Atrial Fibrillation Can Be A Family Affair

Study Finds Genetic Underpinnings

Having a parent with atrial fibrillation (AF) strongly increases an offspring’s risk of developing this heart rhythm disorder, according to a report from the National Heart, Lung, and Blood Institute (NHLBI) Framingham Heart Study.

In the latest study, published in the Journal of the American Medical Association, researchers found the risk doubled for offspring with at least one parent with AF compared to offspring whose parents did not have the condition.

Atrial fibrillation is the most common heart rhythm disorder in the US, affecting more than 2 million adults. The prevalence of the condition is rising and scientists predict that about 5.6 million people will have the disorder by 2050.

Known causes of AF include abnormalities in the heart’s structure and long-term uncontrolled high blood pressure.

Atrial Fibrillation Increases in Offspring

The study of 2,243 adults is the first to find a genetic connection for AF in a community sample, the study authors say.

“This important research finding will need to be confirmed but it opens up a new avenue of research on atrial fibrillation," says Dr. Barbara Alving, acting director of the NHLBI.

"Now scientists can start looking at genetic factors that might contribute to AF - searching for the genes involved in this increasingly common disorder,” she says.

The study’s findings strongly support the notion that AF has genetic underpinnings. Most cases of AF occur in older people.

The disorder affects about 1 in every 10 persons aged 80 and over. In the new study, the risk of AF tripled when both parents and the offspring were under age 75. The risk also tripled when the analysis was limited to offspring who had no clinically apparent heart disease.

“Disorders with a genetic component often occur at a younger age or in the absence of major diseases like heart disease that trigger the condition,” said the study’s lead investigator Dr. Caroline Fox of the Framingham Heart Study.

According to the NHLBI, AF occurs when electrical signals in the heart's upper chambers (the atria) are fired in a very fast, uncontrolled manner. Electrical signals then arrive in the heart's lower chambers (the ventricles) in an erratic pattern, creating an irregular heartbeat and affecting the heart’s ability to pump blood.

Atrial fibrillation can produce symptoms including palpitations, an unexplained, rapid heartbeat, lightheadedness, or occasionally chest pain. It can also be asymptomatic.

AF can lead to complications such as stroke and congestive heart failure. Treatment with medications, surgery, or devices, is designed to slow the heart rate and restore normal rhythm when possible, and to prevent stroke.

Blood-thinning medications (anticoagulants) are an important means of preventing stroke in AF patients.

The Framingham Offspring study of AF involved 1165 women and 1078 men whose parents were members of the “original” Framingham Heart Study.

The offspring were at least 30 years of age and free of atrial fibrillation at the first exam. Offspring and original study participants had routine clinic exams, including physical examinations, interviews, lab tests, and electrocardiograms.

AF in both offspring and original “parental” participants was confirmed by an electrocardiogram. Parental cases occurred from 1949 to 2002 and offspring AF cases occurred from 1983 to 2002.

When the Framingham researchers analyzed the data, they found that 30 percent of participants had at least one parent with AF. Seventy offspring (23 women) developed AF during the study at a mean age of 62 years.

When stated in terms of 1,000 persons per year, the results indicate that the number of offspring developing AF would be 4.5 if a parent had AF and 3 if parents did not have AF.

Findings Suggest Further Study Needed

Dr. Fox cautions that the Framingham findings should not alarm people who have a parent with AF.

“AF with or without a family history is a common condition in the elderly," she says. "Our findings indicate to the scientific community that we need more research on the genetic mechanisms of AF and how they interact with environmental influences."

Dr. Fox added that Framingham scientists hope to conduct further research into the genetic basis of AF.

Always consult your physician for more information.

Arrhythmias Diagnostic Testing Explained

The American Heart Association describes the following methods used to diagnose arrhythmias:

Electrocardiographic techniques
An arrhythmia is considered documented if it can be recorded on an electrocardiogram (ECG or EKG.) This is the standard clinical tool for diagnosing arrhythmias. It records the relative timing of atrial and ventricular electrical events. It can be used to measure how long it takes for impulses to travel through the atria, atrioventricular (AV) conduction system and ventricles. Often, though — because of the fleeting nature of arrhythmias — the ECG of someone who complains of symptoms that suggest arrhythmia appears normal.   
 
Holter monitor
Suspected arrhythmias sometimes may be documented by using a small, portable ECG recorder, called a Holter monitor (or continuous ambulatory electrocardiographic monitor). This can record 48 hours of continuous electrocardiographic signals. While an ECG is sort of a 12-second "snapshot" of the heart's electrical activity, the Holter monitor is more like a "movie." For suspected arrhythmias that occur less than daily, a patient can wear an event monitor. It has a continuously updated memory loop and can allow the heart to be monitored by telephone.

Treadmill testing
This is an option that may provoke arrhythmias and makes their diagnosis (and thus their proper treatment) easier. A treadmill test may be used for people whose suspected arrhythmias are clearly exercise-related. It is important to know if exercise makes an arrhythmia worse. To test this, you will walk on a treadmill - or ride a stationary bicycle - while your heart rate and rhythm are monitored.

Tilt table studies
A tilt test may be advised for some people who have had recurrent fainting spells (syncope). This test shows how your heart rate and blood pressure respond to a change in position from lying down to standing up.

Transtelephonic monitor (or event recorder)
Sometimes arrhythmia symptoms happen infrequently, or pass so quickly that you cannot get to a physician or hospital. In these cases, a "transient event monitor" may be used. These small recorders are sent home with a person for a month or two. When you have symptoms, attach the recorder with bracelets, finger clips, or patches under the arms. The ECG will be recorded and stored. When it's convenient, you can transmit the ECG by phone to the cardiologist to be analyzed.

Echocardiogram
Echocardiography works much like sound waves used to study solid objects in the sea (sonar). You may only think of ultrasound being used to monitor a baby's growth, but ultrasound waves can also show the heart's size, structure, and motion. This simple, painless test often provides valuable information about a heart with an arrhythmia.

Esophageal electrophysiologic procedure
In some situations, your cardiologist may advise doing an esophageal electrophysiologic procedure. This is used to diagnose or treat the type of tachycardia you have.
 
Electrophysiologic testing
This method has become extremely valuable for provoking known but infrequent arrhythmias and for unmasking suspected arrhythmias. This procedure is done using local anesthesia. The ability to electrically stimulate the heart at programmed rates and induce precisely timed premature beats lets a physician assess electrical properties of the heart's conduction system.

Always consult your physician for more information.

August 2004

Atrial Fibrillation Can Be A Family Affair

Atrial Fibrillation Increases in Offspring

Findings Suggest Further Study Needed

Arrhythmias Diagnostic Testing Explained

Heart Health Benefits From Antioxidant-Rich Foods

Online Resources

Heart Health Benefits From Antioxidant-Rich Foods

A variety of veggies, fruits, and nuts battled it out recently for the top spot on a new list of the 20 most antioxidant-rich foods, ranked by nutrition scientists at the US Department of Agriculture (USDA).

In the end, small red beans won the day, narrowly beating out wild blueberries as the food with the highest concentration of disease-fighting compounds per serving.

Antioxidants fight damage to cells from rogue molecules called "free radicals." Experts believe this assault on cells may fuel killer diseases such as heart disease and cancer, and even aging itself.

The new Top 20 list, published in the Journal of Agricultural and Food Chemistry, is a relative ranking of the capacity of foods to interfere with or prevent oxidative processes and to scavenge free radicals," explains list co-creator Ronald L. Prior, a USDA nutritionist and research chemist based in Little Rock, Ark.

Prior and his colleagues used the most advanced technologies available to tabulate antioxidant levels in more than 100 different types of fruits, vegetables, berries, nuts, and spices.

The Top 20 list includes:

• Small red beans (dried)
  
• Wild blueberries
  
• Red Kidney beans
  
• Pinto beans
  
• Blueberries (cultivated)
  
• Cranberries
  
• Artichokes (cooked)
  
• Blackberries
  
• Prunes
  
• Raspberries
  
• Strawberries
  
• Red Delicious apples
  
• Granny Smith apples
  
• Pecans
  
• Sweet cherries
  
• Black plums
  
• Russet potatoes (cooked)
  
• Black beans (dried)
  
• Plums
  
• Gala apples
  

There's "still a lot we haven't learned" about why some foods are richer in antioxidants than others, Prior says.

"Even though the small red bean came out on top berries are better understood," Prior says.

"The components that contribute a lot of the antioxidant activity are what are called anthocyanins, the compounds that give many berries their dark blue color," he says.

In fact, color may be key to spotting foods that fight free radicals, says Roberta Anding, an American Dietetic Association spokeswoman and a nutritionist at Texas Children's Hospital in Houston.

"If you're looking for the best places to get antioxidants, I will usually tell folks to look at the colors of the rainbow," she says.

Anding explains, "You'll find lutein with some of the yellow pigments found in corn; orange can be the pigments from the carotenoid family that are found in cantaloupe, butternut squash, and mango; red could come from things like lycopene, found in tomatoes and watermelon. And then the darker colors - the purples, blues, in berries," she says.

But Prior cautioned that just because a food has proven to be antioxidant-rich in the USDA's lab, that does not mean all those nutrients will be successfully absorbed by the human digestive tract.

"As we learn more and more, we're finding that, depending on the chemical makeup of antioxidants in different foods, some of them aren't apparently absorbed as well, or else they are metabolized in a form where they are no longer antioxidants," he says.

Whether a food is eaten fresh, frozen, processed, or cooked can also affect its antioxidant potency, Prior says. Blueberries are best when eaten fresh rather than cooked in a pie, for example. On the other hand, research has shown that gentle cooking raises the antioxidant power of tomatoes, he notes.

Although experts are working hard on the project, ongoing efforts to come up with daily dietary guidelines for antioxidant consumption will be "a long process," Prior says.

For her part, Anding said people should not focus on one particular food, but attempt to consume daily servings of a variety of fruits, vegetables, and other wholesome foods.

Looking over the USDA list, Anding suggests creating what she called an antioxidant "power salad."

Always consult your physician for more information.

Online Resources

American Heart Association

Centers for Disease Control and Prevention (CDC)

HealthierUS.Gov

National Heart, Lung, and Blood Institute (NHLBI)

National Institutes of Health (NIH)

National Library of Medicine

US Health and Human Services