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Patient Evidence Summary
Doctor, I take warfarin for atrial fibrillation or a mechanical heart valve and have to stop it before a procedure. Do I need to inject myself with blood thinner medication after the procedure?
Not everyone who takes warfarin to prevent stroke due to atrial fibrillation or clotting of a mechanical heart valve needs to inject themselves with another blood thinner while waiting for warfarin to reach a protective level after surgery or an invasive medical procedure. Some people at the highest risk of stroke, such as people with more than one mechanical valve, or a mechanical heart valve and a history of stroke, were excluded from this study. Remember to always check with your doctor before stopping warfarin for a surgical or medical procedure.
Study highlights
People with atrial fibrillation or a mechanical heart valve who did not inject Fragmin® after their surgical or invasive medical procedure did not have more strokes, TIAs, clotted mechanical valves, heart attacks, DVTs, PEs, blood clots in arteries, or death due to these causes, compared to people who did inject Fragmin®.
Understanding the problem
People with atrial fibrillation or mechanical heart valves who need a surgical or invasive medical procedure, are often asked to stop taking warfarin 4-5 days before their procedure to reduce the risk of bleeding during and after the procedure. To reduce their risk of clotting while warfarin has been stopped, they may be advised by their doctor to inject themselves with another type of blood thinner for a few days before the procedure. The injectable blood thinner (for example, Fragmin®) doesn't stay in the blood as long as warfarin does and thus, can be stopped closer to the day of the procedure.
People usually start taking warfarin again, either on the same day as their procedure or 1-2 days later. Warfarin takes several days to reach a protective level after it is restarted. During that time, the risk of developing blood clots may be increased. To reduce this risk, people may be advised to restart injecting Fragmin®, while taking warfarin at the same time. Unlike warfarin, Fragmin® starts to work quickly after injection. This means that if Fragmin® is started too soon, it could cause more bleeding than just taking warfarin alone. Once bleeding occurs, blood thinners are often stopped for a much longer period of time which then puts people at higher risk of developing blood clots.
Researchers wanted to know if starting warfarin alone (without using Fragmin®) after a surgical or invasive medical procedure, would reduce the risk of bleeding without increasing the risk of strokes, TIAs, heart attack, blood clots in arteries, PEs, DVTs, or death due to these causes.
Who? This study included 1471 adults who had either a mechanical heart valve or atrial fibrillation or atrial flutter, and an additional risk factor for stroke. These people were on warfarin but discontinued it for a surgical or invasive medical procedure.
What? The study compared treatment with Fragmin® to placebo after the surgical or invasive medical procedure.
Fragmin® | vs | Placebo |
|---|---|---|
Warfarin stopped 5 days before the procedure. Fragmin® injections once a day for 2 to 3 days before, and several days after, the procedure. Warfarin restarted after the procedure and injections stopped once INR is within the protective range. | Warfarin stopped 5 days before the procedure. Fragmin® injections once a day for 2 to 3 days before the procedure. Placebo injections for several days after the procedure. (Placebo: A pill/needle/lotion containing an inactive substance that has no effect on the outcome.) Warfarin restarted after the procedure and placebo injections stopped once INR is within the protective range. |
Placebo plus warfarin vs. Fragmin® plus warfarin, after a surgical or invasive medical procedure
Outcomes at 90 days | Rate of events with Placebo plus warfarin | Rate of events with Fragmin® plus warfarin | Results |
|---|---|---|---|
Stroke, TIA, heart attack, blood clots in arteries, PE, DVT, or death due to these causes | 12 out of 1000 people | 10 out of 1000 people | No effect* |
| Major bleeding | 20 out of 1000 people | 13 out of 1000 people | No effect* |
*Although the rates for the 2 groups look different, the differences were not statistically significant—this means that the difference could be due to chance rather than due to the different treatments.
This Evidence Summary is based on the following article:
Kovacs MJ, Wells PS, Anderson DR, et al. Postoperative low molecular weight heparin bridging treatment for patients at high risk of arterial thromboembolism (PERIOP2): double blind randomised controlled trial. BMJ. 2021 Jun 9;373:n1205. doi: 10.1136/bmj.n1205. PubMed
Amin Zahrai is a MSc Clinical Epidemiology student and CanVECTOR trainee at the University of Ottawa. His research focuses on the prediction and treatment of VTEs using anticoagulants in adult patients with cancer and gastrointestinal diseases. He hopes to incorporate such clinical interests to provide curative treatments in his future trainings.
Lori-Ann Linkins, MD, MSc (Clin Epi), FRCPC
Dr. Linkins is an Associate Professor of Medicine (thrombosis) at McMaster University in Hamilton, Canada. She holds a Masters Degree in Health Research Methodology and is a Deputy Editor with the Health Information Research Unit, McMaster. She is Co-Editor of the ACP Journal Club and Co-lead on the CanVECTOR Knowledge Translation Platform.
Published: Tuesday, December 6, 2022
Please note that the information contained herein is not to be interpreted as an alternative to medical advice from a professional healthcare provider. If you have any questions about any medical matter, you should consult your professional healthcare providers, and should never delay seeking medical advice, disregard medical advice or discontinue medication based on information provided here.
, McMaster University