| CHIEF DISORDERS OF THE HEART |
Arrhythmia
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Arrhythmia (also called Dysrhythmia) is an abnormal rhythm of the heart, which can cause the heart to pump less effectively.
Arrhythmias can cause problems with contractions of the heart chambers by:
* Not allowing the ventricles (lower chambers) to fill with an adequate amount of blood, because an electrical signal is causing the heart to pump too fast.
* Not allowing a sufficient amount of blood to be pumped out to the body, because an electrical signal is causing the heart to pump too slowly or too irregularly.
In any of these situations, the body may not receive enough blood because the heart cannot pump out an adequate amount with each beat as a result of the arrhythmia's effects on the heart rate.
CAUSES
An arrhythmia can be caused by:
* The heart's natural pacemaker (SA node) developing an abnormal rate or rhythm
* The normal conduction pathway being interrupted
* Another part of the heart taking over as pacemaker.
RISK FACTORS
Risk factors include:
* Excess caffeine
* Stress
* Tobacco use
* Alcohol use
* Certain diet pills or decongestants
* Cocaine
* Certain antidepressant medications
* Digitalis overdose
* Endocrine disorders, such as thyroid or adrenal gland problems
* Anemia
* High blood pressure
* Coronary artery disease
* Problems with heart valves
* Heart muscle damage after heart attack
* Rheumatic heart disease
* Cardiomyopathy
* Diabetes
* Liver disease
* Typhoid fever
* Hypothermia
* Electric shock or lightening strike
* Complication after near-drowning
SYMPTOMS
Some arrhythmias may occur without any symptoms. Others may cause noticeable symptoms, such as:
* Fainting
* Dizziness, sensation of light-headedness
* Sensation of your heart fluttering (palpitations)
* Sensation of a missed or extra heart beat
* Weakness
* Fatigue
* Shortness of breath
* Chest pain
TYPES OF ARRHYTHMIAS
Arrhythmias can be divided into two categories: VENTICULAR and SUPRAVENTICULAR. Ventricular Arrhythmias happen in the heart's two lower chambers, called the Ventricles. Supraventricular Arrhythmias happen in the structures above the ventricles, mainly the Atria, which are the heart's two upper chambers.
VENTRICULAR ARRHYTHMIAS is an arrhythmia caused by abnormal function of the sinus node, an interruption in the electrical conduction pathways, or the development of another area within the heart tissue that takes over the function of the sinus node.
ATRIAL ARRHYTHMIAS or SUPRAVENTICULAR ARRHYTHMIAS is an arrhythmia caused by abnormal function of the sinus node, or by the development of another atrial pacemaker within the heart tissue that takes over the function of the sinus node.
Arrhythmias are further divided by the speed of the heartbeats. A very slow heart rate, called BRADYCARDIA, means the heart rate is less than 60 beats per minute. TACHYCARDIA is a very fast heart rate, meaning the heart beats faster than 100 beats per minute. FIBRILLATION, the most serious form of arrhythmia, is fast, uncoordinated beats, which are contractions of individual heart-muscle fibers.
The various types of Arrhythmias are:
1.BRADYCARDIA
2.TACHYCARDIA
3.VENTRICULAR TACHYCARDIA
4.VENTRICULAR FIBRILLATION
5.PREMATURE VENTRICULAR CONTRACTIONS
6.SUPRAVENTRICULAR TACHYCARDIA
7.ATRIAL FIBRILLATION
8.ATRIAL FLUTTER
9.WOLFF-PARKINSON-WHITE SYNDROME
10.PREMATURE SUPRAVENTRICULAR CONTRACTIONS
BRADYCARDIA - Bradycardia is a very slow heart rate of less than 60 beats per minute. It happens when the electrical impulse that signals the heart to contract is not formed in the heart's natural pacemaker, the Sinoatrial Node (SA node), or is not sent to the heart's lower chambers (the ventricles) through the proper channels.
Bradycardia most often affects elderly people, but it may affect even the very young. It may be caused by one of two sources: The Central Nervous System does not signal that the heart needs to pump more, or the SA node may be damaged.
TACHYCARDIA - Tachycardia is a very fast heart rate of more than 100 beats per minute. The many forms of tachycardia depend on where the fast heart rate begins. If it begins in the ventricles, it is called Ventricular Tachycardia. If it begins above the ventricles, it is called Supraventricular Tachycardia.
VENTRICULAR TACHYCARDIA - Ventricular Tachycardia is a condition in which the SA node no longer controls the beating of the ventricles.
Instead, other areas along the lower electrical pathway take over the pace making role. Since the new signal does not move through the heart muscle along the regular route, the heart muscle does not beat normally. The heartbeat quickens, and one may feel as if the heart is "skipping beats." This rhythm may cause severe shortness of breath, dizziness, or fainting (syncope).
VENTRICULAR FIBRILLATION - The most serious arrhythmia is Ventricular Fibrillation, which is an uncontrolled, irregular beat. Instead of one misplaced beat from the ventricles, one may have several impulses that begin at the same time from different locations.The result is a much faster heartbeat that sometimes reaches 300 beats a minute. This heartbeat means very little blood is pumped from the heart to the brain and body and can result in fainting.
PREMATURE VENTRICULAR CONTRACTIONS(PVC) - This condition happens when the ventricles contract too soon, out of sequence with the normal heartbeat. PVCs (sometimes called PVB for premature ventricular beat) generally are not a cause for alarm and often do not need treatment. But if one has heart disease or a history of ventricular tachycardia, PVCs can cause a more serious arrhythmia. Although most PVCs happen quickly and without warning, they can also happen in response to caffeine, which is found in coffee, tea, sodas, and chocolate. Some kinds of over-the-counter cough and cold medicines may also cause PVCs.
SUPRAVENTRICULAR TACHYCARDIA - Supraventricular tachycardia is a rapid, regular heart rate where the heart beats more than 150 times per minute in the atria. Unlike other types of arrhythmias, supraventricular tachycardia does not start in the SA node.
ATRIAL FIBRILLATION - Atrial fibrillation is a fast, irregular rhythm where single muscle fibers in the heart twitch or contract. It is a main cause of stroke, especially among elderly people. Atrial fibrillation may cause blood to pool in the heart's upper chambers. The pooled blood can lead to the formation of clumps of blood called blood clots. A stroke can occur if a blood clot travels from the heart and blocks a smaller artery in the brain (a cerebral artery).
WOLFF-PARKINSON-WHITE SYNDROME - Wolff-Parkinson-White (WPW) syndrome is a group of abnormalities caused by extra muscle pathways between the atria and the ventricles. The pathways cause the electrical signals to arrive at the ventricles too soon, and the signals are sent back to the atria. The result is a very fast heart rate. People with this syndrome may feel dizzy, have chest palpitations, or have episodes of fainting.
ATRIAL FLUTTER - Atrial flutter happens when the atria beat very fast, causing the ventricles to beat inefficiently as well.
PREMATURE SUPRAVENTRICULAR CONTRACTIONS - Also called as "Premature Atrial Contractions" (PACs), they happen when the atria contract too soon, causing the heart to beat out of sequence.
DIAGNOSIS
Tests may include:
BLOOD TESTS – to look for certain markers in the blood that help the doctor determine what is happening with the heart.
URINE TESTS – to look for certain markers in the urine that help the doctor determine what is happening with the heart.
ELECTROCARDIOGRAM (EKG) – records the heart's activity by measuring electrical currents through the heart muscle.
ECHOCARDIOGRAM – uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart.
24-HOUR HOLTER MONITOR – a portable EKG that one can wear while one can perform normal daily activities.
EXERCISE STRESS TEST – records the heart's electrical activity during increased physical activity. For patients who cannot exercise, an intravenous medication may be given to simulate the effects of physical exertion on the heart.
NUCLEAR SCANNING – radioactive material, such as thallium, is injected into a vein and observed as it is absorbed by the heart muscle. Areas with diminished flow, and therefore uptake of the radioactive material, show up as dark spots on the scan.
CORONARY ANGIOGRAPHY – X-rays taken after a dye is injected into the coronary arteries—allows the doctor to look for abnormalities (narrowing, blockage) in the arteries and evaluate the function of the heart.
ELECTRO PHYSIOLOGICAL STUDY – In this study a series of electrodes is threaded through the blood vessels and attached to various spots in the heart. This allows doctors to see how electric impulses travel through the heart and therefore diagnose problems with conduction and/or identification of tissues that may be causing the arrhythmia.
TILT TABLE TESTING – This test is usally recommended for patients with history of fainting. First, the patient has to lie flat on a table that is later tilted into a vertical position. Heart rate and blood pressure as well as other parameters are closely monitored during the tilting.
TREATMENT
Treatment may include:
ANTIARRHYTHMIC MEDICATIONS - These will help slow down or speed up the heart rate, or return the heart rhythm to normal (cardioversion), depending on the need.
ELECTRICAL CARDIOVERSION or DEFIBRILLATION - These treatments involve placing paddles on the chest or back. An electrical current is passed through the chest wall to the heart to reset its electrical circuits, and attempt to return the heart rhythm to normal.
AUTOMATIC IMPLANTABLE DEFIBRILLATOR - A tiny defibrillator can be surgically implanted in the chest to monitor the heart rhythm. If a dangerous arrhythmia is detected, the device automatically shocks the heart in an attempt to return the heart rhythm to normal.
ARTIFICIAL PACEMAKER - This device is surgically implanted in the chest. It takes over the job of providing the electrical impulses needed for establishing an appropriate heart rhythm.
ABLATION THERAPY - An area of the heart that is responsible for an abnormal rhythm may be surgically removed or altered (ablated) with various techniques (eg, cryoblation) to prevent it from generating an arrhythmia.
PREVENTION
To help prevent arrhythmias:
* Treat underlying conditions that might lead to arrhythmias.
* Avoid substances that might trigger or worsen an arrhythmia, including:
1.Caffeinated beverages
2.Alcohol
3.Tobacco
4.Certain medications
* Follow general advice for preventing the development of heart disease, including:
1.Maintain an appropriate weight.
2.Consult the doctor about a safe exercise program.
3.Do not smoke. If one smokes, quit.
4.Eat a healthful diet, one that is low in saturated fat and rich in whole grains, fruits, and vegetables.
5.Appropriately treat high blood pressure and/or diabetes.
6.Ask the doctor if cholesterol-lowering medications should be taken.
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| Last Modified :
Monday, May 12, 2008 |
Compiled and edited by the Editorial team and
approved by Expert panel of h4heart.com
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