Catheter Ablation of Atrial Fibrillation in Cardiac Amyloidosis

Cardiac amyloidosis has shifted from being a rare curiosity to a frequently recognised cause of restrictive cardiomyopathy in Australia, where the Therapeutic Goods Administration's 2023 approval of tafamidis for transthyretin amyloid cardiomyopathy combined with reimbursement through the Pharmaceutical Benefits Scheme has opened a new therapeutic chapter. Among the rhythm complications that arise once amyloid fibrils infiltrate the atrial walls, atrial fibrillation is the most common, affecting up to three quarters of patients with advanced disease. Whether catheter ablation can durably restore sinus rhythm in this fragile substrate remains one of the most discussed topics in contemporary cardiac electrophysiology.

This article synthesises current evidence on catheter ablation in patients with cardiac amyloidosis and atrial fibrillation, with a focus on pathophysiology, patient selection, procedural strategy, and outcomes. It also reflects on how Australian centres are navigating these complex cases, drawing on insights from established amyloidosis services in Melbourne and Sydney, and on registries maintained by local professional bodies. The aim is to equip electrophysiologists, heart failure specialists, and trainees with an integrated understanding of where ablation fits within the broader care of these patients.

Pathophysiology of Atrial Fibrillation in Amyloid Cardiomyopathy

In cardiac amyloidosis, misfolded protein deposits, most commonly immunoglobulin light chains in AL amyloidosis or transthyretin in ATTR, accumulate within the myocardial interstitium, producing a stiff, non-compliant ventricle. The atria are not spared; in fact, atrial infiltration may precede ventricular involvement and produces a substrate that is fundamentally different from the typical fibrotic remodelling seen in conventional atrial fibrillation. Slowed inter-nodal conduction, reduced atrial voltage, and progressive biatrial enlargement combine with infiltrative loss of myocardial architecture to create a milieu that is highly permissive for sustained arrhythmia.

Beyond structural change, autonomic dysfunction is a frequent companion of amyloid disease, and elevated filling pressures stretch the already infiltrated atrial wall. As a result, atrial fibrillation in these patients is often persistent or long-standing at presentation, accompanied by rapid ventricular rates that aggravate congestion and may precipitate acute decompensation. Recognising this distinct electrophysiological landscape is essential before considering any interventional approach to rhythm control.

Patient Selection and Risk Stratification

Decisions around catheter ablation in amyloidosis must weigh the procedural risks against a more limited substrate reserve than encountered in non-amyloid atrial fibrillation. Patients in advanced National Amyloidosis Centre stage III disease, with severe diastolic dysfunction, a stretched left atrium greater than 50 mm, or evidence of significant conduction system disease requiring pacing, tend to derive less durable benefit. Those identified earlier in the disease course, particularly after disease-modifying therapy has stabilised their cardiac parameters, often tolerate ablation with a more favourable risk-reward balance.

Risk stratification in Australian practice routinely combines transthoracic echocardiography with strain imaging, cardiac magnetic resonance, and, when ATTR is suspected, bone scintigraphy with monoclonal protein exclusion. Natriuretic peptides and troponin serial trends add prognostic weight. Close liaison with amyloid specialists at hubs such as the Victorian Amyloidosis Centre and the multidisciplinary amyloidosis service at St Vincent's Hospital Sydney ensures that the ablation decision is contextualised within disease trajectory, haematological status, and access to ongoing disease-modifying treatment.

Procedural Strategies and Mapping Considerations

Standard pulmonary vein isolation alone is frequently insufficient in amyloidosis because the arrhythmia substrate extends well beyond the venous antra. Contemporary ablation strategies incorporate left atrial roof lines, posterior wall isolation, and extensive substrate modification targeting areas of low voltage and abnormal electrograms. The use of high-resolution electroanatomical mapping has transformed how these complex cases are approached, and a recent practical commentary on The Utility of High-Density Mapping in Complex Atrial Tachycardias outlines the technical considerations relevant to densely infiltrated atria where signal fractionation is prominent.

Energy choice should be individualised. Radiofrequency point-by-point ablation allows titration in scar-prone regions, while cryoballoon pulmonary vein isolation may shorten procedure time in frailer patients who cannot tolerate prolonged general anaesthesia. Anaesthesia teams should be briefed on the autonomic vulnerability common in amyloidosis, where even modest fluid shifts can precipitate hypotension, and on bleeding diatheses that may follow hepatic congestion. Many Australian operators now adopt a minimal-touch strategy with conscious sedation where feasible, complemented by intracardiac echocardiography to detect early pericardial effusion.

Anticoagulation and Peri-Procedural Management

Stasis within the dilated left atrium, combined with the hypercoagulable state linked to protein infiltration and endothelial dysfunction, makes thromboembolic prophylaxis non-negotiable in amyloidosis-related atrial fibrillation. Direct oral anticoagulants such as apixaban and rivaroxaban have largely displaced warfarin in Australian practice, supported by PBS listings that ensure affordable access for the predominantly elderly ATTR cohort. Periprocedurally, patients are typically maintained on uninterrupted anticoagulation with careful attention to renal function and amyloid-related nephrotic syndrome, which can elevate drug levels.

Periprocedural rhythm management also requires careful planning. Many amyloidosis patients are on long-term amiodarone or sotalol, with attendant thyroid, hepatic, and pulmonary toxicities that are amplified in this population. Loading with antiarrhythmic drugs around the ablation procedure may be guided by electrophysiologists in collaboration with heart failure colleagues, ensuring that bradyarrhythmia, common owing to concomitant conduction system disease, is anticipated with backup pacing strategies and clear thresholds for emergency escalation.

Clinical Outcomes and Recurrence Patterns

Evidence indicates that single-procedure freedom from atrial arrhythmia at twelve months in amyloidosis ranges from roughly forty to sixty percent, considerably lower than the seventy to eighty percent reported for non-amyloid paroxysmal fibrillation, even with aggressive substrate ablation. Recurrences tend to cluster in patients with longer disease duration, larger left atrial volume indices, and those who have not yet commenced disease-modifying therapy. Encouragingly, repeat ablation procedures frequently extend arrhythmia-free intervals, and even partial responders often experience meaningful gains in functional class, six-minute walk distance, and quality-of-life scores.

Mortality outcomes following ablation reflect the underlying amyloid disease rather than procedural complications per se. Series from European and North American registries, alongside emerging Australian data now catalogued within Journal of Arrhythmia, suggest that procedural complications such as cardiac tamponade and stroke remain acceptably low when operators experienced in complex ablation perform the case. The conversation with patients and their families should therefore centre on symptomatic gain and avoidance of tachycardia-mediated decompensation rather than the promise of definitive cure.

Australian Practice Patterns and Multidisciplinary Care

Australia's geography shapes how amyloid care is delivered. A small number of high-volume quaternary centres coordinate most complex electrophysiology and amyloid diagnostics, while regional and rural patients access care through hub-and-spoke networks linking the Royal Adelaide Hospital, Royal Melbourne Hospital, and Brisbane's Princess Alexandra to their local cardiologists. This is particularly important during hot and humid summers in places like Townsville and Darwin, when heat-induced volume shifts can destabilise arrhythmia control and prompt hospitalisation. Telehealth-supported case conferences now allow rural physicians to participate in multidisciplinary reviews without lengthy travel.

Professional collaboration is steered nationally through bodies affiliated with the Cardiac Society of Australia and New Zealand, and amyloid-specific research is increasingly catalogued in the Australian New Zealand Clinical Trials Registry. Patient advocacy and education come from the Australasian Amyloidosis Network, which hosts regular webinars and resources for clinicians preparing patients for procedures. Embedding ablation planning within this multidisciplinary fabric helps ensure that procedural decisions remain aligned with the patient's overall prognosis, social circumstances, and personal goals of care.

Future Directions and Research Priorities

Prospective multinational registries, ideally harmonised across the Asia Pacific Heart Rhythm Society membership, are urgently needed to define which amyloidosis phenotypes benefit most from ablation and at what point in the disease course intervention should occur. Refinement of mapping strategies that account for the unique low-voltage milieu of amyloid atria, alongside pulsed-field ablation, which may offer tissue selectivity in fragile substrates, holds genuine promise. Pharmacological adjuncts that stabilise amyloid deposition while arrhythmia substrate is being modified represent an appealing combined strategy.

In Australia, translation of these insights will require sustained funding for amyloidosis-specific biobanks, embedding genetic counselling for the substantial ATTR V122I carrier population, and structured training for the next generation of cardiac electrophysiologists. The contribution of local investigators to international consensus documents is increasingly visible, and the journal continues to welcome original research, reviews, and themed collections that advance shared understanding of these complex patients.

Clinicians managing atrial fibrillation in cardiac amyloidosis are encouraged to consult the latest reviews, case series, and guidelines that inform safe and effective ablation practice. Prospective authors can review submission guidance on the journal's about page or contact the editorial office to discuss themed collections on amyloidosis and multidisciplinary care pathways.