The sudden passing of NBC newsman Tim Russert came as a shock. A shock because, at age 58, the renowned host of NBC's "Meet the Press" died so young. But it seems even more alarming because he had passed a stress test recently and had logged time on a treadmill on the day of his death.

The question on many minds: "How is this possible?" And, of course: "Can this happen to me?"

The answers are that it happens more than you think and, of course it can happen to you.

"This is not a big surprise," said Dr. Paul Hauptman, a Saint Louis University cardiologist. "Stress tests are screening tests and not 100% perfect. They don't detect everything."

In fact, "in cases where there is non-critical blockage [less than 70 percent blockage of an artery], it is very often not detected during a stress test," he said. "The lesion needs to be a critical blockage to show up and even then, it still doesn't always."

Portrait of Sudden Cardiac Death

While many heart diseases can lead to cardiac arrest and sudden cardiac death, the most common is coronary artery disease (caused by atherosclerosis, a fatty build-up inside the arteries of the heart).

More than 300,000 people die of coronary artery disease each year without being hospitalized or admitted to an emergency room, according to the American Heart Association. The majority of these are sudden deaths caused by cardiac arrest.

Dr. Hauptman describes what happen: "There is some blockage that ruptures; the clotting system activates in an attempt to repair the damage. A huge clot then completely blocks off the artery, leading to a heart attack." Hauptman said that Russert likely developed an abnormal heart rhythm known as ventricular fibrillation and then went into sudden cardiac death.

"All this happens within seconds," he said and often to people between the ages of 55 and 60.

Risk Assessment

Dr. Denise Janosik, SLUCare cardiologist and program director of the LIVEWell program outlined risk factors for cardiac death. These include uncontrolled high pressure, diabetes and high cholesterol; smoking; excessive stress; abdominal obesity; and advanced age.

More precise levels of individual risk can be calculated in an assessment tool known as the Framingham risk score. This score takes into account a host of factors, such as those mentioned above, to calculate a patient's 10 year risk of a cardiac event.

In addition to use of these scores and standard stress tests, other methods used to evaluate heart health include cardiac catheterization, ultrasound, electrophysiologic tests and specialized CT scans. Electron beam CT scans can detect levels of calcium in the arteries (another marker of atherosclerosis) and 64-slice CT scans have the added capability of providing data on the actual blood flow through the arteries.

Improving the Odds

Experts recommend working to improve any modifiable risk factors, such as better control of diabetes, improving diet, exercising more and reducing stress. An aspirin might be in order as well, according to Janosik, but "you have to look at the whole picture."