Bradycardia is a change in heart rhythm in which the heart rate decreases to 30-50 beats per minute, due to a decrease in the automation of the sinus node.
The reasons for this condition are varied:
- sclerotic changes in the myocardium affecting the sinus node;
- exposure to cold;
- increased tone of the parasympathetic nervous system;
- increased intracranial pressure (with cerebral edema, tumor, meningitis, cerebral hemorrhage);
- influence of drugs (digitalis, quinidine);
- lead poisoning, nicotine;
- hypothyroidism (decreased thyroid function);
- starvation, typhoid fever, jaundice, etc.
A low heart rate can occur in well-trained athletes and some young healthy people (for example, cyclist Miguel Indurain had a resting heart rate of 28 beats/min[1]). This is normal in the absence of other pathological symptoms such as fatigue, weakness, dizziness, fainting, chest discomfort or difficulty breathing.
Minor disturbances of sinus rhythm may not cause any subjective sensations in a person. If there is a significant decrease in heart rate (less than 40 beats per minute), then the person may complain of weakness, dizziness, cold sweat, fainting due to brain hypoxia (oxygen starvation), since there is no adequate blood supply. In any case, it will be useful to have an examination with a cardiologist.
general information
Modern medicine does not identify a decrease in heart rate as an independent disease, but regards it as a symptom of certain pathological processes. As a rule, in children (including newborns) and adolescents, a sinus form of cardiac bradycardia is detected, which may also be accompanied by arrhythmia.
Assessing the presence or absence of pathology requires an integrated approach, since heart rate norms depending on age are only average values.
How to train pulse zones
Each heart rate zone has its own type of workout.
- The first zone is not considered a training zone; this is the pulse with which we walk, talk, and carry out current affairs.
- The second zone is also not trained, but swimming techniques are practiced in it: calm, effortless crawl, breaststroke, calm backstroke. There should be no shortness of breath when swimming in this area.
- The third zone is trained in a series of longer segments, for example, 4 times 400 meters with a rest of about 40-50% of the swimming time. If you swim 400 meters in 6 minutes, then rest between series should be 2 minutes. And shortness of breath should go away within 30 seconds, then the pulse will return to the first zone.
- Zone 4 is trained in shorter segments than Zone 3 workouts, but at higher intensity and with less rest time in between. For example, 20 times 100 meters. For an amateur who swims 100 meters freestyle in 1 minute 30 seconds, rest should be no more than 1 minute between segments.
The specificity of this zone is that you cannot train in it every day. If the training schedule includes 5 days a week, then a day of intense training in the 4th zone must be followed by a day of work in the 2nd or 3rd zone.
Symptoms of bradycardia in children
A mild form of sinus bradycardia in a child or adolescent does not cause any pathological symptoms.
The body tissues receive a sufficient amount of oxygen, so that the baby does not experience discomfort. With a significant slowdown in heart rate, signs of tissue oxygen starvation appear: fatigue, drowsiness, decreased performance at school, and forgetfulness. As the disease progresses, dizziness of varying severity appears, leading to falls and loss of consciousness. In this case, the skin becomes pale with a bluish tint, blueness appears around the mouth and cold, sticky sweat appears. As a rule, the attack lasts a few seconds. With constant bradycardia, fainting often occurs due to being in a stuffy room, stress, or physical overload.
How to measure your pulse correctly in water
Now there are many gadgets that measure pulse in water. A watch that reads your pulse from your wrist using an electro-optical sensor is quite suitable for this.
Traditional chest heart rate monitors in water will be of little information, since the sensor does not have close contact with the chest, and the information may be incorrect.
You can use the well-known method: place your fingers on the carotid artery, count the number of beats for 10 seconds, multiply the resulting figure by 6. The result will be the actual pulse.
Causes of bradycardia in children
Bradycardia is, first of all, a reaction of the heart to certain conditions. In this regard, the list of reasons that can cause such a problem is very long. The most important factors are:
- physiological: natural causes that do not indicate the presence of pathology;
- cardiac: associated with heart pathology;
- endocrine: associated with disruption of the endocrine glands;
- neurological: caused by a malfunction of the nervous system;
- intoxication: acute or chronic poisoning;
- genetic: hereditary pathology, for example, constitutional familial bradycardia;
- other reasons: gastrointestinal pathology.
Depending on the age of the baby, certain groups of factors predominate among the most likely causes.
Bradycardia in premature and newborn babies
A reduced heart rate at premature birth is physiological and is associated with the immaturity of heart rate regulation systems. With proper care and medication support, the condition gradually improves. The most common causes of bradycardia in a newborn child are heart defects, various types of encephalopathy, and birth injuries. Sometimes a pronounced decrease in heart rate indicates the development of transverse atrioventricular block (AV block). This is a dangerous condition that requires immediate medical attention.
Bradycardia in children of the first year of life (infants)
At this age, the pathological condition can be caused by the same reasons as in newborns. In addition, it is worth paying attention to the level of thyroid hormones. Hypothyroidism often causes a slow heart rate.
Bradycardia in preschool children
Bradycardia in a child aged 2 to 7 years is often associated with infectious diseases that are complicated by myocarditis - inflammation of the heart muscle. Poisoning and drug overdoses are also common at this age. The third common cause of bradycardia in a child aged 3–4 years and older is adenoids. Difficulty in nasal breathing leads to chronic hypoxia, causing a decrease in heart rate.
Bradycardia in schoolchildren and adolescents
A decrease in heart rate at school age may be due to the same reasons as in preschoolers, but they are accompanied by various types of gastritis and duodenitis associated with changes in diet.
Teenagers often encounter the manifestation of vegetative-vascular dystonia, which can occur according to the vagotonic type. A decrease in heart rate is accompanied by a drop in blood pressure, dizziness, and fainting. At the same age, autoimmune diseases and sick sinus syndrome often manifest.
Sinus bradycardia of the heart in adolescent athletes, which is not a symptom of the disease, stands apart. Regular intense exercise leads to the development of a physiological decrease in heart rate at rest, as the heart adapts to the additional work during exercise.
Types of bradycardia
There are several types of bradycardia:
- Physiological. Occurs in professional athletes due to well-trained heart. This type of bradycardia does not pose a health hazard and is normal.
- Absolute. Reduced heart rate in children is observed under any circumstances.
- Relative. Heart rate decreases under certain circumstances. This can happen during illnesses with increased body temperature, during deep breathing, or during long walks in the cold.
There are many causes of bradycardia. It can be a consequence of electrolyte imbalance, congenital heart defects, hypoxia, strong growth during adolescence, etc.
Diagnosis of bradycardia in children
A pediatric cardiologist diagnoses bradycardia in children of any age. Its tasks include not only identifying the fact of a slow heart rate, but also searching for the cause of this condition, as well as selecting adequate treatment. In addition to a basic examination, listening to heart sounds, assessing pulse and measuring blood pressure, the examination includes:
- ECG;
- daily ECG monitoring (Holter);
- Ultrasound of the heart;
- stress tests: bicycle ergometry, treadmill test, atropine test;
- laboratory diagnostics: general blood test, assessment of hormonal status, etc.
Additional research and consultations may be aimed at finding a specific cause. Depending on the indications, an ultrasound scan of the thyroid gland and adrenal glands is performed, the content of electrolytes in the blood is assessed, etc.
How to calculate your maximum heart rate (MHR)
There is a formula for calculating MHR: 220 – age. For example, an athlete who is 30 years old will have an MHR of 190 beats per minute. But this is only a generally accepted formula, so it is better to undergo laboratory testing to obtain accurate data about the capabilities of the heart.
The two most well-known testing methods are exercise tests on a treadmill (on a treadmill) and on a bicycle ergometer (on an exercise bike). A sports doctor will comment on the data obtained.
Read more on the topic: How to calculate maximum heart rate (MHR)
Treatment of bradycardia in children and adolescents
Treatment of mild or moderate bradycardia and arrhythmia in a child of any age is aimed at normalizing the heart rate, as well as eliminating the cause of the pathological condition.
Depending on the situation, emergency medications and ongoing medications may be used to stabilize the heart. The choice of treatment method for bradycardia is made by a cardiologist. If a child develops severe bradycardia, accompanied by frequent fainting, Morgagni-Adams-Stokes attacks and other conditions that disrupt the usual rhythm of life, surgical treatment is used. Experienced cardiac surgeons implant an electrical pacemaker that controls the functioning of the heart. This treatment is also relevant if the condition arose against the background of severe defects and blockades.
How many times a week is it optimal for amateur swimmers to train?
If a person is just starting to learn swimming, then two or three training sessions a week under the guidance of an experienced coach will be enough. These workouts should include a swimming foundation: slow swimming in the 2nd pulse zone, working on technique with the gradual introduction of different types of work on the water.
There is no point in increasing the number of workouts per week at this stage: the body must prepare for the stress and be able to recover.
For those amateurs who know how to swim and are preparing for some kind of competition, for example, a triathlon, it is recommended to train 3-4 times a week. In this case, there should be a weekly or monthly training plan, including different types of exercise in the water.
Read on: How to choose a wetsuit for triathlon and open water swimming
Prognosis and prevention
The prognosis for bradycardia in a child depends on its cause and severity. In some cases, it is enough to adjust lifestyle or hormonal status to normalize heart function, while in others complex treatment and lifelong monitoring are required. Prevention of the development of pathology includes, first of all, teaching the child to a healthy lifestyle, prevention and timely treatment of diseases that can provoke this condition.
If your child or teenager is experiencing bradycardia, do not wait for the disease to progress; make an appointment with the pediatric cardiologists of the SM-Doctor clinic. You will receive a comprehensive examination, modern and effective treatment if necessary, as well as regular supervision by an experienced specialist.
Why do swimmers need pulse training?
In amateur swimming and long-distance swimming, it is not necessary for stayers to work in maximum heart rate zones, but they still need to be done from time to time. These works must be performed under the supervision of a trainer.
Such training is necessary so that the body is prepared for the finishing spurt at the end of the distance, where stayers have to swim in the fifth pulse zone.
Stayers need to work in the fourth pulse zone in order to make turns in the pool or turns around a buoy in open water without losing speed. Working in this zone on 100-meter segments trains stayers' endurance.
What heart rate is best to swim at?
A professional swimmer varies heart rate values, focusing on the type of activity and the task at hand. If you are just starting training, the emphasis should be on your level of physical fitness. It is better to start with zones 1-3 and increase the pace step by step.
Long distance swims are usually performed in the second and third zone ranges. That is, you need to determine your maximum heart rate and keep your heart rate at 70-80% of MHR. For example: if your heart rate is 190 beats per minute, it is better to perform long swims at heart rates of about 160-165 beats per minute.
If you start such a distance at high heart rates, by the middle you will simply run out of steam. The generally accepted practice is to start from the second zone and, remaining in it (or moving to the third at most), gradually increase speed. Swimmers show the highest speed values at the finish line.
