Scuba divers beware: sudden death is not always unannounced

CPR_2Sudden death in adults is often caused by an unexpected loss of pulse due to stop of heart pump (sudden cardiac arrest; SCA) followed shortly by a loss of consciousness and muscular power (collapse) without an external cause. SCA is a cause of over 550,000 deaths in USA including out-of-hospital and hospital patients. Regardless of circumstances, survival remains very low (7%). SCA affects people with and without history of previous heart disease. According to DAN fatality data, about one quarter to one third of scuba fatalities may be caused by SCA which, in addition, may be sealed by drowning.

Although cases of SCA progress rapidly the name does not imply that cardiac arrest occurs without warning signs. Medical professionals know that in some cases warning signs like chest pain and dyspnea precede SCA long enough to initiate pre-emptive intervention. We have also learned from the DAN scuba fatality monitoring program that in some divers death ascribed to SCA obvious warning signs were present before the fatal dive. How prevalent these warning signs are in the general SCA patient population was not known until a study done by Marion Eloi and coauthors published last December.

The study identified SCA patients from Portland, Oregon metropolitan area hospitals who had symptoms assessments done four weeks prior to the SCA event. Total of 839 patients were identified. The mean age of patients was 52 years and most were males (75%). Fifty-one percent of patients had at least one warning symptom. There was no difference in percentage of males and females with warning symptoms. The most common warning symptoms were chest pain and dyspnea. Men had more chest pain and women more dyspnea. Most SCA occurred while patients were at home. Warning symptoms occurred one hour before SCA and in many cases even 24 hours before. Only 19% with warning symptoms called the emergency medical services (911). Callers were more likely to be patients with a known history of heart disease. The mean response time between a 911 call and EMS arrival was seven minutes. Initially shockable rhythm was present in about fifty percent of the cases. Survival in those who call 911 was 32% in comparison to those who did not call.

The takCPR_3e home message is that chest pain and dyspnea in middle age and older individuals even without known heart disease history, should be recognized as a warning sign of a life threatening condition and patients should be prompted to seek emergency medical care before SCA occurs. Even in the best of circumstances, when emergency response is initiated after the occurrence of SCA, chances of survival are slim. However, a prompt reaction to warning signs may prevent SCA and in case it still occurs, it increases survival rate. Other symptoms that may precede SCA but are less specific are syncope, palpitations, abdominal complains and influenza-like symptoms. These symptoms may be difficult to recognize as warning signs of SCA without history of heart disease. For divers it is important not only to acknowledge likely cardiac symptoms (chest pain and dyspnea) and call 911 but also to abstain from diving in case they have any symptoms until they have a clearance from their diving physician.  Once SCA occurs, one does not have time to get surprised but those who act upon warning signs, may pre-empt sudden death.

 

References

Marijon E, et al. Warning Symptoms Are Associated With Survival From Sudden Cardiac ArrestCardiac Arrest. Ann Intern Med. 2016;164:23-29. doi:10.7326/M14-2342.

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