Bradycardia of the heart: what is it and how to treat it, symptoms, causes

In this article we will talk about heart bradycardia, what it is, what types are there and how to treat this condition.

What is bradycardia?

Bradycardia is the medical term for heart ratewhich is slower than usual. In medical textbooks, bradycardia is usually defined as a resting heart rate that is below 60 beats per minute.

However, many (perhaps most) healthy people have resting heart rates below 60. Thus, having bradycardia is not necessarily a bad or even abnormal condition. This is often a sign of good health.

On the other hand, bradycardia can be a serious problem if the heart rate becomes so low that the heart cannot pump enough blood to meet the needs of the body's organs. It is this type of abnormal bradycardia that becomes a medical problem and requires careful diagnosis and treatment.

The two most common types of bradycardia are sinus bradycardia and heart block.

Symptoms

If your heart rate is abnormally low, some organs in the body may not function properly and various symptoms may occur. In general, the symptoms of abnormal bradycardia are usually exacerbated by exertion (because the body needs increase when a person is tense), but signs may also be present during rest if the person is suffering from severe bradycardia.

Symptoms that can result from bradycardia include:

• blurred consciousness or dizziness (especially with physical exertion);
• easy fatigue;
• fainting (syncope) or almost fainting;
• shortness of breath (labored breathing);
• chest pain or discomfort in the area epigastrium.

If the disease is associated with any of these symptoms, it is necessary to determine the cause of the bradycardia and begin treatment to normalize the heart rate.

Causes

Bradycardia is often caused by a sudden increase in vagus nerve activity.

It is a nerve in the brain that helps regulate the functioning of the heart, lungs, and digestive tract.

As soon as the tone of the vagus nerve is restored to normal, the heart rate also returns to normal, so there is no need for constant treatment of the bradycardia itself.

On the other hand, persistent abnormal bradycardia can be caused by various medical conditions. They include:

• ischemic heart disease;
• pericarditis;
• myocarditis;
• heart damage due to trauma or heart surgery;
• amyloidosis;
• hypothyroidism;
• Riley-Day syndrome (familial dysautonomy);
• various types of infections, including Lyme disease, Chagas disease, and Rocky Mountain spotted fever (American tick-borne rickettsiosis);
• brain diseases, especially associated with increased intracranial pressure or stroke;
• hypoxia (low oxygen levels in the blood), as is often the case with obstructive apnea during sleep;
• various drugs, including beta blockers, calcium channel blockers, antiarrhythmics, opioids, lithium, and various chemotherapy drugs.

Sinus bradycardia

Of the two main types of bradycardia, sinus bradycardia is the most common.

The heartbeat is generated and coordinated by electrical pulse of the heartand an electrical impulse is generated in the sinus node, a tiny nest of cells located at the top of the right atrium. When the sinus node emits these electrical impulses at a relatively low frequency, the heart rate slows down, and this indicates the presence of sinus bradycardia.

If sinus bradycardia is causing symptoms, it is considered abnormal in all cases. Abnormal sinus bradycardia can be short-term or persistent (persistent).

Temporary sinus bradycardia: temporary is most often caused by an increased tone of the vagus nerve. Stimulating the vagus nerve slows down the sinus node, causing the heart rate to slow down. Vagus nerve stimulation is often triggered by a variety of gastrointestinal problems (especially nausea or vomiting) or in response to acute pain or sudden emotional stress.

Sinus bradycardia caused by stimulation of the vagus nerve is considered "physiological" (as opposed to pathological), since this is a normal reaction, and it disappears as soon as the tone of the wandering nerve.

Persistent sinus bradycardia: it is an abnormal form of the disease that is persistent, most often caused by internal sinus disease - a disease within the sinus node itself. Internal sinus disease is usually caused by a type of fibrosis (scarring) within the sinus node, which is a common manifestation of aging. Thus, sinus node disease is usually seen in people aged 70 and over.

In people with internal sinus disease, the heart rate may be unreasonably low, both at rest and during exercise. It is often said that people with symptomatic illness have sick sinus syndrome, in which the heart rate can fluctuate between bradycardia and tachycardia (cardiopalmus).

In addition to internal sinus disease, certain other medical conditions can cause sinus bradycardia. Although sinus bradycardia can cause significant symptoms, the risk of dying from it is relatively low.

Normal and abnormal values: at rest, the sinus node usually generates electrical impulses at a rate of 60 to 100 times per minute. Therefore, the heart rate in this range is called “normal sinus rhythm”.

Note:

Resting heartbeats in adults slower than 60 beats per minute are usually attributed to bradycardia. The exception is athletes, who typically have longer rest periods and their heart rate during deep sleep is generally well below 60.

Sinus bradycardia is most often completely normal. A healthy body regulates the heart rate very well to be the way it needs to be in order to maintain bodily functions. And often, this normal heart rate is within the range of what doctors "officially" classify as sinus bradycardia.

Therefore, healthy young people and even older people, when they are in good physical condition, will often have a resting heartbeat of 40-50 beats. It is also common (and normal) that many people have their heart rate within this range during sleep. While this represents sinus bradycardia, it is a "physiological" form of sinus bradycardia - meaning that the heart rate meets the needs of the body, and thus sinus bradycardia is normal.

Sinus bradycardia is considered a problem if the heart rate is too slow for the body to function properly. If the pulse becomes so slow that the heart is not pumping enough blood, symptoms may develop. If sinus bradycardia is causing symptoms, it is abnormal and needs treatment.

Heart block

The second common type of bradycardia is heart block. Unlike sinus bradycardia, which is actually quite normal in most people, heart block is always a pathological condition.

Heart block occurs when electrical impulses from the heart are partially or completely blocked as they travel from the atrium of the heart to the ventricles. Since not all electrical impulses reach the ventricles, the heart rate becomes slower than it should be.

As with abnormal sinus bradycardias, heart block can be either temporary or permanent.

Temporary heart block: temporary heart block can occur (as in transient sinus bradycardia) with episodes of increased vagus tone. This type of temporary heart block is most commonly seen in young, healthy people whose wandering tone is increased by nausea, sudden pain, or sudden stress. This heart block is considered benign and almost never requires treatment other than treating (or preventing) the conditions that have caused the increased vagus nerve tone.

Persistent heart block: this is a more serious problem as it gets worse over time (and can become life-threatening). However, with heart block, even if the underlying condition is persistent, the bradycardia itself may be intermittent.

This means that sometimes, maybe even most of the time, the resting heart rate is actually in the normal range; but the heart rate may suddenly drop to a symptom-causing level for no apparent reason or trigger (because the underlying condition is persistent). Moreover, the blockade can be partial or complete.

Note::

Partial blockade occurs when electrical signals to the heart are delayed or intermittently cut off. A complete blockade occurs when the signals stop completely, reducing the heart rate to about 40 beats per minute.

This fact often makes heart block somewhat more difficult to diagnose than sinus bradycardia. Whether the bradycardia is persistent or intermittent, permanent heart block almost always requires treatment.

Diagnostics

Diagnosing bradycardia is usually fairly straightforward. First, a doctor should examine an electrocardiogram (ECG) if bradycardia is present to determine if it is sinus bradycardia or heart block.

The physician must then determine whether the bradycardia is persistent or transient, caused by increased vagus tone. This can almost always be done simply by taking a thorough medical history.

A stress test can help detect either sinusoidal disease or heart block, which only becomes evident during exercise. Long-term outpatient ECG monitoring can also be helpful in diagnosing bradycardia that occurs only intermittently. Electrophysiological examination can be a definitive method for diagnosing both sinusoidal disease and heart block, but it is usually not necessary.

Treatment

Treatment for bradycardia depends on whether it is sinus bradycardia or heart block, and whether the condition is reversible or not.

Reversible bradycardias may be associated with short-term rises in vagus tone discussed above. In such cases, treatment is to avoid those conditions that cause an increase in vagus nerve tone.

Persistent bradycardia can also be reversible if caused by drug therapy, infectious diseases, pericarditis, myocarditis, or hypothyroidism. In these cases, with aggressive treatment of the underlying problem, a slow heart rate is often observed.

If sinus bradycardia is reversible or causes no symptoms, it can usually be treated simply by periodic follow-up examinations. However, sometimes in older people, sinus node disease only causes symptoms when physically stress, when the heart rate does not increase, as it should with physical load. Thus, a stress test can be quite helpful in determining if sinus node disease is actually causing symptoms.

Sinus bradycardia, which is irreversible and causes symptoms, should be treated with permanent pacemaker.

Footnote:

Heart block is a more serious problem because it tends to progress and increases the risk of death. If the blockage is not due to a mild, reversible condition, treatment with a permanent pacemaker is almost always recommended.

If left untreated, heart block may eventually lead to heart failure, cardiac arrest, or sudden cardiac death.

To summarize

Bradycardia is often normal and does not require a thorough medical examination or special treatment.

But if you have sinus bradycardia that causes symptoms, or heart block, whether there are symptoms or no, you will need to consult with your doctor to determine the cause and decide if you need pacemaker.