Down but not out.

Death from heart attack has decreased nearly 45 percent since the mid-1960s, yet heart disease remains the number one killer.

Large snowflakes, driven by a fierce wind, stung the face of Mark Kelly as he labored to clear the snow drifting across his driveway. He wasn't used to such exertion, and ordinarily he wouldn't stress himself. But the 55-year-old chemical engineer from Midland, Michigan, couldn't afford to miss his flight that morning. As he paused to catch his breath, he noticed a squeezing pain in his chest that was growing increasingly severe. Leaning hard against the snow shovel, a wave of lightheadedness and faintness swept over him. The chest pain became more intense as it spread to his shoulders, neck, and left arm. Despite the biting cold, beads of perspiration dripped from his forehead. He realized something serious was happening as he stumbled back to the house to get help. Rather than making his flight that morning, he had a quick trip to a local hospital, where he was admitted for emergency treatment.

Mark Kelly was having a heart attack. A personal tragedy that, unfortunately, is experienced by thousands of people each day. Throughout the world, diseases of the heart and circulatory system (referred to as cardiovascular disease) are the leading cause of death. Cardiovascular disease includes high blood pressure, coronary heart disease (also called coronary artery disease), stroke, and rheumatic heart disease. Chief among these is coronary heart disease, which can cause a heart attack. Forty-five percent of all heart attacks occur in people under age 65, and 5 percent in people under 40. And heart attacks kill 500,000 people in the United States every year.

Anatomy of a killer. The heart is a four-chambered muscular pump, about the size of your fist, located just left of center in your chest. Pumping life-giving blood throughout your body, it "beats" continuously, resting only between each beat. Each day the average heart beats about 100,000 times and pumps about 2,000 gallons of blood. During a 70-year lifetime an average human heart will beat more than 2.5 billion times.

Leaving the heart, blood circulates through a vast network of arteries, where its cargo of oxygen, nutrients, and other materials is supplied to every part of the body. Blood then returns to the heart through a similarly intricate network of vessels.

Arteries are like living pipes, made of multiple layers of muscle and other cells. Healthy arteries are elastic and unobstructed, and blood flows freely through them. Over a period of time, however, arteries can become diseased. Cholesterol, fatty materials, cellular waste products, calcium, and other substances can accumulate within the inner lining of arteries, forming what is called plaque. This accumulation is called atherosclerosis, and is similar to scale forming on the inside of water pipes.

As atherosclerosis progresses, more and more plaque accumulates within the artery, restricting blood flow, and eventually may partially or totally block it. Atherosclerosis can also increase the likelihood of a blood clot forming within an artery that could easily plug a vessel, cutting off blood to important organs downstream.

Like any muscle, the heart needs a steady supply of oxygen and nutrient-rich blood to carry on its work. This is provided by a network of blood vessels called coronary arteries. Atherosclerosis in these arteries (coronary heart disease) reduces the supply of blood to the heart and can cause myocardial ischemia, a condition in which the heart muscle doesn't get as much blood as it needs for a given level of work.

Chest pain (called angina pectoris) can result when blood flow to the heart is adequate for normal needs but insufficient when the heart's requirements increase. Unusual physical exertion (e.g., shoveling snow when you're not used to it) could cause angina, while casually sweeping the garage might not.

Heart attack and stroke. A heart attack occurs when a coronary artery is blocked, thus cutting off blood supply to that part of the heart supplied by the blocked artery. If the blockage occurs in a major artery supplying a large portion of the heart and if the blockage is not removed quickly, the heart may be severely damaged and no longer able to pump blood. Death can result. Know the warning signals of a heart attack (see box on page 28) and take immediate action should any of them occur.

Stroke can occur when atherosclerosis affects the arteries supplying the brain. If an artery supplying the brain bursts or becomes blocked by plaque or a blood clot, nerve cells in the affected area of the brain will become deprived of oxygen and possibly die. The results of stroke can vary from person to person, depending upon the area of the brain affected. Know the warning signs of stroke (see box on page 28) and take immediate action if any of them occur.

Fighting back. Many people either don't know the warning signs of heart attack or stroke or they fail to take prompt action when they occur. In a recent U.S. hospital survey, heart attack victims waited an average of five hours from the beginning of chest pain until they arrived at the hospital for medical treatment. Is it any wonder that of the 500,000 heart attack deaths each year in the U.S., about 300,000 occur before the victim reaches a hospital? Advances in heart attack treatment have saved thousands of heart attack and stroke victims who otherwise might have died, making it essential to seek help as soon as possible after the onset of symptoms.

Down but not out. How effective have we been in lowering our heart attack and stroke risk? Since peaking in the mid-1960s, death from heart attack has decreased nearly 45 percent, while death from stroke has fallen nearly 60 percent.

In a recent article in the New England Journal of Medicine, "Prevention of Coronary Artery Disease, a Medical Imperative," Alexander Leaf, M.D., of Massachusetts General Hospital, and Thomas J. Ryan, M.D., of Boston University Medical Center, write: "This reduction has been attributed to better medical intervention, but even more, to the modification of risk factors by the public. There will always be some people who will have life-threatening coronary heart disease for genetic or other unavoidable reasons, but the evidence is strong that the incidence of the disease could be reduced substantially if the public were to adopt known preventive measures more broadly."

Surveys show that we are smoking less, reducing our fat intake, and eating more fruits and vegetables. Since the early 1960s our average blood cholesterol level has declined 6 to 8 percent. This modest-appearing decrease actually translates into a substantial 12 to 16 percent decline in heart attack risk. Thus it appears that the adoption of a more healthful diet is paying off.

As you read on in this special issue, you'll learn more about heart disease and how you can prevent it. Keep in mind this thought from Drs. Leaf and Ryan: "Without forgoing many of the benefits (that our society provides), we can each maintain healthful habits of eating, exercising, and the like throughout our lives that will help us avoid atherosclerosis."