A new study reveals that a sudden cardiac arrest is always preceded by telltale signs and may, therefore, not be as sudden as doctors have thought, Philly.com reports.

The new study suggests that about half of cardiac arrest patients experience telltale-warning signs that they may suffer a cardiac arrest a month before their attack.

The symptoms can include chest pain and pressure, shortness of breath, heart palpitations, nausea, back pain and abdominal pain.

"By the time the 911 call is made, it's much too late for at least 90 percent of people," said Dr. Sumeet Chugh of the Cedars-Sinai Heart Institute in Los Angeles, who led the study reported in Annals of Internal Medicine, according to Yahoo News.

"There's this window of opportunity that we really didn't know existed."

However, despite the warning signs, less than one in five of those who experience symptoms actually reach emergency medical assistance.

"Most people who have a sudden cardiac arrest will not make it out alive," warned study co-author Dr. Sumeet Chugh, associate director of the Heart Institute and director of the Heart Rhythm Center at Cedars-Sinai Medical Center in Los Angeles.

"This is the ultimate heart disease, where you die within 10 minutes. And less than 10 percent actually survive," he said.

"For years we have thought that this is a very sudden process," Chugh added.

"But with this study we unexpectedly found that at least half of the patients had a least some warning signs in the weeks before. And this is important, because those who react by calling their loved ones or calling 911 have a fivefold higher chance of living. So, this may open up a whole new paradigm as to how we may be able to nip this problem in the bud before a cardiac arrest even happens."

For the study, the researchers studied nearly 840 patients, aged 35 to 65, whose symptoms were tracked before they experienced a cardiac arrest between 2002 and 2012.

The study concluded that 50 percent of men and 53 percent of women experienced warning symptoms before their hearts stopped.

Dr. John Day, president of the Heart Rhythm Society and director of Heart Rhythm Services at Intermountain Medical Center Heart Institute in Murray, Utah, described the study findings as a "wake-up call for patients and doctors."

Day said that "the problem, of course, is that many of these symptoms may have other explanations. Flu-like symptoms, which can affect nearly everybody at some point during the winter, is a vague thing to really put your finger on and know that it's about your heart. So it's certainly challenging to find the right signal through all the noise," he added.