A low resting heart rate, also called bradycardia, is defined as a heart rate below 60 beats per minute. Some people naturally have a lower heart rate, especially highly trained athletes. However, there are some potential causes for concern if your resting rate is lower than normal.
What is considered a low resting heart rate?
A normal resting heart rate for adults ranges from 60 to 100 beats per minute. A heart rate lower than 60 beats per minute is considered bradycardia. Here are the general categories:
- Normal: 60 to 100 bpm
- Bradycardia: Below 60 bpm
- Athletes or very fit: 40 to 60 bpm
- Abnormal: Below 40 bpm
However, the normal range can vary widely depending on your age and fitness level. For example, the average resting heart rate for elite athletes can be in the 40s or 50s. Bradycardia may be normal if you are very athletic. But if your heart rate is lower than normal for your age and activity level, it could signal an underlying issue.
What causes low resting heart rate?
There are several possible causes for bradycardia. It may be related to:
- Being very athletic or fit
- Hypothyroidism
- Sleep apnea
- Electrolyte imbalances
- Nutrient deficiencies
- Nervous system disorders
- Heart blockages or disease
- Medications like beta blockers or calcium channel blockers
- Sick sinus syndrome
- Infections
Let’s explore some of the most common causes in more detail:
Athletic conditioning
Athletes and people who exercise regularly can develop an athletic bradycardia over time. This is a normal adaptation to exercise that shows the heart muscle has become very efficient. A lower resting heart rate is common in endurance athletes like marathon runners. Their hearts can pump adequate blood with fewer beats per minute.
Hypothyroidism
An underactive thyroid gland (hypothyroidism) can cause bradycardia. Your thyroid helps control your heart rate, so low thyroid hormone levels lead to a slower heartbeat.
Sleep apnea
Obstructive sleep apnea, where your breathing stops and starts during sleep, has also been linked with bradycardia. Sleep apnea increases activity of the vagus nerve, which helps lower the heart rate.
Electrolyte imbalances
Electrolytes like potassium, calcium and magnesium play essential roles in heart functions. Low blood levels of these minerals can disrupt electrical signaling in the heart and cause arrhythmias like bradycardia.
Medications
Some medications can cause bradycardia as a side effect by depressing functions of the sinus node. These include:
- Beta blockers like metoprolol or atenolol, used for high blood pressure
- Calcium channel blockers like diltiazem or verapamil, for high blood pressure
- Digoxin, for heart failure
- Cholinesterase inhibitors, for dementia
Always review potential medication side effects with your doctor and pharmacist.
Aging
As we age, changes in the heart muscle and conductive system can depress the intrinsic heart rate. Bradycardia along with slowed conduction is more common in older adults.
Nervous system disorders
Since the nervous system controls heart rate, any neurological problem can impact heart rate:
- Carotid sinus hypersensitivity – where the carotid sinus nerve is overly sensitive
- Autonomic neuropathy – damage to nerves that control heart rate
- Parkinson’s disease
- Multiple sclerosis
- Spinal cord injuries or disorders
Heart disease
Structural heart disease like heart valve problems, heart muscle disease (cardiomyopathy) or heart blockages can impair electrical conduction and lead to bradycardia. An example is heart block, where electrical signals are partially or fully blocked from reaching the ventricles.
Symptoms
In some cases, a low heart rate does not cause any noticeable symptoms. However, some people may experience:
- Fatigue
- Dizziness or lightheadedness
- Fainting or near fainting
- Shortness of breath
- Chest pain
- Confusion or memory problems
Severe bradycardia can be life-threatening if it leads to low blood pressure, chest pain, heart failure, or sudden cardiac arrest.
Who is at risk?
Certain people have increased risk of bradycardia, including:
- Athletes or people who exercise regularly
- Older adults > 65 years
- People with hypothyroidism or sleep apnea
- Those taking heart medications like beta blockers or calcium channel blockers
- People with electrolyte imbalances
- Those with chronic health conditions affecting the heart or nervous system
Should I be concerned?
In athletes and highly active people, a heart rate in the 40s or 50s is normal and does not require treatment. But if you are not very fit and you develop bradycardia, it can signify an underlying problem.
Consult your doctor if you have a heart rate lower than 60 bpm along with symptoms like dizziness or fainting. Some warning signs that warrant prompt medical attention include:
- Heart rate below 40 bpm
- Lightheadedness, confusion or fainting spells
- Chest pain or shortness of breath
- History of heart disease
It’s important to identify the cause of bradycardia, since leaving it untreated can lead to complications like frequent fainting or even sudden cardiac arrest in severe cases.
Diagnosing low heart rate
To diagnose bradycardia, your doctor will review your symptoms and medical history. Diagnostic tests may include:
- Physical exam – listening to your heart with a stethoscope
- Electrocardiogram (ECG) – to measure heart rate and rhythm
- Ambulatory ECG monitor – worn to track heart rate over 24 hours
- Echocardiogram – ultrasound imaging of the heart
- Blood tests – to check thyroid hormone, electrolytes, and cardiac enzyme levels
- Tilt table test – checks heart rate response to changes in position
- Exercise stress test – monitors heart rate during exercise
Your doctor will look for any underlying cause like hypothyroidism, sleep apnea, or heart disease. Treatment can then focus on the specific cause of the bradycardia.
Treatment for low resting heart rate
Treatment depends on the underlying cause and your symptoms:
- For athletes – no treatment needed since it is normal adaptation to training
- Medications – adjust or stop medications causing it
- Pacemaker – for significant heart block or pauses
- Treat underlying condition – like thyroid disorders or sleep apnea
- Lifestyle changes – more hydration and electrolytes
For severe or symptomatic bradycardia, a pacemaker can help keep the heart rate from dropping too low. This device uses electrical pulses to prompt the heartbeat when the heart’s intrinsic signals are too slow.
In some cases, lifestyle measures like staying well hydrated, getting sufficient electrolytes, and doing light exercise can help improve mild forms of bradycardia.
Prevention
It is not always possible to prevent bradycardia, especially if it results from a chronic medical condition or heart disease. But some tips that may help include:
- Having regular wellness exams to promptly identify emerging health issues
- Staying active with regular exercise appropriate for your age and fitness level
- Avoiding drugs and excess alcohol intake that can impact heart rate
- Managing chronic conditions properly, like hypothyroidism or sleep apnea
- Consuming adequate electrolytes – magnesium, potassium, calcium
- Staying well hydrated by drinking plenty of water
Talk to your doctor about individualized recommendations to help support a normal heart rate and prevent complications of bradycardia.
Outlook for low resting heart rate
The prognosis for bradycardia depends on the underlying cause and how low your heart rate is:
- With prompt treatment, many mild cases resolve without complications
- Athletic bradycardia does not affect life expectancy or health
- Untreated bradycardia can lead to fainting, cardiac arrest, or other heart rhythm problems
- People with underlying heart disease have worse prognosis
Work with your doctor to identify the cause of your bradycardia and decide on the most appropriate treatment. With proper care, many people with mild bradycardia recover fully and have normal heart function.
Key takeaways
- Bradycardia refers to a resting heart rate below 60 bpm
- It may be normal in very athletic people or a sign of an underlying issue
- Common causes include hypothyroidism, sleep apnea, heart block, and some medications
- Symptoms include fatigue, dizziness, and fainting
- See a doctor promptly if you have symptoms along with a heart rate
- Treatment focuses on the underlying cause and may include pacemakers for significant bradycardia
- With treatment, many cases of bradycardia resolve without complications
Conclusion
A heart rate lower than 60 beats per minute may be normal in very fit individuals but can sometimes indicate an underlying problem. Bradycardia on its own may not be concerning, but it warrants medical attention if you experience any symptoms of fatigue, lightheadedness or fainting. With proper diagnosis and treatment focused on the cause of the slow heart rate, many people with bradycardia recover fully without complications. Working closely with your doctor is key to getting your heart rate back into a normal range and preventing significant effects on your daily life and health.
