Clinical Focus
12 JULY 2024 ausdoc . com . au
| THE | HEARTS AND MINDS SPECIAL
Therapy Update
Catheter ablation for AF
ATRIAL fibrillation affects approximately 2.2 % of the general population in Australia and is the most common arrhythmia encountered in clinical practice . It is an independent risk factor for stroke and is associated with heart failure and increased mortality . 1 , 2
The long-term management of this condition encompasses prevention of thromboembolic events , improvement of symptoms and management of comorbidities and lifestyle risk factors . 3 Specifically , the European Society of Cardiology and National Heart Foundation of Australia recommend the strategies outlined in box 1 to
Cardiology
Dr Pierre Qian is a cardiologist and cardiac electrophysiologist at Westmead Hospital , NSW , senior lecturer at Westmead Clinical School , University of Sydney , and senior research fellow at Westmead Applied Research Centre , University of Sydney . Dr Julia Zhou is a cardiology advanced trainee registrar at Westmead Hospital , NSW .
This treatment is a well-established and increasingly utilised strategy for symptomatic atrial fibrillation .
reduce progression and recurrence of atrial fibrillation ( AF ). 3-5
Pharmacological rate control agents are recommended to achieve a target heart rate of less than 110 at rest initially and less than 80 when there are persistent symptoms or presence of tachycardia-induced cardiomyopathy ( see figure 1 ). 3
Despite adequate rate control , many patients remain symptomatic , and would benefit from restoration and maintenance of sinus rhythm . This is particularly the case in those with heart failure . 3 , 4 This article will review the role of catheter ablation techniques in achieving rhythm control , and patients who may benefit
Figure 1 . Rate control therapy algorithm .
Reproduced with permission from Oxford University Press , G Hindricks et al , European Heart Journal , 2021 , 42 / 5 , 373-498 . 3 from this approach .
Rhythm versus rate control — the evidence evolves
Multiple early landmark trials investigated the prognostic impact of rhythm control , with either anti-arrhythmics and / or serial electric cardioversions , compared with rate control . These studies included the AFFIRM , RACE , STAF and AF-CHF trials . They found no difference in all-cause mortality , cardiovascular mortality or stroke outcomes between rhythm and rate control approaches , leading to the presumption that these are equivalent strategies for AF management . 6-9
However , there was also some early evidence of potential benefits to rhythm over rate control . The DIA- MOND-CHF trial randomised patients with AF to receive either dofetilide or placebo ( dofetilide is a class III antiarrhythmic agent , used to terminate and prevent AF and atrial flutter ). In this trial , the treatment group were less likely to be hospitalised with exacerbations of heart failure . While dofetilide therapy carried a risk of torsades de pointes of 3.3 %, there was no difference in mortality , and treated patients who were able to maintain sinus rhythm had improved survival rates . 10
More recently , with increasing use of catheter ablation , new evidence has emerged to indicate better outcomes in some
SR — sinus rhythm ; CRT — cardiac resynchronisation therapy ; CRT-P — cardiac resynchronisation therapy pacemaker ; CRT-D — cardiac resynchronisation therapy defibrillator
NEED TO KNOW
AF is the most common arrhythmia encountered in clinical practice and a cause of significant potential morbidity and mortality .
Many patients benefit from restoration of sinus rhythm , which may be achieved in some cases via catheter ablation techniques .
Rhythm control may achieve better long-term morbidity and mortality outcomes in some patient groups , particularly in patients with heart failure with reduced ejection fraction .
The European Society of Cardiology recommends catheter ablation as a firstline therapy option for AF associated with heart failure with reduced ejection fraction , or for patients with symptomatic AF , if preferred .
Success rates for freedom from AF , 12-months post-ablation may be up to 66 % in patients with paroxysmal AF , and 52 % in those with persistent AF .
Procedural complications are relatively rare , occurring in 1-6 % of cases , with bleeding at the venous access site the most common complication .
patient groups with rhythm control . EAST-AFNET 4 randomised a large cohort of older patients with cardiovascular comorbidities to receive either early rhythm control via antiarrhythmics , catheter ablation or rate control . This study found lower rates of cardiovascular death , stroke and hospitalisations with heart failure , in those with early rhythm control . 11 A subsequent meta-analysis of randomised controlled trials showed catheter ablation was superior to medical therapy at reducing mortality , hospitalisation and recurrence of AF . 12
Patients with heart failure with reduced ejection fraction are a population who can derive particular benefit from catheter ablation . The CASTLE-AF study compared catheter ablation with rate control and demonstrated significant improvement in left ventricular ejection fraction in the ablation group , with a median absolute increase in left ventricular ejection fraction of 8 % compared with 0.2 % in the medication group at 60 months of follow-up . Death or hospitalisation for heart failure was also lower in the ablation group , with an absolute mortality risk reduction of 11.6 % at five years . This is equivalent to a number needed to treat of 8.6 . 13
Similarly , in heart failure subgroup analysis from the CABANA trial , catheter ablation was associated with a 3.1 % absolute risk reduction in all-cause mortality after five years , compared with medication therapy , with a number needed to treat of 32 . 14 This mortality benefit was not observed in anti-arrhythmic drug trials , potentially due to the benefits being neutralised by adverse effects of anti-arrhythmic therapies . 8
Catheter ablation was also shown to be superior to atrioventricular nodal ablation with insertion of cardiac resynchronisation therapy in patients with heart failure and drug-resistant AF . Catheter ablation resulted in greater improvements in ejection