Sinus bradycardia is any heart rhythm slower than 50 bpm, even if transient, owing to sinus node dysfunction and/or atrioventricular (AV) conduction abnormalities.
Causes include intrinsic sinus node, AV nodal, and His-Purkinje disease, or extrinsic influences, which may be reversible.
Common symptoms include syncope, fatigue, and dizziness; however, the patient may be asymptomatic.
Evaluation involves determining the association of symptoms with heart rate and an assessment of underlying cardiovascular conditions. A 12-lead ECG and/or a heart monitor are the diagnostic tests of choice.
Patients with a reversible cause may not require long-term therapy; however, patients with nonreversible causes may require an implantable pacemaker with or without a defibrillator. Urgent treatment may include temporary pacing and drug interventions.
Potentially life-threatening complications, including cardiovascular collapse and death, may occur.
While some consider bradycardia to be a heart rate <60 bpm, this is in dispute and most consider rates of <50 bpm to represent bradycardia. A study of 500 healthy people, using ECG recordings, showed the mean afternoon heart rate to be 70 bpm in men and women, with two standard deviations being 46 to 93 bpm in men and 51 to 95 bpm in women. A slow heart rate is common under various circumstances and does not necessarily require treatment unless it causes symptoms. Nonetheless, some patients, even if asymptomatic, may require interventions to prevent life-threatening complications. This topic focuses on electrical causes of bradycardia.
History and exam
Key diagnostic factors
- pulse rate <50 bpm
- age >70 years
- use of known causative medications
- presence of known underlying cause
- exercise intolerance
- shortness of breath
- cannon a-waves in jugular venous pulse
- jugular venous distension
Other diagnostic factors
- increased intracranial pressure
- abnormal heart sounds
- abdominal or lower extremity edema
- mental status changes
- extremities cool to touch
- chest pain
- thyroid goiter
- use of known causative medications
- age >70 years
- recent myocardial infarction
- percutaneous valve replacement procedures
- electrolyte disorders
- exposure to toxins
- infiltrative diseases
- sleep apnea
1st investigations to order
- 12-lead ECG
- Holter monitoring
- event monitor/mobile cardiac telemetry
- exercise testing
- carotid sinus massage
- thyroid function tests
- basic metabolic panel
- arterial blood gas
- cardiac biomarkers
- serum digoxin level
- serum creatinine
Investigations to consider
- implantable-loop recorder
- tilt-table testing
- Lyme titers
- electrophysiology testing
- nocturnal pulse oximetry or overnight polysomnography
hemodynamically stable: sinus node dysfunction
hemodynamically stable: acquired atrioventricular block
hemodynamically stable: congenital atrioventricular block
hemodynamically stable: vagally mediated bradycardia
hemodynamically stable: bradycardia associated with neurologic disorders
Brian Olshansky, MD, FAHA, FACC, FHRS, FESC
University of Iowa
Des Moines University
Mercy Hospital North Iowa
BO is a national research study coordinator for Boehringer Ingelheim. He is a consultant and speaker for Lundbeck. He is a consultant for Amarin and was chair of the DSMB of REDUCE-IT He is a consultant for Sanofi Aventis and Respicardia.
Sandeep Saha, MD, MS, FACP, FACC
Cardiologist and Cardiac Electrophysiologist
Oregon Heart Center
Consultant, Cardiology and Cardiac Electrophysiology
Salem Health Hospitals and Clinics
SS declares that he has no competing interests.
Rakesh Gopinathannair, MD, MA, FAHA, FACC, FHRS
Director, Cardiac Electrophysiology Laboratories
Kansas City Heart Rhythm Institute and Research Foundation
EP Medical Director
Research Medical Center, HCA Midwest Health
Clinical Professor of Medicine
University of Missouri-Columbia
Associate Professor of Medicine (adjunct)
University of Louisville
RG is a consultant for St. Jude Medical, Biotrionik, and Boston Scientific. He is on the speakers' bureau for Pfizer Inc. and Zoll Medical. He serves as a physician advisor for HealthTrust PG and AltaThera Pharma, and PaceMate. None of these activities are relevant to the content of this topic.
Professor Brian Olshansky, Dr. Sandeep Saha, and Professor Rakesh Gopinathannair would like to gratefully acknowledge Dr Giselle Statz for her contributions to this version of the topic. They would also like to acknowledge Dr Renee M. Sullivan, Dr Weiwei Li, Dr Alexander Mazur, and Dr Chirag M. Sandesara, previous contributors to this topic.
GS, RMS, WL, AM, and CMS declare that they have no competing interests.
Nora Goldschlager, MD
Professor of Clinical Medicine
University of California
San Francisco General Hospital
Coronary Care Unit
ECG Laboratory and Pacemaker Clinic
NG declares that she has no competing interests.
Paul Heidenreich, MD
Associate Professor of Medicine
PH declares that he has no competing interests.
Juan M. Sztajzel, MD
Cardiology Center and Medical Polyclinics
University Hospital Geneva
JMS declares that he has no competing interests.
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