FRCA Notes

Arrhythmia Post-Cardiac Surgery

Resources

  • Arrhythmia, particularly AF, is common after cardiac surgery
  • The erratic atrial contraction caused by these dysrhythmias is associated with a host of negative sequelae:
Negative sequelae of arrhythmia post-cardiac surgery
↓ cardiac output (by 15-30%), especially in those with poor ventricular compliance
Risk of stroke or other embolic phenomena
↑ risk of bleeding (5%)
↑ risk of major neurological events (4.5%)
Prolonged CICU & hospital stay
↑ in-hospital mortality
↑ long-term mortality

  • Up to 50% of patients will develop either AF or atrial flutter post-operatively
  • The incidence depends on the surgery undertaken:
    • Combined CABG/valve surgery: 40-50%
    • Isolated valve surgery: 30%
    • Isolated CABG: 25%
    • Cardiac transplant: lowest incidence
  • The majority occur within 48hrs of surgery, but with treatment resolve over the ensuing 24hrs or so

  • AV nodal block is less common
    • MVR: 24%
    • AVR: 10%
    • CABG: 2.4%

  • Ventricular arrhythmias are less common than atrial arrhythmias


Surgical Medical
Atrial injury during cannulation Use of post-operative catecholamines
Myocardial ischaemia-reperfusion Hypokalaemia
Prolonged CPB Hypomagnesaemia
Injury to conducting system Hypothermia
Existing conduction abnormalities
  • Conduction issues post-operatively may be:
    • Temporary e.g. post-operative myocardial oedema can interfere with AVN conduction
    • Permanent e.g. surgical resection through the conducting system

Address underlying issues

  • Correct:
    • Hypoxia
    • Hypercarbia
    • Electrolyte disturbances
  • Other causes of myocardial ischaemia e.g. graft failure
  • Consider removing cardiac irritants such as drains

Rhythm control

  • Rate control is rarely an option as flutter may transform to AF

  • Synchronised DCCV is preferred for rhythm control
  • Benefits from rapidity (vs. amiodarone that may take hours)

  • Atrial pacing is also a viable option (see below)
  • Approximately 18% of patients admitted to CICU require pacing

Anticoagulation

  • Patients may be heparinised following cardiac surgery anyway
  • Options for ongoing anticoagulation include:
    • Warfarin, which reduces thromboembolic risk by 35%
    • DOACs, which are associated with lower risk of bleeding and major neurological events than warfarin, but no mortality difference

  • A small proportion of patients will require pacing to help liberate them from CPB
  • It is otherwise difficult to establish pre-/intra-operatively who will require pacing during the post-operative period
  • As such, epicardial pacing leads are often placed; two RA leads and two RV leads
  • This facilitates pacing of the atria, ventricles or both
  • Pacing wires are typically removed from day 4 post-operatively onwards

Modes

  • Exact mode of pacing used following cardiac surgery depends on the operation performed and patient factors
    • Typical modes following cardiac surgery include DDD, VVI or AAI (see page on pacemakers)
  • Pacing rate is usually set at 90bpm as this optimises cardiac output and myocardial perfusion

  • For managing post-operative flutter:
    • Pacing rate 10-15bpm higher than the flutter rate
    • If the ventricular rate rises to match the atrial rate (i.e. the rhythm is entrained), then the pacemaker frequency can be reduced
    • This may lead to conversion to sinus rhythm (or AF)

Complications of epicardial pacing

  • Failure to pace
  • Undersensing
  • Oversensing
  • R-on-T induced ventricular arrhythmia
  • Pacemaker-mediated tachycardia
  • Pacemaker crosstalk (between temporary epicardial pacemaker and existing PPM)

  • Microshock and precipitation of VF
  • Cardiac tamponade during removal (<0.02%)
  • Damage to coronary grafts/anastamoses
  • ECG monitors filtering out the high frequency pacing spikes, giving the illusion that the patient isn't being paced

Transition to permanent pacing

  • Typically indications include: Mobitz II heart block, complete heart block, AF with inadequate ventricular response or sinus node dysfunction
  • Risk factors for requiring permanent post-operative pacing:
Patient factors Surgical factors
Advanced age CPB (vs. no CPB)
Pre-existing conduction abnormality/arrhythmia Prolonged CPB
Higher EuroSCORE Type of surgery (MVR > AVR > CABG)
Comorbidities (DM, pulm. HTN, renal failure) More extensive surgery e.g. two valves done
Reduced LVEF Inadequate intra-operative myocardial protection
Aortic root abscess Re-do operation