Symptomatic Bradycardia: Symptoms, Causes, and Treatment

Bradycardia is a condition in which the heart beats at an average rate slower than its normal rate. Recent studies have estimated that symptomatic bradycardias may occur in as many as 5% of the general population at one point in their lives.

Symptomatic bradycardia is a type of heart rate less than 60 beats per minute in which symptoms already manifest. It can affect the quality of life and, at times, require treatment. Early recognition and management are of paramount importance. Thus, this article discusses symptomatic bradycardia in detail, describing its signs, causes, and treatment. 

What is Symptomatic Bradycardia?

Symptomatic bradycardia is a medical condition characterized by a heart rate slower than normal that occurs with the manifestation of associated symptoms. It should be differentiated from asymptomatic bradycardia, wherein the heart rate may be slow but does not cause any evident problems.

In symptomatic bradycardia, the heart rate generally drops below 60 beats per minute, although threshold values can vary depending on individual characteristics such as age and physical fitness. The dominant distinguishing feature is the presence of symptoms directly emanating from the slow heart rate. These symptoms tend to occur because the slow heart rate may not pump enough blood, rich in oxygen, to meet the body’s needs.

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The Electrical System of the Heart and Bradycardia

Bradycardia can be explained by understanding how the heart’s electrical system works. This electrical system guides the heartbeat and its rhythm to the right pace.

The normal heart pacemaker is the sinoatrial node, or the SA node, located in the right atrium. This electrical signal then spreads through the heart and stimulates ventricular contraction, which pumps blood. In a normal individual, this occurs at a resting rate of roughly 60 to 100 beats per minute. The heart rate can reach up to 120-145 beats per minute during vigorous exercise. However, this varies with age and the intensity of physical activity. 

In bradycardia, this electrical system doesn’t work normally. The problem could be in the SA node itself, known as sinus node dysfunction, or in the pathway conducting these electrical impulses to the ventricles, known as atrioventricular block or heart block. Either one of these problems, when present and giving one symptom, is known as symptomatic bradycardia.

Recognizing the Signs and Symptoms of Bradycardia

Some people with slow heart rates are asymptomatic, but patients who present with symptomatic bradycardia have many bothersome symptoms.

The frequency and intensity of bradycardia symptoms tend to vary from one individual to the next. While some patients simply complain of mild discomfort, the condition may be associated with more serious symptoms in some patients, which affect their quality of life. Some of the common symptoms and signs of bradycardia are discussed as follows: 

• Fatigue: Unusual tiredness or exhaustion after very minimal physical exertion is one symptom often associated with bradycardia. This is because the slow heart rate will reduce the oxygen-rich blood circulating through the body.
• Dizziness or Lightheadedness: When the heart fails to pump adequate blood to the brain, a person may experience dizziness or lightheadedness. In extreme cases, this may lead to fainting, also known as syncope.
• Shortness of Breath: Individuals experiencing bradycardia might have difficulty breathing because the slow heartbeat cannot work at an increased rate to supply the body’s tissues with oxygen during physical exertion.
• Chest Pain or Discomfort: This may sometimes lead to chest pain or discomfort. Such pain is sometimes brought about by the heart’s hard work compensating for the slow rhythm.
• Confusion or Memory Problems: This is associated with reduced blood flow to the brain, which might further confuse, an inability to concentrate, or even memory problems.
• Weakness: This is also a very common symptom and might be accompanied by general weakness or lack of energy and fatigue.
• Cold Sweats:  Some people experience cold sweats that come from nowhere. These can indicate that the body is having trouble maintaining appropriate circulation.
• Nauseous Feelings: This reduced flow of blood in such cases may cause nausea or a general feeling of unwellness.

Causes of Symptomatic Bradycardia

The causes of bradycardia can be divided into two broad categories: one affecting the heart’s natural pacemaker or the sinoatrial node and one affecting the heart’s electrical pathways. Let us now examine the details of these causes.

1. Abnormal Sinus Node

Bradycardia often results from an abnormality in the sinus node, also called sick sinus syndrome. During this disease process, the heart’s normal pacemaker malfunctions. Additionally, natural degeneration of the sinus node tissues may occur with increasing age, which results in a slower heart rate.

Patents dealing with diseases such as coronary artery disease or heart attack are also prone to damage to the sinus node. Moreover, some medications, particularly those used to treat high blood pressure or other heart conditions, can affect sinus node function. In addition, abnormal amounts of substances, such as potassium or calcium, in the blood can also disrupt the sinus node’s electrical impulses.

2. Atrioventricular Block

The atrioventricular block is a disorder that occurs when electrical signals from the atria (the upper chamber of the heart) are delayed or blocked before they reach the ventricles, the lower chambers of the heart.

This condition can arise from various causes, including age-related degenerative changes in the AV node, heart attacks that damage the electrical system, inflammatory conditions like Lyme disease or rheumatic fever, congenital heart defects present at birth, or trauma to the heart area. The severity and impact of AV block can vary, potentially leading to irregular heartbeats and compromised cardiac function.

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Diagnosis of Symptomatic Bradycardia

Symptomatic bradycardia is diagnosed based on the clear determination of the condition and its etiology. It involves an appropriate integration of history, physical examination, and confirmatory diagnostic studies. Let’s consider some common methods of diagnosis available for this condition:

1. Medical History: The health professional will question symptoms of bradycardia, for instance, when they occur and how long they last, current medical problems, medications, and a family history of heart problems. 
2. Physical Examination: The physical exam includes listening to the heartbeat with a stethoscope to check for irregular rhythms, as well as blood pressure and pulse rate.
3. Electrocardiogram: This would be the primary test conducted in the diagnosis of bradycardia. An electrocardiogram monitors the heart’s electrical impulses and can detect if the heart beats too slowly or has conduction problems. 
4. Holter Monitor: This is a portable electrocardiogram device that monitors the heart from 24 to 48 hours. It is helpful in detecting bradycardia that occurs on and off.
5. Event Recorder: This device is similar to a Holter monitor but can be worn for longer periods, up to 30 days. The patient activates the symptoms that occur.
6. Echocardiogram: A form of ultrasound in the picture of heart structure and function. It helps to identify possible causative heart diseases.
7. Exercise Stress Test: This test measures the electrical activity of the heart under conditions of stress, such as exercise. Bradycardia may only appear under these conditions.
8. Electrophysiology Study: This test is invasive and may need to be carried out in a few cases. It involves threading catheters into the heart to study its electrical activity in detail.
9. Blood Tests: These tests are ordered to determine if other conditions, such as thyroid disorders or electrolyte imbalances, are contributing to bradycardia.
10. Tilt Table Test: This test helps diagnose bradycardia related to body position changes, as different positions affect blood pressure, heart rhythm, and even heart rate. It can also identify the cause of unexplained dizziness or fainting. 

Treatment Options for Symptomatic Bradycardia

Bradycardia treatment depends more on its management, which can range from life modification and medication adjustment to highly aggressive interventions such as the implantation of an artificial pacemaker. The management strategy would depend on the severity of the symptom, the root cause, and the patient’s health status.

1. Underlying Disease Treatment

There are some cases where a disease-causing bradycardia can, in fact, be treated.

• Medication Adjustment: Bradycardia caused by certain medications is treated by adjusting the dosage or switching to alternative drugs. In cases of hypothyroidism causing bradycardia, thyroid hormone replacement will often normalize the heart rate. 
• Electrolyte Correction: When the cause involves electrolyte imbalances, correction through diet or supplementation may help.
• Sleep Apnea Treatment: Continuous positive airway pressure (CPAP) therapy may be effective in treating sleep apnea-induced bradycardia.

2. Bradycardia Medications

There are not many medications for bradycardia that can slow down the heart rate for a long time, but certain drugs can be employed in urgent conditions or symptoms.

• Atropine: This medication can temporarily elevate a person’s heartbeat and hence is very useful in emergency conditions.
• Epinephrine and Dopamine: These two medications are used as a second line of defense in bradycardia patients, especially when atropine becomes ineffective. 
• Beta-agonists: While primarily utilized to treat asthma, this class of medication increases the heart rate in selected forms of bradycardia.

These medications are not suitable for all patients and are most often considered temporary or for specific situations.

3. Pacemaker Implantation

Generally, a pacemaker is the most effective form of treatment for bradycardia, particularly in symptomatic patients due to sinus node dysfunction or AV block. A pacemaker is a small electronic device placed under the skin of the chest. It senses the heartbeat rhythm and delivers electrical pulses to the heart if necessary to maintain an adequate heart rate.

• Procedure: Pacemaker implantation is usually done under local anesthesia and sedation. It takes about 1-2 hours.
• Types of Pacemakers: The different types of pacemakers include single-chamber, dual-chamber, biventricular, and leadless pacemakers. The type of pacemaker used depends on the particular type of bradycardia and the patient’s overall heart condition.
• Effectiveness: Pacemakers are also effective in treating bradycardia. They greatly improve the quality of life by removing symptoms and permitting a return to normal activities.
• Follow-up Care: Following pacemaker placement, regular follow-up is necessary to ensure proper device function and make any necessary adjustments.

4. Lifestyle Modifications

This is not a cure for symptomatic bradycardia but can complement other forms of treatment and maintain good heart health.

• An exercise program, under the advice of a physician, will help in improving heart health.
• A heart-healthy diet will help in maintaining general cardiovascular functioning within the body.
• Meditation and yoga help with stress management. Stress, too, influences the heart rate.
• Identification and avoidance of stimuli that precipitate symptoms may help.
• It may help in maintaining an adequate blood volume and improving heart function.

Bradycardias usually require close collaboration with healthcare professionals to devise an appropriate treatment plan. In that respect, follow-up and monitoring are important because the selected treatment may become less effective over time.

Staying Ahead of Bradycardia Risks! 

Symptomatic bradycardia has complex features that could considerably affect a person’s quality of life. With early diagnosis, appropriate treatment, and management of the condition, patients can lead full and active lives.

Again, the most important thing with symptomatic bradycardia is to work with your healthcare team to develop a treatment plan that best fits your needs and concerns. There are different ways to handle the condition, through medications, a pacemaker, or changes in one’s lifestyle. Additionally, bystanders should be prepared to handle any emergencies with such patients by being CPR and BLS certified. 

Anybody suspecting symptoms associated with bradycardia should not hesitate to consult a doctor. The earlier the diagnosis and treatment, the better the results in managing this condition and improving one’s life.

Additional Read –

What is Cardiac Arrhythmia

What is Recovery Position

What is Carotid Pulse

What is Synchronized Cardioversion