Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Sinus Bradycardia
Introduction
Overview
Overview
Sinus bradycardia is a heart rhythm that originates from the sinus node and has a rate of under 60 beats per minute. Common causes include sick sinus syndrome and pharmacotherapy such as beta-blockers. Sinus bradycardia is fairly common in highly trained athletes. It only requires treatment if the patient is symptomatic.
References
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Cafer Zorkun, M.D., Ph.D. [2]
Pathophysiology
Overview
Pathophysiology
This rhythm may be caused by one of the following:
- Increased vagal tone
- Intrinsic disease of the SA node
- An effect of drugs, such as the use of digitalis or beta-blockers
- Sleep
- Sinus bradycardia is a normal finding in a healthy, well-conditioned athlete
The HCN4 genetic variant is associated with sinus bradycardia. Certain sodium channelopathies are associated with sinus bradycardia.[1]
References
- ↑ Milanesi R, Baruscotti M, Gnecchi-Ruscone T, DiFrancesco D (2006). “Familial sinus bradycardia associated with a mutation in the cardiac pacemaker channel”. The New England Journal of Medicine. 354 (2): 151–7. doi:10.1056/NEJMoa052475. PMID 16407510. Retrieved 2011-02-23. Unknown parameter
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Cafer Zorkun, M.D., Ph.D. [2]
Causes
Overview
Sinus bradycardia does not necessarily refer to the presence of an obvious pathology; in fact, it may occur in normal, healthy individuals including well-trained athletes, some elderly people or during sleep. It may also be due to an exaggerated response to normal physiological processes (e.g. vomiting, coughing, defecation) or from pathologies involving the SA node such as sick sinus syndrome, myocardial infarction. The most common medications causing sinus bradycardia are beta blockers, digitalis and calcium channel blockers. However, life-threatening conditions including chemical poisoning (organophosphate, sarin), sepsis, electrolyte imbalance should be promptly recognized and treated.
Causes
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
- Beta blocker overdose
- Carbamate poisoning
- Cervical spine injury
- Digitalis toxicity
- Drowning
- Electric shock
- Electrolyte imbalance
- Hypoglycemia
- Increased intracranial pressure
- Lily of the valley poisoning
- Lithium toxicity
- Myocardial infarction
- Nerve agent poisoning e.g. sarin
- Organophosphate poisoning
- Rabies
- Sepsis
Common Causes
- Aging
- Beta blocker
- Calcium channel blocker
- Cardiac catheterization
- Electrolyte imbalance
- Hypothermia
- Hypothyroidism
- Myocardial infarction
- Nausea
- Obstructive sleep apnea
- Sedative
- Sepsis
- Sleep
- Sick sinus syndrome
Causes by Organ System
Causes in Alphabetical Order
References
- ↑ van bogaert, pp.; pittoors, f. (2003). “use-dependent blockade of cardiac pacemaker current (if) by cilobradine and zatebradine”. eur j pharmacol. 478 (2–3): 161–71. PMID 14575801. Unknown parameter
|month=ignored (help) - ↑ 2.0 2.1 2.2 Van Bogaert, PP.; Pittoors, F. (2003). “Use-dependent blockade of cardiac pacemaker current (If) by cilobradine and zatebradine”. Eur J Pharmacol. 478 (2–3): 161–71. PMID 14575801. Unknown parameter
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayokunle Olubaniyi, M.B,B.S [2]
Differentiating Sinus bradycardia from other Diseases
Epidemiology and Demographics
Overview
Epidemiology and Demographics
Among people under 25 years of age, approximately 30% have sinus bradycardia[1]. During sleep, heart rates may decline by 25 beats per minute in young patients, and 15 beats per minutes in the elderly. Heart rates of 30 beats/minute and pauses of up to 2 seconds are not uncommon in healthy people [2][3][4]
References
- ↑ HISS RG, LAMB LE, ALLEN MF (1960). “Electrocardiographic findings in 67,375 asymptomatic subjects. X. Normal values”. The American Journal of Cardiology. 6: 200–31. PMID 13855921. Unknown parameter
|month=ignored (help);|access-date=requires|url=(help) - ↑ Hilgard J, Ezri MD, Denes P (1985). “Significance of ventricular pauses of three seconds or more detected on twenty-four-hour Holter recordings”. The American Journal of Cardiology. 55 (8): 1005–8. PMID 3984858. Retrieved 2011-02-23. Unknown parameter
|month=ignored (help) - ↑ Brodsky M, Wu D, Denes P, Kanakis C, Rosen KM (1977). “Arrhythmias documented by 24 hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease”. The American Journal of Cardiology. 39 (3): 390–5. PMID 65912. Unknown parameter
|month=ignored (help);|access-date=requires|url=(help) - ↑ Bjerregaard P (1983). “Mean 24 hour heart rate, minimal heart rate and pauses in healthy subjects 40-79 years of age”. European Heart Journal. 4 (1): 44–51. PMID 6339245. Retrieved 2011-02-23. Unknown parameter
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Cafer Zorkun, M.D., Ph.D. [2]
Risk Factors
Natural History, Complications and Prognosis
Diagnosis
Diagnosis
History and Symptoms | Physical Examination | Laboratory Findings | Electrocardiogram
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Cafer Zorkun, M.D., Ph.D. [2]