Bradycardia is a condition in which the heart rate is slower than normal, typically below 60 beats per minute in adults. While a resting heart rate between 60 and 100 beats per minute is considered normal, a heart rate under 60 may not always indicate a problem. For instance, athletes or individuals in excellent physical condition may naturally have slower heart rates, which are typically harmless. However, when bradycardia leads to insufficient blood flow to the body, it can become dangerous and may require medical attention.
The causes of bradycardia can include issues such as aging-related changes in the heart, certain medications, or underlying conditions affecting the heart’s electrical system. Symptoms may involve fatigue, dizziness, shortness of breath, or fainting episodes.
What is Bradycardia?
Bradycardia, also known as a low heart rate, occurs when your heart beats slower than normal. This slower heart rate can compromise the heart’s ability to pump enough blood throughout your body, potentially leading to insufficient oxygen delivery to vital organs. Without proper oxygen supply, tissue damage may occur, making this condition potentially dangerous.
What are the Symptoms of Bradycardia?
Bradycardia occurs when the heart rate drops below 60 beats per minute, and particularly when inadequate blood flow prevents the body from meeting its oxygen needs, the following symptoms may appear:
- Fatigue and weakness
- Dizziness and feeling lightheaded
- Shortness of breath (especially with exertion)
- Chest discomfort/pain
- Quick tiredness and reduced exercise capacity
- Mental confusion and difficulty concentrating
- Fainting or near-fainting episodes (syncope/presyncope)
- Headaches
- Nausea
- Drowsiness and sleep problems
Note: These symptoms can vary depending on the severity of bradycardia and its underlying cause. Some people may experience no symptoms from bradycardia, or it may be discovered incidentally.
What Causes Bradycardia?
Bradycardia or low heart rate occurs in two situations:
- The heart generates fewer impulses than normal at its origin
- The electrical conduction slows down or gets blocked while spreading through the heart (Figure-1)
Low heart rate is not always considered a disease. A person can have a low heart rate and be completely healthy. Athletes typically have heart rates below 60. Our heart rate may drop when we sleep. While these are considered normal, certain factors can cause an abnormally slow heart rate, or bradycardia. These may include:
- Natural changes in the heart’s electrical conduction system that occur with aging
- Damage to the conduction system following a heart attack
- Complications following heart surgery
- Medications, especially beta-blockers, heart rhythm regulators, and blood pressure medications
- Electrolyte imbalances, particularly changes in potassium and magnesium levels
- Thyroid disease, especially underactive thyroid (hypothyroidism)
- Congenital heart defects, structural abnormalities in the heart’s electrical conduction system can directly affect heart rhythm and cause bradycardia
- Sleep apnea, repeated breathing stops during sleep impair heart oxygenation and stimulate the vagus nerve. This can lead to slowing of heart rate
- Certain infections, such as heart muscle or heart membrane infections
- An eating disorder called anorexia
What are the Complications of Bradycardia?
Without treatment, bradycardia can lead to complications such as:
- Heart failure risk increases when bradycardia remains untreated, as the heart struggles to pump sufficient blood to meet the body’s needs.
- Sudden fainting episodes and falls are serious immediate complications that can lead to injuries and require emergency care.
- Chronic fatigue and reduced exercise capacity significantly impact daily life and overall quality of life.
- Cognitive function may be affected due to reduced blood flow to the brain, leading to confusion and difficulty concentrating.
- Organ damage can occur over time if tissues and organs consistently receive inadequate oxygen supply.
How is Bradycardia Diagnosed?
The most important step in diagnosing bradycardia is evaluating heart rhythm through ECG and determining the underlying cause. The patient’s symptoms and risk factors also play a crucial role in the diagnostic process.
Basic evaluations required for bradycardia diagnosis can be listed as follows:
- ECG (Electrocardiogram): Evaluation of heart rhythm and rate
- Medical history and physical examination
- Holter monitoring: Heart rhythm monitoring for 24-48 hours
- Tilt table test: Especially for patients with fainting complaints
- Exercise stress test: To evaluate the heart’s response during exercise
- Blood tests: To assess thyroid function, electrolyte levels, and other metabolic conditions
How is Bradycardia Treated?
Bradycardia treatment varies depending on the underlying cause and severity of symptoms. While asymptomatic and healthy individuals (such as athletes) may not require treatment, the following treatment options can be implemented for symptomatic patients:
Treatment of underlying cause: First, the underlying cause must be identified and treated. For example, if medication is causing bradycardia, the medication may need to be discontinued or its dosage adjusted, or if there’s an electrolyte imbalance, it needs to be corrected.
Medication: Drug therapy includes medications that increase heart rate. These medications are particularly preferred in emergencies and for temporary bradycardia treatment.
Temporary pacemaker: A temporary pacemaker is used in emergencies and for short-term treatment of bradycardia due to correctable causes. For example, it may be used for temporary bradycardia that develops during a heart attack.
Permanent pacemaker: A permanent pacemaker is preferred for patients with chronic and severe bradycardia who don’t respond to medication or have advanced heart block. It’s also commonly used in permanent rhythm disorders such as sick sinus syndrome.
FAQs About Bradycardia
Can bradycardia improve?
If you have bradycardia (low heart rate), the following are checked:
- Is the heart rhythm originating from its normal location and being conducted normally to the ventricle?
- Does your heart rate increase to desired levels with exercise?
- Do you have any symptoms?
A decision is made based on the answers to these questions. For example, if your resting heart rate is 50, everything on the ECG is normal except for bradycardia, you have no symptoms, and your heart rate increases sufficiently with effort (called chronotropic response), no intervention is necessary. However, if your heart rate is 55 beats per minute but there’s a problem on the ECG, such as blocked conduction between the atria and ventricles (heart block), then a pacemaker might be needed. In bradycardia, factors other than just heart rate must be evaluated together.
Can bradycardia be treated with ablation?
In some patients, early beats originating from the atria (called atrial extrasystoles) can cause bradycardia or low heart rate. In these patients, bradycardia can be corrected with ablation. Also, people with vasovagal syncope may have low resting heart rates. Cardioneuroablation treatment for vasovagal syncope can also increase resting heart rate.
At what heart rate does death occur?
In healthy, exercising individuals, heart rate can drop to around 40, especially during sleep. This doesn’t necessarily indicate a dangerous situation. If there are no symptoms like dizziness, weakness, or decreased exercise capacity, a heart rate of 45-50 beats per minute isn’t concerning. What’s important here is maintaining the working order between the upper (atria) and lower chambers (ventricles) of the heart, meaning no heart block in the heart’s conduction system. Each patient is evaluated individually to determine if the low heart rate is related to heart block and if it’s causing symptoms. Symptomatic bradycardia should be treated.
How high can my heart rate go during exercise?
During exercise, maximum target heart rate is calculated. To find your maximum rate, subtract your age from 220. If you’re 40 years old, your maximum heart rate during exercise should be 220-40=180. You can increase your heart rate up to 85% of your maximum rate.
Reference: Bradycardia