Sinus bradycardia
Alerts and Notices
Synopsis
If hemodynamically unstable, the patient should be treated with intravenous (IV) atropine 0.5-1 mg push every 3-5 minutes, for a total 3 mg dose. Patients who have undergone cardiac transplantation are unlikely to respond given that the vagal innervation of the heart no longer exists. Other etiologies, including second-degree type II atrioventricular (AV) blocks or third-degree blocks, may not respond to atropine. Consider other beta-adrenergic agonists (eg, epinephrine, isoproterenol) in patients who have failed to improve with atropine while other measures are taken.
If the patient remains hemodynamically unstable, either dopamine or epinephrine should be considered:
- Dopamine: 5-20 μg/kg per minute IV (titrate to patient response; taper slowly)
- Epinephrine: 2-10 μg per minute IV (titrate to patient response)
See also flowchart (Adult Bradycardia) in image stack.
About Sinus Bradycardia:
Sinus bradycardia is a heart rhythm originating in the sinoatrial (SA) node with a slow heart rate, usually classified as a heart rate less than about 50 beats per minute. Although generally benign, patients may report transient dizziness, lightheadedness, near syncope, or syncope in some cases. Severe symptoms such as heart failure or confusion may be present in extreme cases due to poor perfusion.
The SA node is the main pacemaker of the heart's conduction system. The vagus and sympathetic nerves innervate it. The SA nodal artery, which supplies the SA node, originates from the right coronary artery or the left circumflex artery.
Potential causes of sinus bradycardia include but are not limited to athletic conditioning, sick sinus syndrome, rate-lowering medications (eg, beta blockers, nondihydropyridine calcium channel blockers, ivabradine, amiodarone, digoxin, lithium), other medications (eg, narcotics, cannabinoids, remdesivir), obstructive sleep apnea, enhanced vasovagal activity, hypothyroidism, electrolyte derangements (eg, hypokalemia), acute myocardial infarction and other acute / chronic coronary spectrum disease, elevated intracranial pressure, familial ion channelopathies, certain infectious causes (eg, COVID-19, Lyme disease, babesiosis, Chagas disease), infiltrative diseases, and collagen vascular diseases.
Codes
ICD10CM:R00.1 – Bradycardia, unspecified
SNOMEDCT:
49710005 – Sinus bradycardia
Look For
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- Hypoglycemia
- Hypothermia
- Hypothyroidism
- Complete heart block
- Second-degree heart block
- Junctional or ventricular escape rhythm
- Ectopic atrial rhythm
- BRASH syndrome
Best Tests
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Management Pearls
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Therapy
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Drug Reaction Data
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.Subscription Required
References
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Last Reviewed:08/20/2022
Last Updated:09/08/2022
Last Updated:09/08/2022