01Approach to the Critical Patient/attcp53

Immediate stabilization

›Airway and hemodynamic threats

›Hemodynamic compromise from bradycardia

›Heart rate 20 to 40 bpm

›Systolic BP < 90 mmHg

›Altered mental status from cerebral hypoperfusion

›Cardiac arrest risk

›Asystolic pauses >= 3 seconds

›Escape rate < 20 bpm

›No reliable escape rhythm in 24% of complete AV block patients

›If hemodynamically unstable, initiate transcutaneous pacing immediately

›Class I recommendation per AHA 2025 guidelines

›Sedation required in conscious patients

›Rhythm recognition priorities

›Wide QRS escape rhythm identification

›QRS >= 120 ms with bizarre morphology

›Rate 20 to 40 bpm

›AV dissociation on rhythm strip

›Infranodal vs AV nodal block distinction

›Wide QRS = infranodal block, atropine often ineffective

›Narrow QRS junctional escape = AV nodal block, atropine may help

›Dangerous ECG patterns requiring immediate pacing

›Alternating bundle branch block morphology

›QT prolongation with bradycardia and torsades risk

Monitoring and resuscitation targets

›Continuous monitoring bundle

›Continuous cardiac monitoring with telemetry

›Rhythm and rate trend

02History/hx72

Symptom presentation

›Cardinal symptoms

›Syncope or presyncope

›Most critical symptom indicating hemodynamic compromise

›Stokes-Adams attacks

›Frequency and duration

›Prodromal features

›Lightheadedness and dizziness

›Positional relationship

›Exertional trigger

›Fatigue and exercise intolerance

›Chronotropic incompetence pattern

›Functional decline timeline

›Associated symptoms

›Dyspnea

›Exertional dyspnea

›Orthopnea and paroxysmal nocturnal dyspnea

›Chest pain

›Ischemic etiology consideration

›ACS as trigger for AV block

›Palpitations

›Awareness of slow rate

›Irregular beat perception

Risk factor history

›Cardiac history

›Prior myocardial infarction

›Inferior MI associated with AV nodal block

›Anterior MI associated with infranodal block

03Physical Exam/exam52

Vital signs and general

›Hemodynamic assessment

›Heart rate

›Bradycardia 20 to 40 bpm on telemetry

›Rate may rise with atropine if AV nodal block

›Blood pressure

›Hypotension if cardiac output inadequate

›Beat-to-beat variation from AV dissociation

›Respiratory rate and oxygen saturation

›Pulmonary edema from low cardiac output

›SpO2 on room air

›General appearance

›Level of consciousness

›Altered mental status from cerebral hypoperfusion

›Presyncope posture or pallor

›Diaphoresis

›Hemodynamic instability marker

›Cardiogenic shock sign

Cardiovascular exam

›Jugular venous assessment

›Cannon A waves

›Intermittent large A waves from atrial contraction against closed tricuspid valve

›Pathognomonic of AV dissociation

›Elevated JVP

›Right heart failure from chronic bradycardia

›Volume overload

›Heart sounds

›Varying intensity of S1

04Differential Diagnosis/ddx37

Life-threatening rhythms and causes

›Complete AV block etiologies

›Degenerative conduction system fibrosis

›ICD-10 I44.2 complete atrioventricular block

›Most common cause in adults older than 65 years

›Acute inferior MI with AV nodal block

›ICD-10 I21.1 ST elevation MI inferior

›Usually transient with reperfusion

›Acute anterior MI with infranodal block

›High degree block with wide QRS escape

›Often requires urgent pacing

›Drug-induced AV block

›ICD-10 T46.0 digoxin toxicity

›May be drug-revealed rather than purely drug-induced

›Infiltrative and inflammatory causes

›Cardiac sarcoidosis

›ICD-10 D86.85 sarcoidosis of heart

›Predilection for conduction system

›Cardiac amyloidosis

›ICD-10 E85.82 cardiac amyloidosis

›Infiltration of conduction tissue

›Lyme carditis

›ICD-10 A69.20 Lyme disease unspecified

›Median resolution 6 days with range up to 42 days

Rhythm mimics

›Similar wide-complex bradycardias

›Junctional escape rhythm

›Narrow QRS at 40 to 60 bpm

05Laboratory Tests/lt46

Core metabolic and cardiac labs

›Basic metabolic panel

›Potassium

›Hyperkalemia can worsen conduction disease

›Target 4.0 to 5.0 mmol/l

›Digoxin toxicity risk increased with hypokalemia

›Calcium and magnesium

›Electrolyte abnormalities compound conduction disease

›Hypomagnesemia risk with diuretic use

›Creatinine and eGFR

›Drug dosing adjustment

›Digoxin clearance assessment

›Cardiac biomarkers

›Troponin

›ACS as cause of AV block

›Serial measurements if ischemia suspected

›BNP or NT-proBNP

›Heart failure from chronic bradycardia

›Elevated with reduced cardiac output

Drug levels and targeted labs

›Drug toxicity screen

›Digoxin level

›Toxic range > 2 nmol/l in adults

›Toxicity causes AV block

›Comprehensive medication review

›Beta-blocker and calcium channel blocker levels if overdose suspected

›Drug-induced or drug-revealed AV block distinction

›Targeted etiology labs

06Diagnostic Tests/dt65

Scoring Systems

›Risk stratification tools for bradycardia

›AHA Class I pacemaker indications criteria

›Third-degree or advanced second-degree AV block with symptomatic bradycardia

›Asymptomatic third-degree AV block with escape rate < 40 bpm

›Asymptomatic third-degree AV block with infranodal escape

›Asystolic pauses >= 3 seconds in awake patients

›AV block requiring medically necessary drugs causing symptomatic bradycardia

›JACC/HRS 2018 guideline classification

›Class I recommendation based on AHA/ACC/HRS evidence synthesis

›High-degree and complete AV block with ventricular escape warrants pacing regardless of symptoms

›Hemodynamic compromise criteria

›Rate < 40 bpm with hypotension or altered mentation

›Cardiogenic shock pattern

›Asystolic pauses with hemodynamic consequence

MRI

›Cardiac MRI indications

›Unexplained complete AV block in younger patients

›Gold standard for infiltrative cardiomyopathy detection

›Late gadolinium enhancement for sarcoidosis and amyloidosis

›Sarcoidosis evaluation

›Myocardial inflammation and fibrosis characterization

›Mid-wall or patchy enhancement pattern

›Ischemic scar assessment

›Subendocardial vs transmural infarction pattern

›Conduction tissue involvement

›Contraindications and limitations

›Implanted pacemaker or ICD requiring MRI-conditional device check

07Disposition/dispo38

Admission criteria

›All ventricular escape rhythm patients require admission

›Mandatory continuous telemetry monitoring

›Rhythm change detection

›Pause and asystole alert

›Temporary pacing capability on unit

›Transcutaneous pacing at bedside

›Transvenous pacing for hemodynamic instability

›ICU or CCU indications

›Hemodynamic instability

›Systolic BP < 90 mmHg requiring vasopressors

›Altered mental status from hypoperfusion

›Active or imminent temporary pacing requirement

›Transcutaneous pacing in place

›Awaiting transvenous pacemaker placement

›Escape rate < 30 bpm or frequent asystolic pauses

›High arrest risk

›Direct CCU monitoring

›Reversible etiology observation

›Drug-induced AV block

›50% recur and ultimately require permanent pacing

›Monitoring while drug clears

›Lyme carditis temporary pacing

›Temporary pacing needed in approximately 40% of cases

›Median resolution 6 days with range to 42 days

Discharge and transfer criteria

›Discharge criteria

›Permanent pacemaker in place with appropriate function

08Treatment/t83

Immediate pharmacological management

›Atropine

›First-line per AHA 2025 advanced cardiovascular life support guidelines

›0.5 mg IV every 3 to 5 minutes

›Maximum total dose 3 mg

›Class I recommendation for bradycardia with hemodynamic compromise

›Limitations

›Often ineffective for infranodal block

›Wide QRS escape with ventricular origin will not respond reliably

›Do not give to heart transplant patients

›Contraindications

›Denervated transplanted heart risk of paradoxical block or sinus arrest

›Known infranodal block pattern on ECG

›Catecholamine infusions for refractory bradycardia

›Epinephrine infusion

›2 to 10 mcg per minute IV infusion

›Titrate to heart rate and BP response

›Bridge to pacing

›Dopamine infusion

›5 to 20 mcg per kg per minute IV infusion

›Titrate to hemodynamic targets

›Monitor for arrhythmia at higher doses

›Isoproterenol

›May improve infranodal escape rates via catecholamine effect

›2 to 10 mcg per minute IV infusion

›Use with caution in ischemic etiology

Transcutaneous and transvenous pacing

›Transcutaneous pacing

›Immediate bridge for hemodynamic compromise

›Anterior-posterior pad placement preferred for consistent capture

›Start at 200 mA and adjust to minimum effective output

›Electrical capture confirmed by wide QRS paced complex and pulse

›Sedoanalgesia for conscious patients

›Midazolam 1 to 2.5 mg IV titrated

›Fentanyl 1 mcg per kg IV for analgesia

›Ketamine 0.5 to 1 mg per kg IV as alternative

›Temporary transvenous pacing

›Indications

›Hemodynamic instability not corrected by pharmacotherapy

›Bridge to permanent pacemaker implantation

›Atropine failure in symptomatic patient

›Procedure

›Right internal jugular or subclavian access preferred

›Fluoroscopy or ECG guidance for lead positioning

›Target rate 60 to 70 bpm initially

›Monitoring post-placement

›Threshold testing and sensing threshold

›CXR to confirm lead position and exclude pneumothorax

Definitive treatment

›Permanent pacemaker implantation

›Class I indications from 2018 ACC/AHA/HRS Bradycardia Guidelines

›Third-degree or advanced second-degree AV block with symptomatic bradycardia

›Asymptomatic third-degree AV block with escape rate < 40 bpm

›Asymptomatic third-degree AV block with infranodal escape

›Asystolic pauses >= 3 seconds in awake patients

›AV block requiring medically necessary drugs causing symptomatic bradycardia

›Device selection

›Dual-chamber pacing preferred to maintain AV synchrony

›CRT if reduced ejection fraction and bundle branch block pattern

›MRI-conditional device for patients likely to need future MRI

›Post-implantation care

›Wound check at 1 to 2 weeks

›Device interrogation at 1 month then every 6 to 12 months

›Reversible cause treatment

›Digoxin toxicity

›Digoxin-specific Fab antibodies

›Dose based on estimated total body load or empiric 10 vials

›Monitor for rebound toxicity

›Drug discontinuation

›Stop all causative AV nodal blocking agents

›Monitor for 50% recurrence rate suggesting underlying conduction disease

›Lyme carditis treatment

›Doxycycline 100 mg PO twice daily for 14 to 21 days for outpatient-managed mild cases

›Ceftriaxone 2 g IV daily for hospitalized patients with high-degree block

›Temporary pacing until AV block resolves

›Hyperkalemia correction

›Calcium gluconate 10 mL of 10% solution IV for cardiac membrane stabilization

›Insulin and dextrose for cellular potassium shift

›Sodium bicarbonate if severe acidosis

Medications to avoid

›Contraindicated drugs in ventricular escape rhythm

›AV nodal blockers without functioning pacemaker

›Verapamil and diltiazem potentially harmful in wide-complex rhythms

›Beta-blockers worsen infranodal conduction

›Atropine in heart transplant recipients

›Paradoxical sinus arrest or worsening block risk

›Denervated heart does not respond normally

09Special Populations/sp48

Pregnancy

›Pregnancy considerations

›Congenital complete heart block in neonates

›Associated with maternal anti-Ro/SSA antibodies in neonatal lupus

›Surveillance echocardiography during pregnancy in antibody-positive mothers

›Acquired AV block management in pregnancy

›Temporary pacing preferred over pharmacotherapy when possible

›Atropine relatively safe in short term for hemodynamic compromise

›Pacemaker implantation in pregnancy

›Generally safe when indicated

›Lead-free fetal radiation techniques preferred

›Multidisciplinary obstetric and cardiology planning

›Hemodynamic goals

›Maintain adequate cardiac output for uteroplacental perfusion

›Left lateral decubitus positioning to improve venous return

Geriatric

›Older adult specific considerations

›Degenerative fibrosis predominant etiology

›Most common cause of AV block in adults over 65 years

›Lev disease fibrosis of left side of cardiac skeleton

›Lenegre disease progressive fibrosis of conduction bundle

›Polypharmacy and drug interactions

›Multiple AV nodal blocking agents more common in elderly

›Renal impairment increases drug toxicity risk especially digoxin

›QT prolongation risk from multiple agents

›Pacemaker outcomes

›Older patients benefit equally from permanent pacing

›Device longevity and lead revision planning

10Background/b62

Epidemiology

›Incidence and prevalence

›Ventricular escape rhythm as consequence of complete AV block

›Complete AV block prevalence approximately 0.02 to 0.04% in general population

›Increases with age

›Incidence increases sharply after age 70 years

›Etiology distribution in adults

›Degenerative fibrosis accounts for majority of acquired complete AV block

›Coronary artery disease second most common cause

›Drug-induced AV block increasing with polypharmacy

›Outcomes data

›24% of patients with complete AV block have no reliable escape rhythm

›Mean 7 seconds to symptoms in patients without reliable escape

›Infranodal escape carries higher sudden death risk than junctional escape

Pathophysiology

›Pacemaker hierarchy failure

›Normal cardiac automaticity hierarchy

›Sinus node intrinsic rate 60 to 100 bpm

›AV junction intrinsic rate 40 to 60 bpm

›Ventricular myocardium and Purkinje fibers intrinsic rate 20 to 40 bpm

›Ventricular escape activation

›Passively emerges when all higher pacemakers fail or are blocked

›Wide QRS from abnormal ventricular activation sequence

›Irregular depolarization pattern through working myocardium

›AV dissociation mechanism

›P waves continue at sinus rate independent of QRS complexes

›P-wave rate exceeds QRS rate in complete AV block

›Cannon A waves from atrial contraction against closed AV valves

11Patient Discharge Instructions/pdi36

copy discharge instructions

›Ventricular escape rhythm and heart pacemaker home care

›Your heart has been treated for a very slow dangerous heart rhythm

›A permanent pacemaker has been implanted to control your heart rate

›The pacemaker keeps your heart beating at a safe rate

›Pacemaker wound care

›Keep the incision site dry for 48 hours after implant

›No scrubbing or submerging in water until fully healed

›Watch for redness swelling warmth or discharge from the wound

›No heavy lifting or overhead arm activity for 4 to 6 weeks on the pacemaker side

›Activity restrictions

›No driving until cleared by your cardiologist due to syncope risk

›Typically 1 week minimum after pacemaker if no prior syncope

›Follow provincial or state driving regulations

›Avoid contact sports and magnetic resonance environments unless told safe by your doctor

›No direct contact with strong magnetic fields or large electric motors

›Medications

›Do not stop or start heart medications without your doctor's approval

›Bring complete medication list to all appointments

›Avoid any new medications including over the counter without checking with your doctor

›Warning signs to return to ER immediately

›Syncope or loss of consciousness

›Near-fainting or severe dizziness

›Palpitations or sensation of very slow or irregular heartbeat

›Chest pain or pressure

›New shortness of breath at rest

›Confusion or new unusual weakness

›Pacemaker wound signs including redness fever or separation

12References/r19

Guidelines and key sources

›Primary guidelines

›2018 ACC/AHA/HRS Guideline on Evaluation and Management of Bradycardia and Cardiac Conduction Delay

›Kusumoto FM et al. Heart Rhythm 2019

›Journal of the American College of Cardiology 2019

›2025 AHA Guidelines for CPR and Emergency Cardiovascular Care Part 9 Adult Advanced Life Support

›Wigginton JG et al. Circulation 2025

›2012 ACCF/AHA/HRS Focused Update on Device-Based Therapy

›Epstein AE et al. Journal of the American College of Cardiology 2013

›Drug-Induced Arrhythmias AHA Scientific Statement

›Tisdale JE et al. Circulation 2020

›Supporting evidence

›Mangrum JM and DiMarco JP. Evaluation and Management of Bradycardia. NEJM 2000

›Rosenheck S et al. Ventricular Escape Rhythm in Complete AV Block. Pacing and Clinical Electrophysiology 1993

›Sfairopoulos D et al. Drug-Induced or Drug-Revealed AV Block. Journal of Cardiovascular Electrophysiology 2025

›Aldaas OM et al. Pacemakers. NEJM Evidence 2025

›Coding references

›ICD-10 I44.2 complete atrioventricular block

›ICD-10 I44.30 unspecified atrioventricular block

›SNOMED CT complete atrioventricular block disorder concept

Evidence & Review

Evidence & Review