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Several forms of cardiac arrhythmia are life-threatening and a medical emergency.
A rhythm of the heart at a rate of more than 100 beats/minute is considered a tachycardia. If the ventricles of the heart sustain a tachycardia for a sustained period of time, there can be deleterious effects. Individuals may sense a tachycardia as a pounding sensation of the heart; this is known as "palpitations". However, strictly speaking, palpitations are any sensation of an individual's own heart beat, and can occur at rates less than 100 beats/minute.
The causes of tachycardias are numerous, and include stress, ingested or injected substances (ie: caffeine, alcohol, hyperthyroidism, or various drugs). Individuals who have a tachycardia are often advised to limit or remove exposure to any causative agent.
A slow rhythm, known as bradycardia (less than 60 beats/min), is usually not life threatening, but may cause symptoms.
Either arrhythmia requires medical attention to evaluate the risks associated with the arrhythmia.
A more serious variety of arrhythmia is known as fibrillation. Fibrillation occurs when the heart muscle begins a quivering motion instead of a normal, healthy pumping rhythm. Atrial fibrillation is the quivering, chaotic motion in the upper chambers of the heart, known as the atria. Atrial fibrillation is often due to serious underlying medical conditions, and should be evaluated by a physician. It is not typically a medical emergency.
If fibrillation occurs in the ventricles (lower chambers) of the heart, it is always a medical emergency. If left untreated, ventricular fibrillation can lead to death within minutes. When a heart goes into ventricular fibrillation, effective pumping of the blood stops. The individual goes into cardiac arrestA cardiac arrest is the cessation of normal circulation of the blood due to failure of the ventricles of the heart to contract effectively during systole. The resulting lack of blood supply results in cell death from oxygen starvation. Cerebral hypoxia, o, and will not survive unless cardiopulmonary resuscitationSurvival skills For other meanings of CPR, see CPR (disambiguation). This article details Cardiopulmonary resuscitation (CPR) procedure. It is intended as a reminder for those with previous CPR training. It is not intended as a "teach yourself CPR" guide. (CPR) and defibrillationDefibrillation is a medical technique used to counter the onset of ventricular fibrillation, a common cause of cardiac arrest, and ventricular tachycardia, which sometimes precedes ventricular fibrillation but can be just as dangerous on its own. The equi are provided immediately.
CPR can prolong the survival of the heart muscle, but defibrillation is the intervention which is most likely to restore a more healthy heart rhythm. It does this by applying an electric shock to the heart, after which sometimes the heart will revert to a rhythm that can once again pump blood.
Almost every person goes into ventricular fibrillation in the last few minutes of life as the heart muscle reacts to diminished oxygen, blood flow or trauma or irritants.
When an electrical impulse begins in any part of the heart, it will spread throughout the myocardiumMyocardium is the muscular tissue of the heart. Other tissues are the endocardium (inner lining, effectively a specialised endothelium) and the pericardium (a connective tissue layer around the heart). The myocardium is composed of specialized cardiac mus and cause a contraction; see Electrical conduction system of the heartThe normal electrical conduction in the heart allows the impulse that is generated by the SA node of the heart to be propagated to (and stimulate) the myocardium (muscle of the heart). When the myocardium is stimulated, it contracts. It is the ordered sti. Abnormal impulses can begin by one of two mechanisms: automaticity or reentry.
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