Bradycardia: what it is, causes, and when it is dangerous

Bradycardia is a slowing of the heart rate. In reference books it is described as one type of arrhythmia in which the pulse becomes slower than usual. For an adult, the benchmark is less than 60 beats per minute, unless the person is a trained athlete.

What bradycardia is and what pulse is considered slow

The heart works like a pump: the number of its beats per minute reflects the heart rate. Bradycardia means there are fewer contractions than expected for a person's age and condition. In adults who are not trained athletes, the threshold is less than 60 beats per minute; in population studies, the value 59 is more often used. In children and adolescents, the boundaries depend on age: less than 100–60 beats per minute. Bradycardia is one of the common types of arrhythmia and often becomes a reason for consulting a cardiologist.

Bradycardia as a normal variant and as a symptom of disease

A slow pulse occurs in well-trained athletes and in some young healthy people. It may appear in adolescents during growth and hormonal changes, as well as in older people. In such cases, not only the number matters but also the symptoms: in the absence of fatigue, weakness, dizziness, fainting, chest discomfort, and difficulty breathing, a low pulse may be a normal phenomenon. If, however, a slow pulse is combined with complaints or appears against the background of other diseases, it is regarded as a symptom.

Main causes of bradycardia

The causes are divided into several groups: cardiovascular pathologies, thyroid diseases, some infectious diseases, and the use of medications. Among cardiac causes are sick sinus syndrome, coronary heart disease, angina, heart failure, myocardial infarction, cardiomyopathy, myocarditis, and acquired heart valve disease. Slowing of the rhythm is also associated with hypothyroidism, diabetes mellitus, increased intracranial pressure, brain injuries, hypercalcemia, and infections such as diphtheria, toxoplasmosis, and Lyme disease. The use of certain medications can also have an effect; in such a situation, a slow pulse is assessed by a doctor.

Bradycardia at night: why the pulse slows during sleep

Slowing of the pulse during sleep is considered a harmless change in rhythm: the pulse speeds up during physical exertion and slows during sleep. If symptoms appear against the background of a slow pulse at night, a doctor should assess the cause.

What symptoms may accompany a slow pulse

The clinical picture varies, from minimal to pronounced. With significant slowing, less than 40 beats per minute, weakness, dizziness, cold sweat, and fainting are possible due to insufficient blood supply to the brain. Symptoms of bradycardia are often perceived as signs of aging or fatigue.

• pauses in the heart's work;
• shortness of breath and weakness with moderate exertion;
• transient dizziness;
• fainting or a presyncopal state;
• unexplained fatigue, drowsiness, cold sweat.

How bradycardia is detected and when a doctor is needed

An electrocardiogram — a recording of the heart's electrical activity — is used to detect arrhythmia. The doctor asks about symptoms and lifestyle, performs an examination with checking of the pulse and heartbeat, may order blood tests and other heart examinations, check the legs for edema, and look for signs of diseases that can affect the rhythm, such as thyroid pathology. In sinus bradycardia, the ECG shows a rate of 59–40 per minute, a regular sinus rhythm, and a positive P wave in leads I, II, aVF, V4–V6.

People seek medical help if a slow pulse recurs, is accompanied by worsening of well-being, or if the person notices irregularities and a rapid heartbeat. Examination by a cardiologist is useful for unclear episodes, since bradycardia may be the first signal of another pathological process.

Bradycardia by itself is not a reason to call an ambulance; 103 or 112 — if a slow pulse is accompanied by pain or discomfort in the chest, shortness of breath, pronounced dizziness, a presyncopal state, or fainting.

This material is for reference and does not replace consultation with a doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer