Heart Arrhythmias (Irregular heart Beats)

The control mechanism for the heart rate involves electrical impulses. One of the four chambers of the heart, the right atrium, contains a group of cells called the sinus node. The sinus node acts as a pacemaker, producing electrical impulses that signal the muscle of the heart to expand and to contract in the pumping cycle. Your heart rate varies depending on your activity at any given moment. When you are at rest, your heart pumps more slowly and at a regular rate of 60 to 80 beats per minute. When you run, climb stairs, or otherwise exert yourself, the sinus node issues electrical "instructions" to increase the pace of the heart in order to provide your muscles and other tissues with the necessary additional blood and its supply of oxygen. Your heart rate may increase up to 200 beats per minute if you exert yourself strenuously.

If the rhythm of the beat of the heart is disturbed, the problem is termed arrhythmia. Depending on the nature of the arrhythmia, the symptoms vary. Some irregular heartbeats are common and usually harmless, such as when it happens just once in a while or without any other symptoms. It is not uncommon for a person to feel an occasional “missed beat.” It is also normal for someone to have a faster heart rate when excited or exercising. However, when these irregularities happen over and over again, it is important to check with your doctor. Some of the signs and symptoms of arrhythmia include:

1. Dizziness
2. Fluttering, strong, or fast heartbeat called palpitations pronounced
3. Drowsiness
4. Shortness of breath
5. Tiredness
6. Fainting and near-fainting
7. Chest pain
8. Lack of energy
9. Major discomfort when exercising
10. Uncomfortable awareness of your heart beat.

Types of heart rhythm problems

Heart rate that is too fast: A heart rate that is too fast is called tachycardia. Sometimes the electrical signals are sent so quickly and irregularly that they cause the heart muscle to tremble or quiver. There are a number of conditions that result from a fast or quivering heartbeat:

1. Atrial fibrillation
2. Ventricular  fibrillation
3. Ventricular tachycardia
4. Supraventricular tachycardia
5. A-v node reentrant tachycardia
6. Wolff-parkinson-white (wpw) syndrome

Heart rate that is too slow:  A heart rhythm that is too slow is called bradycardia. This happens when the system that sends messages to contract the heart muscle does not work properly. Sometimes the message is not sent. In other cases, the message is sent but blocked, or takes another route. The result is a heart rate that is too slow. Your body does not get the oxygen and blood that it needs to work properly. There are several types of bradycardia:

1. Sinus bradycardia
2. Sick sinus syndrome
3. Heart block .

Diagnostic tests

If your doctor thinks you might have arrhythmia, he or she will do a complete medical history and physical exam. The doctor also may order any of the following tests:

Electrocardiogram

Echocardiogram  these are painless, non-invasive procedures that image the heart’s chambers, valves, and blood flow using high frequency sound waves (ultrasound).

Holter monitor: records your heart rate for 24 hours while you go about your normal activities

Tilt-table study: A Tilt-Table study is a procedure used to evaluate changes in heart rate and blood pressure during changes in body position. The most common indication to perform this test is in patients who have symptoms of temporary loss of consciousness or near fainting. The nurse prepares you prior to the procedure by starting an intravenous (IV) line and connecting you to a machine that continuously monitors your heart rate and blood pressure. Initially, you will be lying in a flat position for 20-30 minutes. Then, the tilt bed will be changed to a near vertical (80 degrees) position for a period of 30 to 45 minutes. During this portion of the vertical tilt position, it is possible that you will experience lightheadedness, dizziness, or a feeling of fainting. It is important that you inform the physician or nurse of any symptoms you may be feeling. Finally, the tilt bed will be placed in a horizontal position and you will be observed for another 20 to 30 minutes while lying in a flat position.

Electrophysiologic Studies (EPS): An electrophysiology study is designed to thoroughly assess the conduction system or “electrical wiring” of the heart and to assess abnormal heart beats. This test may be done to assess for abnormal fast heart rhythms that can lead to palpitation, fainting or even cardiac arrest. It is also used to assess the need for pacemaker implantation, or the need for further special procedures. This test involves the insertion of several thin catheters (tubes) or wires into your groin, and commonly the right neck. These wires are advanced to various locations in the chambers of your heart to record signals and stimulate the heart to identify abnormal rhythms. Once the wires are in place, electrical signals from your heart are monitored and recorded. In addition, the doctor may artificially increase your heart rate in an attempt to provoke any abnormal rhythm disturbances with medication. The entire study may take from one to three hours.

Cardiac catheterization : a test to see if arrhythmia is caused by problems of your coronary arteries.

Brief Explanation of Some Common Arrythmias

Ectopic Atrial Heartbeat:

The least serious of the cardiac arrhythmias is an ectopic atrial heart beat. This problem involves a small variation in an otherwise normal pulse. This is usually explained by patients as "my heart skipped a beat".

An ectopic atrial heartbeat is often termed extrasystole. The extrasystole may show up on a routine electrocardiogram. If there is concern that the ectopic beats are causing some of the symptoms listed above, a 24- hour Holter monitor study may be needed. In most cases, an ectopic heartbeat is harmless and requires no treatment. Often the problem is precipitated by excessive use of tobacco, alcohol, or caffeine containing foods and beverages. Try decreasing or eliminating the use of these substances if you have an ectopic heartbeat.In some cases your physician may prescribe a medication that will control the rhythm of your heart.

Atrial Fibrillation and Flutter:

The upper chambers of the heart are the atria. The atria contract at a rate coordinated with the rates of the other chambers of the heart, the ventricles. In some people, however, the atria may begin to contract much too often, a condition called atrial flutter. The ventricles tend to beat at every second or fourth atrial beat.

When the muscles making up the atrial walls are contracting in an ineffective and uncoordinated manner, the condition is called atrial fibrillation. In atrial fibrillation the electrical impulses are transmitted to the ventricles in an irregular fashion, often more rapidly than normal. Both atrial flutter and atrial fibrillation tend to occur in episodes with occasional attacks separated by long periods of normal heart rhythms. However atrial fibrillation may become persistent and chronic.

In atrial flutter or atrial fibrillation, the ventricles may fail to pump enough blood. The result is faintness and weakness. With atrial fibrillation, you may be aware of the irregularity of your pulse and heartbeat. The failure of the atria to contract normally can allow a clot to form in an atrium. If the clot breaks loose and is carried in the bloodstream to the brain, it may cause a stroke.

Atrial flutter is most often associated with a heart attack or a lung or heart operation. Atrial fibrillation may occur without heart disease or be produced by one of a number of disorders including coronary artery disease, rheumatic heart disease, malfunction of the mitral valve of the heart, heart infection  and various other lung and heart disorders. An excess of thyroid hormone also can result in the problem

Treatment:

In order to establish the diagnosis, your physician or cardiologist will obtain one or more of the diagnostic tests listed above. Once the diagnosis has been confirmed the treatment depends on the cause. Most often, a medication  will be prescribed that will control the rhythm of your heart.

In some cases an electrical stimulus called electrical cardioversion  may be given to help restore normal rhythm. First you will receive a drug treatment to limit the risk of an embolism. Then, after you have been anesthetized by a short-acting painkiller, an electric shock will be delivered from two "paddles." This mild shock will interrupt the pattern of arrhythmia and allow your heart to reestablish a normal rate and rhythm.

Another option for treatment is by ablation  or surgery . 

Paroxysmal Atrial Tachycardia:

If you feel your heart suddenly race, you may be experiencing an attack (paroxysm) of tachycardia or rapid heart rate. During such an attack, which may last for minutes or as long as a day or two, your heart rate may range between 140 and 240 beats per minute. Some people report an accompanying sensation of doom or anxiety. Paroxysmal atrial tachycardia is not a life threatening disorder, although repeated attacks may increase the risk of heart failure developing.

Treatment:

Several self-help treatments are effective in returning the heartbeat to its normal rate. Holding your breath and straining (exerting pressure as if you were blowing up a balloon) while sitting with your upper body bent forward may help. Your physician can instruct you in other helpful techniques after he or she has examined you to make sure the techniques would be safe. You also may be able to prevent future attacks by making some small changes in your lifestyle. Excessive use of tobacco and consumption of alcohol and caffeine containing beverages (coffee, tea, and cola drinks) may increase your risk of such attacks. Try to limit their consumption.

Certain medications may be used, but other methods may be appropriate. Among them may be the gentle application of pressure to the arteries in your neck. in some cases, an electrical stimulus, called electrical cardioversion, may be given to restore normal rhythms. Some types of paroxysmal atrial tachycardia, especially those associated with a rare condition called Wolff-Parkinson-White syndrome, may be permanently cured by surgery . This approach would eliminate the need to take medications on a daily basis.

Ventricular Tachycardia and Fibrillation:

Ventricular tachycardia is the term used to describe too-rapid contractions of the ventricles. It usually is associated with heart disease or occurs in the several days immediately after a heart attack.

Ventricular fibrillation describes a condition in which the muscle fibers of the ventricles contract in an uncoordinated and inefficient manner so that the pumping action virtually ceases. If a normal, organized pumping action is not restored in a matter of minutes, death results.

Treatment:

Defibrillation with an electric shock is usually the first measure of treatment to restore normal heart rhythms. Various medications will be administered also. Occasionally, such arrhythmias can be treated surgically by the use of special autonomic defibrillators  (ICD)  that can be implanted in the body somewhat like a pacemaker

Ventricular premature complexes (VPCs): These resemble ectopic atrial beats. Ectopic ventricular beats are observed in the electrocardiograms of nearly two of every three adults monitored over a period of hours. VPCs usually require no treat- ment unless they are associated with other symptoms or are occurring frequently. However, there is an association between certain patterns of VPCs and sudden cardiac death .Thus, if your physician notes VPCs in your electrocardiogram, he or she may recommend use of an antiarrhythmia drug.

Heart Block:

Your heart rate is controlled by electrical impulses issued by the sinus node in the right atrium. These pacemaker cells produce electrical impulses that travel throughout both atria, causing the muscular walls of the atria to contract. The electrical impulses travel from the atria through a small bed of specialized tissue called the atrioventricular node to specialized fibers (bundle of His) that conduct them to the muscle fibers of the ventricles. These muscles then contract.

In heart block, the electrical impulse passes through the atrioventricular node and bundle of His slowly, intermittently, or not at all. This condition can result from various causes including scarring in the path of the specialized conduction fibers, coronary artery disease (including a heart attack), congenital heart disease, the effects of certain drugs, infections such as Lyme disease and other disorders.

Diagnosis:

In many people with heart block, there are no obvious symptoms. On the other hand, in severe cases, there may be a breathlessness and feeling of exhaustion, extreme breathlessness and weakness, sudden loss of consciousness and convulsions.

Heart block is classified by degrees. First degree heart block is asymptomatic (without symptoms) and is evident only on the electrocardiogram as a delay in the transmission of the impulse from the atria to the ventricles.

In second degree heart block, some of the impulses fail to reach the ventricles. The result is an irregular pulse. In many cases, second degree heart block is a result of an excess of certain heart drugs, and the heart beat returns to normal with the withdrawal of the medication. In others, the use of an artificial cardiac pacemaker is necessary. In third-degree heart block, no impulses reach the ventricles and the ventricles are forced to beat with their own intrinsic rhythm. The beating of the heart at this intrinsic rate is often so slow that the flow of blood to the brain and other parts of the body is insufficient. Loss of consciousness may result.

Treatment:

First-degree heart block and many forms of second-degree heart block are not serious conditions. Only observation or withdrawing or reducing the medication that produced the heart block is necessary.

When the heart is no longer able to pace itself, a procedure to implant an artificial cardiac pacemaker  is required.