Is a heart rate of 55 normal?

If you feel uncomfortable in your heart, you should first check your heart rate to determine whether the heart beats normally. If the heart rate is outside the normal range for a short period of time, it may be caused by exercise or emotional fluctuations, which has no effect on the human body. However, if the heart rate is unstable for a long time, an electrocardiogram should be performed. So, is a heart rate of 55 normal?

Heart rate: An adult's heart beats about 70 to 80 times per minute, and 60 to 100 beats is normal. Normally, if an adult's heart beats more than 100 times per minute when at rest, it is medically considered "tachycardia"; if it is less than 60 beats per minute, it is considered "bradycardia." The heart beats faster when working than when resting, women beat faster than men, children beat faster than adults, and newborns can beat up to 150 times per minute. On average, if a person lives to be 100 years old, his or her heart beats a total of about 4 billion times. Because athletes exercise regularly, their myocardial contractility is strong and the amount of blood returning to the heart during diastole is also large. Therefore, when athletes are at rest, a heart rate of less than 60 beats/minute is enough to ensure blood supply to the body. Some can reach 48-50 beats/minute. They have the ability and endurance to exercise.

There are several types of bradycardia, the most common of which is sinus bradycardia. Sinus bradycardia can be divided into pathological and physiological types. Physiological sinus bradycardia is a normal phenomenon. The general heart rate and pulse are 50 to 60 beats per minute. Athletes may have a heart rate of 40 beats per minute. No treatment is required. It is common in normal people during sleep and those who engage in more physical activities. A heart rate or pulse of less than 50 beats is mostly pathological and requires treatment. In severe cases, a pacemaker may be installed to speed up the heart rate. Sinus bradycardia is mainly caused by excessive vagal tone:

(1) Physiological: Normal people, especially those who participate in long-term physical exercise or heavy physical labor, may experience sinus bradycardia. Sleepiness and fear can also cause temporary bradycardia. For example, some techniques such as compressing the eyeball, pressing the carotid sinus, vomiting, and vasoinhibitory syncope can cause sinus bradycardia.

(2) Drug-induced: β-receptor blockers, reserpine, guanethidine, morphine, digitalis, quinidine, lidocaine, amiodarone, isoprenaline, neostigmine, anesthetics, etc. can cause sinus bradycardia.

(3) Systemic diseases: hypothyroidism, obstructive jaundice, increased intracranial pressure, certain infections such as leptospirosis, typhoid fever, influenza, infectious mononucleosis, diphtheria recovery period, pituitary dysfunction, hyperkalemia, alkali poisoning, esophageal diverticulum, depression, can all cause sinus bradycardia.

(4) Cardiovascular diseases: acute myocardial infarction, chronic ischemic heart disease, sinus node inflammation, myocarditis, endocarditis, pericarditis invading the sinus node, thrombosis, dilatation, inflammation of the sinus node artery, certain cardiomyopathies such as amyloidosis.