You measure your pulse and see 52 beats per minute. Or you notice that an elderly relative's blood pressure monitor shows 48. Before you panic, figure out what causes a low pulse and where the line between normal and pathology lies.
What pulse is considered low
In adults, bradycardia is a slowing of the heart rate to less than 60 beats per minute, unless you are a trained athlete. In population studies, a threshold of 59 beats per minute is more often used. In children and adolescents, the boundaries are different — less than 100–60 depending on age. A significant slowing, less than 40 beats per minute, already makes itself felt with weakness and dizziness.
When a low pulse is a normal variant
A low pulse is not always a disease. It is normal in well-trained athletes and some young healthy people: cyclist Miguel Indurain had a resting pulse of 28 beats per minute. Physiological bradycardia occurs in adolescents during peak growth and hormonal changes, as well as in older adults. The key criterion is the absence of other symptoms: fatigue, weakness, dizziness, fainting, chest discomfort, or difficulty breathing.
What causes a low pulse: main causes
A slow pulse occurs when the heart's electrical system goes wrong — the sinus node, atrioventricular nodal tissue, or the His–Purkinje conduction system. The causes are varied:
- cardiovascular pathologies: sick sinus syndrome, coronary heart disease, myocardial infarction, heart failure, myocarditis, acquired valvular disease;
- thyroid diseases, primarily hypothyroidism, as well as diabetes mellitus and hypercalcemia;
- taking medications: beta-blockers, potassium antagonists, antiarrhythmic agents, digitalis, quinidine;
- infections (diphtheria, toxoplasmosis, Lyme disease), increased intracranial pressure, brain injuries, poisoning.
The pulse can slow from cold, during fasting, and under the influence of nicotine and lead.
Low pulse with normal blood pressure and with high blood pressure in older adults
The combination of "high blood pressure and low pulse in an elderly person" is a common cause of alarm. In older adults, physiological bradycardia occurs on its own, but it can also be behind sclerotic changes in the myocardium affecting the sinus node, and the use of medications such as beta-blockers. A low pulse on its own can be normal in the absence of symptoms (fatigue, weakness, dizziness, fainting, chest discomfort, difficulty breathing), so blood pressure and pulse are assessed together with how you feel. The numbers should be assessed together with how you feel, not separately.
How the cause of a slow pulse is determined
The doctor asks about symptoms and lifestyle, performs an examination with checking the pulse and heartbeat, and looks for leg swelling. The most common method for detecting arrhythmia is an electrocardiogram (ECG), which records the heart's electrical activity. Additionally, blood tests and other heart tests are prescribed, and signs of diseases that can cause bradycardia are sought, such as thyroid pathologies.
When a low pulse is dangerous and a doctor is needed
A slight decrease in heart rate does not pose a direct threat to life, but it can be the first signal of pathology in other organs. Significant fainting is dangerous: during these periods the risk of sudden cardiac arrest increases. Go to a doctor if you notice a rare pulse (less than 50 at rest, if you are not trained), pauses in the heart's work, shortness of breath and weakness with moderate exertion, episodes of loss of consciousness, unexplained fatigue and drowsiness.
Bradycardia on its own is not a reason to call an ambulance; 103 or 112 — if with a slow pulse there is pain or discomfort in the chest, shortness of breath, severe dizziness, fainting, or a feeling that you are about to lose consciousness.
Myth: "a rare pulse always means a healthy heart." Fact: in athletes it is normal, but in a person with fainting and weakness it is a reason to check the sinus node and thyroid. This material is for reference: the numbers on the blood pressure monitor do not make a diagnosis, so discuss them with a doctor.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer