4/30/2017 CardiacArrhythmiasGuide:Causes,SymptomsandTreatmentOptions

CardiacArrhythmias
What Is It?
A cardiac arrhythmia is any abnormal heart rate or rhythm.

In normal adults, the heart beats regularly at a rate of 60 to 100 times per minute. And the pulse felt at the wrist, neck or
elsewhere matches the contractions of the heart's two powerful lower chambers, called the ventricles. The heart's two
upper chambers, called the atria, also contract to help fill the ventricles. But this milder contraction occurs just before the
ventricles contract, and it is not felt in the pulse.

Under normal circumstances, the signal for a heartbeat comes from the heart's sinus node. It's the natural pacemaker
located in the upper portion of the right atrium. From the sinus node, the heartbeat signal travels to the atrioventricular
node or "AV node," which is located between the atria. Next the signal travels through the bundle of His pronounced
HISS. It's made up of a series of modified heart muscle fibers located between the ventricles. The signal enters the
muscles of the ventricles. This causes the ventricles to contract and produces a heartbeat.

Cardiac arrhythmias sometimes are classified according to their origin as either ventricular arrhythmias originating in the
ventricles or supraventricular arrhythmias originating in heart areas above the ventricles, typically the atria. They also
can be classified according to their effect on the heart rate, with bradycardia indicating a heart rate of less than 60 beats
per minute and tachycardia indicating a heart rate of more than 100 beats per minute.

Some common types of cardiac arrhythmias include:

Sinus node dysfunction This usually causes a slow heart rate bradycardia, with a heart rate of 50 beats per minute
or less. The most common cause is scar tissue that develops and eventually replaces the sinus node. Why this happens
is not known. Sinus node dysfunction also can be caused by coronary artery disease, hypothyroidism, severe liver
disease, hypothermia, typhoid fever or other conditions. It also can be the result of vasovagal hypertonia, an unusually
active vagus nerve.
Supraventricular tachyarrhythmias This diverse family of cardiac arrhythmias causes rapid heartbeats tachycardias
that start in parts of the heart above the ventricles. In most cases, the problem is either an abnormality in the AV
node or an abnormal pathway that bypasses the typical route for heartbeat signals.
Atrial fibrillation This is a supraventricular arrhythmia that causes a rapid and irregular heartbeat, during which the
atria quiver or "fibrillate" instead of beating normally. During atrial fibrillation, heartbeat signals begin in many
different locations in the atria rather than in the sinus node.
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Although these abnormal signals manage to trigger 300 to 500 contractions per minute within the atria, the
extraordinarily high number of heartbeat signals overwhelms the AV node. As a result, the AV node sends sporadic,
irregular signals to the ventricles, causing an irregular and usually rapid heartbeat of 100 to 180 beats per minute. But
the ventricular rate can be slower.
The disordered heartbeat of atrial fibrillation cannot pump blood out of the heart efficiently. This causes blood to pool
in the heart chambers and increases the risk of a blood clot forming inside the heart. The major risk factors for atrial
fibrillation are age, high blood pressure, heart valve abnormalities, diabetes, and heart failure.

A-V block or heart block In this family of arrhythmias, there is some problem conducting the heartbeat signal from
the sinus node to the ventricles. There are three degrees of AV block:
Firstdegree AV block, where the signal gets through, but may take longer than normal to travel from the sinus
node to the ventricles
Seconddegree AV block, in which some heartbeat signals are lost between the atria and ventricles
Thirddegree AV block, in which no signals reach the ventricles, so the ventricles beat slowly on their own with no
direction from above
Some causes of AV block include cardiomyopathy, coronary artery disease, and medications such as beta blockers
and digoxin.
Ventricular tachycardia (VT) This is an abnormal heart rhythm that begins in either the right or left ventricle. It may
last for a few seconds nonsustained VT or for many minutes or even hours sustained VT. Sustained VT is a
dangerous rhythm and if it is not treated, it often progresses to ventricular fibrillation.
Ventricular fibrillation In this arrhythmia, the ventricles quiver ineffectively, producing no real heartbeat. The result is
unconsciousness, with brain damage and death within minutes. Ventricular fibrillation is a cardiac emergency.
Ventricular fibrillation can be caused by a heart attack, an electrical accident, a lightning strike or drowning.

Symptoms
Symptoms of specific arrhythmias include:

Sinus node dysfunction There may not be any symptoms, or it may cause dizziness, fainting and extreme fatigue.
Supraventricular tachyarrhythmias These can cause palpitations awareness of a rapid heartbeat, low blood
pressure and fainting.
Atrial fibrillation Sometimes, there are no symptoms. This can cause palpitations; fainting; dizziness; weakness;
shortness of breath; and angina, which is chest pain caused by a reduced blood supply to the heart muscle. Some
people with atrial fibrillation alternate between the irregular heartbeat and long periods of completely normal
heartbeats.
A-V block or heart block Firstdegree AV block does not cause any symptoms. Seconddegree AV block causes an
irregular pulse or slow pulse. Thirddegree AV block can cause a very slow heartbeat, dizziness and fainting.
VT Nonsustained VT may not cause any symptoms or cause a mild fluttering in the chest. Sustained VT usually
causes lightheadedness or loss of consciousness and can be lethal.

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Ventricular fibrillation This causes absent pulse, unconsciousness and death.

Diagnosis
Your doctor will ask about your family history of coronary artery disease, cardiac arrhythmias, fainting spells or sudden
death from heart problems. Your doctor also will review your personal medical history, including any possible risk factors
for cardiac arrhythmias such as coronary artery disease, cardiomyopathy, thyroid disorders, and medications. You will be
asked to describe your specific cardiac symptoms, including any possible triggers for those symptoms.

During the physical examination, your doctor will check your heart rate and rhythm, together with your pulses. This is
because certain cardiac arrhythmias cause a mismatch of the pulse and the heart sounds. Your doctor also will check for
physical signs of an enlarged heart and for heart murmurs, one sign of a heart valve problem.

A test called an electrocardiogram EKG often can confirm the diagnosis of a cardiac arrhythmia. However, because
cardiac arrhythmias may come and go, a onetime office EKG may be normal. If this is the case, an ambulatory EKG may
be required. During an ambulatory EKG, the patient wears a portable EKG machine called a Holter monitor, usually for 24
hours, but sometimes much longer. You will be taught to press a button to record the EKG reading whenever you
experience symptoms. This approach is especially useful if your symptoms are infrequent.

When a patient has ventricular fibrillation, it is an emergency. The patient is unconscious, not breathing, and doesn't have
a pulse. If available, electrical cardioversion must be administered as soon as possible. If not available, then
cardiopulmonary resuscitation CPR should be started.

Expected Duration
How long a cardiac arrhythmia lasts depends on its cause. For example, atrial fibrillation that is caused by an overactive
thyroid may go away when the thyroid problem is treated. However, cardiac arrhythmias that result from progressive or
permanent damage to the heart tend to be longterm problems. When a heart attack causes ventricular fibrillation, death
can occur within minutes.

Prevention
Cardiac arrhythmias that result from coronary artery disease can be prevented by taking the following actions to modify
your risk factors:

Eat a heart healthy diet, including eating an abundance of vegetables and fruits, fish, and plant sources for protein and
avoiding saturated and trans fats.
Control your cholesterol and high blood pressure.
Quit smoking.
Control your weight.
Get regular exercise.

Cardiac arrhythmias related to medications can be minimized by checking with a health care professional or pharmacist
about any potential drug interactions. You might have to switch to another medication or reduce the dose of a problem

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medication. Ventricular fibrillation resulting from electrical shock can be prevented by following routine safety precautions
around live wires and by seeking shelter during electrical storms.

Not all cardiac arrhythmias can be prevented.

Treatment
The treatment of a cardiac arrhythmia depends on its cause:

Sinus node dysfunction In people with frequent, severe symptoms, the usual treatment is a permanent pacemaker.
Supraventricular tachyarrhythmias The specific treatment depends on the cause of the arrhythmia. In some people,
massaging the carotid sinus in the neck will stop the problem. Other people need medications such as betablockers,
calcium channel blockers, digoxin Lanoxin and amiodarone Cordarone. Some patients respond only to a procedure
called radiofrequency catheter ablation, which destroys an area of tissue in the AV node to prevent excess electrical
impulses from being passed from the atria to the ventricles.

Atrial fibrillation Atrial fibrillation resulting from an overactive thyroid can be treated with medications or surgery.
Fibrillation resulting from mitral or aortic valve disease may be treated by replacing damaged heart valves.
Medications, such as betablockers for example atenolol and metoprolol, amiodarone, diltiazem Cardizem, Tiazac
or verapamil Calan, Isoptin, Verelan, can be used to slow the heart rate. Drugs such as amiodarone can be used to
reduce the chances that the atrial fibrillation will return. Other treatment options include radiofrequency catheter
ablation, or electrical cardioversion, a procedure that delivers a timed electrical shock to the heart to restore normal
heart rhythm.
A-V block Firstdegree AV block typically does not require any treatment. People with seconddegree AV block
may be monitored with frequent EKGs, especially if they do not have any symptoms and have a heart rate that is
adequate for their daily activities. Some patients with seconddegree heart block may require permanent pacemakers.
Thirddegree AV block is almost always treated with a permanent pacemaker.
VT Nonsustained VT may not need to be treated if there is no structural damage to the heart. Sustained VT always
needs treatment, either with intravenous medication or emergency electrical shock defibrillation, which can restore
the heart's normal rhythm.
Ventricular fibrillation This is treated with defibrillation, giving the heart a measured electrical shock to restore
normal rhythm. The electrical shock can be delivered on the skin over the heart in an emergency situation. People who
have survived ventricular fibrillation and those at high risk are potential candidates for an automatic implantable
cardioverter defibrillator. The device is similar to a pacemaker, with wires attached to the heart that connect an energy
source placed under the skin. The procedure is done in the operating room.

When To Call a Professional

Prognosis
The outlook for cardiac arrhythmias depends on the type of rhythm disturbance and whether the person has coronary
artery disease, congestive heart failure, or some other heart muscle disorder. The prognosis for ventricular fibrillation is
grave, and death follows quickly without emergency treatment. Most atrial arrhythmias have an excellent prognosis. The
outlook is good for heart block, even thirddegree AV block, the most serious type.
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The availability of permanent pacemakers, implanted cardioversion/defibrillation devices and effective medications has
improved the prognosis for many people with serious cardiac arrhythmias.

External resources
American Heart Association (AHA)
7272 Greenville Ave.
Dallas, TX 75231
TollFree: 18002428721
http://www.americanheart.org/

National Heart, Lung, and Blood Institute (NHLBI)

American College of Cardiology

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