202501051424

Status:

Tags: Cardiology

Peri-operative atrial fibrillation

Postoperative atrial fibrillation is defined as AF that occurs after any surgery, typically developing within 7 days, with the peak onset typically around 48 h

Postoperative AF a/w

• ↑ morbidity and mortality,
• ↑ LOS in hospital & ICU,
• ↑ readmission rate,
• ↑ healthcare costs.

Complications a/w POAF include

• thromboembolic events (including stroke),
• perioperative cardiac complications
  • MI
  • CHF

Pathophysiology

not fully understood

↑ sympathetic nervous system activation from surgical stress or pain, with release of catecholamines, is a significant mechanism

Other contributory factors may include

• direct surgical irritation or injury,
• hyper- or hypovolaemia,
• intraoperative hypotension,
• anaemia,
• hypoxaemia,
• hypercarbia
• metabolic imbalances

Hypoxaemia → direct cellular ischaemia → altering atrial conduction velocities, refractoriness and ↑ anisotropy

pulmonary vasoconstriction caused by hypoxaemia, or alternatively hypercarbia, leads to ↑ right heart pressures and atrial dilation which contributes to altered conduction through atrial tissue and dispersion of electrical activity

Risk factors

Pre-op

• Advanced age
• Male
• High BMI
• Hypertension
  • ↑ LAP → LA remodelling & dilation
• Diabetes mellitus
• OSAS
• Pre-existing cardiac disease
  • Low LVEF
  • CAD / CMP / CHF / valvular
• Hepatic dysfunction
• Elevated MELD score
• Renal dysfunction
  Intra-op
• Type of surgery
  • Cardiac
    • Isolated CABG
    • Isolated valve
    • Mitral highest risk
    • Combined CABG + valve
  • Open abdominal
• Use of cardiopulmonary bypass
  • duration of myocardial ischaemia
  • cardioplegia
  • iatrogenic atrial injury from cannulation
• Longer aortic cross-clamp time
  Post-op
• Discontinuation of previous beta-blocker therapy
• Discontinuation of previous ACEI therapy
• Electrolyte imbalances
  • Hypomagnesaemia
• Critical illness
  • sepsis
  • hypovolaemia
  • hypoxaemia
• therapeutic use of catecholamine e.g. adrenaline / dopamine
• Prolonged ICU length of stay

Scores

CHA2DS2-VASc, which was designed to assign risk for thromboembolic complications in patients with AF, has been prospectively and retrospectively validated for also predicting AF after cardiac surgery

POAF score

Machine learning

Prevention

Euvolaemia and electrolyte balance should always be the goal

Potassium and magnesium supplementation are especially critical in lowering the risk of perioperative arrhythmias including AF

Beta-blocker therapy, most commonly with medications such as metoprolol or carvedilol, is a mainstay of the prevention of POAF.

Amiodarone is typically reserved as a second-line drug when beta-blockers are contraindicated, and has a class IIa recommendation in patients at increased risk

Previous comparisons of amiodarone with beta-blockers in preventing POAF showed no difference in incidence, efficacy and safety, but, while amiodarone has a high success rate of maintenance of sinus rhythm, it (like sotalol) is hindered by significant adverse effects

Non-dihydropyridine calcium channel blockers are another preventative medication and are a recommended alternative if beta-blockers are not tolerated or are contraindicated
their use is limited by an association with ↑ AV block and low output syndrome

Vasopressor choice: norad > AVP (also ↓ RRT)

Other possible agents:

• statin
• atrial pacing + posterior pericardiotomy
• NSAIDs
• Colchicine
  • COPPS trial (+ve)
  • COP-AF trial (-ve)
• Steroids during cardiac surgery
  • Class IIb recommendation in European guidelines

Dexmedetomidine
? ↓AF but ↑ hypotension
Possible mechanisms for this preventative effect include:

• ↓ inflammatory response,
• ↓ sympathetic tone
• alteration in calcium currents across cardiomyocyte
  • ↑ effective refractory period

?Regional anaesthesia
thoracic EA: not for cardiac surgery ∵ systemic heparinisation

Prognosis

↑ post-op stroke

• POISE
  ↑ CHF / cardiac arrest / PNA / LOS

Mx

Postoperative AF is commonly self-limited, averaging a duration of 11–12 h after surgery, with minimal acute alterations in haemodynamics, and 80% of patients who develop POAF convert back to sinus rhythm spontaneously within the first 24 h after onset

Beta-blocker therapy for rate control is the standard treatment choice, particularly in patients with concomitant ischaemic heart disease

Other medications, such as amiodarone, non-dihydropyridine calcium channel blockers (such as diltiazem) and digoxin can also be considered to control heart rate depending on the patient's characteristics and comorbidities

The optimal target heart rate is unclear, with recent guidelines suggesting <100 bpm in stable or chronic AF based on data in the AFFIRM and RACE II studies

a stricter control of <80 bpm may be beneficial in symptomatic patients or those with reduction in left ventricular systolic function
Specifically after cardiac surgery, <100 bpm should be targeted in asymptomatic patients

Vernakalant is an atrial-selective antiarrhythmic approved in Europe but not by the US Food and Drug Administration (FDA). It was studied in the setting of POAF after cardiac surgery specifically and carries a class IIb recommendation from the European Society of Cardiology

Initial Mx:

• Unstable haemodynamics, symptoms, or both
  • Synchronised DC cardioversion
  • Consider pharmacological cardioversion if the patient is haemodynamically stable, but unable to obtain adequate rate control or intolerant to rate control medication (recommend consultation with electrophysiologist; medications include amiodarone, procainamide, flecainide, propafenone, vernakalant
• Stable haemodynamics and asymptomatic
  • Typically self-limiting
  • Pharmacological rate control (medications include beta-blockers, amiodarone, non-dihydropyridine calcium channel blockers, digoxin)
    Long term
• Electrical or pharmacologic cardioversion
• Ablation therapy
  • Pulmonary vein isolation (PVI)
  • Surgical, catheter-based or hybrid approach
  • More effective at maintaining longer-term rhythm control than pharmacological management
• Anticoagulation for primary risk prevention of thromboembolic sequelae

Most guidelines recommend starting anticoagulation in POAF persisting more than 48 h; the balance of risks and benefit should be assessed and the decision to start anticoagulation should be made using the CHA2DS2-VASc score for thrombotic risk and HAS-BLED score for bleeding risk

Atrial fibrillation ablation has been compared with pharmacological control of rhythm in several randomised trials, and may be a more effective treatment choice for maintaining long-term sinus rhythm while also conferring a mortality benefit in patients with concomitant CHF

References

Perioperative atrial fibrillation - BJA Education
Perioperative Atrial Fibrillation - BJA Ed