Definition:
The heart is a pump that functions by pushing the blood through its four chambers. The blood is “pushed” through in a controlled sequence of muscular contractions. The sequence is controlled by bundles of cells which control the electrical activity of the heart. When the sequence is disturbed, heart arrhythmias occur.
Arrhythmias are abnormal rhythms of the heart. Arrhythmias cause the heart to pump blood less effectively. Most cardiac arrhythmias are temporary and benign. Most temporary and benign arrhythmias are those where your heart skips a beat or has an extra beat. The occasional skip or extra beat is often caused by strong emotions or exercise. Nonetheless, some arrhythmias may be life-threatening and require treatment.
Types of Arrhythmias:
Arrhythmias can be divided into two main categories ventricular and supraventricular. Supraventricular arrhythmias occur in the heart’s two upper chambers called the atrium. Ventricular arrhythmias occur in the heart’s two lower chambers called the ventricles.
Electrical conduction in the heart originates in the SA node and travels through the AV node to the ventricles, resulting in a heart beat.
Supraventricular and Ventricular arrhythmias are further defined by the speed of the heartbeats: very slow, very fast and fast uncoordinated. A very slow heart rate is called bradycardia. In bradycardia, the heart rate is less than 60 beats per minute. A very fast heart rate is called Tachycardia meaning the heart beats faster than 100 beats per minute. A fast uncoordinated heart rate is called Fibrillation. Fibrillation is the most serious form of arrhythmia are contractions of individual heart muscle fibers. Arrhythmias cause nearly 250,000 deaths each year.
Supraventricular Arrhythmia
A very common long term arrhythmia is atrial fibrillation. Atrial fibrillation is very abnormal. A normal heart beats between 60 and 100 times a minute. However, in atrial fibrillation, the atria (upper lobes of the heart) beat 400 to 600 times per minute. In response to this, the ventricles usually beat irregularly at a rate of 170 to 200 times per minute. So in Atrial Fibrillation, the upper part of the heart may beat up to 8 times as much as a normal heart. Unfortunately, atrial fibrillation is seen in many types of heart disease; once established, it usually lasts a lifetime.
Ventricular Arrhythmia
One of the most serious arrhythmias is sustained ventricular tachycardia. In sustained ventricular tachycardia, there are consecutive impulses that arise from the ventricles at a heart rate of 100 beats or more per minute until stopped by drug treatment or electrical conversion. This condition is very dangerous. It is dangerous because it may degenerate further into a totally disorganized electrical activity known as ventricular fibrillation. In ventricular fibrillation, heart’s action is so disorganized that it quivers and does not contract, thus failing to pump blood.
SADS:
SADS, or sudden arrhythmic death syndrome, is a term used to describe sudden death due to cardiac arrest brought on by an arrhythmia in the absence of any structural heart disease on autopsy. The most common cause of sudden death in the US is coronary artery disease.[citation needed] Approximately 300,000 people die suddenly of this cause every year in the US.[citation needed] SADS occurs from other causes. There are many inherited conditions and heart diseases that can affect young people and subsequently cause sudden death. Many of these victims have no symptoms before dying suddenly.
Causes of SADS in young people include viral myocarditis, long QT syndrome, Brugada syndrome, Catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia
Signs and symptoms:
The term cardiac arrhythmia covers a very large number of very different conditions.
The most common symptom of arrhythmia is an abnormal awareness of heartbeat, called palpitations. These may be infrequent, frequent, or continuous. Some of these arrhythmias are harmless (though distracting for patients) but many of them predispose to adverse outcomes.
Some arrhythmias do not cause symptoms, and are not associated with increased mortality. However, some asymptomatic arrhythmias are associated with adverse events. Examples include a higher risk of blood clotting within the heart and a higher risk of insufficient blood being transported to the heart because of weak heartbeat. Other increased risks are of embolisation and stroke, heart failure and sudden cardiac death.
If an arrhythmia results in a heartbeat that is too fast, too slow or too weak to supply the body’s needs, this manifests as a lower blood pressure and may cause lightheadedness or dizziness, or fainting.
Some types of arrhythmia result in cardiac arrest, or sudden death.
Medical assessment of the abnormality using an electrocardiogram is one way to diagnose and assess the risk of any given arrhythmia.
Causes:
Many types of heart disease cause arrhythmia. Coronary disease is often a trigger. It triggers arrhythmia because coronary heart disease produces scar tissue in the heart. This scar tissue disrupts the transmission of signals which control the heart rhythm. Some people are born with arrhythmias, meaning the condition is congenital. Atherosclerosis is also a factor in causing arrhythmia. Other medical conditions such as diabetes and high blood pressure also are factors. Furthermore, stress, caffeine, smoking, alcohol, and some over-the-counter cough and cold medicines can affect your heart’s natural beating pattern.
Diagnosis:
Many different techniques are used to diagnose arrhythmia. The techniques include:
•A standard electrocardiogram (ECG or EKG). An EKG is the best test for diagnosing arrhythmia. This test helps doctors analyze the electrical currents of your heart and determines the type of arrhythmia you have.
•Holter monitoring. Holter monitoring gets a continuous reading of your heart rate and rhythm over a 24-hour period (or more). You wear a recording device (the Holter monitor), which is connected to small metal disks on your chest. With certain types of monitors, you can push a “record” button to capture a rhythm when you feel symptoms. Doctors can then look at a printout of the recording to find out what causes your arrhythmia.
•Trans telephonic monitoring. Transtelephonic monitoring documents problems that may not be detected within a 24-hour period. The devices used for this type of test are smaller than a Holter monitor. One of the devises is about the size of a beeper, the other device is worn like a wristwatch. Like with Holter monitoring, you wear the recording device. When you feel the symptoms of an arrhythmia, you can telephone a monitoring station, where a record can be made. If you cannot get to a telephone during your symptoms, you can turn on the device’s memory function. Later, you can send the recorded information to a monitoring station by using a telephone. These devices also work during episodes of fainting.
•Electrophysiology studies (EPS). Electrophysiology studies are usually performed in a cardiac catheterization laboratory. In this procedure, a long, thin tube (called a catheter) is inserted through an artery in your leg and guided to your heart. A map of electrical impulses from your heart is sent through the wire to find out what kind of arrhythmia you have and where it starts. During the study, doctors can give you controlled electrical impulses to show how your heart reacts. Medicines may also be tested at this time to see which medicines will stop the arrhythmia. Once the electrical pathways causing the arrhythmia are found, radio waves can be sent through the catheter to destroy them.
•A tilt-table exam. A tilt-table exam is a way to evaluate your heart’s rhythm in cases of fainting. The test is noninvasive, which means that doctors will not use needles or catheters. Your heart rate and blood pressure are monitored as you lie flat on a table. The table is then tilted to 65 degrees. The changing angle puts stress on the area of the nervous system that maintains your heart rate and blood pressure. Doctors can see how your heart responds under carefully supervised conditions of stress.
Treatment:
Treatment of arrhythmia depend on the type of arrhythmia, the patients age, physical condition and age. Methods are available for prevention of arrhythmia. These methods include relaxation techniques to reduce stress, limit intake of caffeine, nicotine, alcohol and stimulant drugs. Many arrhythmias require no treatment, they are naturally controlled by the body’s immune system. However if it is necessary that arrhythmias must be controlled, they can be controlled by drugs, Cardioversion, Automatic implantable defibrillators or an Artificial pacemaker. Arrhythmias are very serious.
Arrhythmias that start in the lower chambers of the heart (the ventricles) are more serious than those that start in the upper chambers (the atria).
Management:
The method of cardiac rhythm management depends firstly on whether or not the affected person is stable or unstable. Treatments may include physical maneuvers, medications, electricity conversion, or electro or cryo cautery.
Physical maneuvers
A number of physical acts can increase parasympathetic nervous supply to the heart, resulting in blocking of electrical conduction through the AV node. This can slow down or stop a number of arrhythmias that originate above or at the AV node (you may click to see: supraventricular tachycardias). Parasympathetic nervous supply to the heart is via the vagus nerve, and these maneuvers are collectively known as vagal maneuvers.
Antiarrhy
thmic drugsMain article: Antiarrhythmic agents
There are many classes of antiarrhythmic medications, with different mechanisms of action and many different individual drugs within these classes. Although the goal of drug therapy is to prevent arrhythmia, nearly every antiarrhythmic drug has the potential to act as a pro-arrhythmic, and so must be carefully selected and used under medical supervision.
Other drugs
A number of other drugs can be useful in cardiac arrhythmias.
Several groups of drugs slow conduction through the heart, without actually preventing an arrhythmia. These drugs can be used to “rate control” a fast rhythm and make it physically tolerable for the patient.
Some arrhythmias promote blood clotting within the heart, and increase risk of embolus and stroke. Anticoagulant medications such as warfarin and heparins, and anti-platelet drugs such as aspirin can reduce the risk of clotting.
Electricity
Dysrhythmias may also be treated electrically, by applying a shock across the heart — either externally to the chest wall, or internally to the heart via implanted electrodes.
Cardioversion is either achieved pharmacologically or via the application of a shock synchronised to the underlying heartbeat. It is used for treatment of supraventricular tachycardias. In elective cardioversion, the recipient is usually sedated or lightly anesthetized for the procedure.
Defibrillation differs in that the shock is not synchronised. It is needed for the chaotic rhythm of ventricular fibrillation and is also used for pulseless ventricular tachycardia. Often, more electricity is required for defibrillation than for cardioversion. In most defibrillation, the recipient has lost consciousness so there is no need for sedation.
Defibrillation or cardioversion may be accomplished by an implantable cardioverter-defibrillator (ICD).
Electrical treatment of dysrhythmia also includes cardiac pacing. Temporary pacing may be necessary for reversible causes of very slow heartbeats, or bradycardia, (for example, from drug overdose or myocardial infarction). A permanent pacemaker may be placed in situations where the bradycardia is not expected to recover.
Electrical cautery
Some cardiologists further sub-specialise into electrophysiology. In specialised catheter laboratories, they use fine probes inserted through the blood vessels to map electrical activity from within the heart. This allows abnormal areas of conduction to be located very accurately, and subsequently destroyed with heat, cold, electrical or laser probes.
This may be completely curative for some forms of arrhythmia, but for others, the success rate remains disappointing. AV nodal reentrant tachycardia is often curable. Atrial fibrillation can also be treated with this technique (e.g. pulmonary vein isolation), but the results are less reliable.
Click to learn more about arrhythmia
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.
Resources:
http://www.mamashealth.com/ardiag.asp
http://www.mamashealth.com/arrhythmia.asp
http://hrssc.com/hrssc-patient-resource-how-to-diagnose-arrhythmias.html
http://www.nsmc.partners.org/web/service/heart_arrhythmia
http://www1.ecardio.com/PS/Cardiac.aspx
http://www.medicompinc.com/holter_service.html
http://www.nhlbi.nih.gov/health/dci/Diseases/ekg/ekg_during.html
http://commons.wikimedia.org/wiki/File:Heart_conduct_atrialfib.gif
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