Arrhythmia

An irregular heartbeat. People with diabetes are at greater risk for developing a type of arrhythmia called atrial fibrillation.

The heart has four chambers — two upper chambers, called atria, and two lower chambers, called ventricles. During a normal heartbeat, a complex set of electrical signals causes the atria to contract, sending blood into the ventricles, and then causes the ventricles to contract, sending blood to the lungs and the rest of the body. When the electrical impulses that coordinate heartbeats don’t work properly, the result is an arrhythmia.

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The risk of developing an arrhythmia increases with age; arrhythmias are common in older adults, and most serious arrhythmias affect people over the age of 60. Other risk factors for arrhythmia include having had a heart attack or heart failure — both of which indicate damage to the heart muscle — leaking or narrowed heart valves, and congenital heart defects. Other conditions that can increase the risk include high blood pressure, infections that damage the heart, diabetes, sleep apnea (in which breathing briefly and repeatedly stops during sleep), and an overactive or underactive thyroid gland.

There are three common types of arrhythmias. Supraventricular arrhythmias originate in the atria or the AV node, a tiny area of tissue that allows electrical signals to pass between the atria and the ventricles. Types of supraventricular arrhythmias include premature beats, atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia.

The most common type of arrhythmia is premature beats, which usually are harmless and cause no symptoms. When symptoms occur, they usually take the form of a feeling of fluttering in the chest or a skipped beat. Other supraventricular arrhythmias fall under the category of tachycardias (abnormally fast heart rates). Atrial fibrillation is a very fast and irregular contraction of the atria and is the most common type of serious arrhythmia. In atrial fibrillation, the signals that begin a heartbeat originate in the wrong part of the heart and are conducted abnormally. This causes the walls of the atria to quiver instead of beating normally, keeping them from pumping blood as they should. Atrial fibrillation usually isn’t life-threatening. However, blood clots can form from the blood pooling in the fibrillating atria rather than flowing into the ventricles. The clot can travel to the brain, causing a stroke. Atrial fibrillation that persists for a long period of time can weaken the heart and inhibit its ability to pump blood efficiently, causing heart failure.

Atrial flutter is similar to atrial fibrillation in terms of symptoms and complications, but the electrical signals spread through the atria in a regular rhythm. Paroxysmal supraventricular tachycardia is a very fast heart rate that begins and ends suddenly. It, too, is the result of problems with the electrical connection between the atria and the ventricles. Usually, this type of arrhythmia is not dangerous.

Ventricular arrhythmias, which include ventricular tachycardia and ventricular fibrillation, start in the ventricles and are very dangerous. In ventricular tachycardia, the ventricles beat quickly, but in a regular fashion. Ventricular tachycardia can turn into other, more dangerous arrhythmias, such as ventricular fibrillation. In ventricular fibrillation, the ventricles quiver instead of beating normally. Ventricular fibrillation can cause people to lose consciousness and, if not treated within minutes, die.

Bradyarrhythmias are characterized by abnormally slow heartbeats, which can keep enough blood from reaching the brain, thus causing the person to lose consciousness. Bradyarrhythmias can be caused by a heart attack, conditions that change the heart’s electrical activity, an imbalance of potassium and other chemicals in the blood, and certain medicines, such as beta-blockers.

Some arrhythmias cause no signs or symptoms, but some can cause heart palpitations (the sensation that the heart is skipping a beat, fluttering, or beating too hard) or a slow heartbeat or irregular heartbeat. Some more serious signs and symptoms include anxiety, weakness, dizziness, lightheadedness, fainting or nearly fainting, sweating, shortness of breath, and chest pain. If you experience symptoms of a cardiac arrhythmia, see your doctor immediately.

A number of types of medicines are used to treat cardiac arrhythmias. Some are used to slow down a fast heart rate, including beta-blockers, calcium channel blockers, and digoxin (brand names Lanoxin, Digox, Digitek, Lanoxicaps). Another class of drugs, called antiarrhythmics, is used for restoring an abnormal heart rhythm to normal. People with atrial fibrillation or certain other arrhythmias are often treated with blood thinners to reduce the risk of clots.

Surgery is sometimes used to treat arrhythmias. A small electronic device (either a pacemaker or an implantable cardioverter defibrillator [ICD]) is placed under the skin of the chest or abdomen to help control an abnormal heart rhythm using electrical pulses to prompt the heart to beat at a normal rate.

In a procedure called catheter ablation, a long, flexible tube called a catheter is inserted into a blood vessel in the arm, upper thigh, or neck and is guided to the heart. A machine sends energy through the catheter to the heart, destroying small areas of the heart tissue where the arrhythmia originates.

A common type of surgery for treating atrial fibrillation is called maze surgery, in which the surgeon makes small cuts or burns in the atria that prevent the spread of haphazard electrical signals.

Vagal maneuvers are simple exercises that are sometimes used to slow down certain types of supraventricular tachycardias by affecting the vagus nerve, which helps control the heart rate. Your health-care provider can advise you on how and when to use vagal maneuvers if he believes they’d be helpful for you.

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