Chest pain, shortness of breath, and other common heart attack warning signs often precede sudden cardiac arrests.

Sudden cardiac arrest is the Hollywood picture of a heart attack: A middle-aged man clutches his chest, slumps to the floor, and expires. It’s disastrously common and deadly. A whopping 20% of all deaths in the United States each year are due to a sudden cardiac arrest; barely 5% of people who have one survive.

The perception of sudden cardiac arrest, certainly furthered by its name, is that it comes as a bolt out of the blue. A meticulous study by German researchers suggests that it is more like real lightning, which is usually preceded by clouds, wind, and rain.

Although sudden cardiac arrest is sometimes the very first sign of heart disease, most of its victims already have some cardiovascular problems. That was the case in this study. Two-thirds of those who collapsed had been diagnosed with heart disease, had survived a previous cardiac arrest, or had angina or other signs of heart disease.

One disturbing finding was that people who collapsed at home were less likely to get CPR than those who collapsed in public. Resuscitation was started 11% of the time at home, compared with 26% of the time in public. The researchers suggest this is because you are more likely to find someone trained in CPR in public than at home.

Heart attack or cardiac arrest?

The term “heart attack” is often used to cover two different events. Technically, heart attack refers to a myocardial infarction. This is the damage or death of heart muscle that occurs when a blood clot blocks an artery-nourishing part of the heart. The heart continues beating even as the besieged section of the muscle slows or falters.

Heart attack, usually “massive heart attack,” is also sometimes used to describe a cardiac arrest. Here the entire heart suddenly stops pumping blood to the body.

Most cardiac arrests stem from an electrical malfunction that causes the heart’s powerful lower chambers, the ventricles, to start beating very fast (ventricular tachycardia) or fast and chaotically (ventricular fibrillation). Contractions are so close together that the heart can’t relax enough to fill with blood. Circulation stops. Lack of oxygen makes muscles twitch and the eyes roll back. Even that activity stops in less than a minute. The only hope for survival is to start CPR and follow it with a jolt from a defibrillator to shock the heart back into a normal rhythm.

Sudden cardiac arrest sometimes strikes seemingly healthy people who have never had a moment’s worry about heart disease. Usually, though, some type of cardiac trouble is at its root. Cumulative damage from cholesterol-clogged arteries or high blood pressure is the most common cause. Narrowed or stiff arteries may have trouble supplying the heart with the oxygen-rich blood it needs. Oxygen deprivation from a myocardial infarction can nudge the heart toward a potentially deadly rhythm. Silent changes to the size or muscular bulk of the ventricles can short-circuit vital electrical connections. And inherited conditions that result in electrical disturbances can also lead to sudden cardiac death.

Warning signs

Chest pain is only one of several possible signs of an impending heart attack or sudden cardiac arrest. If you notice one or more of the signs below in yourself or someone else, call 911 or your local emergency number right away.

• Uncomfortable pressure, squeezing, fullness, burning, tightness, or pain in the center of the chest
• Pain, numbness, pinching, prickling, or other uncomfortable sensations in one or both arms, the back, neck, jaw, or stomach
• Unexplained shortness of breath
• Sudden nausea or vomiting
• Lightheadedness or dizziness
• Unusual fatigue
• Heat and flushing, or a cold sweat
• Sudden heaviness, weakness, or aching in one or both arms

Don’t delay

The Berlin study offers yet another reason to learn “” and act on “” the warning signs of a myocardial infarction (see “Warning signs”). We’ve long advocated being aware of these so you can get to the hospital fast. The sooner a diagnosis is made, the sooner treatment can begin and the less likely the attack will permanently damage the heart muscle. Many sudden cardiac arrests, it turns out, are preceded by warning signs much like those that accompany slower-moving myocardial infarctions.

No one wants to cry wolf or put others out for what might be a trifling bout of indigestion or anxiety. But acknowledging that you suddenly aren’t feeling well could save your life as well as your heart.