>First recognized in the 19th century, this autosomal dominant vascular disorder has a variety of clinical manifestations and a range of disease severity. Reported incidence rates range from 1:5000 – 1:8000, with higher rates seen in Curacao and Bonaire. Common manifestations of HHT include: nose bleeds (epistaxis), gastrointestinal bleeding and iron deficiency anemia secondary to bleeding. Vascular abnormalities / arterio-veneous malformations (AVMs), commonly occur in the pulmonary, hepatic and cerebral circulations – all of which demand an appreciation of the risks and benefits of screening, treatment and various activities that may put an individual at elevated risk of harm, should bleeding spontaneously occur. Disease expression increases with age, with over 90 percent of people developing clinical signs of HHT by age 40.
>As for evaluative work-up and screening, there are multiple tests that can be performed, but no universally accepted guidelines for particular tests or frequency of evaluations. That said, pulmonary and cerebral screening are of greatest importance and are aimed at reducing the incidence of stroke and brain abscess formation. Appropriate screening schedules and treatment are also case dependent, where those who manifest more severe disease will likely undergo more frequent or involved screening programs in an effort to minimize the potential impact of AVM formations.
>Uncontrolled bleeding, bleeding in the brain or lungs, stroke, loss of consciousness and seizure. These risks are especially important to consider for anyone who travels outside of areas proximate to emergency medical services. Due to the location of potential bleeding sites, general, thoracic or neurosurgical services may be necessary – specialties that usually require proximity to metropolitan areas.
>For those who have recently suffered blood loss, anemia (low levels of red blood cells) may suffer from fatigue and have reduced exercise capacity.
>Pulmonary AVMs may enable emboli (blood clots, bacteria, bubbles) to reach the brain. These can cause strokes or enable the development of brain abscesses. While rarely of clinical importance, pulmonary AVMs may prevent blood from getting adequate oxygenation, as alveoli (where gas exchange occurs in the lung) are bypassed. This can lead to reduced blood oxygen levels and prompt elevations in red blood cell production, a condition known as polycythemia. It should be noted that the majority of pulmonary AVM patients have no respiratory symptoms.
>Liver involvement is frequently present, though less commonly symptomatic. Signs of liver involvement include: liver enlargement, elevations in blood levels of liver enzymes (indicating liver cell death).
>Impact on Divers:
>The risk associated with HHT and diving results, not from the act of diving per se, but from the risk of sudden incapacitation while immersed or while traveling to remote locations. The decision to dive or not to dive, comes down to a very personal choice that is optimally arrived at after appropriate work-up and discussion with your physician; and weighed against the desire to dive, personal risk tolerance and the willingness to embark upon regular medical screenings. As this disease evolves with time, a diver must also accept that the day may come when the risk outweighs the benefits. Those with mild disease can likely dive and travel safely, with the knowledge that the probability of severe and sudden complications is low. Others with a known history of acute gastrointestinal, brain or lung bleeds should strongly consider refraining from scuba diving and remote travel; as such environments may limit timely access to medical services.
>While AVMs may exist throughout the body with this condition, the primary area of concern for divers is the lungs and brain. The pulmonary vasculature plays a key role in filtering bubbles conveyed from the right ventricle. Any breech in the vascular integrity, whether that is a patent foramen ovale (PFO) or arteriovenous malformation (AVM), can increase the chances of right-to-left shunts. This may enable bubbles to bypass the "pulmonary filter" and enter the arterial circulation and quickly pass to the brain. AVMs in the brain are of particular interest due to the possibility of bleeds, which may result in hemorrhagic strokes, seizures, or altered consciousness.
>We hope that this information helps. For further questions please call Divers Alert Network (919) 684-2948 or write to ask a medic: http://www.diversalertnetwork.org/myaccount/mscc/emailmedic.asp
>Nicholas Bird MD, MMM
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