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Bradycardia Resident Survival Guide Microchapters
Overview
Causes
FIRE
Diagnosis
Treatment
Do's
Don'ts

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]

Overview

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. The evaluation of bradycardia includes assessment of heart rhythm, symptoms and associated medical conditions. The management of symptomatic bradycardia typically involves treating the underlying causes, the use of medications (e.g. atropine) or insertion of temporary or permanent pacemaker. Nevertheless, some asymtomatic bradycardias may require treatment to prevent complications.

Causes

Life Threatening Causes

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

• Hyperkalemia
• Hypoxemia
• Inferior myocardial infarction
• Intracranial hypertension

Common Causes

• Carotid sinus hypersensitivity
• Medications

Amiodarone

Amitriptyline

Beta-blockers

Cardiac glycosides

Clonidine

Diltiazem

Dronedarone

Flecainide

Lithium

Methyldopa

Phenothiazines

Procainamide

Propafenone

Quinidine

Reserpine

Verapamil

• Sick sinus syndrome

Click here for the complete list of causes.

FIRE: Focused Initial Rapid Evaluation

A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients in need of immediate intervention. The initial rapid evaluation is based on the 2005 AHA guidelines for cardiopulmonary resuscitation and emergency cardiovascular care.
Boxes in red signify that an urgent management is needed.

Abbreviations: IV: Intravenous; ECG: Electrocardiogram

Identify cardinal findings that increase the pretest probability of bradycardia ❑ Heart rate < 50 beats/min

Does the patient have any of the following findings of hemodyanamic instability that require urgent treatment? ❑ Shock ❑ Altered mental status ❑ Hypotension ❑ Hypothermia ❑ Oliguria

Yes

No

Continue with the complete diagnostic approach below

Initial Stabilization Do the following simultaneously without delaying the treatment ❑ Maintain patent airway ❑ Assist breathing if required ❑ Place patient on cardiac monitor ❑ Give supplemental oxygen ❑ Monitor blood pressure and evaluate oxyhemoglobin saturation ❑ Establish IV access ❑ Obtain ECG to define rhythm ❑ Evaluate clinical status and identify reversible causes simultaneously

Is there an AV block?

No

Yes

Second degree AV block/Third-degree AV block

First degree AV block

First Line Treatment Option ❑ Administer atropine 0.5 mg IV bolus and repeat every 3-5 mins with a maximum dose of 3 mg Second Line Treatment Options ❑ Administer Dopamine infusion (2-10 mcg/kg/min) OR ❑ Administer Epinephrine infusion (2-10 mcg/min) OR ❑ Proceed with transcutaneous pacing (Class IIa, level of evidence B)

DO NOT GIVE ATROPINE ❑ Proceed with transcutaneous pacing

First Line Treatment Option ❑ Administer atropine 0.5 mg IV bolus and repeat every 3-5 mins with a maximum dose of 3 mg Second Line Treatment Options ❑ Administer Dopamine infusion (2-10 mcg/kg/min) OR ❑ Administer Epinephrine infusion (2-10 mcg/min) OR ❑ Proceed with transcutaneous pacing (Class IIa, level of evidence B)

Are the signs of poor perfusion or shock persisting?

Yes

No

❑ Consult a cardiologist and ❑ Prepare patient for transvenous pacing

Continue with the complete diagnostic approach below

Complete Diagnostic Approach

A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

Abbreviations: CK-MB: Creatine kinase myocardial type; ECG: Electrocardiogram; TSH: Thyroid stimulating hormone

Characterize the symptoms: ❑ Lightheadedness or dizziness ❑ Dyspnea ❑ Chest pain ❑ Altered mental status ❑ Syncope ❑ Fatigue ❑ Exercise intolerance Obtain a detailed history: ❑ Age (bradycardia is commonly seen in the elderly) ❑ Use of negative chronotropic medications ❑ Beta blockers ❑ Calcium channel blockers ❑ Digoxin ❑ Past medical history ❑ Disease in the sinus node ❑ AV nodal disease ❑ Age-related fibrosis and sclerosis ❑ Infection ❑ Increased intracranial pressure ❑ Electrolyte disturbance ❑ Exposure to toxins ❑ Surgery ❑ Heart transplant ❑ Sleep apnea ❑ Myocardial infarction ❑ Hypothyroidism

Examine the patient: Vitals ❑ Pulse ❑ Rate ❑ Heart rate < 60/min ❑ Rhythm ❑ Slow regular ❑ Irregular pulse of varying intensity (suggestive of the 2nd and 3rd degrees of AV block) ❑ Respiration ❑ Tachypnea ❑ Blood pressure ❑ Hypotension in some cases Skin ❑ Inspection ❑ Dry or coarse skin ❑ Dry or coarse hair ❑ Pallor ❑ Facial edema (not common) ❑ Palpation ❑ Cool lower extremities (due to poor cardiac output) Neck ❑ Jugular venous distension (suggestive of heart failure) ❑ Cannon a waves in jugular venous pulse (suggestive of complete heart block) Respiratory examination ❑ Assessment of respiratory effort movement ❑ Intercostal retractions ❑ Suprasternal retractions ❑ Auscultation ❑ Rales (uncommon) Cardiovascular examination ❑ Auscultation ❑ Heart sounds ❑ S3 (uncommon) Abdominal examination ❑ Percussion ❑ Ascites - suggestive of heart failure (uncommon) Extremities ❑ Inspection/palpation ❑ Lower extremity edema - suggestive of heart failure (uncommon)

Consider alternative diagnosses: ❑ Ventricular bigeminy ❑ Frequent premature ventricular contractions (PVCs) ❑ Atrial fibrillation ❑ Blocked premature atrial contractions (PACs) ❑ Cardiac tamponade

Order tests: First initial test ❑ 12-lead ECG (to determine rhythm) 12-lead ECG showing sinus bradycardia Other initial tests ❑ Holter monitoring- to evaluate ❑ Severe sinus bradycardia ❑ Sinus pauses ❑ Sinus arrest ❑ Second-or third-degree AV block ❑ Exercise stress testing (for diagnoses of sick sinus syndrome and ischemic heart disease) ❑ Carotid sinus massage (to evaluate carotid sinus hypersensitivity) ❑ Echocardiogram (to evaluate valvular heart disease) Laboratory tests ❑ Thyroid function tests (elevated TSH in hypothyroidism) ❑ Basic metabolic panel (to determine electrolyte disturbances) ❑ Cardiac enzymes (creatine kinase, CK-MB and troponin) ❑ Serum creatinine (elevated in renal impairment) ❑ Serum digoxin (for junctional bradycardia) Other Investigations ❑ Tilt-table testing (to evaluate autonomic system and diagnosis of neurocardiogenic syncope) ❑ Electrophysiologic testing (to evaluate bradyarrhythmias)

Treatment

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

Bradycardia/Bradyarrhythmia with heart rate < 60/min

Identify underlying causes: ❑ Acidosis ❑ Carotid sinus hypersensitivity ❑ Electrolyte imbalance e.g. Hyperkalemia ❑ Hypoglycemia ❑ Hypothermia ❑ Hypoxemia ❑ Sick sinus syndrome ❑ Toxins

Determine signs and symptoms of hemodynamic instability ❑ Hypotension ❑ Acutely altered mental status ❑ Signs of shock ❑ Ischemic chest discomfort ❑ Acute heart failure

Unstable

Stable

Continue with focused initial rapid evaluation above

❑ Close follow up and monitoring ❑ Identify and treat underlying causes

Sinus node dysfunction ❑ Treat underlying cause ❑ Withdrawal of medication ❑ Administer electrolytes to correct for imbalance ❑ Correction of thyroid dysfunction ❑ Correction of hypoglycemia ❑ Give Theophylline 200-400mg PO twice daily for fatigue and/or dizziness ❑ Temporary pacing for severe symptoms ❑ Permanent pacing for irreversible causes with severe symptoms (e.g. Sinus node dysfunction with AV block or Afib

AV Block Acquired or Congenital ❑ Treat underlying cause ❑ Temporary pacing if indicated ❑ Reassurance for irreversible causes without indication for pacing ❑ Permanent pacing for symptomatic irreversible causes

Carotid sinus hypersensitivity Permanent pacing

Neurocardiogenic syncope ❑ Lifestyle modification ❑ Adequate salt and fluid intake ❑ Elevation of legs, lying down and tensing maneuvers ❑ Avoid precipitating factors ❑ Fludrocortisone 0.1-0.2mg PO once daily OR ❑ Midodrine 2.5-10mg PO tid OR ❑ Fluoxetine 20mg PO once daily OR ❑ Permanent 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 and acute coronary syndrome because it increases oxygen demand and could worsen the ischemia and increase infarction size.
• Consider immediate pacing in unstable patients with high degree AV block when IV access isn't available.(Class IIb, level of evidence C)

Don'ts

• Do not treat asymptomatic or minimally symptomatic patients, unless the rhythm is likely to progress to symptoms or become life threatening.
• 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.
• Do not use 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 as the transplanted heart lacks vagal innervation.
• Do not use atropine to treat type II second degree and third degree heart blocks since their management requires transcutaneous/transvenous pacing.