Palpitations (cont.)
What are symptoms of arrhythmias?
Arrhythmias are pattern and/or speed changes from the normal heart rhythm. Some patients are totally unaware of their arrhythmias. Others may report symptoms including palpitations, skipping or fluttering sensations, dizziness, fainting,
shortness of breath, or
chest pain.
In both tachycardias and bradycardias, lack of blood flow to the brain,
the coronary arteries, or the rest of the body can occur. Lack of blood
flow to the brain can cause dizziness or loss of consciousness (syncope).
Lack of blood supply to the coronary arteries can cause chest pain or
pressure (angina). Inadequate blood supply to the rest of the body can
cause weakness and shortness of breath.
What are the causes of arrhythmias?
In some patients, arrhythmias are caused by diseases of the heart
muscle, valves or coronary arteries. In others, arrhythmias can reflect
disease of the electrical system of the heart only, while the rest of the
heart is healthy. Other causes of arrhythmias include medications, alcohol
excess, excessive levels of thyroid hormone, low blood oxygen levels,
stress, and
smoking.
Atrial tachycardias
Examples of atrial tachycardias include atrial fibrillation, atrial
flutter, and paroxysmal atrial tachycardia (PAT). These arrhythmias occur
because of electrical disturbances in the atria and/or the AV node,
leading to fast heart beats.
- Atrial fibrillation is a common atrial tachycardia. In atrial fibrillation, multiple, rapid, and chaotic electrical signals fire rapidly from different areas in the atria, rather than from one single area pacemaker at the SA node. These signals in turn cause rapid irregular contractions of the ventricles. Causes of atrial fibrillation include heart attack, high blood pressure,
heart failure, mitral valve diseases (such as mitral valve prolapse), overactive thyroid, blood clots in the lung (pulmonary embolism),
alcohol excess,
emphysema, and inflammation of heart lining (pericarditis). For further information, please refer the
Atrial Fibrillation article.
- Atrial flutter is a more regular (less chaotic) version of atrial fibrillation as the electrical signal initiates in the atria..
Conditions that cause atrial fibrillation can also cause atrial flutter.
Treatment of atrial flutter and atrial fibrillation are also similar (see
below).
- Paroxysmal atrial tachycardia (PAT) represent bouts of rapid, regular
heart beating originating in the atrium. Patients with PAT are believed to
have abnormalities in the AV node "relay station" that lead to
rapid firing of the electrical impulses from the atrium which bypass the
AV node under certain conditions. These conditions include alcohol excess,
stress, caffeine, overactive thyroid or excessive thyroid hormone intake,
and certain drugs. PAT is an example of an arrhythmia where the
abnormality is in the electrical system of the heart, while the heart
muscle and valves may be normal.
Ventricular Arrhythmias
Ventricular arrhythmias are rapid arrhythmias that originate in the lower chambers of the heart (the ventricles). Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation. Ventricular tachycardia is a rapid regular arrythmia which originates from an area of the ventricle. Ventricular fibrillation is an irregular arrhythmia that is a result of multiple rapid and chaotic electrical signals firing from many different areas in the ventricles.
Ventricular tachycardias and fibrillation are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack. For further information, please read the
Heart Attack article. Less
common causes of ventricular arrhythmias include severe heart muscle
failure (cardiomyopathy), medication toxicity
[such as digoxin (Lanoxin) toxicity],
medication side effects, and
blood electrolyte disturbances (such as low
potassium level). Ironically, some medications used in treating heart
arrhythmias can cause ventricular tachycardias (see the treatment section
below).
Bradycardias
Diseases of the SA node, the AV node, and the conduction system in the
ventricles can lead to slow arrhythmias (bradycardias).
Calcium channel
blockers, such as verapamil (Calan),
beta-blockers, such as
propanolol (Inderal), and digoxin (Lanoxin) can cause bradycardias. These
medications can also seriously aggravate bradycardias in patients with
existing diseases of the SA node, AV node and other parts of the conduction
system. Even though
some patients experience no ill effects from bradycardias, serious
bradycardias can lead to low blood pressure (shock), and passing out
(syncope).
Premature Contractions
Early heartbeats that don't originate from the SA node pacemaker are called premature contractions. Premature atrial contractions (PACs) and premature ventricular contractions (PVCs) can be caused by stress, caffeine,
cigarette smoking, and excessive alcohol intake. Generally, PACs and PVCs, when they are infrequent and isolated, are not associated with significant heart disease.
Next: How are palpitations evaluated? »
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- Arrhythmia (Irregular Heartbeat) - Arrhythmia (irregular heartbeat or abnormal heart rhythm) symptoms include palpitations, dizziness, fainting, shortness of breath and chest discomfort. Learn how to recognize the warning signs and treatment of arrhythmia on MedicineNet.com.
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