What is arrythmia? What are signs and symtoms? What causes it and how is it treated?
Arrhythmias or dysrhythmias are abnormal heart rhythms. They can cause the heart to pump less effectively.
Normally the heartbeat starts in the right atrium when a special group of cells sends an electrical signal. (These cells are called the sinoatrial or SA node, the sinus node or "pacemaker" of the heart.) This signal spreads throughout the atria and to the atrioventricular (A-V) node. The A-V node connects to a group of fibers in the ventricles that conduct the electric signal. The impulse travels down these specialized fibers (the His-Purkinje system) to all parts of the ventricles. This exact route must be followed for the heart to pump properly.
Cardiac arrhythmia is the leading cause of death in the Western world. Every minute a person in the United States dies instantly and unexpectedly, such that, in the United States alone, as many as 400,000 people die suddenly each year. Although approximately seventy-five percent of sudden death victims have a history of heart disease or damage, arrhythmias may strike young and apparently healthy men and women. In addition, among those who have heart disease, it is usually an acute lethal arrhythmia rather than sudden deterioration of the heart that kills.
What causes arrhythmias? Under some conditions almost all heart tissue can start a heartbeat. In other words, another part of the heart can become the pacemaker. An arrhythmia occurs
· when the heart's natural pacemaker develops an abnormal rate or rhythm;
· when the normal conduction pathway is interrupted; or
· when another part of the heart takes over as pacemaker.
These problems can produce a heartbeat that's either too slow or too fast. A heart rhythm that's too slow (bradycardia) can cause fatigue, dizziness, lightheadedness, fainting or near-fainting spells. These symptoms can be easily corrected by implanting an electronic pacemaker under the skin to speed up the heart rhythm.
Rapid heart beating, called tachycardia or tachyarrhythmia , can produce symptoms of palpitations, rapid heart action, dizziness, lightheadedness, fainting or near fainting if the heart beats too fast to circulate blood effectively. Heartbeats may be either regular or irregular in rhythm.
When rapid heart beating arises in the ventricles - called ventricular tachycardia - a life-threatening situation can arise. The most serious cardiac rhythm disturbance is ventricular fibrillation , where the lower chambers quiver and the heart can't pump any blood. Collapse and sudden death follows unless medical help is provided immediately.
If treated in time, ventricular tachycardia and ventricular fibrillation can be converted into normal rhythm with electrical shock. Rapid heart beating can be controlled with medications by identifying or destroying the focus of rhythm disturbances. Today one effective way of correcting these life-threatening rhythms is by using an electronic device called an implantable cardioverter / defibrillator .
