Atrial Fibrillation in the Failing Heart – A Clinical Review
rhythm, while sotalol was about 40% effective at one year. With somewhat effective AADs, multiple studies evaluated the treatment strategy of rate control versus rhythm maintenance.
The largest study to evaluate rate control drug therapy versus rhythm control drug therapy was the AFFIRM trial, with over 4,000 patients.6 The conclusion demonstrated no difference in mortality or thromboembolic events between the two treatment groups. At the five-year follow-up, 63% of the patients in the rhythm control group and 35% of those in the rate control group were in sinus rhythm. In the AFFIRM study, patients with EF <40% comprised only 23% of the total cohort, with only 9% having NYHA functional class II or higher.30
Additional smaller studies, such as the Pharmacological Intervention in Atrial Fibrillation (PIAF) trial, Rate Control versus Electrical Cardioversion for Persistent Atrial Fibrillation Study Group (RACE) trial, How to Treat Chronic Atrial Fibrillation (HOT CAFÉ) trial and Strategies of Treatment of Atrial Fibrillation (STAF) study, also found no statistical difference between the defined clinical end-points.32–34,39
The PIAF trial
did demonstrate better exercise capacity for the rhythm control patients.33
Again, The largest cohort of the smaller studies, the RACE trial,
randomised 522 patients to AADs, with the initial AAD being sotalol or rate control.39
there was no significant difference in
cardiovascular mortality. There was improvement in quality of life associated with the presence of sinus rhythm and shorter AF duration regardless of the assigned strategy.
The AF-CHF trial was a multicentre randomised trial of 1,376 patients with AF, EF <35% and clinical HF with NYHA II–IV, who were randomised to rhythm versus rate control for a mean of 37 months.31 Patients in the rhythm-control group mostly used amiodarone (82%). The rate-control patients were taking beta-blockers or digoxin or both. Approximately 90% of all patients received anticoagulation. At follow-up after 37 months, 70–80% of patients in the rhythm control versus 40% of those in the rate-control group were in sinus rhythm. There was no statistical difference in the primary outcome, cardiovascular mortality, between the rhythm- and rate-controlled groups (hazard ratio 1.06, confidence interval [CI] 0.86–1.30; p=0.59).
There have been several explanations for the results of the AFFIRM and AF-CHF trials and other trials demonstrating no significant difference between rhythm- and rate-control strategies. The main argument is that our current AADs are not effective in maintaining sinus rhythm, and are also associated with an increase in adverse side effects, including mortality. In addition, up to 40% of patients in the rate control group were in sinus rhythm at some time during their follow-up in the AF-CHF trial.31
Radiofrequency ablation was
not offered as a treatment modality for rhythm control and could have offset the adverse side effects of AADs. Finally, only 16% of patients had implantable cardioverter–defibrillators (ICDs) in the AF-CHF trial. This could have altered outcomes, as one-third of all deaths in the trial were presumed to be arrhythmia-related. Due to the adverse side-effect profile and poor efficacy of AADs, cardiologists have started to investigate the role of catheter ablation for the treatment of AF. The two current treatment options are ‘ablate and pace’ or AF ablation.
Ablation in Heart Failure Patients
For drug-refractory AF, catheter ablation options are ablate and pace or AF ablation. As previously described, AF decreases cardiac output,
EUROPEAN CARDIOLOGY
Since the advent and improved success of AF ablations in restoration of sinus rhythm, AF ablation for HF patients has begun to emerge as a viable treatment option. In the early studies of AF ablation, patients with LV dysfunction were excluded or comprised only a small percentage of study patients. The ablate and pace strategy still requires the patient to undergo anticoagulation and does not resolve the haemodynamic consequences of AF. Several studies have evaluated catheter ablation of AF in patients with LV dysfunction. Chen reported that AF ablation in patients with EF <40% resulted not only in improved EF, but also in 73% of the study patients being free of AF at 14 months.8
Haissaguerre and Hsu ablated AF patients with
EF <45%; they found a statistically significant improvement in EF, LV dimensions, exercise capacity, symptoms and quality of life, even in the presence of concurrent structural heart disease and appropriate ventricular rate control prior to ablation.11
Restoration of sinus
rhythm resulted in a mean increase in LVEF of 21%. Tondo showed not only significant improvement in quality of life, symptoms and LV function, but also no higher rate of associated procedural complications with AF ablations.48
Efremidis et al. reported that AF HF
patients who remained in sinus rhythm after ablation had a statistically significant increase in EF, decrease in LV end-diastolic diameter and decrease in left atrial (LA) diameter.9
Overall, studies
evaluating AF ablation in HF patients have consistently demonstrated that AF ablation improves EF with less dependence on AADs.10,13
The Pulmonary Vein Antral Isolation versus Atrioventricular Node Ablation with Biventricular Pacing for the Treatment of AF in Patients with CHF (PABA-CHF) trial is a prospective multicentre trial randomising 81 symptomatic, drug-refractory AF patients with EF ≤40% and NYHA class II–III to AF ablation via pulmonary vein antral isolation or AV node ablation with biventricular pacing.12
By six months,
88% of patients who received an AF ablation were free of AF with or without AADs, and 71% of patients were free of AF without AADs. The PABA-CHF trial reported that pulmonary vein isolation improved LV function, 6MWT and quality of life compared with patients treated with AV node ablation and biventricular pacing.12 non-paroxysmal derived the greatest benefit.
AF patients who were
77
which results in atrial contractile dysfunction, loss of AV synchrony and an irregular ventricular rhythm.4
An AV nodal ablation is highly effective
at producing heart block. Either a single- or dual-chamber permanent pacemaker is implanted to maintain adequate heart rate. This was the concept of the ablate and pace strategy for rate control.40
This option
controlled the rate, but did not restore sinus rhythm, atrial contraction or AV synchrony.41–43
dyssynchrony and progression of heart failure.44,45
Right ventricular pacing also results in cardiac The Left Ventricular-
based Cardiac Stimulation Post AV Nodal Ablation Evaluation (PAVE) study evaluated LV versus right ventricular (RV) pacing for patients with AF and HF undergoing an ablate and pace treatment plan.46
Doshi et al.
found a significant increase in the 6MWT distance at six months for the LV pacing patients compared with RV pacing. In addition, patients with EF ≤45% or who had NYHA II or III demonstrated a greater response to LV pacing over RV pacing, regardless of the native QRS duration. It should be noted that the difference was due to the deleterious effects of RV pacing, such as a decline in EF and hallway distance, rather than an increase in the LV pacing group. Gasparini demonstrated in a prospective multicentre study that AF HF patients who received AV node ablation with CRT had a significant increase in EF, improved exercise tolerance and increased reverse remodelling, which was not seen in the AF patients who did not undergo AV node ablation with CRT.47
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