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Health & Diving
The Heart & Diving

The Heart & Diving

Antiplatelets and Anticoagulants

Antiplatelets and anticoagulants are two classes of drugs — popularly known as "blood thinners" — that reduce the risk of clot formation and thus the risk of deep vein thrombosis, pulmonary embolism, heart attack and stroke. They may also be prescribed for individuals who have been diagnosed with atrial fibrillation or for those who have had heart-valve surgery or who have received a stent, an implanted pacemaker or an implanted defibrillator. (See other sections for detailed descriptions of these conditions.)

Clots form when blood cells known as platelets stick together, and then proteins in the blood bind them together into a solid mass. Clotting is a normal function that limits and stops bleeding when a blood vessel is injured. However, if a clot grows out of control or starts to travel within the circulatory system, it then poses a danger. Clots may get lodged in a pulmonary artery and cause a pulmonary embolism; in the arteries of the heart and cause a heart attack; or in the vessels of the brain and cause a stroke. All of these events can be life-threatening.


Antiplatelets and anticoagulants keep blood from clotting as quickly or as effectively as usual by preventing the platelets from adhering to one another and by preventing the clotting proteins from binding together. They can even help to break up clots that have already formed.

Antiplatelets — such as aspirin and clopidogrel (also known by the brand name Plavix) — work by preventing the platelets from adhering to one another.

Anticoagulants — such as heparin and warfarin (Coumadin) — inhibit the action of the clotting proteins and thus slow down the chemical reactions that lead to the formation of a clot. There were also several new anticoagulants approved between 2010 and 2012, including rivaroxaban (Xarelto), dabigatran (Pradaxa) and apixaban (Eliquis).

The major side effect of all antiplatelets and anticoagulants is excessive bleeding. Those taking such drugs — especially at too high a dosage — may bleed or bruise easily or may experience bleeding that does not stop as quickly as usual.

Special Caution Regarding Warfarin

Individuals who take warfarin (Coumadin) are generally advised to avoid any activities that may cause abrasions, bruising or cuts — such as contact sports. They are also urged to exercise caution while brushing their teeth and shaving. Even such trivial injuries as insect bites may cause complications in anyone taking warfarin.

There are additional risks involving warfarin particular to diving. Most significantly, there is an appreciable chance of serious injury in any diving environment, despite one's best efforts to mitigate the risk. Cuts and bruises are unavoidable, for example. And in anyone taking warfarin, a decompression injury or difficulty equalizing ear pressure could cause bleeding in the ears or the spinal cord that would otherwise not occur.

In addition, both travel and any resulting dietary disruption can interfere with the action of warfarin in dangerous ways. Furthermore, the health-care capabilities in many popular dive destinations may not be up to providing the care that would be required in case of an adverse event.

For all these reasons, anyone taking warfarin is generally advised not to dive. Nevertheless, many people who take warfarin are able to dive without major complications. The keys to safe diving while using warfarin are strict adherence to monthly blood tests and regular surveillance by a physician. With good control of blood-thinning, the risk of a bleeding complication is quite low.

According to Dr. Alfred Bove, a dive-medicine specialist, "For divers, the most important question is whether the condition that requires the use of Coumadin or Plavix prohibits diving. In many cases, the illness is over, or chronic but well adjusted, and does not interfere with safe recreational diving. Safe diving with Coumadin or Plavix depends on the absence of illness that would limit diving, careful control of clotting time, avoiding ear or sinus squeeze, and a thorough education on drugs and foods which cause changes in the effects of Coumadin. There are many divers using Coumadin and Plavix safely, but a special effort must be made to understand how to avoid problems of excess or not enough anticoagulation."
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