More than half of patients in a prospective, population-based study had warning symptoms in the four weeks before suffering a sudden cardiac arrest. However, only 19 percent of patients called emergency medical services to report their symptoms.

The survival rates were 32.1 percent for patients who called 911 compared with 6 percent for those who did not report their symptoms.

Lead researcher Eloi Marijon, PhD, of European Georges Pompi-dou Hospital in France, and colleagues published their results online in the Annals of Internal Medicine on Dec. 21.

“Our findings emphasize the need to encourage efforts that target public awareness of [sudden cardiac arrest] as a largely fatal event,” they wrote. “It is important to reinforce knowledge of prodromal symptoms of [sudden cardiac arrest] in the general public and in patients affected by heart disease and their family members.”

Each year, more than 550,000 people in the U.S. have sudden cardiac arrest, which accounts for more than half of cardiovascular deaths. Despite increased investments in identifying and treating sudden cardiac arrest, only 7 percent of patients survive, according to the researchers. They added that details on the medical history of patients with sudden cardiac arrest are typically sparse.

In this ongoing study, called Oregon SUDS (Sudden Unexpected Death Study), researchers collected information on symptoms and clinical history of patients with SCA in the Portland area. They defined sudden cardiac arrest as “an unexpected loss of pulse, without obvious extracardiac cause, and rapid collapse with specific resuscitation records available.”

From February 2002 to February 2012, the authors analyzed symptoms during the four weeks before sudden cardiac arrest among patients between 35 and 65 years old. They obtained information from EMS team, intensivists or cardiologists at 16 hospitals and physicians in the community.

The symptoms were classified as chest pain, dyspnea, palpitations, syncope and others, including abdominal pain, nausea or vomiting, back pain and miscellaneous symptoms.

Of the 839 patients, 51 percent had at least one symptom within four weeks before sudden cardiac arrest, including 50 percent of men and 53 percent of women. Of the 430 patients with symptoms, 11.9 percent consulted a family or specialist physician about the symptoms.

Symptoms began more than an hour before sudden cardiac arrest in 80 percent of patients, while symptoms began more than 24 hour before sudden cardiac arrest in 34 percent of patients.

Of the 430 patients with symptoms, 199 had chest pain, 78 had dyspnea, 41 had flu-like symptoms, 22 had syncope or palpitation and 86 had other symptoms. Data were missing from four patients.

Of the patients with symptoms, 19 percent called EMS before suffering a sudden cardiac arrest. Of the patients who called EMS, 78 percent developed sudden cardiac arrest before emergency medical responders arrived at the scene, while 18 percent had sudden cardiac arrest in the ambulance on their way to the hospital.

After adjusting for multiple variables, the researchers said there was a significant association between calling 911 and survival to hospital discharge.

They added that the study had a few limitations, including that 24 percent of patients could not have their symptoms assessed and that the benefit of early symptom alerts may be underestimated because the trial only included patients who eventually developed sudden cardiac arrest. Also, they noted they could not make a causal association between early 911 call and survival because of the study’s observational design.

“A high proportion of middle-aged men and women in the community had warning symptoms before [sudden cardiac arrest], but most symptoms were ignored,” they wrote. “Because timely response to such symptoms was associated with an increase in survival, our results highlight the potential importance of developing new community-based strategies for short-term prevention of [sudden cardiac arrest]. 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 [sudden cardiac arrest].”