University of Virginia Health System

Sleep Apnea Tied To Heartbeat Abnormality

Atrial Fibrillation A Concern For People With This Sleep Problem

< June 4, 2003 >A new study finds a close association between sleep apnea and atrial fibrillation, a heartbeat abnormality that can be fatal.

Sleep apnea is a serious, potentially life-threatening condition that occurs in all age groups and both genders. It is more common in men, although it may be under-diagnosed in women. It is estimated that as many as 18 million Americans have sleep apnea.

Early recognition and treatment of sleep apnea is important. In addition to its link to atrial fibrillation, it is associated with high blood pressure (hypertension), heart attack, and stroke.

Risk for Heart Irregularity Doubles

The risk of recurrent atrial fibrillation is doubled in people with untreated sleep apnea, says a Mayo Clinic study reported in the medical journal Circulation.

In the Mayo Clinic study, obstructive sleep apnea, in which there is a blockage of the airway, was the single factor most closely associated with recurrence of atrial fibrillation.

"To our knowledge, this is the first study showing that untreated obstructive sleep apnea is associated with an increased risk of recurrent atrial fibrillation, and that the risk is not explained by other factors," says Dr. Virend Somers, the Mayo Clinic cardiologist who led the study.

Atrial fibrillation is a type of arrthymia (irregular heart rhythm). With atrial fibrillation, the electrical signals in the atria (the two upper chambers of the heart) are fired in a very fast and uncontrolled manner. The atria quiver instead of contract.

The electrical signals then arrive in the ventricles in an irregular fashion. When the heart does not beat effectively, the blood may pool or clot. If a blood clot becomes lodged in an artery in the brain, a stroke may occur.

Cardiologists and Sleep Experts Collaborate

"Cardiologists are now awakening to the importance of identifying and treating sleep-disordered breathing in their patients," says Dr. Barbara Phillips, director of the University of Kentucky Sleep Disorders Center and a spokeswoman for the National Sleep Foundation.

The Mayo Clinic study followed 79 people treated for atrial fibrillation who had not been diagnosed with sleep apnea and 39 patients with both fibrillation and sleep apnea.

Of the 39 apnea patients, 27 got either no treatment or inadequate treatment for the condition. After a year, fibrillation recurred in 22 (or 81 percent) of the apnea patients with untreated apnea and five (or 42 percent) of the apnea patients who received adequate treatment.

Drugs or CPAP - continuous positive airway pressure, using a machine to force air into the nasal passages - can help treat sleep apnea, but it comes back in more than half of all patients within a year.

This is an important study because it is the first to describe the results of treating sleep apnea in atrial fibrillation patients, Dr. Phillips says. "CPAP made a big difference for those patients who used it," she says.

Experts say the results are important because obesity increases the incidence of sleep apnea. The rise in the numbers of Americans who are obese could contribute to the rising incidence of sleep apnea.

"Appropriate treatment for those with both conditions is CPAP first," Dr. Phillips says. "Not only can it help a fibrillation, it improves blood pressure, reduces the risk of heart attacks, reduces other cardiac arrhythmias, and improves heart function in patients with heart failure."

Always consult your physician for more information.

What Is Sleep Apnea?

Sleep apnea is characterized by a number of involuntary breathing pauses or "apneic events" during a single night's sleep - may be as many as 20 to 30 or more events per hour.

These events are almost always accompanied by snoring between apneic episodes (although not everyone who snores has sleep apnea). Sleep apnea may also be characterized by choking sensations.

The frequent interruptions of deep, restorative sleep often lead to early morning headaches and excessive daytime sleepiness.

During the apneic event, the person is unable to breathe in oxygen and to exhale carbon dioxide, resulting in low levels of oxygen and increased levels of carbon dioxide in the blood.

The reduction in oxygen and increase in carbon dioxide alert the brain to resume breathing and cause an arousal. With each arousal, a signal is sent from the brain to the upper airway muscles to open the airway; breathing is resumed, often with a loud snort or gasp.

Frequent arousals, although necessary for breathing to restart, prevent a person from getting enough restorative, deep sleep.

How Are Arrhythmias Diagnosed?

There are several different types of procedures that may be used to diagnose arrhythmias:

electrocardiogram (EKG or ECG)
An electrocardiogram is a measurement of the electrical activity of the heart. By placing electrodes at specific locations on the body (chest, arms, and legs), a graphic representation, or tracing, of the electrical activity can be obtained as the electrical activity is received and interpreted by an EKG machine.

There are several variations of the EKG test:

resting EKG
For this procedure, small sticky patches called electrodes are attached to the chest, arms, and legs. These electrodes are connected to the EKG machine by wires. The EKG machine is then started and records the heart's electrical activity for a minute or so. The patient is lying down during this EKG.

exercise EKG, or stress test
The patient is attached to the EKG machine as described above. However, rather than lying down, the patient exercises by walking on a treadmill or pedaling a stationary bicycle while the EKG is recorded.

signal-average EKG
This procedure is done in the same manner as a resting EKG, except that the heart's electrical activity is recorded over a longer period of time, usually 15-20 minutes. Signal-average EKG is done when arrhythmia is suspected but not seen on a resting EKG.

electrophysiologic studies (EPS)
This is an invasive test in which a small catheter (hollow tube) is inserted through the groin or neck into the heart. This gives the physician the capability of finding the site of the arrhythmia's origin within the heart tissue, thus, determining how to best treat it.

Holter monitor
A Holter monitor is an EKG recording done over a period of 24 or more hours. Three electrodes are attached to the patient's chest and connected to a small portable EKG recorder by lead wires. The patient goes about his/her usual daily activities (except for activities causing an excessive amount of sweating which would cause the electrodes to become loose or fall off) during this procedure.

Online Resources

(Our Organization is not responsible for the content of Internet sites.)

American Heart Association

Centers for Disease Control and Prevention (CDC)

Circulation

DASH Eating Plan, NHLBI

Eat Five to Nine A Day, National Cancer Institute (NCI)

Healthier US.Gov

National Heart, Lung, and Blood Institute (NHLBI)

National Institutes of Health (NIH)

For more information on health and wellness, please visit health information modules on this Web site.

Fish Oil Prevents Irregular Heartbeats in Lab Study

According to a new study reported in the medical journal Circulation, fatty acids in certain types of fish are stored in individual heart cells and serve to prevent irregular heart rhythms (also known as arrhythmias) by working through the heart's calcium and sodium channels.

Researchers reporting in Circulation hope their study in animals will further the understanding of how fish oil may work to help prevent some heart problems in humans.

Sudden cardiac death causes at least 250,000 deaths each year in the US alone, reports the American Heart Association (AHA).

As its name implies, this type of death occurs unexpectedly and in people who may or may not have diagnosed heart disease.

AHA Guidelines Recommend Fatty Acids

The body requires two types of polyunsaturated fatty acids (PUFAs) in order to function: n-6 and n-3, experts say.

Both must come from the diet, because the body does not produce them.

Since 2000, AHA dietary guidelines have recommended that healthy adults eat at least two servings a week, especially fish high in omega-3 fatty acids, such as mackerel, lake trout, herring, sardines, albacore tuna, and salmon.

"The heartbeat itself is due to electrical activity which, in turn, results from small ions - sodium, calcium, and potassium - moving through specific ion channels in the cell membrane of heart cells.

These channels recognize the specific ions," says Dr. Alexander Leaf, lead author of the study and a Harvard University scientist.

When a person has a heart attack, the cells in the area that is no longer receiving blood may die. There remain a few cells in the peripheral area between the dead cells and the remaining normal heart muscle, which become "mischief makers," Dr. Leaf says.

"They are much more ready to shoot off an electrical signal that causes a contraction of the heart, and they do this out of the normal electrical cycle that produces the regular rhythm of the heartbeat," he says. "It can produce arrhythmia."

The fatty acids eliminate the mischief makers by blocking excessive sodium and calcium currents in the channels of the heart. "By modulating these two ion channels, they preserve the normal electrical activity of the heart," Dr. Leaf explains.

And the benefit takes place very quickly. "The effect comes on very soon if one starts eating these fatty acids regularly," Dr. Leaf says. "It takes just a small amount."

Expert Suggests Further Study

Dr. J. Anthony Gomes, professor of medicine and director of cardiac electrophysiology and electrocardiography at the Mount Sinai School of Medicine in New York City, says that further study in humans should be conducted in order to best understand now fish oil addresses heart rhythm irregularities.

Always consult your physician for more information.

What Are Fatty Acids?

Fatty acids are the basic chemical units in fat. They may be saturated, polyunsaturated, monounsaturated, or trans fats. These fatty acids differ in their chemical compositions and structures, and in the way in which they affect your blood cholesterol levels.

Saturated fats:

• is used by the liver to manufacture cholesterol.
  
  
• is considered the most dangerous kind of fat because it has been shown to raise blood cholesterol levels, particularly the LDL.
  
  
• should comprise no more than 10 percent of your daily calorie intake.
  
  
• examples include: meats, butter, cocoa butter, coconut, and palm oils.
  

Polyunsaturated fats:

• do not appear to raise blood cholesterol levels.
  
  
• examples include: safflower, sunflower, corn, and vegetable oils, margarines, and soybean oils.
  

Monounsaturated fats:

• do not seem to have any affect on blood cholesterol.
  
  
• examples include olive and canola oils.
  

Trans fats:

• by-products of hydrogenation, a chemical process used to change liquid unsaturated fat to a more solid fat.
  
  
• structurally similar to saturated fat, trans fatty acids may have a great impact on raising total and LDL cholesterol levels.
  
  
• examples include stick margarine and fats found in commercially prepared cakes, cookies, and snack foods.