Bradycardia resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]: Associate Editor(s)-in-Chief: Ogheneochuko Ajari, MB.BS, MS [2]; Vidit Bhargava, M.B.B.S [3]

Definition

Bradycardia is defined as a sinus rhythm with a rate <60 beats per minute. A heart rate of <50 beats per minute is used as a working definition of bradycardia causing symptoms.

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Hyperkalemia
• Hypoxia
• Inferior myocardial infarction
• Intracranial hypertension

Common Causes

• Carotid sinus hypersensitivity
• Medications

Diltiazem

Amiodarone

Amitriptyline

Beta-blockers

Cardiac glycosides

Clonidine

Dronedarone

Flecainide

Lithium

Methyldopa

Phenothiazines

Procainamide

Propafenone

Quinidine

Reserpine

Verapamil

• Sick sinus syndrome

Management

Shown below is an algorithm depicting the management of bradycardia based on the 2010 AHA guidelines for cardiopulmonary resuscitation and emergency cardiovascular care.

Characterize the symptoms: ❑ Palpitations ❑ Lightheadedness ❑ Dyspnea ❑ Chest pain ❑ Altered mental status

Examine the patient: ❑ Heart rate < 50/min ❑ Signs of increased work of breathing ♦ Tachypnea ♦ Intercostal retractions ♦ Suprasternal retractions ♦ Paradoxical abdominal breathing ❑ Signs of poor perfusion ♦ Hypotension ♦ Signs of shock

Identify and treat underlying cause: ❑ Maintain patent airway; assist breathing as necessary ❑ Oxygen (if hypoxemic) ❑ Cardiac monitor to identify rhythm ❑ Monitor blood pressure and oximetry ❑ IV access ❑ 12-lead ECG if available; don’t delay therapy

Persistent bradyarrhythmia causing: ❑ Hypotension? ❑ Acutely altered mental status? ❑ Signs of shock? ❑ Ischemic chest discomfort? ❑ Acute heart failure?

Yes

No

Atropine ❑ First dose - 0.5 mg IV bolus ❑ Repeat every 3-5 minutes ❑ Maximum 3 mg

❑ Monitor and observe

If atropine ineffective: ❑ Transcutaneous pacing, OR ❑ Dopamine infusion (2-10 mcg/kg/min), OR ❑ Epinephrine infusion (2-10 mcg/min)

❑ Consider expert consultation ❑ Consider transvenous pacing

Do's

• Prepare for transcutaneous pacing if perfusion is poor.
• Consider using sodium bicarbonate for severe metabolic acidosis.
• Use atropine with caution in the presence of myocardial ischemia because it increases oxygen demand and could worsen the ischemia.

Don'ts

• Do not delay pacing if the rhythm is Mobitz type II second degree block or third-degree AV block even if the patient is asymptomatic.
• Avoid using atropine in hypothermic patients with either bradycardia or Mobitz type II second degree AV block.
• Do not use atropine to treat bradycardia in cardiac transplant patients.
• Do not use atropine to treat Type II second degree and third degree heart blocks since their management requires transcutaneous/transvenous pacing.