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Heart arrhythmiasBy Mayo Clinic staff
Original Article: http://www.mayoclinic.com/health/heart-arrhythmias/DS00290
Heart rhythm problems (heart arrhythmias) occur when the electrical impulses in your heart that coordinate your heartbeats don't work properly, causing your heart to beat too fast, too slow or irregularly.
Heart arrhythmias (uh-RITH-me-uhs) may feel like a fluttering or racing heart, and they're often harmless. However, some heart arrhythmias may cause bothersome — sometimes even life-threatening — signs and symptoms.
Heart arrhythmia treatment can often control or eliminate irregular heartbeats. In addition, because troublesome heart 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.
Arrhythmias may not cause any signs or symptoms. In fact, your doctor might find you have an arrhythmia before you do, during a routine examination. Noticeable signs and symptoms don't necessarily mean you have a serious problem, however.
Noticeable arrhythmia symptoms may include:
- A fluttering in your chest
- A racing heartbeat (tachycardia)
- A slow heartbeat (bradycardia)
- Chest pain
- Shortness of breath
- Fainting (syncope) or near fainting
When to see a doctor
Arrhythmias may cause you to feel premature heartbeats, or you may feel that your heart is racing or beating too slowly. Other signs and symptoms may be related to reduced 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.
Ventricular fibrillation (VF) is one type of arrhythmia that can be deadly. It occurs when the heart beats with rapid, erratic electrical impulses. This causes pumping chambers in your heart (the ventricles) to quiver uselessly instead of pumping blood. Without an effective heartbeat, blood pressure plummets, cutting off blood supply to your vital organs. 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 there's no one nearby trained in cardiopulmonary resuscitation (CPR), provide hands-only CPR. That means uninterrupted chest compressions of about 100 a minute until paramedics arrive. To do chest compressions, push hard and fast in the center of the chest. You don't need to do rescue breathing.
- If you or someone nearby knows CPR, begin providing it if it's needed. CPR can help maintain blood flow to the organs until an electrical shock (defibrillation) can be given.
- Find out if an automated external defibrillator (AED) is available nearby. These portable defibrillators, which can deliver an electric shock that may restart heartbeats, are available in an increasing number of places, such as in airplanes, police cars and shopping malls. They can even be purchased for your home. No training is required. The AED will tell you what to do. They're programmed to allow a shock only when appropriate.
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Many things can lead to, or cause, an arrhythmia, including:
- A heart attack that's occurring right now
- Scarring of heart tissue from a prior heart attack
- Changes to your heart's structure, such as from cardiomyopathy
- Blocked arteries in your heart (coronary artery disease)
- High blood pressure
- Overactive thyroid gland (hyperthyroidism)
- Drinking too much alcohol or caffeine
- Drug abuse
- Dietary supplements and herbal treatments
- Electrical shock
- Air pollution
What's a normal heartbeat?
When your heart beats, the electrical impulses that cause it to contract follow a precise pathway through your heart. Any interruption in these impulses can cause an arrhythmia.
Your heart is divided into four chambers. 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 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 center of your heart, to the atrioventricular node that lies on the pathway between your atria and your ventricles. From here, the impulse exits the atrioventricular node and travels through your ventricles.
In a healthy heart, this process usually goes smoothly, resulting in a normal resting heart rate of 60 to 100 beats a minute. Conditioned athletes at rest commonly have a heart rate less than 60 beats a minute because their hearts are so efficient.
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-dee-uh). This refers to a fast heartbeat — a resting heart rate greater than 100 beats a minute.
- Bradycardia (brad-e-KAHR-dee-uh). This refers to a slow heartbeat — a resting heart rate less than 60 beats a minute.
Not all tachycardias or bradycardias mean you have heart disease. For example, during exercise it's normal to develop 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 often affects older people. Your risk of developing atrial fibrillation increases with age, mostly due to wear and tear on your heart, especially if you've had high blood pressure or other heart problems. During atrial fibrillation, the electrical signal that causes your heart to beat becomes uncoordinated. The atria beat so rapidly — as fast as 300 or more beats a minute — that instead of producing a single forceful contraction, they quiver (fibrillate). Atrial fibrillation can be dangerous, for over time it can cause more-serious conditions, such as stroke.
- Atrial flutter. Atrial flutter is similar to atrial fibrillation. Both can occur, coming and going in an alternating fashion. The heartbeats in atrial flutter are more-organized and more-rhythmic electrical impulses than in atrial fibrillation.
- 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 begins and ends suddenly and can last from seconds to hours. These bursts often start when the electrical impulse from a heartbeat begins to circle repeatedly through an extra pathway. Although SVT is generally not life-threatening in an otherwise normal heart, symptoms from the racing heart may feel quite uncomfortable.
- Wolff-Parkinson-White syndrome. One cause of SVT is known as Wolff-Parkinson-White syndrome. People with this condition have an extra electrical pathway between the atria and the ventricles. This pathway may allow electrical signals to pass between the atria and the ventricles without passing through the atrioventricular 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 that start in the ventricles. Often these are due to a problem with the electrical impulse traveling around a scar from a previous heart attack. VT can cause the ventricles to contract more than 200 beats a minute.
Most VT episodes occur 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 VT can last for 30 seconds or less (unsustained), and it might not cause any symptoms, although it causes inefficient heartbeats. Still, an unsustained VT may put you at risk of more-serious ventricular arrhythmias, such as longer lasting (sustained) VT. An episode of sustained VT is a medical emergency. Without prompt medical treatment, sustained ventricular tachycardia often worsens into ventricular fibrillation.
- Ventricular fibrillation. In ventricular fibrillation, rapid, chaotic electrical impulses cause your ventricles to quiver uselessly instead of pumping blood. Without an effective heartbeat, your blood pressure plummets, cutting off blood supply to your vital organs — including your brain. Most people lose consciousness within seconds and require immediate medical assistance, including chest compressions, defibrillation and cardiopulmonary resuscitation (CPR). Your chances of survival are better if chest compressions are 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. Long QT syndrome (LQTS) is a heart disorder that carries an increased risk of fast, chaotic heartbeats. The rapid heartbeats, caused by changes in the electrical system of your heart, may lead to fainting, which can be life-threatening. In some cases, your heart's rhythm may be so erratic that it can cause sudden death.
You can be born with a genetic mutation that puts you at risk of long QT syndrome. In addition, more than 50 medications, many of them common, may cause long QT syndrome. Some medical conditions, such as congenital heart defects, also may cause long QT syndrome.
Bradycardia — a slow heartbeat
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 sinus node, which is responsible for setting the pace of your heart, isn't sending impulses properly, your heart rate may be too slow, or it may speed up and slow down intermittently. Sick sinus can also be caused by scarring near the sinus node that's slowing, disrupting or blocking the travel of impulses.
- Conduction block. A block of your heart's electrical pathways can occur in or near the atrioventricular node, which lies on the pathway between your atria and your ventricles. A block can also occur along other pathways to each ventricle. Depending on the location and type of block, the impulses between the upper and lower halves of your heart may be slowed or blocked. If the signal is completely blocked, certain cells in the atrioventricular node or ventricles can make a steady, although usually slower, heartbeat. Some blocks may cause no signs or symptoms, and others may cause skipped beats or bradycardia.
Although it often feels like a skipped heartbeat, a premature heartbeat is actually an extra beat. Even though you may feel an occasional premature beat, it seldom means you have a more serious problem. Still, a premature beat can trigger a longer lasting arrhythmia — especially in people with heart disease. Premature heartbeats 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.
Certain factors may increase your risk of developing an arrhythmia. These include:
- 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.
- High blood pressure. This increases your risk of developing coronary artery disease. It may also cause the walls of your left ventricle to become stiff and thick, which can change how electrical impulses travel through your heart.
- Congenital heart disease. Being born with a heart abnormality may affect your heart's rhythm.
- Thyroid problems. Your metabolism speeds up when your thyroid gland releases too much thyroid hormone. This may cause fast or irregular heartbeats and may be linked to atrial fibrillation. Your metabolism slows when your thyroid gland doesn't release enough thyroid hormone, 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.
- Diabetes. Your risk of developing coronary artery disease and high blood pressure greatly increases with uncontrolled diabetes.
- Obstructive sleep apnea. This disorder, in which your breathing is interrupted during sleep, can increase your risk of bradycardia, atrial fibrillation and other arrhythmias.
- Electrolyte imbalance. Substances in your blood called 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.
- Drinking too much alcohol. Drinking too much alcohol can affect the electrical impulses in your heart or increase the chance of developing atrial fibrillation. In fact, development of atrial fibrillation after an episode of heavy drinking is sometimes called "holiday heart syndrome." Chronic alcohol abuse may cause your heart to beat less effectively and can lead to cardiomyopathy.
- Caffeine or nicotine use. Caffeine, nicotine and other stimulants can cause your heart to beat faster and may contribute to the development of more-serious arrhythmias. Illegal 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.
Certain arrhythmias may increase your risk of developing conditions such as:
- Stroke. When your heart quivers, it's unable to pump blood effectively, which can cause blood to pool. This can cause blood clots to form. If a clot breaks loose, it can travel to and obstruct a brain artery, causing a stroke. This may damage a portion of your brain or lead to death. For people who have atrial fibrillation, the medications warfarin (Coumadin) or dabigatran (Pradaxa) or rivaroxaban (Xarelto) may help prevent blood clots, which can cause a stroke.
- 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 heart failure can improve your heart's function.
Preparing for your appointment
If you think you may have a heart arrhythmia, make an appointment with your family doctor. If a heart arrhythmia is found early, your treatment may be easier and more effective. Eventually, however, you may be referred to a heart specialist (cardiologist).
If your heart arrhythmia persists for more than a few minutes or is accompanied by fainting, shortness of breath or chest pain, call 911 or your local emergency number or have someone drive you to the nearest emergency room.
Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.
What you can do
- Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet. You may need to do this if your doctor orders any blood tests.
- Write down any symptoms you're experiencing, including any that may seem unrelated to heart arrhythmia.
- Write down key personal information, including a family history of heart disease, stroke, high blood pressure or diabetes, and any major stresses or recent life changes.
- Make a list of all medications, vitamins or supplements that you're taking.
- Take a family member or friend along, if possible. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
- Write down questions to ask your doctor.
Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. For heart arrhythmias, some basic questions to ask your doctor include:
- What's the most likely cause of my symptoms?
- Are there other possible causes for my symptoms?
- What kinds of tests will I need? Do I need to do anything to prepare for these tests?
- What's the best treatment?
- Are there any foods or drinks that you recommend I avoid? Is there anything you suggest that I add to my diet?
- What's an appropriate level of physical activity?
- How often should I be screened for heart disease or other complications of an arrhythmia?
- I have other health conditions. How can I best manage these conditions together?
- Is there a generic alternative to the medicine you're prescribing?
- Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:
- When did you first begin experiencing symptoms?
- Have your symptoms been continuous, or do they come and go?
- How severe are your symptoms?
- Does anything seem to improve your symptoms?
- What, if anything, appears to worsen your symptoms?
Tests 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 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 pressing a button when you have symptoms. This lets your doctor check your heart rhythm at the time of your symptoms.
- Echocardiogram. In this noninvasive test, a hand-held device (transducer) placed on your chest uses sound waves to produce images of your heart's size, structure and motion.
If your doctor doesn't find an arrhythmia during those tests, he or she may try to trigger your arrhythmia with other tests, which may 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. If you have difficulty exercising, your doctor may use a drug to stimulate your heart in a way that's similar to exercise.
- Tilt table test. Your doctor may recommend this test if you've had 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 it respond to the change in angle.
- Electrophysiological 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 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 see the location of the arrhythmia and what may be causing it.
Treatments and drugs
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|Cardiac catheter ablation|
|Home automated external defibrillator (AED)|
If you have an 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 slow heartbeats
If slow heartbeats (bradycardias) don't have a cause that can be corrected — such as low thyroid hormone levels or a drug side effect &dmash; doctors often treat them with a pacemaker because there aren't any medications that can reliably speed up your heart. A pacemaker is a small 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.
Treating fast heartbeats
For fast heartbeats (tachycardias), treatments may include one or more of the following:
- Vagal maneuvers. You may be able to stop an arrhythmia that begins above the lower half of your heart (supraventricular tachycardia, or SVT) by using particular maneuvers that include holding your breath and straining, dunking your face in ice water, or coughing. These maneuvers affect the nervous system that controls your heartbeat (vagus 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 minimize complications.
If you have atrial fibrillation, your doctor will likely prescribe blood-thinning medication — such as warfarin (Coumadin) or dabigatran (Pradaxa) or rivaroxaban (Xarelto) — to help keep dangerous clots from forming. These drugs can cause excessive bleeding. Dabigatran isn't recommended for the treatment of atrial fibrillation in anyone who has mechanical heart valves.
- Cardioversion. If you have a tachycardia that starts in the top half of your heart (atria), 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 relax you during the procedure, so there's no pain involved. Emergency cardioversion (defibrillation) is also used for ventricular tachycardia and fibrillation.
- Ablation therapy. 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 that your doctor believes are the sources of 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.
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 device is placed under the skin near the collarbone in a minor surgical procedure. An insulated wire extends from the device to 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.
- Implantable cardioverter-defibrillator (ICD). Your doctor may recommend this device if you're at high risk of developing a dangerously fast or irregular heartbeat in the lower half of your heart (ventricular tachycardia or ventricle fibrillation).
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.
In some cases, surgery may be the recommended treatment for heart arrhythmias:
- Maze procedure. This involves making a series of surgical incisions in the upper half of your heart (atria). These heal into carefully placed scars in the atria that form boundaries that force electrical impulses in your heart to travel properly to cause the heart to beat efficiently. The procedure is effective, but because it requires surgery, it's usually reserved for people who don't respond to other treatments or for those who are having heart surgery for other reasons. The surgeon may use a an instrument for applying extreme cold to tissue (cryoprobe) or a hand-held radiofrequency probe, rather than a scalpel, to create the scars.
- 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.
Lifestyle and home remedies
Many arrhythmias can be blamed on underlying heart disease, so your doctor may suggest that, in addition to other treatments, you make lifestyle changes that will keep your heart as healthy as possible. Making healthy lifestyle changes can also help prevent heart arrhythmias from developing in the first place.
These lifestyle changes may include:
- Eating heart-healthy foods
- Increasing your physical activity
- Quitting smoking
- Cutting back on caffeine and alcohol consumption
- Finding ways to reduce the amount of stress in your life
- Avoiding stimulant medications, such as medications found in over-the-counter treatments for colds and nasal congestion
The role of omega-3 fatty acids, a nutrient found mostly in fish, in the prevention and treatment of arrhythmias isn't yet clear. But it appears as though this substance may be helpful in preventing and treating some arrhythmias.
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