Post-op AF

Note that post-op atrial fibrillation and atrial flutter can be managed the same, according to UTD

Epidemiology

• Incidence 0.4-3% after non-cardiac surgery
• Incidence peaks post-op day 2

Secondary precipitant

• Always consider missed medication
• Infection/systemic inflammation
• Sympathetic activation in general
• Pain
• Low serum magnesium/other electrolytes
• Anaemia
• Hypothermia
• Hypoxia
• Hypervolaemia
• Acidosis
• Acute MI
• Acute alcohol consumption
• Thyrotoxicosis
• Acute pericardial disease
• Acute PE
• Other acute pulmonary pathology
• Caffeine is not proven to increase risk

Classification

• Unstable
  • Hypotension (for which AF is suspected to be causal or contributory, and standard therapy to treat other underlying causes has failed)
  • Altered mental status
  • Ischaemia
  • Heart failure
  • Cardiogenic shock
  • Very rapid ventricular rates (accessory pathway)

Investigation/initial management

• ECG
• Bloods including electrolytes, free T4, TSH
• Troponin if clinical suspicion for ACS or ECG evidence of cardiac ischaemia, or uncertainty thereof
• Septic screen including CXR
• Fix reversible causes above

Drug options

• Amiodarone
  • Rate control and rhythm control (can be a problem if not anticoagulated)
  • Contraindications
    • Sino-atrial block
    • Severe hypotension
    • Thyroid disease
    • CCF
    • Pregnancy and breastfeeding
• Flecainide
  • Contraindications
    • Atrial flutter
    • CCF
    • Structural heart disease
    • Recent MI
• Beta-blockers
  • Indications
    • Preferred agents when AF is associated hyper-adrenergic states
  • Contraindications
    • Asthma/COPD
    • Uncontrolled heart failure
    • Sick sinus syndrome
    • Heart block
    • Hypotension (approx <100)
    • Severe peripheral vascular disease
    • Pregnancy and breastfeeding
• Calcium channel blockers
  • Contraindications
    • Heart failure
    • Hypotension
    • Sick sinus syndrome
    • Heart block
    • AF with WPW
    • VT
    • Pregnancy and breastfeeding
    • Already on beta-blocker
• Digoxin
  • Popular for long-term rate control, but slow response in acute setting (peak response at least 6 hours)
  • Mostly has a role in AF with heart failure
  • Often used in combination with beta blockers or CCBs - works synergistically
  • Doesn't tend to drop BP

Initial management

• Approach
  • Rate-control strategy first, unless unstable and successful ventricular rate control cannot be achieved
  • Avoid RVR and the possibility of ensuing cardiac ischaemia
  • HR target of <120 is reasonable post-op
  • Indications for rhythm control:
    • Symptomatic AF despite good rate control
    • Rate control difficult to achieve
    • Patients unlikely to have a recurrence of AF (younger, less comorbidities, small left atrium)
    • Consider when good reason to avoid anticoagulation
  • >50% with new post-op AF will convert to sinus rhythm within 24 hours
    • If this occurs, no need for further management, but should have outpatient Holter and TTE
• For rate control
  • Metoprolol 25mg PO BD (75mg max; can start with 12.5mg BD in a stable patient sometimes, particularly if there might be chronicity to AF and you’d like to start slowly) or 5mg IV (in increments up to 15mg - not good on ward) OR
  • Amiodarone 300mg IV (up to 5mg/kg) OR
  • Digoxin 0.25mg IV every two hours, to a total dose of 1.5mg, then 0.125-0.375mg IV daily
  • Calcium channel blocker or a second agent at discretion of cardiology
• For rhythm control (unstable patient, or other indication for rhythm control)
  • IV amiodarone 300mg (up to 5mg/kg) or diltiazem/flecainide)
  • Synchronised DCR (requires peri-procedural anticoagulation and then for 4/52 afterwards)
• Specific situations
  • Able to give PO, stable - PO metoprolol, with consideration of digoxin in CCF, or PO amiodarone if second agent is required
    • Generally worth trying PO metoprolol first, even if absorption is considered to be borderline or questionable, as long as the patient is stable
  • Unable to give PO, stable on ward - IV digoxin
  • Able to give PO, unstable - IV amiodarone and ICU
  • Unable to give PO, unstable - IV amiodarone and ICU

Subsequent management

• Approach
  • Re-evaluate rate control vs rhythm control
    • Rhythm - amiodarone 200mg BD for one month, then 200mg daily
    • Rate - metoprolol 25mg BD, or amiodarone same dose as above
• Anticoagulation
  • If already on it, restart when safe
  • Single episode AF lasting <48 hours: no anticoagulation unless other high-risk features
  • Multiple episodes of AF or a single episode lasting >48 hours: anticoagulation for four weeks if CHA2DS2-VASc = 2 or more
  • Reassess after four weeks and continue anticoagulation if there are recurrences after four weeks
• Telemetry
  • Definitely needed
    • Significant bradycardia <40bpm or pauses
    • Use of a second agent
  • Ideal but not mandatory
    • Syncope
    • Unexplained collapse
    • Non-sustained ventricular arrhythmias
  • Other patients do not need telemetry, according to Austin protocol
• CCU
  • Ischaemic chest pain
  • Significant elevation in troponin
• TTE
• Cardiology F/U