Heart Disease: Abnormal Heart Rhythm
An arrhythmia (also called dysrhythmia) is an irregular heartbeat. Heart rates can also be irregular. A normal heart rate is 50 to 100 beats per minute. Arrhythmias and abnormal heart rates don't necessarily occur together. arrhythmias can occur with a normal heart rate, or with heart rates that are slow (called bradyarrhythmias -- less than 60 beats per minute). arrhythmias can also occur with rapid heart rates (called tachyarrhythmias -- faster than 100 beats per minute).
What Causes an Arrhythmia?
Arrhythmias may be caused by many different factors, including:
* Coronary artery disease
* Electrolyte imbalances in your blood (such as sodium or potassium).
* Changes in your heart muscle.
* Injury from a heart attack
* Healing process after heart surgery.
Irregular heart rhythms can also occur in "normal, healthy" hearts.
What Are the Types of Arrhythmias?
* Premature atrial contractions. These are early extra beats that originate in the atria (upper chambers of the heart). They are harmless and do not require treatment.
* Premature ventricular contractions (PVCs). These are among the most common arrhythmias and occur in people with and without heart disease. This is the skipped heartbeat we all occasionally experience. In some people, it can be related to stress, too much caffeine or nicotine, or too much exercise. But sometimes, PVCs can be caused by heart disease or electrolyte imbalance. People who have a lot of PVCs, and/or symptoms associated with them, should be evaluated by a heart doctor. However, in most people, PVCs are usually harmless and rarely need treatment.
* Atrial fibrillation. AF is a very common irregular heart rhythm that causes the atria, the upper chambers of the heart to contract abnormally.
* Atrial flutter. This is an arrhythmia caused by one or more rapid circuits in the atrium. Atrial flutter is usually more organized and regular than atrial fibrillation. This arrhythmia occurs most often in people with heart disease, and in the first week after heart surgery. It often converts to atrial fibrillation.
* Paroxysmal supraventricular tachycardia
(PSVT). A rapid heart rate, usually with a regular rhythm, originating from above the ventricles. PSVT begins and ends suddenly. There are two main types: accessory path tachycardias and AV nodal reentrant tachycardias (see below).
* Accessory pathway tachycardias. A rapid heart rate due to an extra abnormal pathway or connection between the atria and the ventricles. The impulses travel through the extra pathways as well as through the usual route. This allows the impulses to travel around the heart very quickly, causing the heart to beat unusually fast.
* AV nodal reentrant tachycardia. A rapid heart rate due to more than one pathway through the AV node. It can cause heart palpitations, fainting or heart failure . In many cases, it can be terminated using a simple maneuver performed by a trained medical professional, medications or a pacemaker.
* Ventricular tachycardia (V-tach). A rapid heart rhythm originating from the lower chambers (or ventricles) of the heart. The rapid rate prevents the heart from filling adequately with blood; therefore, less blood is able to pump through the body. This can be a serious arrhythmia, especially in people with heart disease, and may be associated with more symptoms. A heart doctor should evaluate this arrhythmia.
* Ventricular fibrillation
. An erratic, disorganized firing of impulses from the ventricles. The ventricles quiver and are unable to contract or pump blood to the body. This is a medical emergency that must be treated with cardiopulmonary resuscitation
(CPR) and defibrillation as soon as possible.
* Long QT syndrome
. The QT interval is the area on the electrocardiogram (ECG) that represents the time it takes for the heart muscle to contract and then recover, or for the electrical impulse to fire impulses and then recharge. When the QT interval is longer than normal, it increases the risk for "torsade de pointes," a life-threatening form of ventricular tachycardia. Long QT syndrome is an inherited condition that can cause sudden death in young people. It can be treated with antiarrhythmic drugs , pacemaker , electrical cardioversion, defibrillation, implanted cardioverter/defibrillator or ablation therapy.
* Bradyarrhythmias. These are slow heart rhythms, which may arise from disease in the heart's electrical conduction system. Examples include sinus node dysfunction
and heart block.
* Sinus node dysfunction. A slow heart rhythm due to an abnormal SA (sinus) node. Sinus node dysfunction is treated with a pacemaker.
* Heart block. A delay or complete block of the electrical impulse as it travels from the sinus node to the ventricles. The level of the block or delay may occur in the AV node or HIS-Purkinje system. The heart may beat irregularly and, often, more slowly. If serious, heart block is treated with a pacemaker.
What Are the Symptoms of Arrhythmias?
An arrhythmia can be silent and not cause any symptoms. A doctor can detect an irregular heartbeat during a physical exam by taking your pulse or through an electrocardiogram (ECG).
When symptoms occur, they may include:
* Palpitations (a feeling of skipped heart beats, fluttering or "flip-flops," or feeling that your heart is "running away").
* Pounding in your chest.
* Dizziness or feeling light-headed.
* Shortness of breath
* Chest discomfort
* Weakness or fatigue (feeling very tired).
How Are Arrhythmias Diagnosed?
Tests used to diagnose an arrhythmia or determine its cause include:
* Ambulatory monitors
* Holter monitor
* Transtelephonic monitor
* Transtelephonic monitor with memory loop
* Stress test
* Cardiac catheterization
* Electrophysiology study (EPS)
* Head-up tilt table test
How Are Arrhythmias Treated?
Treatment depends on the type and seriousness of your arrhythmia. Some people with arrhythmias require no treatment. For others, treatments can include medication, making lifestyle changes and undergoing surgical procedures.
What Medications Are Used to Treat Arrhythmias?
A variety of drugs are available to treat arrhythmias. These include:
* Antiarrhythmic drugs. These drugs control heart-rate, and include beta-blockers .
* Anticoagulant or antiplatelet therapy. These drugs reduce the risk of blood clots and include warfarin (a "blood thinner") or aspirin .
Because everyone is different, it may take trials of several medications and doses to find the one that works best for you.
What Lifestyle Changes Should Be Made?
* If you notice that your irregular heart rhythm occurs more often with certain activities, you should avoid them.
* If you smoke, stop.
* Limit your intake of alcohol.
* Limit or stop using caffeine. Some people are sensitive to caffeine and may notice more symptoms when using caffeine products (such as tea, coffee, colas and some over-the-counter medications).
* Stay away from stimulants used in cough and cold medications. Some such medications contain ingredients that promote irregular heart rhythms. Read the label and ask your doctor or pharmacist what medication would be best for you.
What Is Electrical Cardioversion?
If drugs are not able to control a persistent irregular heart rhythm (such as atrial fibrillation), cardioversion may be required. After administration of a short-acting anesthesia, an electrical shock is delivered to your chest wall that synchronizes the heart and allows the normal rhythm to restart.
What Is a Pacemaker?
A pacemaker is a device that sends small electrical impulses to the heart muscle to maintain a suitable heart rate. Pacemakers primarily prevent the heart from beating too slowly. The pacemaker has a pulse generator (which houses the battery and a tiny computer) and leads (wires) that send impulses from the pulse generator to the heart muscle. Newer pacemakers have many sophisticated features that are designed to help manage arrhythmias and optimize heart-rate-related function as much as possible.
What Is an Implantable Cardioverter-Defibrillator
An ICD is a sophisticated device used primarily to treat ventricular tachycardia and ventricular fibrillation, two life-threatening heart rhythms. The ICD constantly monitors the heart rhythm. When it detects a very fast, abnormal heart rhythm, it delivers energy to the heart muscle to cause the heart to beat in a normal rhythm again. There are several ways the ICD can be used to restore normal heart rhythm. They include:
* Anti-tachycardia pacing (ATP). When the heart beats too fast, a series of small electrical impulses may be delivered to the heart muscle to restore a normal heart rate and rhythm.
* Cardioversion. A low energy shock may be delivered at the same time as the heart beats to restore normal heart rhythm.
* Defibrillation. When the heart is beating dangerously fast or irregularly, a higher energy shock may be delivered to the heart muscle to restore a normal rhythm.
* Anti-bradycardia pacing. Many ICDs provide back-up pacing to prevent too slow of a heart rhythm.
tachycardia, fast heartbeat
A rapid heartbeat is defined as a heart rate that is faster than normal. The heart normally beats fewer than 100 times per minute in adults. In children, the heart can beat slightly faster than 100 times per minute and still be considered normal.
What is going on in the body?
At rest, a person's heart rate usually stays within a standard range. This range is usually 50 to 100 times per minute in adults and slightly faster in children. With increased physical activity, stress, or other conditions, however, the heart rate may increase above the normal level.
What are the signs and symptoms of the condition?
A person with a rapid heartbeat may have no symptoms at all. When symptoms do occur, they may include:
* palpitations, or an unusual awareness of the heartbeat
* excessive sweating
* fatigue or weakness
* shortness of breath
* chest pain
* lightheadedness or dizziness
* symptoms related to the cause of the rapid heart rate
What are the causes and risks of the condition?
There are many possible causes of a rapid heartbeat, including:
* exercise, heavy lifting or other activity that requires exertion
* fear, pain, anxiety, stress, anger, or nervousness
* dehydration. This may be caused by too little intake of fluids, loss of blood, diarrhea, vomiting, or medications such as diuretics, sometimes called "water pills."
* low blood pressure, also called hypotension
, which is a level of thyroid hormone in the body that is too high
* congestive heart failure, a condition in which the heart cannot pump blood effectively
* irregular heartbeats, known as arrhythmias, such as atrial fibrillation or ventricular tachycardia. These may be caused by salt imbalances, heart attack, and other conditions.
* low red blood cell count known as anemia
* medications or drugs. Albuterol, which is commonly used to treat asthma, as well as some over the counter and prescription decongestants can cause rapid heartbeat. Cocaine abuse and alcohol withdrawal
are other causes of rapid heartbeat.
* excessive caffeine intake
* some herbal therapies such as ephedra, also called ma huang
* infections. These may include such as a serious blood infection called sepsis and pneumonia.
* nerve damage, known as peripheral neuropathy
, that affects the nerves attached to the heart. This is often due to diabetes, a condition that results in a high level of blood sugar.
* low oxygen in the blood, also called hypoxia. There can be many causes for this. Examples include asthma and emphysema.
Other causes are possible. Sometimes, no cause can be found.
What can be done to prevent the condition?
Prevention is related to the cause. Many cases cannot be prevented. In most people, regular exercise is advised even though it causes a rapid heartbeat. In this case, prevention is not an issue. Avoidance of cocaine or alcohol can prevent cases from these drugs. Getting enough fluids can prevent many cases due to dehydration.
How is the condition diagnosed?
The speed of the heartbeat usually can be measured by checking the pulse or listening to the heartbeat with a stethoscope. A test that measures the electrical activity of the heart, called an electrocardiogram or ECG, can also be used to measure the heart rate.
Diagnosis of the cause starts with a history and physical exam. The healthcare provider may order tests such as:
* electrocardiogram, or ECG, to help diagnose irregular heartbeats and heart attacks
* chest x-ray
* echocardiogram, or an ultrasound of the heart, to help diagnose congestive heart failure
* thyroid function tests
to diagnose high thyroid levels
* arterial blood gases to measure oxygen levels in the blood
What are the long-term effects of the condition?
If the heart beats too quickly, it may not be able to pump blood well enough to keep a person alive. Most long-term effects are related to the cause. For example, rapid heartbeat due to anxiety or exercise often goes away quickly and has no long-term effects. Rapid heartbeat due to an arrhythmia or sepsis may sometimes result in death.
What are the risks to others?
A rapid heartbeat is not contagious and poses no risks to others. If the cause of the rapid heartbeat is an infection, the infection may be contagious.
What are the treatments for the condition?
Treatment is directed at the cause. For example, someone who is dehydrated can be given fluids. A person with a fever may be given acetaminophen. Someone with an infection may need antibiotics or surgery. An individual with an arrhythmia may need heart medications to slow the heart rate, such as atenolol or lidocaine.
What are the side effects of the treatments?
Potential side effects depend on the treatments used. For example, antibiotics may cause allergic reactions or stomach upset. Surgery can result in infection, bleeding, or allergic reaction to the anesthesia.
What happens after treatment for the condition?
The heartbeat usually returns to normal after treatment of the cause. For example, when fever, infection, or pain are the cause, no further treatment for the rapid heartbeat is needed if these condition go away. Someone with congestive heart failure or diabetes, however, often needs lifelong treatment and monitoring.
How is the condition monitored?
The speed of the heartbeat can be monitored closely if needed. This is done with special equipment that measures the electrical activity in the heart. Other monitoring is related to the cause. For example, those with a heart attack may need close monitoring in the intensive care unit.