In a normal rhythm, an area of the heart called the sinus node sends regular electrical impulses to start a heartbeat 50 to 100 times per minute. The mini-shocks stimulate the heart’s four chambers (two atria and two ventricles) to contract in the right order, forcing blood out to the lungs and through the circulatory system.Nervous and chemical reactions trigger the impulses at a faster rate, speeding up the heartbeat. A rhythm greater than 100 beats per minute is known as tachycardia. One of the chemicals stimulated, adrenaline, is the same that is released by fear, helping to pump enough blood to prepare the body for "fight or flight."
A heart rate lower than 50 beats per minute is known as bradycardia.
An ectopic (extra) beat can occur in any of the heart’s chambers. A normal individual has at least one every 24 hours. They are usually harmless and even unnoticed, although they may be felt as a thump, especially if fatigue or alcohol consumption are present.
In addition to normal sinus tachycardia, two other types of fast, regular heartbeat can be alarming although they are commonly experienced: superventricular and ventricular tachycardia.
Rapid electrical activity in the heart’s upper chambers causes supraventricular tachycardia (SVT), at a rate of 140 to 240 beats per minute, sometimes accompanied by dizziness or even loss of consciousness. An episode of SVT can be very brief or last minutes or hours. SVT can be chronic, occurring less often with age.
A particular type of SVT affects patients with "pre-excitation syndrome," in which the impulses from the sinus node reach the ventricles along an extra, abnormal electrical pathway.
The second type of fast, regular heartbeat, known as ventricular tachycardia, is less common. Ventricular tachycardia produces a rate of 120 to 200 beats per minute in the heart’s larger chambers (the ventricles), while the rate in the smaller chambers (atria) may remain normal. Immediate medical assistance should be sought at the onset of ventricular tachycardia, since attacks sometimes do not subside by themselves.
A type of fast, irregular heartbeat known as atrial fibrillation (AF) produces extremely uncomfortable palpitations as the atria beat at speeds up to 400 beats per minute, accelerating the ventricles’ rate to around 180 and eventually affecting the pumping action of the heart, with attendant loss of breath. AF should be treated promptly to reduce the risk of blood clot formation.
Causes
Normal sinus tachycardia, or rapid heartbeat, is brought on simply by exercising. Other causes include fever, an overactive thyroid, or anemia.
Bradycardia, or slow heartbeat, may result from age or be caused by a reduced blood flow or by diseases such as lupus, rheumatoid arthritis, and myotonic muscular dystrophy. Some athletes may have very slow heart rates normally.
Ectopic (extra) beats may be normal. If experienced frequently, they may be the result of heart disease.
Fast but regular heartbeat:
An attack of supraventricular tachycarditis (SVT) may sometimes be stimulated by alcohol, caffeine, exertion or emotional stress. Ventricular tachycardia is usually a complication of heart disease.
Fast and irregular heartbeat:
Atrial fibrillation (AF) may be the result of heart disease, or may be brought on by a hyperactive thyroid, infections of the lung, high blood pressure, or overconsumption of alcohol.
Ventricular fibrillation usually results from severe heart disease.
Symptoms
Often they may be noticed simply because the individual is hyper-aware of the heart’s rhythm. An ectopic (extra) beat may be "amplified" into a distinct thump in the chest if the individual is tired or sensitized by alcohol.
However, in case of symptoms such as chest pain, perspiration or disorientation, prompt medical attention is indicated.
Dizziness and sometimes fainting may accompany supraventricular tachycardia (SVT). Ventricular tachycardia may cause the individual to feel faint or experience chest pain or loss of breath.
Most palpitations are normal and harmless. Some may be alleviated by avoiding known stimulants, including caffeine, alcohol, and certain medications. Persistent irregularities may be treated with prescription drugs to treat arrhythmia.Interventionary measures that have proved effective include cardioversion (an electrical shock treatment used with atrial fibrillation and ventricular tachycardia – the two most serious forms of rapid heartbeat), pacemaker implantation (doing the job of the sinus node), catheter ablation therapy (destruction of abnormal areas such as the electrical conduits causing pre-excitation syndrome), and surgical implantation of a defibrillator.
