Editor’s note: These letters are in response to Lennard Zinn’s recent columns focused on the risks of riding while taking blood thinners. Any advice or recommendations included in these reader letters are not endorsed by VeloNews or Pocket Outdoor Media. Please consult your physician if you have any questions or concerns about your health or the use of blood thinners.

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Dear Lennard,
My friend suffered a catastrophic brain bleed following a training ride. No crash.

He was on Warfarin following a DVT. He has not worked or ridden since.

I think it’s worth mentioning that an impact injury may not be the only danger of training/riding while on blood thinners: the cardiovascular stress we place our bodies under could be an issue.

Neither the doctors nor my friend made the connection at the time, so thank you for bringing this, and other health issues, to a wider audience.
— James

Dear Lennard,
I recently came across your article and wanted to add my two cents. By coincidence, a friend who has had several DVTs and competes regularly in triathlons posed this same question to me (I am an emergency physician and toxicologist). He has been on warfarin for several years, and all his bike training is indoors. Prior to a race, he would discontinue warfarin and bridge up to the day of competition and after with enoxaparin (Lovenox). His hematologist has recommended he switch to one of the newer drugs (Eliquis- apixaban or Xarelto- rivaroxaban).

He had some hesitation, and I agreed with his concerns. Although there is no one right answer here, and everyone needs to come to their own decision, my concerns revolve around the availability of this antidote. When it was approved last year, availability initially was limited to those hospitals that had participated in the approval process. It appears that availability is more widespread now. However, it is still limited as you can see by the product locator map. Also, even as it becomes more readily available, this product is crazy expensive, and some smaller hospitals may elect not to stock an expensive and seldom-used product like this. This is also true of the reversal agent for dabigatran (Pradaxa).

In comparison, the products available to reverse warfarin (Coumadin), such as vitamin K, fresh frozen plasma, and 4-factor protein complex concentrate, are all much more readily available (and inexpensive).

Consider the Lake Placid Triathlon this summer. According to the product locator map, the nearest hospitals (currently) with andexanet alfa are Syracuse, New York or Rutland, Vermont, both a considerable distance. Considering that many races are in more remote or rural locations, timely access to one of these newer antidotes for these newer anticoagulants may be more limited.
In considering what type of anticoagulation one chooses, these factors should be considered.
— Mike

Dear Lennard,
Just read your extensive article about reader experience with blood thinners, in particular, the first letter from Kenneth. I too had a cryptogenic stroke (actually a TIA, not a full stroke) back in 1989 when I was 25. That is very rare in people my age back then and I went through a lot of workups, but no cause was found. I do have some mitral valve prolapse, but the multiple cardiologists who examined me didn’t think that was the cause. I’ve been on 325mg aspirin (enteric coated) since then, with no ill effects (other than a little more bleeding when cut). Nothing like the side effects from the heavy-duty anticoagulants mentioned in your article.

Spring forward about 20 years. I developed mild hypertension when I was 40 and ended up going to a cardiologist after my PCP thought it was a good idea to prescribe a diuretic to a competitive cyclist (hint: lack of sodium sucks in a hot road race!). I mentioned my TIA history to the cardiologist, and he asked if I had ever been diagnosed with a PFO (patent foramen ovale), a condition found in about 25 percent of the population where the atrial shunt in the womb doesn’t fully close, allowing some blood (and clot) leakage over to the wrong side. Turns out that the first scientific paper linking a PFO with cryptogenic stroke came out about the same time I had my TIA. I went in for a transesophogeal ultrasound and sure enough, I had a PFO. No change in my aspirin regimen, though, though the cardiologist did offer to switch me over to Plavix.

Long story short, I haven’t had a TIA repeat. I don’t know whether that’s due to the aspirin or just luck. I do take a higher aspirin dose than usual since colon cancer runs in my family.
— Brett

Dear Lennard,
Thanks for this very timely and educational article. I was put on a three-month prescription of Xarelto three weeks ago, and I made the decision to pause from any bike riding and skiing. Using a risk matrix for evaluation, the risk of getting hurt doing these activities may be very low, but the risk for the possible effects from an injury is very high. This is an informed decision that everyone needs to make for themselves, but three months on a stationary bike is worth the peace of mind.
— Edward

Dear Lennard,
I have been on Eliquis for three years since I had a DVT followed by a pulmonary embolism.

From reading all the letters regarding blood thinners, there are a few things that come to mind.

  1. Work with a hematologist who works with athletes. They understand the desires of athletes to keep competing and have strategies for working around this. For example, there is a professional hockey goalie who is on blood thinners. He and his hematologist understand that certain blood thinners wash out of the system in 12 hours, so 12 hours before the game, he stops his blood thinners, and right after the game (or practice he takes his blood thinner). It lowers his chance of a bleed out on the ice to nil.
  2. Every year they are developing new and better blood thinners, my father has been taking Coumadin for 30 years until he asked his general practitioner if there is a better drug. You need to be your own advocate and learn everything about your specific condition. If your spouse’s eyes do not glaze over when you start talking about it, you do not know enough.
  3. Take your medicine; only 20 percent of people on blood thinners are still taking their medicine 18 months after having been prescribed, and blood clots are one of the leading causes of death worldwide.

I am racing Leadville this summer; my hematologist and I have worked on timing and dosage of my blood thinner so that I will be able to train and ride every up (and down) as fast as I can.

Keep the rubber side down and take your blood thinners like a religion.
— Sam Osborne

Dear Lennard,
I think it’s probably best for cyclists to just take Warfarin/Coumadin, and if you crash, always have like a small 1 oz. vial of dissolved Vitamin K concentrate that you swig, and your blood will clot. So, if you crash, just drink the Vitamin K vial. You can also inject Vitamin K via a needle, but it has to go intravenously, not sub-Q or IM (intramuscularly).

Also, for all cyclists who did blood transfusions (a.k.a. blood doping), all those transfused bags of blood were loaded with anticoagulants (likely heparin or EDTA). There were no exceptions to this.

So, basically, Lance and lots of top guys raced the Tour de France and major races while loaded on blood thinners; that would be wild if it turns out blood doping actually served as a prophylaxis to a lot of riders getting DVT! A lot of those Operacion Puerto guys definitely crashed; it would be interesting to know if they knew to take a reversing agent (i.e. protamine sulfate for heparin) to help their blood clot in the event they crashed.

I hear a lot of cyclists worried about getting blood clots while flying, but pretty much all airlines keep the pressure in their cabin at around 7,400 feet or so (11 to 12psi compared to 14.7 psi at sea level). Airbus 320 is the highest at around 8,000 feet. A Boeing 777 and pretty much all the Boeing fleet aircraft peg their cabin altitude at 7,420 feet if memory serves me correct from my simulator time. The new Boeing aircraft like the Dreamliner (787) pressurize to 6,000 feet which is basically Boulder, Colorado. Aircraft manufacturers and airlines like to keep it as high as possible because it extends the service life of the pressurized bulkhead from succumbing to metal fatigue cycles (just like aluminum bike frames). The new airliners constructed of carbon fiber composites (like the 787, A350 and the next-gen 777x slated for release in 2019) don’t have to worry about metal fatigue so they can keep it at 6,000 feet. Any lower than 6,000 feet, and it’s too dangerous of a pressure differential with the outside air pressure at cruise altitude in the event of a catastrophic decompression. The new aircraft like the 787 Dreamliner will be far worse for passengers if they ever have any kind of sudden depressurization event like what happened to that Southwest flight where an engine exploded and sent a fan blade and metal parts through the window that killed that woman.

So, for most classic Boeing passenger aircraft (7,420 feet) that’s basically a bit better than living in Aspen, Colorado, and only 2,000 feet ‘worse’ than Boulder. Is Tejay van Garderen or Lance worried about getting DVT when they watch Netflix [in Colorado] and don’t get up from the sofa for a few hours? How about sleeping for 8 to 10 hours?

I think when flying, it’s best to keep your legs elevated on the footrest or ottoman thing if you’re lucky enough to fly first class. Or at least to recline as much as possible to make it easier for blood in your legs to be pumped back up to your heart. I would think compression socks make the chances of getting DVT worse, not better. Cabin temperature is also probably way too cold for athletes. Warm is better for preventing clots; cold is worse.

If you live in Colorado, the longest domestic flight you will ever be on maxes out at four hours, and most connections will be less than three hours. So, a transcontinental plane flight is really like watching a movie or football game on TV while living in Aspen. I dunno; do the people in Aspen have a higher incidence of chronic DVT than everywhere else in the country?

Flying to Europe will be seven hours or so at Aspen altitude, albeit sitting in a chair being worse for DVT in the legs than laying down sleeping.

I can tell you this much: A lot of the DVT cases with women are caused by their use of birth control. And the risk is exacerbated by flying and being an athlete. I really think a lot of women cyclists that are getting DVT are in fact on birth control. I actually can name several female cyclists who have had DVT that I know for a fact were on birth control. And in one case, I had warned her prior to going on it, and within 2 months of going on it, she wound up in the emergency room because of a blood clot! The acute incident happened right after a flight from Philadelphia to San Francisco.

So, birth control is a massive DVT risk for women, and they are probably the highest-risk category. Worse for female athletes of course because of their low blood pressure and low heart rate like you said.
— Phil

Dear Lennard,
I noticed a number of the people responding said they limit their training to riding just a trainer. I have a spin bike I use. A few years ago, when I sat up at the end of a session, my seatpost broke off, and I fell backwards, hitting my head on a cabinet. Lucky I wasn’t on blood thinners yet. And I’ve tripped and fallen hard a few times hiking also. So, nothing is without risk.
— Bill

Dear Lennard,
I, too, had a DVT and pulmonary embolus. I am taking Warfarin at the low end of the therapeutic range. Two other suggestions that are not mentioned …

  1. I wear compression socks (or calf sleeves) on any ride over an hour. There are many stylish brands.
  2. Hydration is more important than ever, and I force myself to hydrate.

Interesting problem, but certainly not a game stopper for cyclists.
— David

Dear David,
Having just read “Good to Go,” I feel compelled to put up a red flag about the statement “hydration is more important than ever, and I force myself to hydrate.” While your particular case may have extra hydration requirements, I believe that, in general, the entire idea of drinking more than one’s body’s thirst response indicates is a poor one.

It is quite clear that over-hydrating is more of an issue in many athletic events than is dehydration. As Christie Aschwanden says in “Good to Go,” “There’s never been a case of a runner dying of dehydration on a marathon course, but since 1993, at least five marathoners have died from hyponatremia they developed during a race” (footnoted study is from Noakes and Speedy, entitled, “Case Proven: Exercise Associated Hyponatraemia”). All of us who started our athletic career since the 1967 Orange Bowl, in which the Florida Gators’ victory over Georgia Tech on a hot day was attributed to the drink dubbed “Gatorade” that a group of University of Florida physicians had developed for its football team, have been subject to urgings about hydrating according to formulas and not to just listening to our bodies for when (and what) to drink.

― Lennard