AF/A-Flut

Introduction

  • Speaker: Dr. Hui Chen Han, Cardiologist and Group Physiologist at the Victorian Heart Hospital and Victorian Heart Institute.
  • Topic: Atrial Fibrillation (AF) and Atrial Flutter.

Global and Australian Prevalence of Atrial Fibrillation

  • AF is the most common arrhythmic condition globally.
    • Estimated prevalence of AF: 33.5 million in 2010 and 43.6 million in 2016.
    • Developed regions, such as North America and Western Europe, have the highest prevalence rates.
    • Australia: approximately 800 cases per 100,000 population (0.8%).

Burden of AF in Australia

  • Study using international estimates with data from the Australian Bureau of Statistics:
    • Estimated AF prevalence in Australians aged 55 years or older: 5.35%.
    • Noticeable gender difference: Men more affected than women.
    • Prevalence increases with age:
    • 2014: 329,000 people affected.
    • 2022: 422,000 people affected.
    • 2034 prediction: 606,000 people affected.

Atrial Activity in Sinus Rhythm

  • Diagrammatic representation:
    • Panel A: Sinus node initiates an electrical impulse.
    • Panel B: Wave propagation across the right and left atria.
    • Panel C: Impulse reaches AV node, leading to ventricular depolarization.
  • Mechanisms of AF:
    • Rapid discharges from focal areas in the atrium (grotus).
    • Reentry circuits occurring around scar tissue.
    • Resulting in chaotic atrial activity (irregular ventricular rhythm observed in ECG).

Historical Context of AF Ablation

  • Landmark study (1998) established the origin of AF triggers:
    • 94% of triggers originate from pulmonary veins (veins carrying oxygenated blood from the lungs to the left atrium).
    • This discovery led to the procedure of pulmonary vein isolation for AF ablation, an invasive treatment technique.

Risk Factors Contributing to Atrial Fibrillation

  • Classifications:
    • Non-modifiable: (age, gender, family history)
    • Modifiable: (hypertension, obesity, lifestyle factors)
    • Comorbid conditions: may be treated to reduce AF risk.
  • Awareness and management considerations:
    • Counseling regarding lifestyle factors for all patients.
    • Kidney disease affects anticoagulation decisions.
    • Heart failure patients may need aggressive treatment for AF.

Diagnosis of Atrial Fibrillation

  • Importance of a standard 12-lead ECG:
    • Typical changes seen in AF:
    • Irregular ventricular rhythm with no discernible P waves.
    • Differentiating conditions, such as:
    • Multifocal atrial tachycardia - discrete P waves of different morphologies.
    • Atrial ectopy - sinus rhythm interspersed with premature atrial contractions.
  • Alternative monitoring methods:
    • 24-hour Holter monitors for persistent AF.
    • Continuous telemetry in hospital for paroxysmal AF detection.
    • Patch monitors (2-4 weeks monitoring duration).
    • Portable technologies (mobile ECG devices, smartwatches) require patient funding.
    • Implanted devices (loop recorders, pacemakers) also help in AF detection.

Investigations Following Diagnosis

  • Importance of echocardiograms:
    • Determines left ventricular function and left atrial size.
  • Baseline blood tests:
    • Identify contributing factors for AF and prepare for anticoagulation.
  • Clinical outcomes and guidelines from the European Society of Cardiology:
    • Patients with evidence of hemodynamic instability require immediate evaluation and potential cardioversion.
    • In hemodynamically stable patients, consider:
    • Symptoms: palpitations, chest discomfort, dyspnea, stroke prevention.
    • Assess impact on quality of life and outcomes like cognitive decline and depression.

Management of Atrial Fibrillation

Stroke Prevention

  • Valvular AF:
    • Anticoagulation with warfarin for patients with rheumatic mitral stenosis or mechanical valves.
  • Non-valvular AF:
    • Use of CHA2DS2-VASc score for anticoagulation decisions:
    • Score 0: Avoid anticoagulation.
    • Score ≥ 2: Anticoagulation indicated.
    • Score = 1: Consider anticoagulation.
    • Non-vitamin K antagonist oral anticoagulants recommended (adjust doses based on renal function, age, etc.).
    • No role for aspirin or other antiplatelets in stroke prevention for AF.
    • Left atrial appendage occlusion for those unable to use anticoagulation.

Risk Factor Modification

  • A study from Adelaide on risk factor modification:
    • 150 patients demonstrated a reduction in AF burden via:
    • Intensive modification strategies (blood pressure control, weight loss, glycaemic control, OSA treatment).
    • Sustained effects even post-AF ablation.

Rate Control vs. Rhythm Control Strategies

  • Factors favoring rate control:
    • Minimal symptoms from AF.
    • Greater comorbidity burden.
    • Patient preference.
    • Normal left ventricular function.
    • Severe left atrial enlargement reduces chances of lasting sinus rhythm.
    • Rate control is a safer initial approach.
  • AFFIRM trial (2002):
    • No survival difference between rhythm and rate control; however, fewer adverse drug events in rate control.
  • Lenient rate control strategy recommended:
    • Aim for resting heart rate < 110 beats per minute.
    • Referral to a cardiologist if > 2 medications required.
  • Pacemaker and AV node ablation as a last resort for symptomatic patients where rhythm control has failed.

Rhythm Control Strategies

  • Preferred for patients with significant AF symptoms or left ventricular dysfunction.
  • Advancements in techniques:
    • Recent literature supports rhythm control strategies (especially with ablation).
    • Notable studies:
    • Castle AF - showed better outcomes for ablation over medical therapy in AF and heart failure.
    • East AF NET - rhythm control (ablation or medication) superior to rate control in new onset AF.
    • Early AF study - cryoballoon ablation better than medical therapy for paroxysmal AF.

Pharmacotherapy Options for Rhythm Control

  • Medications:
    • Flecainide, amiodarone, sotalol.
  • Electrical cardioversion may act as a bridge to ablation or assess symptomatic benefits from sinus rhythm.

Atrial Flutter

Definition and Mechanisms

  • Atrial flutter characterized by a macro reentry circuit, mainly occurring in the right atrium.
  • Typical atrial flutter produces a sawtooth pattern on ECG due to the circuit activity.

Treatment

  • Similar to AF, involving anticoagulation, risk factor modification, and rate/rhythm control.
  • Early consideration for ablation, particularly for typical flutter, as it yields good long-term results through cavotricuspid isthmus ablation.
  • Patients with atrial flutter have a high likelihood of developing AF long-term and require ongoing cardiology reviews.

Conclusion

  • Atrial fibrillation and flutter present significant clinical challenges necessitating a multidisciplinary approach for effective management. Understanding the pathophysiology, indicating risks, diagnosis, and appropriate treatment strategies is crucial for ensuring the best patient outcomes.

Thank you.