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Cardiovascular System - DVT

Dr Jules Eden, dive medicine specialist and founder of e-med, answers divers' questions - as published in Sport Diver magazine:
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Q - I've recently been diagnosed with something called Factor V Leiden after my sister had a blood clot (deep vein thrombosis, or DVT). The doctors told me it makes me more susceptible to DVT myself, but does it increase my risk of getting a bend?

A - Blood clotting is a complicated series of events involving a chain of “factors”, imaginatively referred to in Roman numerals from 1 to 12 (I – XII). So when you slice open your unprotected scalp on a sharp bit of wreck (as I have done on several occasions, I REALLY must wear a hood) this cascade is triggered, rather like someone pushing over the first domino in a line, and the end result is that the blood thickens up and stops hosing from the wound. Some people have faulty genes however that make them more (or sometimes less) likely to clot. The commonest is Factor V Leiden, named after the town in the Netherlands where it was discovered in 1994. It is a mutant gene now known to be carried by about 5% of white Europeans.

Now to my knowledge no diving related problem, bend or otherwise, has been directly attributed to Factor V Leiden, but there are a few issues to mention. You are more likely to develop a DVT on one of those long dehydrating plane flights to exotic dive locations, so get up and move around as much as possible and keep glugging the water. If you need to take anticoagulants for a clot then these can increase your risk of bleeding due to barotrauma, so I would be very cautious about diving if you ever get put on warfarin or one of the heparins. Tight-fitting dive gear and weight belts could conceivably reduce the flow of blood and make you more likely to clot at depth. You should plan your diving to try to minimise your risk of bubble formation and injury, as the clotting cascade could be triggered in response to either. So just be aware of all these factors and plan your diving accordingly.

Q - Basically, in summer 2003 my partner suffered a DVT and recovered. He became an instructor in late 2003. He last dived in February this year. We moved to Spain from the UK in April (very long drive) and in July following a few long evening shifts on his feet suffered another bout of thrombosis, this time superficial, with a vein on the outer part of the leg affected. He was treated with Clexane and rest until the end of August and an ultrasound in September showed that the leg is clear of thrombosis. He still has discomfort in the leg (still recovering/healing?) but is desperate to get back in the water in the near future. Is it likely he will be able to dive again as a job? His doctors here do not really understand what scuba is. He is due to have a blood test next week to see if there is an underlying cause as to why a man of 42 should have suffered two bouts of thrombosis. We have already turned down a great job in Africa for fear it was in a too remote location and too soon but would like some idea about how long it might be before he could safely dive again. Any advice would be much appreciated as finding anyone here that understands, is near on impossible!

A - 2 sets of clots in 2 different venous systems of the legs has got to be due to something. There is a chance it is bad luck, or the sheer standy-up-all-dayness of a shift, but before embarking on a career as an Instructor, it is imperative that he has the triple blood test to look for proneness to clotting problems. If it is negative, then cool, all he has to do is make sure he is always hydrated and all should be OK. If it is positive, then he may be put on regular daily aspirin or clopidogrel, its less acidic cousin. If this is the case, then there is a good likelihood he will be allowed to instruct. Abroad definitely, as medical rules are frankly slacker, but there could be issues in the UK. However for his own safety, I suggest that either way, it would be best to dive nitrox, and if doing repetitive dives, then set the comp for air tables. Why? Well in cases of DCI and also with microbubbles, they have been shown to cause a tiny clotting cascade around the surface of the bubble. If you are prone to clotting, then this can be enhanced. So the best way of making sure there’s no darn bubbles, it to 02 it up with the nitrox.

Word. As they say in my part of London.

Q - I have been given this email address by a PADI member to ask if you can help me to obtain medical clearance to enable me to take up scuba diving in spite of the fact my doctor will not give me clearance based on contacting one of the PADI consultants.
Basically I have had a DVT in each leg and take a low dosage of warfarin. My INR is maintained at 2-3.

I imagine there must be many people like me who are otherwise very fit and strong and still exercise regularly.

I did attend one session with PADI and this gave me greater incentive to see if somehow I can get my GP to reconsider proving I can give him evidence of other divers together with references who have suffered like I have and happen to take warfarin.

Hope you help - PLEASE!

A - I don't like stepping on other doctors toes or going against their decisions. However the fact is that you are allowed do dive if you are on warfarin. Your depth will be restricted to 20metres as this lowers the risk of the bends. The risk being that a hit could cause a bleed into the spine and paralysis. A shallow depth should prevent that.

But, and there's always a but, a DVT in both legs is pretty unlucky. I assume all is well now, but you must have one of those clotting disorders where you are prone to this illness and the warfarin might be a lifetime's treatment.

I suggest you see a dive doc face to face and make sure they are aware of the recent warfarin guidelines, and look forward to doing your course.

Q - I have heard about the sad death of a young girl from a clot in her legs and lungs after the long haul flight from Australia, and as I am flying to and from there next month to dive the Barrier Reef, I would like to know what I can do to prevent this and if diving has any effects of increasing the chances of these clots forming.

A - What happened to this girl was sadly preventable and also becoming more frequent as flights get longer and seats get more cramped. It even has a name now, being called "Economy Class Syndrome"
She suffered a blood clot in the deep venous system of her calf. This is called a deep venous thrombosis or DVT. If part of this clot dislodges, it travels up the venous system back to the heart, through the right side of the heart and to the lungs. This is what happens to cause death , as if a big enough piece of the clot gets to the lungs then it causes the blockage of the blood supply there. This is called a pulmonary embolus and it can be fatal.

Recent research has shown that up to 1 in 4 people that get a DVT have all been in a long haul flight in the last few weeks. You can see that this is an incredible statistic as a lot of the smaller DVTs go undiagnosed as they don't cause the classic symptoms of swelling of the calf with redness and pain in the same area. The reason that air travel can cause this problem is due to several factors, all which seem to coexist on these flights.

Firstly for a clot to form the blood needs to be very slow moving. This occurs in-flight as passengers sit in a cramped position with their knees bent. This can restrict the flow back of the blood and help a clot form. The next problem is with dehydration. It is said that you should drink a litre of fluid every 3 hours on a flight, but what is normally given out, i.e. alcohol can actually dehydrate you more as it makes you need to urinate more often. As you now have less circulating fluid volume the chances of clot formation are a lot higher.

Finally the swelling in your lower legs due to the position you sit in also causes to constrict the veins too. So these factors can cause a clot, but also being on the contraceptive pill, obesity and smoking too will all increase the risk.

What is recommended to stay alright in-flight is to keep your toes moving by regularly going for a walk up and down the aisle, and also keeping well hydrated. I would also suggest that anyone who is high risk, and by that I mean overweight, Pill taking smokers who have a family history of clots forming, take a dose of 75mg of aspirin before they fly, as this thins the blood enough to stop the DVT forming. However if you suffer from stomach ulceration or allergy to aspirin then there is a shot of a blood thinning agent called heparin available.

If anyone experiences tender calf swelling or chest pain and shortness of breath after a flight, then please seek medical attention immediately.

There is little evidence to suggest that diving would increase the chances of in-flight clot formation on your return home, but again as most divers seem to spend their 24 hours pre flight non-diving time in a state of post alcohol dehydration then it is doubly important to make sure you have enough fluids with you to drink during the flight back.

(other dive medical questions)



   


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