Option 1: Unstable bradycardia

Last updated: May 1, 2025

Reading the signs

The patient has signs of unstable bradycardia. You perform an ABCDE survey. She has a pulse, but her heart rate is 35 beats/minute, her blood pressure is 85/52 mm Hg, and she does not respond when you call her name. The nurse states that the patient looks much worse now than she did a few minutes ago.

While you wait for the rapid response team to arrive, you must start to stabilize the patient. Luckily, the nurse has already placed two large-bore IVs.

Question: What is your next step?

Make your choice, then click on the explanation bubble to reveal the answer.

Obtain a 12-lead ECG.
Call your attending to give them an update on the patient's status.
Bring a crash cart to the bedside and attach pacer pads.

Ensure immediate delivery of a crash cart to the bedside of a patient with unstable bradycardia. Attach pads to the patient to prepare for temporary cardiac pacing.

Initial management approach

The crash cart is at the bedside, the pads are attached to the patient, and the rapid response team has arrived.

Question: What are the initial steps in the management of unstable bradycardia?

Do the following steps concurrently to manage this patient's unstable bradycardia. Click on the explanation bubbles for more information.

Ensure continuous cardiac and respiratory monitoring.
Obtain a rhythm strip to help identify the patient's cardiac rhythm.
Identify and treat reversible causes of bradycardia (e.g., hypoxemia).
Administer IV atropine.
If bradycardia is refractory to atropine, begin temporizing measures:
- Transcutaneous pacing
- Alternative pharmacotherapy
If bradycardia is refractory to pharmacotherapy, consult cardiology for transvenous pacing.

Always consider reversible causes of bradycardia (e.g., hypoxemia, beta blocker toxicity, hyperkalemia, acute coronary syndrome) while working through the initial management steps.

Practice

Etiologies of bradycardia

Activate the table quiz to test your knowledge of causes of bradycardia. See how many you can remember!

	Cause ^[1]^[2]^[3]
Increased vagal tone	Can be physiological (particularly in athletes) Obstructive sleep apnea Neurocardiogenic (i.e., vasovagal response) Pain Carotid sinus hypersensitivity
Ischemia	Acute myocardial infarction Unstable angina or variant angina Ischemic cardiomyopathy
Inflammatory or infiltrative	Myocarditis Endocarditis Amyloidosis or fibrosis Acute rheumatic fever Lymphoma Hemochromatosis Guillain-Barré syndrome Sarcoidosis Systemic sclerosis SLE Rheumatoid arthritis Reactive arthritis
Infections	Lyme disease Chagas disease Diphtheria Legionella Psittacosis Typhoid fever Typhus Listeria Malaria Leptospirosis Toxoplasmosis Dengue fever Viral hemorrhagic fevers Infective endocarditis
Metabolic or endocrine	Electrolyte imbalance Hypokalemia Hyperkalemia Hypocalcemia Poisoning or overdose Carbon monoxide (see “CO intoxication”) Cyanide (see “Cyanide intoxication”) Mercury Grayanotoxin Hypothyroidism Hypoaldosteronism
Congenital	Neuromuscular disease (e.g., myotonic dystrophy, Kearns-Sayre syndrome, limb-girdle muscular dystrophy) Congenital AV block (associated with maternal SLE) Congenital heart disease (e.g., TGA) Genetic mutations (e.g., SCN5A mutations) Hereditary motor sensory neuropathy
Degeneration of the conducting system	Senile amyloidosis Familial progressive cardiac conduction defect Aortic stenosis Mitral stenosis Idiopathic degenerative fibrosis
Iatrogenic	Valve surgery (e.g., transcatheter aortic valve replacement for LBBB) Catheter ablation TAVR Alcohol septal ablation Complications of heart transplant: acute rejection, chronic rejection, cardiac remodeling Septal myectomy Right heart catheter Cardiac pacemaker malfunction
Medication	Antiarrhythmic drugs Adenosine Amiodarone Dronedarone Flecainide Procainamide Propafenone Quinidine Sotalol Digoxin Antihypertensive drugs Beta blockers Nondihydropyridine calcium channel blockers Clonidine Methyldopa Reserpine Psychoactive drugs Lithium Opioids Donepezil Phenothiazine Phenytoin SSRIs Tricyclic antidepressants Intoxication with other agents Propofol Ivabradine Cannabis
Other	Hypothermia Anorexia nervosa Elevated intracranial pressure Hypertension Hypertensive cardiomyopathy Increased right ventricular pressure (RBBB) Valvular disease (LAFB) Extensive arteriosclerotic and/or cardiovascular disease

Dive deeper

Soon the rapid response team arrives. Together you stabilize the patient, preventing a total eclipse of the heart. For a detailed dive into the management approach, see “Management of bradycardia.”

Related resources

Continue the adventure

Want to explore the other scenario? Jump over to “Option 2: Stable bradycardia.” You can also return to the main module; see “Stuck in slow motion wrap-up.”

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