by the pines

Introduction

Heart rhythm problems (arrhythmias) occur when the electrical impulses in your heart that coordinate your heartbeats don’t function properly, causing your heart to beat too fast, too slow or irregularly.

Arrhythmias are common and usually harmless. Most people have occasional, irregular heartbeats that may feel like a skipped, fluttering or racing heart. However, some heart arrhythmias may cause bothersome — sometimes even life-threatening — signs and symptoms.

Advances in medical technology have added new treatment methods to the procedures that doctors may use to try to control or eliminate arrhythmias. In addition, because troublesome arrhythmias are often made worse — or are even caused — by a weak or damaged heart, you may be able to reduce your arrhythmia risk by adopting a heart-healthy lifestyle.

Signs and symptoms

Arrhythmias may not cause any signs or symptoms. In fact, your doctor might detect them before you do, during a routine examination. But often, abnormal heart rhythms cause noticeable signs and symptoms, which may include:

• A fluttering in your chest
• A racing heartbeat
• A slow heartbeat
• Chest pain
• Shortness of breath
• Lightheadedness
• Dizziness
• Fainting (syncope) or near fainting

Noticeable signs and symptoms don’t always indicate a serious problem. Some people who feel arrhythmias don’t have a serious problem, while others who have life-threatening arrhythmias have no symptoms at all.

What’s a normal heartbeat?
When your heart beats, the electrical impulses that cause it to contract must follow a precise pathway through your heart. Any interruption in these impulses can cause an arrhythmia.

Before learning about what can cause an arrhythmia, first consider what should happen during a normal heartbeat.

Your heart is divided into four hollow chambers. Divided top to bottom, the chambers on each half of your heart form two adjoining pumps with an upper chamber (atrium) and a lower chamber (ventricle).

During a heartbeat, the smaller, less muscular atria contract and fill the relaxed ventricles with blood. This contraction starts when the sinus node — a small group of cells in your right atrium — sends an electrical impulse causing your right and left atria to contract.

The impulse then travels to the atrioventricular node, located at the center of your heart and which lies on the pathway between your atria and your ventricles. From here, the signal exits the atrioventricular node and travels through your ventricles, causing them to contract and discharge blood throughout your body.

In a healthy heart, this process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute. Athletes at rest commonly have a heart rate less than 60 beats a minute because their hearts are so efficient.

Causes

Common causes of arrhythmias, or conditions that can lead to arrhythmias, include heart disease, high blood pressure, diabetes, smoking, excessive use of alcohol or caffeine, drug abuse, and stress. Over-the-counter medications, prescription medications, dietary supplements and herbal remedies also can cause arrhythmias in some people.

Scarring can result from numerous problems — most commonly, from a previous heart attack — and this scarring may disrupt the initiation or conduction of electrical impulses.

In a healthy person with a normal, healthy heart, it’s unlikely for a sustained arrhythmia to develop without some outside trigger, such as an electrical shock or the use of illicit drugs. That’s primarily because a healthy person’s heart is free from any abnormal conditions, such as an area of scarred tissue.

However, in a heart with some evidence of disease or deformity, the initiation or conduction of the heart’s electrical impulses may be destabilized, making arrhythmias more likely to develop.

Any pre-existing structural heart condition can lead to arrhythmia development due to:

• Inadequate blood supply. If blood supply to the heart is somehow reduced, this can alter the ability of heart tissue — including the cells that conduct electrical impulses — to function properly.
• Damage or death of heart tissue. When heart tissue becomes damaged or dies, this can affect the way electrical impulses spread in the heart.

These pre-existing heart conditions may include:

• Coronary artery disease (CAD). Although it has been linked to many arrhythmias, CAD is most closely associated with ventricular arrhythmias and sudden cardiac death. Narrowing of the arteries that occurs with CAD can progress until a portion of the heart dies as a result of lack of blood flow (heart attack). A previous heart attack leaves behind a scar. Electrical short circuits around the scar can prevent normal heart function by causing the heart to beat dangerously fast (ventricular tachycardia) or to quiver (ventricular fibrillation).
• Cardiomyopathy. This occurs primarily when the heart’s ventricular walls stretch and enlarge (dilated cardiomyopathy) or when the left ventricle wall thickens and constricts (hypertrophic cardiomyopathy). In either case, cardiomyopathy decreases your heart’s blood-pumping efficiency and often leads to heart tissue damage.
• Valvular heart diseases. Leaking or narrowing of your heart valves can lead to stretching and thickening of your heart muscle (myocardium). When the chambers become enlarged or weakened due to the added stress caused by the tight or leaking valve, there’s an increased risk of developing arrhythmia.

Types of arrhythmias
Doctors classify arrhythmias not only by where they originate (atria or ventricles) but also by the speed of heart rate they cause:

• Tachycardia (tak-ih-KAHR-de-uh). This refers to a fast heartbeat — a heart rate greater than 100 beats a minute.
• Bradycardia (brad-e-KAHR-de-uh). This refers to a slow heartbeat — a resting heart rate less than 60 beats a minute.

Not all tachycardias or bradycardias indicate disease. For example, during exercise it’s normal to develop sinus tachycardia as the heart speeds up to provide your tissues with more oxygen-rich blood.

Tachycardias in the atria
Tachycardias originating in the atria include:

• Atrial fibrillation. This fast and chaotic beating of the atrial chambers is a common arrhythmia. It mainly affects older people. Your risk of developing atrial fibrillation increases past age 60, mostly due to the wear and tear that may affect your heart’s function as you age, especially if you’ve had high blood pressure or other heart problems. During atrial fibrillation, the electrical activity of the atria becomes uncoordinated. The atria beat so rapidly — as fast as 350 to 600 beats a minute — that instead of producing a single, forceful contraction, they quiver (fibrillate). Atrial fibrillation can be intermittent (paroxysmal), lasting a few minutes to an hour or more before returning to a regular heart rhythm. It can also be chronic, causing an ongoing problem. Atrial fibrillation is seldom a life-threatening arrhythmia, but over time it can be the cause of more serious conditions, such as stroke.
• Atrial flutter. Atrial flutter is similar to atrial fibrillation. Both can coexist in your heart, coming and going in an alternating fashion. The key distinction is that more-organized and more-rhythmic electrical impulses are called atrial flutter. These occur because atrial flutter, unlike atrial fibrillation, arises from a short circuit. In typical atrial flutter, this short circuit exists in the right atrium. This is an important distinction because typical right atrial flutter is more amenable to some forms of treatment, such as catheter ablation.
• Supraventricular tachycardia (SVT). SVT is a broad term that includes many forms of arrhythmia originating above the ventricles (supraventricular). SVTs usually cause a burst of rapid heartbeats that begin and end suddenly and can last from seconds to hours. These often start when the electrical impulse from a premature heartbeat begins to circle repeatedly through an extra pathway. SVT may cause your heart to beat 160 to 200 times a minute. Although generally not life-threatening in an otherwise normal heart, symptoms from the racing heart may feel quite uncomfortable. These arrhythmias are common in young people.
• Wolff-Parkinson-White syndrome. One cause of SVT is known as Wolff-Parkinson-White syndrome. This arrhythmia is caused by an extra electrical pathway between the atria and the ventricles. This pathway may allow electrical current to pass between the atria and the ventricles without passing through the AV node, leading to short circuits and rapid heartbeats.

Tachycardias in the ventricles
Tachycardias occurring in the ventricles include:

• Ventricular tachycardia (VT). This fast, regular beating of the heart is caused by abnormal electrical impulses originating in the ventricles. Often, these are due to a short circuit around a scar from a previous heart attack and can cause the ventricles to contract more than 200 beats a minute. Most VT occurs in people with some form of heart-related problem, such as scars or damage within the ventricle muscle from coronary artery disease or a heart attack. Sometimes, ventricular tachycardia last for 30 seconds or less (unsustained) and are usually harmless, although they cause inefficient heartbeats. Still, an unsustained VT may be a predictor for more-serious ventricular arrhythmias, such as longer lasting (sustained) VT. An episode of sustained VT is a medical emergency. It may be associated with palpitations, dizziness, fainting or possibly death. Without prompt medical treatment, sustained ventricular tachycardia often degenerates into ventricular fibrillation. Rarely, VT occurs in an otherwise normal heart. In this setting, it’s far less dangerous, but the condition still needs the attention of a doctor.
• Ventricular fibrillation. About 300,000 Americans die every year of sudden cardiac death believed to be caused by ventricular fibrillation. With ventricular fibrillation, rapid, chaotic electrical impulses cause your ventricles to quiver uselessly instead of pumping blood. Without an effective heartbeat, your blood pressure plummets, instantly cutting off blood supply to your vital organs — including your brain. Most people lose consciousness within seconds and require immediate medical assistance including cardiopulmonary resuscitation (CPR). Your chances of survival may be prolonged if CPR is delivered until your heart can be shocked back into a normal rhythm with a device called a defibrillator. Without CPR or defibrillation, death results in minutes. Most cases of ventricular fibrillation are linked to some form of heart disease. Ventricular fibrillation is frequently triggered by a heart attack.
• Long QT syndrome. This syndrome may be either an acquired or an inherited condition. In older adults, this rare arrhythmia may be triggered by certain drugs — many of them commonly used — taken alone or in combination. These drugs affect the heart’s electrical function. On an electrocardiogram, the letter Q marks the point where an electrical impulse signals the ventricles to contract. The letter T marks the point where the cells of your ventricles have electrically recharged for the next heartbeat. When the QT interval is prolonged, ventricle cells may not have recovered in time to properly conduct the next heartbeat. People with long QT syndrome are prone to palpitations and fainting spells, and may have an increased risk of sudden death.

Bradycardias
Although a heart rate below 60 beats a minute while at rest is considered bradycardia, a low resting heart rate doesn’t always signal a problem. If you’re physically fit, you may have an efficient heart capable of pumping an adequate supply of blood with fewer than 60 beats a minute at rest. However, if you have a slow heart rate and your heart isn’t pumping enough blood, you may have one of several bradycardias including:

• Sick sinus. If your pacemaking sinus node isn’t sending impulses properly, your heart rate may be too slow, or it may speed up and slow down intermittently. If your sinus node is functioning properly, sick sinus can be caused by an impulse block near the sinus node that’s slowing, disrupting or completely blocking conduction.
• Conduction block. A block of your heart’s electrical pathways can occur in or near the AV node or along pathways that conduct impulses to each ventricle. Depending on the location and type of block, the impulses between your atria and ventricles may be slowed or partially or completely blocked. If the signal is completely blocked, certain cells in the AV node or ventricles are capable of initiating a steady, although usually slower, heartbeat. Some blocks may cause no signs or symptoms, and others may cause skipped beats or bradycardia. Even without signs or symptoms, a conduction block is usually detectable on an electrocardiogram (ECG). Since some blocks are caused by heart disease, an ECG showing a block may be an early sign of heart problems.

Premature heartbeats
Premature heartbeats can originate in either the atria or the ventricles. Although it often feels like a skipped heartbeat, a premature heartbeat is actually an extra beat between two normal heartbeats. Premature heartbeats occurring in the ventricles come before the ventricles have had time to fill with blood following a regular heartbeat.

Although you may feel an occasional premature beat, it seldom indicates a more serious problem. Still, a premature beat can trigger a longer lasting arrhythmia — especially in people with heart disease. These types of arrhythmias are commonly caused by stimulants, such as caffeine from coffee, tea and soft drinks, over-the-counter cold remedies containing pseudoephedrine, and some asthma medications.

Risk factors

Certain factors may increase your risk of developing an arrhythmia. These include:

• Age. With age, your heart muscle naturally weakens and loses some of its suppleness. This may affect how electrical impulses are conducted.
• Genetics. Being born with a heart abnormality may affect your heart’s electrical function.
• Coronary artery disease, other heart problems and previous heart surgery. Narrowed heart arteries, heart attack, abnormal valves, prior heart surgery, cardiomyopathy and other heart damage are risk factors for almost any kind of arrhythmia.
• Thyroid problems. Your metabolism speeds up when your thyroid gland releases excess hormones. This may cause fast or irregular heartbeats and is most commonly associated with atrial fibrillation. Your metabolism slows when your thyroid gland hormone levels are inadequate, which may cause a bradycardia.
• Drugs and supplements. Over-the-counter cough and cold medicines containing pseudoephedrine and certain prescription drugs may contribute to arrhythmia development. The herbal supplement ephedra also increases the risk of arrhythmia, but in early 2004, the Food and Drug Administration banned ephedra from the marketplace because of such health concerns.
• High blood pressure. This increases your risk of developing coronary artery disease. It may also cause the walls of your left ventricle to thicken, possibly altering how your heart’s electrical impulses are conducted.
• Obesity. Along with being a risk factor for coronary artery disease, obesity may increase your risk of developing an arrhythmia.
• Diabetes. Your risk of developing coronary artery disease and hypertension greatly increases with uncontrolled diabetes. In addition, episodes of low blood sugar (hypoglycemia) can trigger an arrhythmia.
• Obstructive sleep apnea. This disorder can cause bradycardia and bursts of atrial fibrillation.
• Electrolyte imbalance. Electrolytes, such as potassium, sodium, calcium and magnesium, help trigger and conduct the electrical impulses in your heart. Electrolyte levels that are too high or too low can affect your heart’s electrical impulses and contribute to arrhythmia development.
• Alcohol consumption. Drinking too much alcohol can affect factors that alter the conduction of electrical impulses in your heart or increase the chance of developing atrial fibrillation. In fact, development of atrial fibrillation after an episode of heavy alcohol intake is sometimes called “holiday heart syndrome.” Chronic alcohol abuse may depress the function of your heart and can lead to cardiomyopathy. Both are factors in arrhythmia development.
• Stimulant use. Stimulants, such as caffeine and nicotine, can cause premature heartbeats and may contribute to the development of more serious arrhythmias. Illicit drugs, such as amphetamines and cocaine, may profoundly affect the heart and lead to many types of arrhythmias or to sudden death due to ventricular fibrillation.

When to seek medical advice

Arrhythmias may cause you to feel premature beats, or you may feel that your heart is racing or beating too slowly. Other signs and symptoms may be related to diminished blood output from your heart. These include shortness of breath or wheezing, weakness, dizziness, lightheadedness, fainting or near fainting, and chest pain or discomfort. Seek urgent medical care if you suddenly or frequently experience any of these signs and symptoms at a time when you wouldn’t expect to feel them.

With little or no blood being pumped through the body, a person with ventricular fibrillation will collapse within seconds and soon won’t be breathing or have a pulse. If this occurs, follow these steps:

• Call 911 or the emergency number in your area.
• If you or someone nearby knows cardiopulmonary resuscitation (CPR), administer it if it’s needed. CPR can help maintain blood flow to the organs until an electrical shock (defibrillation) can be given.

Portable defibrillators are available in an increasing number of places, such as airplanes, police cars and shopping malls, and can even be purchased for your home. These automatic external defibrillators come with built-in instructions for their use. They’re programmed to allow a shock only when appropriate.

Screening and diagnosis

To diagnose a heart arrhythmia, your doctor may ask about — or test for — conditions that may trigger your arrhythmia, such as heart disease or a problem with your thyroid gland. Your doctor may also perform heart monitoring tests specific to arrhythmias. These tests either passively monitor your heart or try to actively induce an arrhythmia while closely monitoring your heart.

Passive heart monitoring tests may include:

• Electrocardiogram (ECG). During an ECG, sensors (electrodes) that can detect the electrical activity of your heart are attached to your chest and sometimes to your limbs. An ECG measures the timing and duration of each electrical phase in your heartbeat.
• Holter monitor. This portable ECG device can be worn for a day or more to record your heart’s activity as you go about your routine.
• Event monitor. For sporadic arrhythmias, you keep this portable ECG device at home, attaching it to your body and activating it only when you experience symptoms of an arrhythmia. This permits your doctor to determine your heart rhythm at the time of your symptoms, to see if there’s an association.
• Echocardiogram. A hand-held device (transducer) placed on your chest uses sound waves to produce images of your heart’s size, structure and motion.

Heart monitoring tests that your doctor may use to induce an arrhythmia include:

• Stress test. Some arrhythmias are triggered or worsened by exercise. During a stress test, you’ll be asked to exercise on a treadmill or stationary bicycle while your heart activity is monitored by an ECG. Your doctor may use a drug to stimulate your heart in a way that’s similar to exercise. This may be particularly helpful if you have difficulty doing exercises, and it can also be used to detect coronary artery disease.
• Tilt table test. Your doctor may recommend this test if you’ve had recurrent fainting spells. Your heart rate and blood pressure are monitored as you lie flat on a table. The table is then tilted as if you were standing up. Your doctor observes how your heart — and the nervous system that controls your heart — respond to the change in angle.
• Electrophysiologic testing and mapping. In this test, thin, flexible tubes (catheters) tipped with electrodes are threaded through your blood vessels to a variety of spots within your heart. Once in place, the electrodes can precisely map the spread of electrical impulses through your heart. In addition, your cardiologist can use the electrodes to stimulate your heart to beat at rates that may trigger — or halt — an arrhythmia. This allows your doctor to observe the location of the arrhythmia and the mechanisms that may be causing it. If your cardiologist determines that radiofrequency catheter ablation— a catheter-based treatment option for many arrhythmias — is appropriate, he or she can perform this procedure during an electrophysiologic test.

Complications

Certain arrhythmias may increase your risk of developing conditions such as:

• Stroke. When your atrial chambers fibrillate, they’re unable to pump blood effectively. Stagnant blood in the atria can form blood clots. If a clot breaks loose, it can travel to and obstruct a brain artery, causing an ischemic stroke. This may damage or kill a portion of your brain or lead to death.
• Congestive heart failure. This can result if your heart is pumping ineffectively for a prolonged period due to a bradycardia or tachycardia, such as atrial fibrillation. Sometimes, controlling the rate of an arrhythmia that’s causing congestive heart failure can lead to improved heart function.

Treatment

If you’ve received a diagnosis of arrhythmia, treatment may or may not be necessary. Usually, it’s required only if the arrhythmia is causing significant symptoms or if it’s putting you at risk of a more serious arrhythmia or arrhythmia complication.

Treating bradycardias
If symptom-producing bradycardias don’t have a cause that can be corrected — such as hypothyroidism or a drug side effect — doctors often treat them with a pacemaker. A pacemaker is a small, battery-powered device that’s usually implanted near your collarbone. One or more electrode-tipped wires run from the pacemaker through your blood vessels to your inner heart. If your heart rate is too slow or if it stops, the pacemaker sends out electrical impulses that stimulate your heart to beat at a steady, proper rate. The newest pacemakers can monitor and pace your atria or ventricles — or both — in proper sequence to maximize the output of blood from your heart. In addition, your doctor can program your pacemaker to meet your pacing needs.

Treating tachycardias
For tachycardias originating in the atria or ventricles, treatments may include one or more of the following:

• Vagal maneuvers. You may be able to stop a supraventricular tachycardia (SVT) by using particular maneuvers, which include holding your breath and straining, dunking your face in ice water, or coughing. Your doctor may be able to recommend other maneuvers to halt a fast heartbeat. These maneuvers affect the nervous system that controls your heartbeat (vagal nerves), often causing your heart rate to slow.
• Medications. Many types of tachycardias respond well to anti-arrhythmic medications. Though they don’t cure the problem, they can reduce episodes of tachycardia or slow down the heart when an episode occurs. Some medications can slow down your heart so much that you may need a pacemaker. It’s very important to take any anti-arrhythmic medication exactly as directed by your doctor in order to avoid complications.
• Cardioversion. If you have an atrial tachycardia, including atrial fibrillation, your doctor may use cardioversion, which is an electrical shock used to reset your heart to its regular rhythm. Usually this is done externally in a monitored setting, and you’re given medication to sedate you during the procedure, so there’s no pain involved.
• Cardiac ablation. In this procedure, one or more catheters are threaded through your blood vessels to your inner heart. They’re positioned on areas of your heart identified by your doctor as causing your arrhythmia. Electrodes at the catheter tips are heated with radiofrequency energy. Another method involves cooling the tips of the catheters, which freezes the problem tissue. Either method destroys (ablates) a small spot of heart tissue and creates an electrical block along the pathway that’s causing your arrhythmia. Usually, this stops your arrhythmia.

Implantable devices
Treatment for heart arrhythmias also may involve use of an implantable device:

• Pacemaker. A pacemaker is an implantable device that helps regulate slow heartbeats (bradycardia). A small battery-driven device is placed under the skin near the collarbone in a minor surgical procedure. An insulated wire extends from the device to the right side of the heart, where it’s permanently anchored. If a pacemaker detects a heart rate that’s too slow or no heartbeat at all, it emits electrical impulses that stimulate your heart to speed up or begin beating again. Most pacemakers have a sensing device that turns them off when your heartbeat is above a certain level. It turns back on when your heartbeat is too slow. Most people can be discharged from the hospital one to two days after a pacemaker is implanted.
• Implantable cardioverter-defibrillator (ICD). Your doctor may recommend this device if you’re at high risk of developing a dangerous ventricular tachycardia (VT) or ventricle fibrillation (VF). Implantable defibrillator units designed to treat atrial fibrillation also are available. An ICD is a battery-powered unit that’s implanted near the left collarbone. One or more electrode-tipped wires from the ICD run through veins to the heart. The ICD continuously monitors your heart rhythm. If it detects a rhythm that’s too slow, it paces the heart as a pacemaker would. If it detects VT or VF, it sends out low- or high-energy shocks to reset the heart to a normal rhythm. An ICD may lessen your chance of having a fatal arrhythmia, compared with preventive drug treatment.

Surgical treatments
In some cases, surgery may be the recommended treatment for heart arrhythmias:

• Maze procedure. This involves making a series of surgical incisions in the atria. These heal into carefully placed scars in the atria that form boundaries that force electrical activation to proceed in an orderly manner from top to bottom. The procedure has a high success rate, but because it requires open-heart surgery, it’s usually reserved for people who don’t respond to other treatments. The surgeon may use a cryoprobe — an instrument for applying extreme cold to tissue — or a hand-held radiofrequency probe, rather than a scalpel, to create the scars.
• Ventricular aneurysm surgery. In some cases, an aneurysm in the heart is the cause of an arrhythmia. If catheter ablation and implanted ICD don’t work, you may need this surgery. It involves removing the bulge (aneurysm) that’s causing your arrhythmia. By removing the source of the abnormal impulses, the arrhythmia often can be eliminated.
• Coronary bypass surgery. If you have severe coronary artery disease in addition to frequent ventricular tachycardia, your doctor may recommend coronary bypass surgery. This may improve the blood supply to your heart and reduce the frequency of your ventricular tachycardia.

Self-care

Many arrhythmias can be blamed on underlying heart disease, so your doctor may advise that, in addition to other treatments, you make lifestyle changes that will keep your heart as healthy as possible.

For instance, he or she may advise that you:

• Eat heart-healthy foods
• Increase your physical activity
• Quit smoking
• Cut back on caffeine and alcohol
• Find ways to reduce the amount of stress in your life
• Avoid stimulant medications, such as medications found in over-the-counter treatments for colds and nasal congestion

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