Low Heart Rate & Bradycardia: When to Worry

What counts as a slow heart rate?

For most adults, a normal resting heart rate falls between 60 and 100 bpm. A rate below 60 bpm is medically defined as bradycardia. That said, the number alone does not determine whether something is wrong.

Many endurance athletes — runners, cyclists, swimmers — have resting heart rates in the 40s or 50s. This reflects a heart that has become more efficient at pumping blood with each beat, so it does not need to beat as often to deliver adequate circulation. A trained heart rate in the 40s or 50s, with no symptoms, is generally not a concern 1Ref 1National Heart, Lung, and Blood Institute (2024).Arrhythmias — Types.Bradycardia defined as resting heart rate below 60 bpm; notes that physically fit people may normally have slower heart rates as an expected adaptation to cardiovascular conditioning.

What causes bradycardia in people who are not athletes?

When a slow heart rate occurs in someone who is not highly fit, the most common causes include 2Ref 2Kusumoto FM, Schoenfeld MH, Barrett C, et al. (2019).2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay.Causes of bradycardia including sinus node dysfunction, heart block, and medication effects; symptomatic evaluation including ECG, Holter, and echocardiogram; pacemaker indications for symptomatic conduction disease:

Cardiac conduction problems. The heart's natural pacemaker (the sinus node) or its electrical pathways may not be firing normally. Sick sinus syndrome and heart block are examples. These may require evaluation and, in some cases, a pacemaker.

Medications. Beta-blockers (used for high blood pressure, heart failure, and anxiety) and certain calcium channel blockers are among the most common drug causes of a slow heart rate. If you take one of these medications and your heart rate has dropped noticeably, that is worth a conversation with your prescribing clinician.

Hypothyroidism. An underactive thyroid slows many body processes, including heart rate. A simple blood test (TSH) can check thyroid function.

Electrolyte imbalances. Low potassium or other electrolyte problems can affect heart rhythm.

Sleep. During deep sleep, heart rate naturally slows, sometimes well below 60 bpm — this is normal and not a problem.

What symptoms suggest bradycardia is a problem?

A slow heart rate becomes medically significant when the heart is not moving enough blood to meet the body's needs. Symptoms that suggest this include 2Ref 2Kusumoto FM, Schoenfeld MH, Barrett C, et al. (2019).2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay.Causes of bradycardia including sinus node dysfunction, heart block, and medication effects; symptomatic evaluation including ECG, Holter, and echocardiogram; pacemaker indications for symptomatic conduction disease:

• Fatigue, low energy, or difficulty with exertion that is new or worsening
• Dizziness or lightheadedness, especially when standing or active
• Shortness of breath with activities that used to be easy
• Near-fainting (presyncope) or actual fainting (syncope)
• Chest discomfort
• Brain fog or difficulty concentrating

If you have a slow heart rate and any of these symptoms, it is worth being evaluated rather than waiting.

How is bradycardia evaluated?

A primary care clinician will typically start with a physical exam, review of medications, and an electrocardiogram (ECG or EKG), which records the heart's electrical activity in real time 2Ref 2Kusumoto FM, Schoenfeld MH, Barrett C, et al. (2019).2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay.Causes of bradycardia including sinus node dysfunction, heart block, and medication effects; symptomatic evaluation including ECG, Holter, and echocardiogram; pacemaker indications for symptomatic conduction disease. For intermittent symptoms, a Holter monitor — a portable ECG worn for 24 to 48 hours — can catch rhythm 3Ref 3National Heart, Lung, and Blood Institute (2024).Arrhythmias — What Is an Arrhythmia?.Overview of cardiac arrhythmia diagnosis including use of ambulatory monitoring and evaluation of symptomatic bradycardia problems that do not show up in a brief office recording.

Blood tests to check thyroid function and electrolytes are often part of the initial workup. If a structural heart problem is suspected, an echocardiogram (heart ultrasound) may be ordered.

Diagnosis and management of significant bradycardia are guided by the 2018 ACC/AHA/HRS guideline on bradycardia and cardiac conduction delay 2Ref 2Kusumoto FM, Schoenfeld MH, Barrett C, et al. (2019).2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay.Causes of bradycardia including sinus node dysfunction, heart block, and medication effects; symptomatic evaluation including ECG, Holter, and echocardiogram; pacemaker indications for symptomatic conduction disease.

When does bradycardia require treatment?

If no symptoms are present and no structural cause is found, many people with a slow resting heart rate simply need periodic monitoring rather than treatment. Lifestyle factors — good fitness, healthy sleep, not drinking alcohol excessively — support a healthy rhythm 1Ref 1National Heart, Lung, and Blood Institute (2024).Arrhythmias — Types.Bradycardia defined as resting heart rate below 60 bpm; notes that physically fit people may normally have slower heart rates as an expected adaptation to cardiovascular conditioning.

When bradycardia is symptomatic or caused by a conduction problem, treatment depends on the underlying cause 2Ref 2Kusumoto FM, Schoenfeld MH, Barrett C, et al. (2019).2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay.Causes of bradycardia including sinus node dysfunction, heart block, and medication effects; symptomatic evaluation including ECG, Holter, and echocardiogram; pacemaker indications for symptomatic conduction disease:

• Medication adjustment. If a drug is driving the slow rate and it can be safely changed or dosed differently, that is often the first step.
• Treating the underlying condition. Correcting hypothyroidism or an electrolyte abnormality typically restores heart rate.
• Pacemaker. For significant electrical conduction disease that cannot be corrected another way, a small implanted pacemaker reliably keeps the heart rate adequate. Pacing is indicated for symptomatic patients with documented bradycardia responsible for their symptoms.

A Gale primary care clinician can evaluate your symptoms, review your medications, order an ECG and relevant labs, and refer you to a cardiologist if needed.