Bradyarrhythmias, Emergency Medicine

Basics

Description

Ventricular heart rate <60 beats/min:
- Sinus bradycardia can be normal variant.
- All other rhythms are pathologic.
May be asymptomatic or have hypotension, altered mental status, fatigue, nausea, syncope.
Treatment varies based on ECG findings and clinical status.

Etiology

Idiopathic:
- Healthy athletes
Intrinsic cardiac disorders:
- Sinus node dysfunction such as sick sinus syndrome (may alternate with tachycardia)
- Atrioventricular block:
- Junctional or ventricular escape rhythm
- Infiltrative disease:
  - Amyloidosis, sarcoidosis, hemochromatosis
- Collagen vascular disease:
  - Systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis
- Anatomic abnormalities:
  - Congenital, postsurgical, post-transplant, postradiation
- Muscular disorders:
  - Myotonic muscular dystrophy
- Trauma with myocardial contusion
Extrinsic disorders:
- Cardiac injury and infarction:
  - RCA infarction can cause sinus bradycardia.
  - LAD infarction can cause high-grade block.
- Acidemia
- Medication and toxin effects:
  - β-Blockers, calcium channel blockers, digoxin, clonidine, antiarrhythmics, lithium, organophosphate
- Electrolyte abnormalities:
  - Hypo-/hyperkalemia, hypoglycemia, hypo-/hypercalcemia, hypermagnesemia
- Vital sign abnormalities:
  - Hypoxia, hypothermia, hypotension, HTN
- Endocrine abnormalities:
  - Hypothyroidism
- Infectious disease:
  - Lyme disease, Chagas disease, diphtheria, endocarditis, myocarditis
- Neurologic disorders:
  - Increased intracranial pressure, increased vagal tone, carotid sinus hypersensitivity, spinal cord injury
  - Can be triggered by micturition, defecation, coughing, vomiting, ocular pressure, or other Valsalva maneuvers

Hypoxia is the most common etiology in children. �
Maternal SLE can result in congenital complete heart block. �

Diagnosis

Signs and Symptoms

Often asymptomatic
Lightheadedness, confusion, fatigue, decreased level of consciousness
Dyspnea, cyanosis, pallor
Chest pain/pressure, diaphoresis
Hypotension
Syncope
Hypothermia
Cardiac arrest

History

Medication changes, especially cardiac
Urine output:
- Hypokalemia with diuretics
- Hyperkalemia with renal failure
Trauma:
- Intracranial injury
- Myocardial contusion
Activity at time of symptom onset:
- Increased vagal tone

Physical Exam

Respiratory status
Perfusion status, pulses
Regular vs. irregular cardiac rhythm
Mental status, thorough neuro exam
Body habitus, skin/hair/nails
Temperature

Essential Workup

ECG and continuous cardiac monitoring
Pulse oximetry
BP monitoring
Glucose and electrolytes

Diagnosis Tests & Interpretation

Lab

Serum glucose
Serum electrolytes
BUN and creatinine
Cardiac enzymes
Digoxin level
Thyroid function tests
ANA, RF, other rheumatologic testing
Lyme titers
Iron levels

Imaging

CXR
CT head if patient has altered mental status

Diagnostic Procedures/Surgery
EKG: �

Sinus bradycardia:
- P wave before every QRS, QRS after every P wave, usually narrow QRS
Sinoatrial block: Abnormal conduction between sinus node and atrium
Sinus arrest:
- No sinus activity, no P waves
Atrioventricular block: Abnormal conduction between atria and ventricles:
- 1st degree: PR >0.2 sec, every P wave conducts a QRS complex
- 2nd-degree type I, Mobitz I, Wenckebach: Progressive prolongation of PR interval with eventual dropped QRS, grouped beats
- 2nd-degree type II, Mobitz II: Stable PR interval and intermittent dropped QRS, high risk of degeneration into 3rd-degree block
- 3rd-degree, complete heart block: Complete dissociation of atrial and ventricular activity, constant P-P interval and constant R-R interval, but no relation between the 2, unstable rhythm
Junctional rhythm:
- Loss of atrial conduction, AV pacemaker "escapes"� at 40-60 bpm
- Retrograde P waves may occur before, during, or after QRS, and QRS can be any duration
Idioventricular rhythm:
- Loss of both SA and AV nodal activity, bundle of His or Purkinje network takes over at 30-40 bpm
- QRS always >0.12 sec
- Preterminal rhythm

Differential Diagnosis

Normal variant
Cardiac ischemia
Medication toxicity
Pacemaker malfunction
Hypoxia
Hypothermia
Electrolyte abnormality
Renal failure
Hypothyroidism
Infection
Rheumatologic disease
Neuromuscular disease
Increased intracranial pressure
Myocardial contusion

Treatment

Pre-Hospital

Treat the patient, not the heart rate
Oxygen:
- For all patients, especially children
If hypothermic, warm the patient and give magnesium:
- Do NOT pace; move patient gently as rough handling can induce v-fib.
Atropine or epinephrine:
- Only with hypotension or altered mental status
- Often ineffective or harmful in 3rd-degree block
Transcutaneous pacing:
- If other measures ineffective

Initial Stabilization/Therapy

ABCs
Oxygen therapy
Apply pacing pads and continuous cardiac monitoring
IV access

Ed Treatment/Procedures

Asymptomatic bradycardia:
- Monitor while continuing workup
Symptomatic or unstable bradycardia:
- Oxygen
- Atropine:
  - Symptomatic sinus bradycardia and symptomatic 1st- and 2nd-degree type I AV blocks
  - Usually ineffective for high-grade AV blocks
- Epinephrine
- Transcutaneous pacing
- Transvenous pacing if transcutaneous pacing unsuccessful
Find and treat underlying cause:
- Hypoglycemia:
  - D50
- Hypocalcemia:
  - Calcium gluconate
- Hypercalcemia:
  - NS +/- Lasix
- β-Blocker or calcium channel blocker overdose:
  - Glucagon, calcium gluconate, insulin, D50, intralipid emulsion
- Hyperkalemia:
  - IV calcium, insulin with D50, albuterol, bicarb if acidotic, Lasix, Kayexalate, dialysis
- Hypokalemia:
  - Potassium
- Digoxin toxicity:
  - Digibind (Digoxin immune Fab)
- MI:
  - ASA, Plavix, heparin, statin, cath lab
- Hypothyroidism:
  - Levothyroxine
- Hypothermia:
  - Warm O2, warm IVF, Bair Hugger, blankets, warming lights, consider warm bladder and gastric irrigation, cardiopulmonary bypass
- Infection:
  - Targeted antibiotics, antivirals, or antifungals
- Myocardial contusion:
  - Supportive care
- Increased intracranial pressure:
  - Mannitol, neurosurgical consult
- Pacemaker malfunction:
  - Interrogate pacemaker, cardiology consult
- Idiopathic:
  - Cardiology consult for ICU admission and pacemaker placement

Medication

Atropine: 0.5-1 mg (peds: 0.02 mg/kg; min. 0.1 mg) IV q3-5 min; max. 3 mg or 0.04 mg/kg
Calcium gluconate: 1,000 mg (peds: 60 mg/kg) IV q3-5min, max. 3 g
D50: 1-2 amps (peds: D10 or D25 2-4 mL/kg) IV
Digoxin immune Fab: Dose varies with amount of digoxin ingested, average 6 vials (peds: Average dose, 1 vial) IV bolus; see package insert
Epinephrine: 0.1-0.5 mg (peds: 0.01-0.03 μg/kg/min) IV q3-5min; infusion 2-10 μg/min (peds: 0.1-1 μg/kg/min) IV
Glucagon: 3-5 mg (peds: 0.05 mg/kg) IV, can repeat once; infusion 1-5 mg/h (peds: 0.07 mg/kg/h) IV for BB or CCB overdose
Insulin regular: 10 U (peds: 0.1 U/kg) IV � 1 with glucagon for BB or CCB overdose. Higher doses may be appropriate after tox. consult.

First Line
Atropine, epinephrine, pacing �
Second Line
Treatment for specific disorders �

Follow-Up

Disposition

Admission Criteria

ICU:
- Hemodynamically unstable bradycardia
- 2nd-degree type II or 3rd-degree block
- Transcutaneous or transvenous pacer
- Pressors
- Acute myocardial infarction or ischemia
Telemetry:
- Hemodynamically stable bradycardia

Discharge Criteria
Asymptomatic sinus bradycardia �
Issues for Referral

All patients without existing primary care physicians should be referred to a generalist for follow-up as needed.
1st- and 2nd-degree type I AV block need cardiology referral.
Severe endocrine, rheumatologic, infectious, renal, or neurologic disorders require appropriate specialty referral.

Follow-Up Recommendations

Minor lab abnormalities that do not require admission require PCP follow-up.
All patients except asymptomatic sinus bradycardia require cardiology follow-up.
Specific disorders require appropriate specialty follow-up.

Pearls and Pitfalls

Asymptomatic sinus bradycardia is the ONLY potentially "normal"� bradycardia. All others require treatment or follow-up.
O2, O2 sat, IV, ECG, cardiac monitor for all patients.
Pediatric bradycardia is likely secondary to hypoxia.
Have pacing pads available for all symptomatic patients.
The most important treatment targets the underlying cause.

Additional Reading

Dovgalyuk �J, Holstege �C, Mattu �A, et al. The electrocardiogram in the patient with syncope. Am J Emerg Med. 2007;25:688-701.
Haro �LH, Hess �EP, Decker �WW. Arrhythmias in the office. Med Clin North Am. 2006;90:417-438.
Mottram �AR, Svenson �JE. Rhythm disturbances. Emerg Med Clin North Am. 2011;29(4):729-746.
Ufberg �JW, Clark �JS. Bradydysrhythmias and atrioventricular conduction blocks. Emerg Med Clin North Am. 2006;24:1-9.

Codes

ICD9

427.81 Sinoatrial node dysfunction
427.89 Other specified cardiac dysrhythmias

ICD10

I49.5 Sick sinus syndrome
I49.8 Other specified cardiac arrhythmias

SNOMED

421869004 bradyarrhythmia (disorder)
444605001 Symptomatic sinus bradycardia
74615001 Tachycardia-bradycardia (disorder)
251162005 Atrio-ventricular-junctional (nodal) bradycardia (disorder)

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