Bradyarrhythmias, Emergency Medicine

Basics

Description

- Idiopathic: - 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

- Acidemia - Medication and toxin effects: - β-Blockers, calcium channel blockers, digoxin, clonidine, antiarrhythmics, lithium, organophosphate

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

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:
Intrinsic cardiac disorders:Sinus node dysfunction such as sick sinus syndrome (may alternate with tachycardia)Atrioventricular block:Junctional or ventricular escape rhythmInfiltrative disease:Amyloidosis, sarcoidosis, hemochromatosisCollagen vascular disease:Systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritisAnatomic abnormalities:Congenital, postsurgical, post-transplant, postradiationMuscular disorders:Myotonic muscular dystrophyTrauma with myocardial contusion
Extrinsic disorders:Cardiac injury and infarction:RCA infarction can cause sinus bradycardia.LAD infarction can cause high-grade block.AcidemiaMedication and toxin effects:β-Blockers, calcium channel blockers, digoxin, clonidine, antiarrhythmics, lithium, organophosphateElectrolyte abnormalities:Hypo-/hyperkalemia, hypoglycemia, hypo-/hypercalcemia, hypermagnesemiaVital sign abnormalities:Hypoxia, hypothermia, hypotension, HTNEndocrine abnormalities:Infectious disease:Lyme disease, Chagas disease, diphtheria, endocarditis, myocarditisNeurologic disorders:Increased intracranial pressure, increased vagal tone, carotid sinus hypersensitivity, spinal cord injuryCan be triggered by micturition, defecation, coughing, vomiting, ocular pressure, or other Valsalva maneuvers

Hypoxia is the most common etiology in children. пїЅ

Maternal SLE can result in congenital complete heart block. пїЅ

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 diureticsHyperkalemia with renal failure
Trauma:Intracranial injuryMyocardial contusion
Activity at time of symptom onset:

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: пїЅ

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 complex2nd-degree type I, Mobitz I, Wenckebach: Progressive prolongation of PR interval with eventual dropped QRS, grouped beats2nd-degree type II, Mobitz II: Stable PR interval and intermittent dropped QRS, high risk of degeneration into 3rd-degree block3rd-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"пїЅ at 40-60 bpmRetrograde 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 bpmQRS always >0.12 secPreterminal 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 statusOften 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:OxygenAtropine:Symptomatic sinus bradycardia and symptomatic 1st- and 2nd-degree type I AV blocksUsually ineffective for high-grade AV blocksEpinephrineTranscutaneous pacingTransvenous pacing if transcutaneous pacing unsuccessful
Find and treat underlying cause:Hypoglycemia:Hypocalcemia:Hypercalcemia:β-Blocker or calcium channel blocker overdose:Glucagon, calcium gluconate, insulin, D50, intralipid emulsionHyperkalemia:IV calcium, insulin with D50, albuterol, bicarb if acidotic, Lasix, Kayexalate, dialysisHypokalemia:Digoxin toxicity:Digibind (Digoxin immune Fab)MI:ASA, Plavix, heparin, statin, cath labHypothyroidism:Hypothermia:Warm O2, warm IVF, Bair Hugger, blankets, warming lights, consider warm bladder and gastric irrigation, cardiopulmonary bypassInfection:Targeted antibiotics, antivirals, or antifungalsMyocardial contusion:Increased intracranial pressure:Mannitol, neurosurgical consultPacemaker malfunction:Interrogate pacemaker, cardiology consultIdiopathic: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 Ојg/kg/min) IV q3-5min; infusion 2-10 Ојg/min (peds: 0.1-1 Ојg/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 пїЅ 1 with glucagon for BB or CCB overdose. Higher doses may be appropriate after tox. consult.

First Line

Atropine, epinephrine, pacing пїЅ

Second Line

Treatment for specific disorders пїЅ

Follow-Up

Disposition

Admission Criteria

ICU:Hemodynamically unstable bradycardia2nd-degree type II or 3rd-degree blockTranscutaneous or transvenous pacerPressorsAcute myocardial infarction or ischemia
Telemetry:Hemodynamically stable bradycardia

Discharge Criteria

Asymptomatic sinus bradycardia пїЅ

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"пїЅ 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 пїЅJ, Holstege пїЅC, Mattu пїЅA, et al. The electrocardiogram in the patient with syncope. Am J Emerg Med. 2007;25:688-701.
Haro пїЅLH, Hess пїЅEP, Decker пїЅWW. Arrhythmias in the office. Med Clin North Am. 2006;90:417-438.
Mottram пїЅAR, Svenson пїЅJE. Rhythm disturbances. Emerg Med Clin North Am. 2011;29(4):729-746.
Ufberg пїЅJW, Clark пїЅJS. 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)