Sudden cardiac arrest is apparently not so sudden. Researchers from Cedars-Sinai Medical Center reported in a medical first that people experience symptoms up to one month before sudden cardiac arrest.

The condition, which is different from heart attack or myocardial infarction, is caused by defective electrical activity in the heart. In the U.S., an estimated 350,000 people die from sudden cardiac arrest every year, about half of all cardiovascular deaths in the country.

"Sudden cardiac arrest in middle age hits society hard since most who are affected are their families' primary breadwinners," lead study author Dr. Sumeet S. Chugh, medical director of the Heart Rhythm Center in the Cedars-Sinai Heart Institute, said in a news release. "Fewer than 7 percent survive a sudden cardiac arrest, which has historically made it difficult to pinpoint symptoms."

The researchers investigated 839 patients ages 35 to 65 and identified the common symptoms of sudden cardiac arrest: intermittent chest pain and feeling pressure in the chest, palpitations, shortness of breath and continuing flu-like symptoms like nausea, back pain and abdominal pain.

The researchers found out that of the 839 patients, 51 percent experienced the warning symptoms, with chest pain being the most common symptom felt. Of these, 93 percent reported experiencing the symptoms again within 24 hours before the sudden cardiac arrest.

A small percentage - 19 percent - of those who felt the symptoms sought medical help, and their survival rate was 32 percent. Those who did not seek treatment had a survival rate of only 6 percent.

"These new findings give good reason not to ignore unusual sensations, as vague as they may be," Dr. Eduardo Marbán, Cedars-Sinai Heart Institute director, said. "Better to seek medical attention early than to risk dying suddenly."

The researchers said the study findings could help develop approaches to prevent sudden cardiac arrest.

"Now that we realize that sudden death may not be so sudden, there is also potential for new shorter-term approaches by increasing awareness and education of patients and their healthcare providers," Chugh said.

The study was published online Dec. 22 in the Annals of Internal Medicine.