Sudden death isn't always so sudden

Content provided by the Faculty of the Harvard Medical School

Sudden death isn't always so sudden

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.

On-the-spot information

Studying sudden cardiac arrest isn't easy. Since it is generally fatal, you can't ask the victims how they were feeling before the attack. Interviewing witnesses or bystanders can help, but that is often done days or weeks later, long after memory has faltered or fudged things.

Researchers at the University of Berlin tried to fill in some of the blanks by asking doctors who worked as part of the city's emergency response teams to interview witnesses on the spot following a sudden cardiac arrest. The doctors also recorded where the arrest happened, whether cardiopulmonary resuscitation (CPR) was started, and information about the victim. What they learned paints a more complex, and more troubling, picture of sudden cardiac arrest.

The emergency doctors gathered information on 406 cases of cardiac arrest. In two-thirds of these, someone saw or heard the victim collapse. That someone tended to be a family member, since nearly three-quarters of the arrests happened at home.

Warning signs were surprisingly common among people whose cardiac arrests were witnessed. These included chest pain, shortness of breath, nausea or vomiting, and dizziness. Some people began to experience these hours before the arrest (see "Arrest signals"). In 90% of the cases, symptoms lasted for at least five minutes. Only 25% of the victims had true out-of-the-blue arrests that weren't preceded by symptoms. The results were published in the Sept. 12, 2006, Circulation.

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.

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.

Last updated:	September 05, 2008