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Heart rhythm disorders (arrhythmias) occur either independently or as a result of other
cardiac conditions, such as coronary artery disease and myocardial infarction (heart attack). In any case, rhythm
disorders signal abnormalities in the conduction system of the heart.
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Types of Heart Rhythm Disorders
Heart rhythm disorders are categorized as either bradycardia (slow heartbeat) or
tachycardia (rapid heartbeat). Tachycardia may further sub-divided into ventricular
tachycardias (involving only the ventricles) and supraventricular tachycardias (involving
both the atria and the ventricles).
Symptoms of
bradycardia
(slow heartbeat) |
Symptoms of
tachycardia
(fast heartbeat) |
- Fatigue
- Dizziness
- Lightheadedness
- Fainting spells
|
- Heart palpitations
- Rapid heart action
- Dizziness
- Lightheadedness
- Fainting spells
|
Examples of specific arrhythmias include:
- Atrial fibrillation: Rapid and irregular heartbeat due to signals in the atria that
cause the ventricles to contract abnormally. This condition prevents blood from flowing
through the heart's chambers, often causing it to accumulate in the atria. A blood clot
may form as a result of atrial fibrillation, leading to stroke or
myocardial infarction (heart attack).
- Ventricular fibrillation: Rapid contractions of the heart caused by irregular
electrical signals in the ventricles. The condition is common after myocardial infarction
(heart attack) or from electrocution or drowning. The condition is life-threatening and
should be treated immediately with electric shock (defibrillation) to the heart followed
by anti-arrhythmic drugs.
- Premature ventricular contraction: An abnormal signal from the ventricles
causes the heart to beat prematurely (early). Premature ventricular contraction is common
in children and teenagers and may not require treatment. However, in some cases when the
condition is caused by disease or injury, it could lead to ventricular tachycardia and
also fibrillation.
- Heart block: Interruption of electrical communication between the
atria and ventricles. This results in the ventricles contracting less often than the
atria. The condition leads to episodes of dizziness, fainting spells or stroke. Heart
block is categorized by its severity. More severe cases are commonly treated with an
artificial pacemaker, or less commonly, with drugs (such as isoproterenol).
Diagnosing Heart Rhythm Disorders
Early detection and treatment are key in preventing death or disability from certain
heart rhythm disorders. Rhythm disorders may be diagnosed by careful examination of the
symptoms (palpitations, fainting spells, lightheadedness, dizziness, rapid heart action,
etc.) and several diagnostic tests, including:
- Electrocardiogram (ECG or EKG): An electrocardiogram is a graphical record of
the electrical activity of the heart. A normal ECG, in most cases, rules out the presence
of other cardiac diseases. An abnormal ECG indicates the presence of a cardiac disease and
further investigations are performed. An ECG can be beneficial in detecting the disease
and sometimes even the extent of the disease.
- Stress test: A stress test involves taking an ECG before, during and after a
treadmill workout to detect cardiac disease and/or damage, including the extent of
coronary artery disease. However, false positive results are possible with stress tests.
- Echocardiogram (heart ultrasound): This diagnostic technique is an excellent
tool to provide details of the cardiac structures – vessels, valves, and muscle.
Echocardiography is a non-invasive exam in which images are acquired and viewed in real
time without the use of radiation. Echocardiography is often useful in studying the
beating heart and provides some information on functional abnormalities of the heart wall,
valves and blood vessels. Echocardiography with Doppler is used to measure blood flow
across valves, across septal defects (shunts), extent of regurgitations, etc. Color flow
mapping capability is extremely useful in the detection of shunts. Abnormal operation of
the valves can be detected by studying the opening and closing function versus normal
valve function. Echocardiography may also be used to study congenital heart defects such
as a septal defect (a hole in the wall that separates the two chambers of the heart).
- Tilt table study: This study is typically performed to determine the
cause of fainting spells. The patient is secured on a special table, an intravenous line
is drawn, and the patient is quickly titled upright. Blood pressure, heart rate, and other
factors are monitored for abnormal readings.
- Electrophysiology (EP) study: This study involves inserting a catheter in a vein or
artery in the groin and guiding it to the heart using angiography
for guidance. The heart’s electrical activity is then monitored in multiple places
using sophisticated in-vivo EKG leads to help diagnose tachycardias or bradycardias.
Electrophysiology studies are also useful before surgery to help plan implantation of
pacemaker or cardioverter defibrillator.
Treating Heart Rhythm Disorders
The treatment of heart rhythm disorders depends on the type of disorder and its
severity. Many abnormal heart rhythms may be treated by dietary and lifestyle changes such
as not smoking, reducing caffeine intake, limiting alcohol intake, avoiding decongestants,
and minimizing stress. Drug therapy may also be necessary.
The following chart summarizes types of drugs that may be used to help treat heart
rhythm disorders. Brand names are shown in parentheses.
| Type of Drug |
Function |
Examples |
| Anti-arrhythmics |
temporarily correct slow or fast heartbeat |
amiodarone (Cordarone), disopyramide (Norpace),
lidocaine (Xylocaine), procainamide (Procan), propafenone (Rythmol), propranolol
(Inderal), sotalol (Betapace) |
| Beta blockers |
reduce the heart’s workload |
nadolol (Corgard), metoprolol (Lopressor, Toprol
XL), pindolol (Visken), bisoprolol (Zebeta), and acebutolol (Sectral). |
| Calcium channel blockers |
increase blood flow through the heart and help
prevent blood vessel constriction by blocking calcium ions |
verapamil (Calan, Isoptin, Verelan), diltiazem
(Cardizem, Tiamate, etc.) and nifedipine (Adalat). |
| Anticoagulants or antiplatelets |
work as blood thinners |
aspirin, warfarin (Coumadin) |
In some cases, surgery may be necessary to help treat heart rhythm
disorders. Depending on the type of disorder and its severity, one of the following
procedures may be performed:
- Pacemaker implantation: An artificial pacemaker can be surgically implanted to help
correct bradycardia (slow heartbeat), a condition that can worsen congestive heart failure. The surgery involves implanting an
artificial pacemaker into the patient’s chest, which uses batteries to deliver an
electrical impulse when an irregularity of the heart rhythm is detected. Many pacemakers
have sophisticated sensory systems which allow them to function only when necessary.
- Cardioverter defibrillator implantation: Involves implanting leads on the
heart’s surface, which are connected to a pulse generator implanted under the skin
near the chest or abdomen. The device delivers electrical shocks to the heart to help
restore a normal rhythm. Like pacemakers, implantable cardioverter defibrillators have
sophisticated sensory systems that allow them to record activity and adjust electrical
pulses based on the heart’s activity.
Radiofrequency ablation: Involves using angiography
to guide insertion of a catheter with an electrode on its tip to a portion of the
myocardium (heart muscle) with access to an electrical pathway. Mild radiofrequency pulses
are then emitted to the pathway, causing a small area of myocardium cells to stop
conducting extra impulses (the source of rapid heartbeats). Radiofrequency ablation may be
used to treat supraventricular tachycardias (fast heartbeats) or other arrhythmias such as
Wolff-Parkinson-White syndrome.
Updated: February 28, 2008
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