Extrasystole, or premature heartbeats, is the most common type of arrhythmia. It is characterized by the premature onset of one or several heart beats (contractions). Extrasystole comes from outside the impulse-generating tissue located in the right atrium of the heart (sinus node). It spreads through the heart muscle in between the normal impulses, thus, causing premature contraction of the heart.
This rhythm disturbance is diagnosed in 60%-70% of patients, and most of these people are healthy. According to some scientific studies, this condition can be found in 70-80% of the people who are over 50. Sometimes premature contractions may occur even in young people including athletes with trained hearts. Although extrasystole is considered to be relatively safe, for some people who suffer from severe cardiovascular disorders, it may be an increased risk factor.
It is considered normal for a healthy person to experience up to 200 premature contractions a day. When presented against the background of good health, extrasystole causes from stress, smoking, alcohol, and strong tea or coffee, are functional by nature. Sometimes it may result from significant physical activity, and vegetative and psycho-emotional disturbances. However, if premature heartbeats appear with underlying cardiovascular diseases such as myocarditis, coronary heart disease, valve defects, and cardiomyopathy, this condition, as a rule, is considered pathological. Extrasystole may be asymptomatic, but sometimes patients experience a thump in the chest or heart stopping for a short while.
Basing on its causes, extrasystole is divided into two main groups:
- Functional. These premature contractions can be diagnosed even during normal cardiac performance. In this case, they may result from some disturbances of the autonomic nervous system (aka, vegetative nervous system). Functional extrasystole can be provoked by prolonged emotional tension, consumption of alcohol, smoking or electrolyte disturbances.
- Organic. Extrasystoles of this type are diagnosed if a patient has any disorder of the cardiovascular system, including cardiomyopathy, coronary heart disease, arterial hypertension and chronic heart failure.
There is another classification based on the localization of the excitation focus:
- Atrial extrasystole or premature atrial contraction. The focus of the pathologic excitation is located in atria. Atrial extrasystoles can often be registered in the ECG even in healthy people, although they may appear because of any heart pathology: coronary heart disease, hypertensive disease, congenital heart diseases, myocarditis, pericarditis etc.;
- Ventricular extrasystole or premature ventricular contraction. The pathologic impulse is generated in the ventricles and spreads only through the ventricles. In most cases, premature ventricular heartbeats are caused by cardiovascular diseases and are observed in hypertensive patients and those with cardiomyopathy or coronary heart disease;
- Junctional or atrioventricular extrasystole. The pathologic impulse is generated in the atrioventricular node located in the junction between the atria and ventricles and then it spreads through the ventricles;
- Sinus extrasystole arises in the sinus node. It is rather rare and clinically safe condition.