on the summary slide, that I've tried to make it as clear as I can, based on some evidence that’s pretty strong and it's not; it's expert opinion. 

Having said all that, I think one take-home would be aspirin is still gold standard for our bypass patients whichever type of graft you use. Anytime you use prosthetic below-the-knee, you need to have some type of anticoagulant, probably full strength that's not low dose. I think with any vein graft bypass, aspirin plus a low-dose direct oral anticoagulant should confer benefit in terms of increasing the latency and potentially limb salvage. I think those are the 3 main things. Tf they take that away from it, it will be good.

Amanda Balbi: Is there anything else that you might want to add or any final thoughts?

Peter Henke: As surgeons, vascular medicine specialists, cardiologists, primary care, anyone who deals with elderly patients who are on potentially both antiplatelet and anticoagulant therapies—I think there's more recognition now that there are some real dangers for overprescribing these in patients who may not have a benefit.

Vascular surgeons, in particular, are generally more worried about thrombosis and bleeding long term, but our colleagues oftentimes see the downside of this, where the patient is admitted with a big gastrointestinal bleed or some other major thing. Keeping that in mind and going with, as the evidence comes out…I think one of the things from these trials is that lower-dose, safer DOAC is probably as effective as warfarin. That was not compared directly. It’s just my guess, but it's safer.

It's keeping that safety aspect in mind that sometimes we get so focused on saving the limb that we hit them hard with anticoagulants and antiplatelet therapies, but we don't often consider the downside of that. So, that's just a cautionary note as one additional thing.

Amanda Balbi: Thank you so much for answering my questions and speaking with me today.

Peter Henke: Thanks for having the interest. I love talking about this stuff.