Sudden cardiac arrest may not be so sudden. According to one study, warning signs may occur in the hours, days, or even weeks before.

Each year, about 350,000 people in the United States die from sudden cardiac arrest, a catastrophic event that is fatal about 90 percent of the time.

Researchers at Cedars-Sinai Heart Institute in Los Angeles reviewed the records of 1,100 people ages 35 to 65 who had suffered a cardiac arrest between 2002 and 2012.

About a quarter contained no reference to any previous symptoms. But of 839 patients, half of them had evidence of at least one symptom in the previous month.

For most, the symptoms began within 24 hours of their collapse, although some came a week before, and a few up to a month prior.

Chest pain was most common in men, while women were more likely to experience shortness of breath.

Other symptoms included fainting and heart palpitations.

Importantly, a fraction of patients — 19 percent — had considered their symptoms bad enough to call 911 before they collapsed. They were more likely to survive.

Most of these people were patients who had already been diagnosed with heart disease or who were having recurrent symptoms.

Their survival rate was 32 percent, compared with just 6 percent for other patients.

In addition, about half of middle-age patients for whom symptom information could be found had experienced warning signs, mostly chest pain or shortness of breath, in the month before suffering a cardiac arrest, researchers reported in the Annals of Internal Medicine.