Slow heart rate - bradycardia

Normally, your heart works as a pump that sends blood to the lungs and the rest of the body.

To help this happen, your heart has an electrical system that makes sure it squeezes (contracts) in an orderly way. This process includes:

• The electrical impulse that signals your heart to contract begins in an area of the heart called the sinoatrial node (also called the sinus node or SA node). This is your heart's natural pacemaker.
• The signal leaves the SA node and travels through the heart along a set electrical pathway.
• Different nerve messages signal your heart to beat slower or faster.

Bradycardia is caused by problems with the heart's electrical conduction system. If your heart's natural pacemaker slows down or the signals are blocked, the time between your heartbeats also slows down. A slow heartbeat can be dangerous if it means your heart can't pump enough blood throughout your body.

The most common type of bradycardia is sinus bradycardia. It originates from the sinus node of the heart. Other types of bradycardia are:

• Sinus node dysfunction (also called sick sinus syndrome)
• Heart block

Several factors can affect your heart’s electrical system and cause bradycardia. These factors may include:

• Age-related changes of the heart
• Heart conditions such as heart attack or cardiomyopathy
• Congenital heart disease
• Inflammatory diseases such as rheumatoid arthritis, scleroderma, and lupus
• Conditions such as amyloidosis, hemochromatosis, and sarcoidosis
• Infections such as endocarditis, Chagas disease, and Lyme disease
• Complications from heart surgeries and other cardiac procedures
• Hypothyroidism
• Electrolyte imbalances, hypothermia, and hypoxia (lack of oxygen)
• Medicines such as beta-blockers, calcium channel blockers, antiarrhythmic medicines, opioids, and some antidepressants
• Obstructive sleep apnea

Common symptoms of bradycardia include:

• Heart palpitations
• Fainting (syncope) or near fainting
• Lightheadedness
• Tiredness
• Weakness
• Confusion
• Breathing difficulty
• Chest pain
• Chest tightness or breathing discomfort during physical activity

Your health care provider will ask about your medical history and the medicines you are taking. Your provider will do a physical exam and listen to your heart with a stethoscope for heart murmurs or other abnormal heart sounds. Your blood pressure and pulse rate will be measured.

Your provider may order the following tests:

• Electrocardiogram (ECG)
• 24-hour Holter or event monitor recording

Other tests that may be done include:

• Echocardiogram
• Coronary angiography
• Electrophysiology study (EPS)
• Exercise stress test
• Heart CT scan
• MRI
• Blood tests to check for underlying conditions such as hypothyroidism or electrolyte imbalance

Treatment depends upon the cause of bradycardia and what symptoms you have. People with mild or no symptoms may not need treatment.

Your treatment may include:

• Lowering the dose or changing the medicine that may be causing your slow heart rate
• Treating any underlying condition
• Using medicines (such as atropine, isoproterenol, dopamine, and epinephrine) to increase your heart rate in emergency situations
• Implanting a heart pacemaker
• Using a procedure to stop heart nerve signals (cardiac neural ablation) that may be slowing down your heart's natural pacemaker

The outlook depends upon:

• The type of bradycardia you have
• Your heart function
• The underlying cause

The outlook for people with bradycardia is good if the condition is diagnosed and treated early.

Untreated bradycardia may lead to:

• Fainting
• Heart failure
• Sudden cardiac arrest (rare)

Contact your provider if:

• You develop symptoms of bradycardia
• You have been diagnosed with bradycardia and your symptoms get worse or don’t improve with treatment

Call 911 or the local emergency number right away if you have:

• Chest pain
• Breathing difficulty
• Fainting

Not all cases of bradycardia can be prevented. Taking steps to prevent coronary artery disease may help reduce your chance of developing heart rate problems.

Slow heart rate; Bradyarrhythmia

American Heart Association website. Bradycardia: slow heart rate. www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate. Updated September 25, 2024. Accessed July 22, 2026.

Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS Guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society. J Am Coll Cardiol. 2019;74(7):932-987. PMID: 30412710 pubmed.ncbi.nlm.nih.gov/30412710/.

Patton KK, Olgin JE. Bradyarrhythmias and atrioventricular block. In: Bonow RO, Mann DL, Tomaselli GF, et al, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 13th ed. Philadelphia, PA: Elsevier; 2026:chap 50.

Zimetbaum P, Goldman L. Bradycardias and conduction system delays. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 51.

Updated by: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.