›Monitor for ventricular ectopy
›Epinephrine infusion
›Epinephrine 2-10 mcg/min IV continuous infusion
›Titrate to haemodynamic response
›Start at 2 mcg/min; increase every 5 minutes
›Preferred in cardiac arrest or peri-arrest with bradycardia
›Isoproterenol infusion
›Isoproterenol 1-20 mcg/min IV
›Pure beta-1 agonist — increases AV nodal conduction rate
›Avoid if coronary ischaemia suspected (increases myocardial oxygen demand)
›Useful in Lyme carditis-associated bradycardia as bridge to pacing
›Aminophylline
›Aminophylline 250 mg IV bolus over 5-10 minutes
›Specific indication: acute inferior MI with refractory AV nodal block
›Adenosine antagonism mechanism
›Less commonly used; reserve for atropine and pacing-refractory cases
Temporary transvenous pacing
›Indications for temporary transvenous pacing (TVP)
›Transcutaneous pacing failure or inadequate patient tolerance
›Haemodynamic instability requiring more reliable rate control
›Bridge to permanent pacemaker in recurrent symptomatic block
›Acute MI with persistent high-degree block
›Approach
›Right internal jugular or subclavian venous access preferred
›Fluoroscopy or ECG-guided lead positioning in right ventricle apex
›Rate: set to 60 bpm minimum; increase if haemodynamic compromise
›Output 2-3x capture threshold for safety margin
Reversal of iatrogenic causes
›Medication dose reduction or discontinuation
›Beta-blockers — taper dose if causing symptomatic bradycardia
›Do not abruptly discontinue post-MI (rebound ischaemia risk)
›Digoxin — hold doses; IV digoxin-specific Fab fragments for severe toxicity
›Digibind: 10-20 vials IV depending on estimated toxic load
›Non-dihydropyridine CCBs — dose reduce or switch to dihydropyridine
›Electrolyte correction
›Hyperkalaemia: IV calcium gluconate 10 mL of 10% solution for cardiac protection
›Insulin 10 units IV + 50 mL of 50% dextrose for potassium redistribution
›Hypomagnesaemia: magnesium sulphate 2 g IV over 10-15 minutes
›Repeat dose if symptomatic and level < 0.7 mmol/L
Treating underlying cause
›Lyme carditis treatment
›Mild to moderate (PR > 300 ms, symptomatic): IV ceftriaxone 2 g daily
›Duration: 14-21 days IV then oral completion
›Oral alternative for mild disease: doxycycline 100 mg twice daily for 21 days
›Amoxicillin 500 mg three times daily as alternative
›AV block usually resolves within days to weeks with appropriate antibiotics
›Acute inferior MI management
›Primary PCI for acute STEMI — reperfusion reverses ischaemic AV block
›AV block usually resolves within 24-72 hours post-reperfusion
›Temporary pacing if haemodynamic compromise before PCI
›Hypothyroidism treatment
›Levothyroxine replacement — start at 25-50 mcg daily in elderly
›Conduction normalizes over weeks with adequate thyroid replacement
›Indications for permanent pacemaker (PPM)
›Symptomatic Mobitz I with confirmed symptom-rhythm correlation
›Class IIa recommendation — ACC/AHA/HRS 2018
›Quality-of-life impairment despite medication adjustment
›Infranodal Mobitz I on EP study (prolonged HV interval > 70 ms)
›Class IIa recommendation regardless of symptoms
›Contraindications to PPM
›Asymptomatic Mobitz I at AV nodal level — Class III: Harm (do not pace)
›Per 2018 ACC/AHA/HRS guidelines — pacing not indicated
›Reversible and fully corrected cause (medication, Lyme, inferior MI)
›Device selection
›Dual-chamber pacemaker (DDD) preferred for physiological pacing
›Preserves AV synchrony; avoids pacemaker syndrome
›Single-chamber rate-responsive (VVIR) acceptable if permanent AF
›CRT-D consideration if LVEF < 35% with expected high pacing burden