Tim Russert with son Luke and wife Maureen Orth on vacation earlier this month at the Vatican Museum at the Vatican. The day after returning from the family’s trip to Italy, Russert died of a massive heart attack.

AP / Russert Family

My father was planning a trip to Europe one summer when he went to the bathroom and didn’t return. My mother found him dead of a heart attack on the floor. My husband’s grandfather’s heart gave out as he was walking down the sidewalk.

Everybody knows somebody who has had a sudden, fatal heart attack, and it’s many people’s secret fear. More than 300,000 Americans die of heart disease without making it to the hospital each year; most of them from sudden cardiac arrest, according to the American Heart Association. In about half of those cases, the heart attack itself is the first symptom.

Deaths from cardiovascular disease in general have dropped dramatically in recent years, but it is still the number one killer of men and women in the United States — claiming more lives than cancer, chronic respiratory diseases, accidents and diabetes combined.

That’s in part because, for all the advances doctors have made in understanding risk factors, lowering cholesterol with statins and propping open narrowed arteries with stents, most heart attacks are caused when bits of plaque break loose and burst like popcorn kernels, forming clots that block arteries. That prevents blood from reaching areas of heart muscle, which start to die. It’s hard to predict when that might happen — which is why people who never knew they had heart disease, and people who thought it was under control, still have sudden heart attacks.

“We have terrific therapies unimaginable 25 years ago,” says E. Scott Monrad, director of the cardiac catheterization lab at Montefiore Medical Center in Bronx, N.Y. “But one of the biggest risks is dying before you even get to see a doctor.”

Last weekend, scores of commentators offered theories about what might have been done to save NBC’s Tim Russert, who died of a sudden heart attack. Few details were released, other than that the much-loved Meet the Press moderator was being treated for asymptomatic coronary artery disease, had diabetes and an enlarged heart, and had a stress test in April.

Many blog-posters argued that Russert should have had an angiogram — a test in which the coronary arteries are injected with dye and X-rayed to spot blockages. But even if he had had the procedure an hour before the attack, doctors might not have been alarmed. More than two-thirds of heart attacks occur in arteries less than 50 percent narrowed by plaque buildup.

Similarly, the stress test Russert had is better at detecting significantly narrowed arteries than the small, soft unstable kind of plaque that often causes fatal blood clots.

Indeed, about a third of people who have heart attacks don’t have the usual risk factors: family history of heart disease, abdominal fat, high blood pressure or cholesterol.

(And not all heart attacks are fatal. Most of the 1.2 million Americans who had one last year survived. If the area of oxygen-starved heart muscle is small, or in the right ventricle, the heart can often keep pumping, allowing the patient to make it to a hospital, where doctors can break up the blockage with a clot-dissolving drug or catheterization. The situation becomes fatal if the heart starts beating wildly, and ineffectively, and is not jolted back into a normal rhythm within a few minutes.)

Prediman K. Shah, director of cardiology at Cedars-Sinai Heart Institute in Los Angeles, is one of many experts who think wider use of coronary calcium CT scans could help spot more people at risk of soft-plaque blockages. The noninvasive procedure takes 15 minutes and costs a few hundred dollars. Few insurers cover it because there is scant evidence that treating people on that basis saves lives.

At a minimum, seeing a picture of the calcium lining their arteries can be a wake-up call for patients to take their coronary-artery disease seriously and make lifestyle changes.

Russert’s colleagues said the 58-year-old journalist had been working to control his condition with exercise and diet, though his weight was an ongoing struggle.

Indeed, stents, angioplasty and bypass surgery are only stop-gap measures that don’t do anything to halt the progress of the underlying disease. “The bottom line, says Edmund Herrold of Weill Cornell Medical College: “Get a regular checkup. Watch your weight and your blood pressure and your cholesterol. Get diabetes under control. Exercise. Take an aspirin every day. Eliminate meat. You can dramatically lower the risk of a cardiac event if you pay attention to these issues.”