The Mystery of Sudden Cardiac Arrest

% of readers think this story is Fact. Add your two cents.

by Forbes

“When cardiologist Sumeet Chugh was a medical resident in Minneapolis in 1992, a beautiful 19-year-old woman was rushed into the emergency room after collapsing while dancing. Her heart had suddenly stopped. Chugh and his colleagues worked for almost an hour but couldn’t save her. An autopsy found nothing. The only clue was her mother, who had also died abruptly at a young age. “It was devastating to me,” says Chugh, now associate director of the Cedars-Sinai Heart Institute in Los Angeles. He dedicated his career to solving the biggest mystery of heart disease, why many healthy people suddenly keel over and die. He runs a study that has tracked every sudden cardiac death in Portland, Ore. since 2002 to find some answers. “It’s like a Rubik’s cube,” he says. “You have to put it together piece by piece. 

Sudden cardiac arrest kills 200,000 to 300,000 Americans a year. It is often wrongly equated with a heart attack. In fact, what kills people who die suddenly is not the artery clogging (which destroys heart muscle but is not immediately lethal); it’s the ventricular fib, a rapid quivering of the main pumping chambers in the bottom of the heart, called the ventricles. When this occurs, little blood gets out. Brain cells die within minutes. For every minute that goes by without the heart being restored to a normal rhythm, the patient’s odds of survival drop by 10%. After ten minutes they’re gone.

Heart attacks are one trigger but may account for only a minority of sudden cardiac deaths, says Chugh. Past heart attacks, which leave scar tissue that changes the electrical patterns of the heart, are another risk factor. Genetic disorders that cause subtle changes to the heart rhythm are a third. “The biggest bugaboo in the field is we don’t know how to predict arrest,” says Benjamin Abella, director of the Center for Resuscitation Science at the University of Pennsylvania. “The stars just align in the wrong way.”

Performing cardiopulmonary resuscitation (CPR) can keep a patient alive by pushing blood through the body. But there is only one treatment that halts the deadly arrhythmia: an electric shock, called defibrillation, that sets the heartbeat back into a regular rhythm. Defibrillators come in two forms: external versions used by paramedics and surgically implanted versions for patients at high risk.

Scientists developed defibrillation in the 1950s after linemen stringing electrical wires across the country were dying suddenly of cardiac arrest from electrocution. The idea emerged that maybe a counter-shock could set the heart right. In the 1960s Harvard researcher Bernard Lown invented a device that could be used in hospitals called the cardioverter defibrillator. Easy-to-use versions are now common in airports, casinos and other crowded public places. Studies have found they boost the cardiac arrest survival rate significantly. But a 2008 study failed to find any benefit from putting defibrillators in typical heart patients’ homes. It isn’t often that a patient suffers arrhythmia when there is someone present to help him.

Each year 300,000 heart patients worldwide at very high risk of sudden death get automatic defibrillators surgically implanted. The gadgets reduce the death risk 25% in patients whose hearts, because of slow deterioration or scars from heart attacks, are inefficient at pumping blood. It’s a $6.4 billion market for Medtronic and other device manufacturers, according to analysts at Wachovia. But implantable defibrillators, which cost $30,000 installed, are an expensive insurance policy for something that might never happen, and there are potential complications from surgery. Some of the devices or their associated wires have had to be recalled because of potentially catastrophic flaws.

But sudden deaths often occur in people without known heart problems, so scientists are racing to find other risk factors. One clue to pinpointing who is at risk is a genetic disorder called long QT syndrome, named after an unusual reading on an electrocardiogram. In this condition, the heart is just a little slow to recover between beats. This and related disorders hit one in several thousand people and may account for 5% of sudden-death cases.

Gloria Davis, 67, of Tucson, Ariz., just found out she has this genetic disorder. She had been healthy her entire life- until she almost died a few hours before her daughter’s wedding in April. The night before she felt a funny swirling sensation in her chest. The next day, while picking up a vegetable platter for the reception, she passed out in her car. Luckily, her friend was in the car and called paramedics. At Duke University Hospital she kept going in and out of normal rhythm. At one point doctors had to shock her twice to avert cardiac arrest. Her daughter got married in the hospital room the next day. A few days later cardiologists implanted a defibrillator in her chest. Now she is fine- and her daughter just had a baby girl.

Common gene variations may alter the heart rhythm in slight ways that don’t cause problems under normal conditions but may predispose people to sudden death during a heart attack or if they take certain drugs that affect heart rhythm. Two recent studies in Nature Genetics found ten gene variations that slightly alter heart rhythm and could be involved in sudden cardiac death. “What we are beginning to understand is why one person who has a heart attack dies suddenly whereas another person who has a heart attack doesn’t,” says Duke University cardiac electrophysiologist Patrick Hranitzky. “A lot of it has to do with genetics.”

Doctors like Chugh and Hranitzky hope they can uncover more conditions like weakened hearts or long QT that identify which patients will have sudden cardiac arrest. The goal is to do for sudden cardiac death what the Framingham Heart Study did for heart attacks: pinpoint a battery of factors that can better identify people at risk so they can be treated well in advance. Until they do, exercise, eat well and keep your blood pressure and cholesterol low. Eighty percent of those who die suddenly from heart disease have some sign of coronary trouble.

Sudden Cardiac Death: The heart suddenly stops when its electrical rhythms are disrupted, causing the heart’s lower chamber to quiver. Death occurs within minutes.

Prevention: Patients with damaged hearts are at risk. An implanted defibrillator slashes deaths in patients whose pumping capacity is below a certain threshold. Drugs called beta blockers reduce the rate of sudden cardiac deaths.

Treatment: Immediate action is essential. Cardiopulmonary resuscitation keeps blood flowing, limiting damage. An electric shock from an automated defibrillator can reset the heart rhythm. Many public venues now have them. Cooling a patient to 90 to 93 F degrees can slow brain damage.”

- http://www.forbes.com/