The unforeseen death of NBC’s prominent figure Tim Russert has raised serious questions about what exactly makes a person more vulnerable to heart attack than another.

Tim Russert, 58, the host of NBC News’ “Meet the Press” passed away on Friday while recording voiceovers for the Sunday edition of the show. His physician Dr. Michael Newman determined that a cholesterol plaque ruptured in an artery, blocking the blood flow to the heart, causing him a heart attack.

His death came as a shock for his colleagues from media as well as for all politicians whom he had invited and interviewed during his two-decade career. Also, millions of Americans who had watched “Meet the Press” along the years remained speechless in front of Russert’s death.

Besides disappointment and tears, this death highlights people’s helplessness in fighting heart attack, which may strike without warning at any time. Heart attack accounts for 310,000 deaths in the U.S. yearly, or 850 a day, a number equaling deaths caused by breast cancer, lung cancer, stroke and AIDS combined. According to the U.S. Centers for Disease Control and Prevention, about 770,000 Americans will have a new coronary attack in 2008 and about 430,000 will have a recurrent attack.

However frequent heart attack is, doctors still face serious trouble in telling what exactly predisposes a person to it and not another.

Heart attacks running in the family could be the only major factor that doctors consider a threat for a person’s heart. Age and gender are important risk factors as well, being the more dangerous as drugs cannot control them properly. Risk factors that people could control, although sometimes not efficiently, include quitting smoking, losing weight by following a healthy diet, exercising regularly, treating diabetes and hypertension.

It appears that Russert was at risk for heart attack, as he had been previously diagnosed with diabetes and was being treated for coronary artery disease, which was asymptomatic. His autopsy on Friday also revealed an enlarged heart. However, he performed well in a stress test two months ago. What’s most surprising in his death is that he had no signs of heart attack.

According to the American Heart Association, there are four major signs that could mean you are at risk of a heart attack. They include chest discomfort that lasts more than a few minutes or goes away and comes back; discomfort in one or both arms, the back, neck, jaw or stomach; shortness of breath with or without chest discomfort and breaking out in cold sweat, nausea or lightheadedness.

However, a study by researchers from School of Nursing at the University of California, released last month, found that almost half of patients with a history of heart attack, participating in the study, were poorly informed about heart attack symptoms. However, women, the most educated patients, younger patients, those who had undergone cardiac rehabilitation, and those treated by a heart specialist not a family doctor appeared to be better informed about heart symptoms.

It is no longer a secret that survival rates improve by up to 50 percent if patients receive treatment within one hour. Delaying treatment by 30 minutes cuts the mean life expectancy by a year.