The “sudden” in sudden cardiac arrest (SCA) may actually be a misnomer for a large proportion of its sufferers, suggests a new study published Monday in the Annals Of Internal Medicine.

Analyzing the recent medical history of nearly 1,000 people who had succumbed to SCA since 2002, the researchers found that just about half had symptoms like chest pain or difficulty breathing in the four weeks prior to their cardiac arrest, most often within a 24-hour period. However, less than one-fifth of people who experienced these early warning signs took the step of calling emergency medical services (EMS) afterwards. It’s a step that might have greatly increased their chance of survival, since those who called 911 after were six times more likely to survive their SCA than those who hadn’t.

“Warning symptoms frequently occur before SCA, but most are ignored. Emergent medical care was associated with survival in patients with symptoms, so new approaches are needed for short-term prevention of SCA,” wrote the authors.

It’s estimated that 350,000 people are beset by SCA annually, with its more than 90 percent fatality rate making SCA the second leading cause of cardiovascular death in America.

Since 2002, the Arrhythmia Research Laboratory at the Cedars-Sinai Heart Institute in Los Angeles has kept extensive tabs on people who have suffered from SCA, defined as an
“unexpected loss of pulse due to a collapse of the heart's electrical system” in the Portland, Oregon metropolitan area. They’ve done so by obtaining the medical history and demographics of SCA patients as well as through interviews with survivors or those close to the patient, all in an effort to better understand the mysterious, often fatal, condition. This effort has uncreatively, if accurately, been called the Oregon Sudden Unexpected Death Study (SUDS).

For the latest study, the researchers initially looked at the records of 1099 people collected by Oregon SUDS (ages 35 to 65). In part because SCA so rarely leaves behind survivors, though, they only had enough detailed information on 839 patients. Of these, 430 (51 percent) experienced symptoms prior to their SCA, most often chest pains (199 patients) or trouble breathing (78 patients). Though the percentage of warning signs was similar among both genders, women were more likely to experience the latter while men more often reported the former. Regardless of whether they experienced warning symptoms or not, 23 percent had a history of diabetes, while 37 percent already had prior heart issues, most often coronary artery disease.

More crucially, though only 81 people called 911 upon experiencing their symptoms, this group had a 32 percent survival rate compared to 6 percent among non-callers. The former group was more likely to contain people who already had prior heart issues, indicating that their greater awareness of potential warning signs. Those who experienced symptoms earlier than others were also more likely to have them recur in the hours right before their SCA.

“Our findings emphasize the need to encourage efforts that target public awareness of SCA as a largely fatal event,” the researchers wrote, “It is important to reinforce knowledge of prodromal (early) symptoms of SCA in the general public and in patients affected by heart disease and their family members.”

These efforts may not only involve public education campaigns but the development of technologies that take advantage of smart phones to instantly locate emergency defibrillators, the researchers suggested as an example. As reported by Medical Daily this June, there are ongoing efforts to design apps that actively recruit bystanders to provide CPR to cardiac arrest victims, with some degree of success.

“Further studies are needed to improve risk stratification among patients with symptoms as well as investigations of whether early intervention based on symptoms may improve outcomes or even prevent SCA,” they concluded.

Source: Marijon E, Uy-Evanado A, Dumas F, et al. Warning Symptoms Are Associated With Survival From Sudden Cardiac Arrest. Annals of Internal Medicine. 2015.