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 and AV nodal 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. ECG is the diagnostic test 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 normal 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.
University of Iowa
Des Moines University
Mercy North Iowa
BO is a national research study coordinator for Boehringer Ingelheim and is on the data safety monitoring board for Amarin. He is a consultant and speaker for Lundbeck and On-X.
Director of Cardiac Electrophysiology
Assistant Professor of Medicine
Division of Cardiovascular Medicine
University of Louisville School of Medicine and Jewish Hospital
RG is a consultant for St. Jude Medical and Boston Scientific. He is on the speakers’ bureau for American Heart Association, Pfizer Inc., Bristol Myers Squibb, and Zoll Medical. He serves on the advisory board of HealthTrust PG.
Professor Brian Olshansky and Dr Rakesh Gopinathannair would like to gratefully acknowledge Dr Renee M. Sullivan, Dr Weiwei Li, Dr Alexander Mazur, and Dr Chirag M. Sandesara, previous contributors to this monograph. RMS, WL, AM, and CMS declare that they have no competing interests.
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.
Associate Professor of Medicine
PH declares that he has no competing interests.
Cardiology Center and Medical Polyclinics
University Hospital Geneva
JMS declares that he has no competing interests.
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