Can a coronary calcium scan improve the prediction of heart attacks in older divers?

In the July 2015 issue of Undercurrent, an article titled “A better heart-check tool than a stress test?” discusses the possible benefits of a coronary calcium scan for older divers to reduce the risk of experiencing a heart attack while diving.1 This article is a follow-up to a May 2015 Undercurrent report about an overweight 65-year-old diver who died shortly into his dive while on a dive trip.2 That article, which considered preventive options such as a stress test, also presented views from Dr. Alfred Bove and DAN’s Dr. Petar Denoble and Dr. James Chimiak, who agreed with the American College of Physicians (ACP) guidelines that recommend a graded and individualized approach to preventive testing and diagnostics.

Another physician suggests in the July 2015 article, however, that older divers should have a coronary calcium scan, which he claims may provide information that will help them avoid a heart attack on their dive trips. Many walk-in clinics offer the test at a low price. “A coronary calcium scan can tell you years before a positive stress test that you are headed in that direction [of significant coronary disease] so that you can do some kind of intervention,” he said. While the statement has merit, it may be misleading in this context.


Medical Examination of Diving Fatalities Symposium 2014

03A39050On June 18, 2014 in collaboration with the Undersea Hyperbaric Medical Society, Divers Alert Network sponsored the Medical Examination of Diving Fatalities Symposium. The talks covered specifics of autopsy in scuba fatalities, field investigation of diving accidents, the complexity of rebreather accidents investigation, integration of various aspects of an investigation into final analysis and principles of the epidemiological approach.

Sudden Cardiac Death (SCD) while scuba diving was discussed extensively. While many cardiac-related deaths in scuba diving may be classified as “natural death” associated with preexisting cardiac conditions, the provocative role of diving could not be excluded in some cases. Cardiac causes were suspected in one-quarter to one-third of all recreational diving accidents in recent decades. Rates of cardiac-related deaths vary reflecting regional demographic differences and trends among divers. Current trends of the increasing age of divers are of concern, but on the other hand, cardiac-related deaths in the general population seem to be gradually decreasing thanks to preventive efforts to reduce exposure to lifestyle risk factors and to control involuntary risk factors. Thus, it is not possible to predict whether the current trends in scuba diving fatalities will continue, but cardiac issues will remain for a concern for divers in years to come. Effective trend monitoring requires reliable data including medical examination, and meetings like this one help to advance medical examination practice.


Snorkeling-related, swimming-related or coincidental deaths?


In “Snorkelling-related deaths in Australia, 1994–2006” John M. Lippmann, et al. presented an analysis of 140 snorkeling-related deaths that occurred in Australia during the period of 1994-2006. The majority of the cases occurred due to cardiac-related causes (60) or drowning while at the surface (33). Only 19 deaths occurred after prolonged breath-hold diving and 10 were caused by trauma.

Cardiac cause was established based on medical examiners’ findings.

  • In 34 cases there was a history of cardiac disease.
  • In 19 cases cardiac pathology was established for the first time at autopsy.
  • The remaining five there was neither a history nor conclusive autopsy finding. Medical experts believed these five occurred as a result of cardiac arrhythmias.
  • Most deaths due to cardiac causes occurred in male snorkelers of a median age of 65, who were found silently floating in the water. Authors propose the term “fatal silent snorkeling syndrome” for these cases.

Overall, the incidence rate of snorkeling deaths is very small; with an average 10 cases per year and about 2 million snorkelers annually, it is approximately five deaths per 1 million snorkelers. In cases of cardiac death, there are about 2 deaths per 1 million snorkelers. While this small overall risk does not require any particular intervention, there are some people that may be at much higher risk. This includes individuals with a family history of sudden cardiac death and people with known heart disease. Among other causes of snorkeling death, there were four cases of epileptic seizures while snorkeling which may be either unrelated or provoked by water immersion (so called “water immersion epilepsy”).

There were only 19 breath-hold diving deaths including prolonged or deep diving in apnea; however, the number of people practicing breath-hold diving was not known and the relative risk could not be established. One may reasonably assume that true breath-hold diving involves greater risk than surface snorkeling (when controlled for age).

Snorkeling is widespread among recreational swimmers and does not necessarily involve submersion. Hazards for snorkelers are same as for swimmers, but statistics for drowning deaths were not compared here. According to this paper, in 2006 in Australia, out of 16 dive-related deaths, 10 were snorkeling related. Another source reports that diving-related deaths make up approximately 7% of drowning in open waters. Incidence rate for snorkeling deaths due to cardiac causes may not be different than incidence rate of drowning due to cardiac causes. The point is that “snorkeling deaths” and “swimming deaths,” with exclusion of true breath-hold diving deaths, may be the result of the same causes. While specific provocative factors may be present in immersion, beyond channelopathies and “immersion epilepsy,” they may not amount to a greater risk than the risk people are exposed to in their daily lives.

The paper brings out many other interesting details and is worth a read.

Post written by: Petar Denoble, MD, D.Sc.