Bradycardia is an abnormally slow heart rate. In adults, it is defined as a heart rate of less than 60 beats per minute. Different types of bradycardia are collectively referred to as bradyarrhythmias. They include:
Sinus bradycardia—an unusually slow heartbeat due to heart disease, a reaction to medication, or harmless causes, such as excellent fitness or deep relaxationSick sinus syndrome—an unusually slow heartbeat due to a malfunction of the sinoatrial node, which is the heart's natural pacemakerHeart block (atrioventricular block or AV block)—an unusually slow heartbeat due to a slowing or blocking of electrical impulses in the heart’s conduction system
Heartbeat: Anatomy of the Heart
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Bradycardia may be caused by:
Normal responses to:
Deep relaxationBeing in excellent physical shapeThe heart’s natural pacemaker developing an abnormal rate or rhythmThe normal electrical conduction pathway being interruptedAnother part of the heart taking over as pacemaker
Some types of bradycardia produce no symptoms. Others may cause noticeable symptoms, such as:
Fainting or loss of consciousnessDizziness or light-headednessWeaknessMild fatigueIrregular heart beat Shortness of breathChest pain
Serious forms of bradycardia, such as complete heart block, are medical emergencies. They can lead to loss of consciousness or sudden
The doctor will ask about your symptoms and medical history. A physical exam will be done. Your heart will be examined with a stethoscope. Your doctor may need you to have blood tests. These tests will look for problems that may explain the bradycardia.Your doctor may need to test your heart function. This can be done with:
ElectrocardiogramEchocardiogramA portable, continuous heart rhythm monitor that you wear as you perform normal daily activitiesExercise stress testNuclear scanningCoronary angiography
Treatment may not be required if you do not have cardiac symptoms and conditions. Your doctor may choose to monitor your heart rate and rhythm instead.
Treatment may include:
Stopping any medications that slow the heart rateDiagnosing and treating any underlying conditionsMedication to temporarily increase your heart rateAn artificial pacemaker to establish and maintain a normal heart rhythm
To help prevent bradycardia:
Treat conditions that might lead to bradycardia.Carefully follow your doctor’s directions when using medications, especially those that can cause bradycardia.Check with your physician or pharmacist before using any over-the-counter medication or natural supplement. Make sure it does not interact with your other medications.
Follow general advice for preventing heart disease, including:
Maintain a healthy weight.Consult with your doctor about a safe exercise program.Avoid smoking.Eat a healthy diet that is low in saturated fat and rich in whole grains, fruits, and vegetables.
high blood pressure
Fleg J. Arrhythmias and conduction disturbances. In: Beers MH, Berkow R, eds.
The Merck Manual of Geriatrics
[online]. Merck & Co.; 2000:486.
Hurst's The Heart
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Last reviewed December 2013 by Michael J. Fucci, DO
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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