Bradycardia: When the heart beats too slowly

Bradycardia: When the heart beats too slowly

A slow heartbeat, also known as bradycardia, can have a variety of causes and does not always indicate an illness. Possible symptoms of cardiac arrhythmia are weakness, dizziness and fainting spells. But what exactly is bradycardia? What happens when the heart beats too slowly? What can be done with bradycardia, and what drugs help? You can find out more about this here.

What does bradycardia mean?

Bradycardia means a slow heartbeat. Bradycardia is defined as an adult heart rate below 60 beats per minute.

The heartbeat is determined by what is known as the sinus node, which is located in the right atrium of the heart. From there, the rhythm is passed on to the slightly lower AV node (atrioventricular node) and then transmitted to the heart muscle via other nerve lines. As a result, the heart muscle contracts and pumps blood into the body.

If the sinus node is compromised and sets a too-slow rhythm below 40 beats per minute, other centres, such as the AV node, can kick in and put the rhythm in the heart. However, this is not in the normal range and practically always leads to bradycardia.

When the heart beats too slowly, insufficient blood is pumped through the body, resulting in a lack of oxygen and nutrients. However, this does not always have to be dangerous. Those affected often do not notice in everyday life that they have a bradycardic heartbeat. Only during physical exertion do those affected realize that their heart rate does not increase in line with the exertion.


Bradycardia symptoms

A variety of body reactions can occur when the heartbeat is too slow. The signs can appear individually or in combination or be absent altogether.

The following possible symptoms can occur with bradycardia:

  • weakness
  • reduced resilience
  • exhaustion
  • fatigue
  • dizziness
  • Syncope (fainting spells)
  • Missing pulse (pulse deficit)
  • visual disturbances
  • nervousness
  • Angst
  • shortness of breath

How do you diagnose bradycardia yourself?

A slow heartbeat may also be self-detecting. The best way to do this is to feel your resting pulse on your wrist with your index and middle fingers and count the beats you can feel within a minute. It is better not to use the thumb to measure the heart rate, as it has a very pronounced pulse, which can be mistaken for the estimated heart rate.


If the pulse rate is below 50 to 60 beats per minute several times at different times, this could be the first indication of bradycardia.


When is bradycardia dangerous?

Fainting spells and dizziness occur when the brain does not get enough oxygen. An isolated seizure is usually not problematic. More often, it is the situations themselves that are dangerous. A sudden tipping over often leads to accidents and injuries to those affected.

In rare cases, bradycardia can also become life-threatening. Ventricular fibrillation is possible if the heartbeat is not only for a very short time but remains in a frequency range below 40 beats per minute. Left untreated, this condition leads to cardiac death.

Causes of bradycardia

The causes of bradycardia are varied and can be divided into so-called physiological (natural) and pathological (morbid) causes. Bradycardia can also occur as a side effect of medication or in alternation with tachycardia. The various causes of a slow heartbeat are explained below.

Physiological causes

A slow heartbeat at rest is nothing unusual in endurance athletes and is not a sign of a disease. The heart muscle is well-trained and works in a very low-frequency range at rest. During physical activity, the heart rate increases according to the load, which is typical for a healthy heart.

With hypothermia and malnutrition, it is also possible for the heart to beat in a low heart rate range. The body works at a low level in both states, and many non-essential metabolic processes are stopped. Because of this, the body gets by with a humble heart rate.

Conversely, there is the phenomenon of relative bradycardia. The heartbeat remains below 60 beats per minute, although one would expect an increased heartbeat. This can occur, for example, with infections with specific pathogens such as salmonella or yellow fever. As a rule, an infection leads to increased body temperature and metabolic activity, which also increases the heartbeat. In the case of relative bradycardia, body temperature rises, but heart activity remains low.


pathological causes

So-called pathological causes mean that the symptom, in this case, bradycardia, is based on a disease. This includes, among other things, an underactive thyroid gland also known as hypothyroidism in technical jargon. The thyroid plays a significant role in metabolism and influences heart activity.

Furthermore, heart diseases such as cardiac insufficiency, a diseased or inflamed heart muscle or coronary artery disease can be possible causes of bradycardia.

In addition, a disturbed electrolyte balance can lead to a slow heartbeat. Caution should be exercised, especially with an elevated potassium level, also known as hyperkalemia, since potassium directly influences the heart rhythm and can massively slow it down. This can lead to a rate of less than 50 to 60 beats per minute and, thus, to bradycardia. A pathological consumption of alcohol or the use of drugs also leads to electrolyte shifts that affect the heart rhythm. In addition, certain medications, such as opioids, act directly on the heart via receptor binding, which can also cause bradycardia.

What drugs cause bradycardia?

Some heart-affecting medications can also cause a heartbeat that is too slow if taken in the wrong dose.

Typical medications that can cause a low heart rate include beta-blockers, cardiac glycosides, and calcium channel blockers. These drugs are usually used to treat heart disease with a rapid heartbeat, heart failure, or hypertension (high blood pressure). If bradycardia occurs under this medication, the dosage is usually too high or intolerant.

The best-known representative of the beta blockers is bisoprolol, which often leads to bradycardia symptoms. The drug group of the so-called calcium antagonists is divided into three subgroups based on their chemical structure. Of these, the diltiazem and verapamil types, in particular, can induce bradycardia.

Clinical pictures as a cause of bradycardia

The heart rate is always given in beats per minute, and bradycardia (too slow) or tachycardia (accelerated) can be expected.

Bradycardia, like tachycardia, i.e. a heartbeat that is too fast, belongs to the heart rhythm disorders, also known as arrhythmias. This is either brief bradycardia or a permanent, abnormally reduced heart rate. 

In a so-called bradycardia-tachycardia syndrome, fast and slow phases of the heart rate alternate. As a rule, there is a tachycardic phase with more than 100 beats per minute followed by a pause in which there is no heartbeat for a few seconds. A bradycardic episode follows this. Depending on the respective heart rate, the affected person feels the typical symptoms of a heartbeat that is too fast or too slow. For example, symptoms such as tachycardia, shortness of breath, and tightness in the chest appear during a tachycardia phase.


Diagnosis: how to diagnose bradycardia?

An electrocardiogram (ECG) is usually used to record the heart rate. First, ten electrodes are attached to the chest, forearms and calves. These measure the electrical excitation that occurs in the heart and how it is transmitted within the heart, as well as the rhythm and frequency of the heartbeat. Under certain circumstances, an ECG must be carried out during a physical stress test (spiroergometry) for diagnosis.

If a patient reports recurring episodes of bradycardia that mainly occur at night, a 24-hour ECG is performed. The patient receives a measuring device to record heart activity, which they can take home and carry with them at all times. Three or four electrodes are attached to the chest. The stored data can inform the doctor about irregularities at night.

Was there a Bradycardia?

If symptoms occur due to a heartbeat that is too slow, a targeted therapy should follow after the detailed diagnosis. First, the cause of the bradycardia is sought and treated. If the origin of the symptoms lies in the heart, medication to increase the heart rate can be helpful.

For the use of home remedies, there is no suitable data that proves an improvement.

If bradycardia persists with symptoms and no response to medication, a cardiac pacemaker is required for the person affected. In this case, the symptoms are so severe that there is no other treatment option and no scope for self-help. Most of those affected are symptom-free after the implantation of a pacemaker and thus regain a part of their quality of life.

Bradycardia rescue medication

In emergencies, i.e. if you have severe symptoms and a heartbeat of less than 40 beats per minute, an emergency service should be alerted. He will initiate medical measures as soon as possible.

These are carried out according to a defined scheme. The first step is to administer adrenaline or atropine through a vein. Adrenaline belongs to the drug group of sympathomimetics, whereas atropine belongs to the so-called parasympatholytics. Both drugs activate the sympathetic nervous system, putting us in alert, active mode. This leads, among other things, to an increase in heart rate.

If symptoms and slow heartbeat persist despite medication, the next step is to use an external defibrillator to stimulate the heart. It is also possible that chest compressions may be required due to bradycardia.


Bradycardia in children

Bradycardia can also occur in children. It is essential to know that the heart rate has age-dependent limit ranges.

For example, a toddler up to three can have a heart rate between 90 and 160 beats per minute. As the heart grows, the heart rate decreases as the heart increases in size, and thus, a larger stroke volume is possible. As a result, the frequency decreases as the child grows.

Premature babies can develop what is known as apnea-bradycardia syndrome, in which the children suffer from shortness of breath and a slow heartbeat. Bradycardia is present in newborns below 80 beats per minute.

The problem here is the combination of the two symptoms: Apnea, which means something like cessation of breathing, can lead to reduced blood flow in the brain. Depending on how long it lasts, the affected children can develop developmental disorders in speech and movement, as well as retinal disease. One immediately tries to prevent such episodes and treats the affected children with oxygen and caffeine to increase blood pressure and frequency.

Conclusion: when to treat bradycardia

Bradycardia, which causes symptoms and occurs more than once, requires investigation. Since the signs can be very distressing, try to find the cause and treat it. If an underlying heart condition and bradycardia are present, a pacemaker can relieve those affected.

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