ARRHYTHMIAS
The electrical system of the heart causes it to contract. These electrical impulses begin in the sinoatrial node (SA node). The SA node is referred to as the natural pacemaker of the heart since it determines the pace or speed that the heart beats. It is located in the upper right chamber of the heart or the right atrium. The impulses then travel through the atria to the atrioventricular node (AV node). The AV node distributes the electrical signals to the lower chambers of the heart, or ventricles, via the bundle branches
An arrhythmia is a disturbance in the conduction along the electrical pathway described above. The term, arrhythmia, is used to describe an abnormal rhythm of the heart. Arrhythmias are caused by a problem with the electrical system of the heart. Arrhythmias can also occur if there is a problem with the heart muscles' response to the electrical signal within the heart. There are two types of arrhythmias. The first type involves fast heart beats, or tachycardias, when the heart rate is over 100 beats per minute (bpm). The second type involves slow heart beats, or bradycardias, when the heart rate is less than 60 bpm. They are also classified by their location in the heart.
Bradycardia (slow heart rate)
- Sinus bradycardia: a normal impulse, but slow
- Heart block: failure in the conduction of the heartbeat.
- Sick sinus syndrome: persistent slow heartbeats that may alternate with fast heartbeats, a block in conduction (heart block), or long pauses in the heartbeat.
Tachycardia (fast heart rate)
- Supraventricular tachycardia: Fast heart rates that are caused by problems in the SA or AV nodes. Examples are:
- Atrial tachycardia: fast heartbeat that starts from an area in the atria
- Premature atrial contractions: early heartbeat of the atria
- Paroxysmal atrial tachycardia: atrial tachycardia that begins and ends suddenly usually from 150-240 bpm
- Atrial fibrillation: irregular and rapid impulses from the atria that cause quivering of the atria and variable rates of the ventricle
- Atrial flutter: rapid, regular heart beat that starts in the atria (approx. 300 bpm) with ventricular rates of approx. 150 bpm.
- Ventricular tachycardia: Fast heart rates that are caused by problems in the ventricles or lower chambers of the heart. Examples are:
- Premature ventricular contractions: early contraction of the ventricle.
- Ventricular tachycardia: a series of beats from an area in the ventricle at a rate greater than 100 bpm, usually between 150-200 bpm.
- Ventricular fibrillation: Life-threatening arrhythmia seen in cardiac arrest.; unorganized electrical activity and pumping of the heart.
Controlled rates: The following usually have rates between 60-100 bpm but can also be slow or fast.
- First degree AV block: a delay in electrical impulse between the SA and AV node.
- Second degree AV block: intermittent delay or block in electrical impulse due to prolonged conduction of the AV node.
- Third degree AV block (complete heart block): uncoordinated beating of the atria and ventricles with one another.
- Bundle branch block: impulses that are blocked in one of the branches of the bundle of His that results in one ventricle beating slightly before the other.
The symptoms you may experience vary according to the type of arrhythmia you have. Arrhythmias may also occur without any noticeable symptoms. Some common symptoms that people experience include:
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There are many tests that are available to diagnose an arrhythmia. One of the tests is an electrocardiogram (EKG or ECG) which records the heart's current electrical activity on paper. Holter monitors records all electrical activity for a 24 hour time period. Event monitors record EKGs for a month when you activate the recorder. These are often ordered in cases where arrhythmias are not predictable. A stress test also records the EKG and is able to detect any changes such as activity-related arrhythmias with exercise. An electrophysiology study (EPS) is done to closely monitor the heart rhythm and to study any rhythm changes. During the EPS an electrophysiologist (a cardiologist who specializes in treating arrhythmias) looks at the heart and is able to "map out" (track) the electrical activity of the heart and induce (trigger) the arrhythmia.
There are a variety of choices in treating arrhythmias depending on the type and severity of the arrhythmia:
- Lifestyle changes: These changes are recommended for those who do not have dangerous arrhythmias. They include quitting or reducing caffeine intake, limiting alcohol use, quitting smoking, avoiding certain medications (i.e decongestants, diet supplements), and managing stress.
- Medications: A variety of medications are available to control the cause of an arrhythmia. Anticoagulants, such as Coumadin, are used in patients with atrial fibrillation/flutter in order to reduce the risk of clotting or stroke.
- Cardioversion/defibrillation: This procedure involves giving an electrical shock through the chest. This treatment is used to convert atrial fibrillation/flutter to a normal rhythm. It is also used to convert more dangerous and life-threatening arrhythmias to a normal rhythm.
- Catheter ablation: During this procedure, a catheter (or thin tube) is introduced into the heart from blood vessels in the legs and/or neck. Radiofrequency energy is used to carefully destroy (ablate) tissue that is interfering with the normal impulses through the heart.
- Pacemaker: This is a small electronic device surgically placed under the skin near the collarbone in order to keep your heart beating at the right pace. It prevents a dangerously slow or uneven heart beat.
- Implantable Cardiodefibrillator (ICD): This is similar to the pacemaker but works to monitor and correct a dangerously fast heartbeat. It is often used for patients with ventricular fibrillation or ventricular tachycardia, or those at risk for these arrhythmias. There are also devices that act both as a pacemaker and an ICD.