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May 2015    Download the Entire Issue (PDF) Available to the Public Vol. 30, No. 5   RSS Feed for Undercurrent Issues
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Heart Health in Older Divers

are stress tests and defibrillators really that helpful?

from the May, 2015 issue of Undercurrent   Subscribe Now

When subscriber Ted Doering (Jupiter, FL) spotted one of his fellow divers -- a chubby 65-year-old who said he had 400 dives under his belt but looked like he rarely exercised -- he sensed trouble. Doering, a pediatric oncologist, and his wife were on a May cruise that had stopped in the Galapagos, and had booked a two-tank dive. They got in a dive boat with the chubby diver, and the captain, who didn't speak English, took them offshore for the first dive. The divemaster had only two weeks' experience in the Galapagos and had no medical background. To make sure they had the right gear and had buoyancy, she wanted her divers to test their gear on the surface before descending. The chubby diver immediately jumped in, but shocked by the cold water, he tried to climb up the ladder. He couldn't do it unaided, and after a struggle, he fell back into the water, unconscious.

"The divemaster said, 'Oh my God, he's not breathing,' and the boat captain was also useless," Doering says. Doering got the diver on the boat and started pulmonary respiration but couldn't get a pulse. Within 10 minutes, the diver's pupils were dilated. The boat had oxygen but no automated external defibrillator (AED), an electronic device used to treat a person in cardiac arrest. The diver died due to a blocked blood flow in a coronary artery. "The man had no idea that he had heart disease," Doering says. "I asked his wife about his heart condition and she said, 'He never went to the doctor. He hadn't seen one in 20 years.'"

That Galapagos trip was six years ago, but Doering treated it as a wakeup call. When he returned home, he vowed to take a heart stress test every two years. "I was 65 years old (I'm 71 now), and I hadn't had one yet. The trip got me thinking, 'That dead diver hadn't had an EKG in years, and the dive boat didn't have an EKG, which could have helped to save his life.' These kinds of deaths need further evaluation, so that old folks like me can have a better idea of what we need to do to make our diving safe, or safer. Can Undercurrent do a story on whether older divers need routine stress tests, and what are the criteria for stress test abnormalities and high-risk indicators?"

In our research, we learned that there are no clear guidelines for whether older divers should have regular stress tests, and no mandates for dive boats to have AEDs onboard. In fact, the medical juries are still out on whether either of those options is helpful, as we'll explain.

The Concern over Stress Tests

According to statistics gathered by Divers Alert Network, one-third of all diving fatalities are associated with an acute cardiac event. In a recent study of DAN members, the incidence of diving-related deaths was 16 per 100,000 divers per year, and the deaths due to cardiac causes were nearly a third of that number, so five per 100,000 divers annually. The risk of cardiac-related death while diving is 10 times higher in divers over age 50, and the study of DAN members showed a continuous increase in risk with increasing age. The dead diver on Doering's Galapagos trip was far from uncommon -- diving, or simply immersion, can provoke disturbances of the heart's rhythm, which can thus result in sudden death, especially in older divers.

Petar DeNoble, vice president of mission for DAN, says his organization refers to the American Heart Association's guidelines when it comes to fitness for exercise, screening for cardiac risk factors and testing for specific conditions. On its website, DAN says older divers and those who have a family history of heart attacks, especially at an early age, should get the appropriate evaluations to detect early signs of coronary artery disease.

"An incident will likely happen while diving or on the surface after waiting for pickup. This means getting the patient to the AED will take some time."

For divers who've suffered heart attacks, DAN recommends a six- to 12-month hiatus from diving. Then they should have a thorough cardiovascular evaluation, including an exercise stress test, which requires a fairly brisk level of exercise, equal to progressively running faster until you reach a pace slightly faster than an eight-minute mile (for a very brief time period, that is). Performance at that level without symptoms or EKG changes indicates normal exercise tolerance, and a passing grade.

Alfred Bove, past president of the American College of Cardiology and professor emeritus at Temple University (as well as a diver), recommends that divers be able to swim continuously for 15 to 20 minutes to avoid a risky diving situation that may arise unpredictably. "This level of exercise can be tested on a treadmill with cardiac monitoring to be sure the diver is capable of this exercise level without showing evidence of cardiac problems like inadequate blood flow to the heart, abnormal heart rhythms or severe shortness of breath that would induce panic."

While Bove doesn't generally recommend routine exercise testing for screening in asymptomatic individuals, for older individuals doing sports requiring increased exercise levels, safety dictates that they have a stress test. He also says an assessment of cardiovascular risk factors, such as blood pressure, cholesterol levels and diabetes status should be calculated, and then intermediate- or high-risk individuals should have further testing to ensure diving is safe.

However, in March, the American College of Physicians published guidelines in the Annals of Internal Medicine stating that routine cardiac testing of adults without symptoms hasn't been shown to improve patient outcomes, and it can actually lead to potential harms. They say there is no evidence that stress tests or electrocardiograms have any advantages over routine risk assessment in asymptomatic people. All the tests commonly produce false positives that lead to further unnecessary, and costly, testing. However, DAN supports the American College of Physicians' new guidelines, even though divers predictably go under significant stress in water, and stress tests could determine if older divers' hearts can handle that stress. Says DeNoble, "We believe [the guidelines are] evidence-based and we follow them."

The Shocker about Defibrilators

Doering says the diver he tried to resuscitate in the Galapagos might well still be alive had there been an AED on the dive boat. "The average cost of one is $1,500, and every golf course and tennis court in Florida has an AED within two minutes of any player. This is common sense as well as a liability issue, and a case could be made for not having an AED on dive boats with seniors as a serious legal liability. This should be a DAN goal."

DeNoble says DAN sells AEDs and provides training for their use, "but we cannot mandate all operators to have it." Undercurrent published a story on AEDs, "A Shock to Divers' Hearts," in March 2012, and we found that while AEDs are common in U.S.-based dive boats, they becomes less common as a diver travels farther overseas. That's still the case, Bove says. "Most dive boats in the Caribbean carry AEDs on board, and many of the organized programs that serve U.S. divers have them, but I don't think there are any regulations that require it. In remote locations like the South Pacific, I don't think they would be found on many dive boats."

The need for AEDs is rare, and they may not work in standard dive conditions. DeNoble says older divers should keep in mind that application of AED within three to five minutes saves about 10 percent of those who suffer cardiac arrest outside of the hospital. "Our ability to predict who will suffer an arrest is quite weak and does not provide practical information," he says.

Peter Hughes, who these days runs the M/V Galapagos Sky, described the shortcomings of an AED in his operation. "Like all Galapagos liveaboards, we conduct 100 percent of our diving activities from small, inflatable pangas. There is no safe, secure, dry storage easily available aboard the pangas, so our AED is stored safely and under the watchful eye of our captain -- on the bridge of the liveaboard! An incident will likely happen while diving, or on the surface after waiting for pickup. This means getting the patient to the AED will take some time -- getting the diver aboard the panga, figuring out what to do with the other divers, transporting the diver to the mother ship and using the AED as required. The time lapse and moving the diver to the liveaboard takes time, and creates hardship for the patient. So the question about whether portable AEDs should be common on dive boats is not easy to answer with a simple yes or no."

Still, there's certainly no harm in having an AED stored on the dive boat, but because there's no regulation in any country to do so, DeNoble says the pressure for that to happen needs to come from us divers. "Customers need to regularly press the boat owner to invest in more safety in general, including having AEDs available. In the meantime, people with heart disease or with a high risk of sudden cardiac arrest may consider avoiding travel to remote areas."

-- Vanessa Richardson

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