Atrial fibrillation in HCM: ablation versus rate control

Atrial fibrillation is the most common sustained arrhythmia seen in people living with hypertrophic cardiomyopathy, and its presence shifts the clinical course dramatically. In the HCM population, AF is associated with higher rates of stroke, heart failure hospitalisation, and sudden cardiac death than in patients without the underlying myopathy. Managing this dual problem means reconciling the principles that govern AF treatment with the unique structural and electrical quirks of the hypertrophied ventricle and atrium.

For Australian cardiologists and electrophysiologists, the choice between a rate-control-first approach and an early ablation strategy is rarely academic. It plays out in everyday decisions made in outpatient clinics from the western suburbs of Sydney to the remote communities of the Northern Territory, where patients may have limited access to tertiary electrophysiology laboratories. The current evidence, combined with local realities around funding, service availability, and patient preference, helps shape a practical framework for choosing between strategies.

Why atrial fibrillation behaves differently in hypertrophic cardiomyopathy

The substrate for AF in HCM is not identical to the substrate in hypertensive or ischaemic heart disease. Chronic diastolic dysfunction raises left atrial pressure, while myocyte disarray and interstitial fibrosis provide the electrical scaffolding for re-entry. Atrial enlargement progresses faster than in matched controls without HCM, and pulmonary vein triggers remain important even when the atria are severely remodelled. As a result, AF tends to be more symptomatic, more persistent, and more resistant to drug therapy in this group.

The haemodynamic consequences also differ. Loss of atrial contraction in a stiff, non-compliant ventricle can precipitate pulmonary oedema within hours, particularly in patients with outflow obstruction. Exercise capacity, already limited by HCM physiology, falls further when AF is present. These features raise the stakes for rhythm preservation and shape how aggressively clinicians pursue sinus restoration. Decision-making therefore weighs stroke and mortality risk against the immediate functional impact of irregular ventricular response in a ventricle that depends on atrial kick.

When rate control becomes the pragmatic first step

For many patients, especially older individuals with longstanding persistent AF and substantial atrial scarring, a rate-control strategy is the more attainable goal. Beta-blockers remain a cornerstone in Australian practice because they slow AV nodal conduction and also help manage dynamic outflow obstruction. Non-dihydropyridine calcium antagonists such as verapamil are used cautiously and generally avoided in patients with significant gradients, leaving digoxin as a third-line option in sedentary patients. Doses are titrated to ambulatory heart rates and symptom response rather than to any rigid target.

Rate control is also the path of least resistance in remote and regional areas. A general physician in Cairns or a GP in Ballarat can adjust a beta-blocker by phone, while a remote tele-cardiology consult through services such as the New South Wales Health TeleECG platform can support monitoring without travel. For some patients, particularly those with multimorbidity, frailty, or a preference to avoid procedural risk, accepting permanent AF and a well-controlled ventricular rate is a reasonable, even preferable, outcome.

Where medication fails or intolerance develops, ablation of the AV node combined with permanent pacemaker implantation offers reliable rate control. The technique is widely available across Australian tertiary centres, and modern algorithms for right ventricular pacing have made outcomes more predictable. Recent work on pacing and heart failure shows how device programming and conduction-system pacing can now limit the long-term dyssynchrony that historically complicated this approach.

Antiarrhythmic drugs in the HCM setting

When rhythm control is the agreed plan, the drug cupboard is smaller than for the general AF population. Sotalol is used selectively because of concerns about QT prolongation and negative inotropy, while flecainide and propafenone are generally avoided in the presence of structural disease. Amiodarone remains the most frequently prescribed agent in Australia for HCM patients with symptomatic AF, including those with impaired systolic function or significant hypertrophy. Loading regimens are typically delivered in hospital with thyroid, hepatic, and pulmonary surveillance arranged through the patient's GP and local pathology provider.

The Australian Pharmaceutical Benefits Scheme subsidises amiodarone and sotalol for rhythm control, which lowers out-of-pocket cost compared with some newer agents available only on private prescription. That access is a real advantage in a country where private health insurance uptake varies widely and many pensioners rely on PBS-listed medicines. Clinicians still must remain alert to the proarrhythmic potential of antiarrhythmic drugs, particularly when overlapping with other QT-prolonging therapies. A practical summary on common Brugada-pattern triggers reminds prescribers to consider sodium-channel effects and electrolyte status, especially during intercurrent illness or peri-procedurally.

Drug therapy can stabilise rhythm for years in well-selected patients, but recurrence rates in HCM are higher than in the broader AF population. When breakthrough episodes become frequent, or when patients become dependent on chronic amiodarone with emerging organ toxicity, the conversation usually shifts toward catheter ablation as a more durable option.

Catheter ablation: when the data support an early call

Outcomes from catheter ablation in HCM have improved substantially over the past decade. Pulmonary vein isolation remains the procedural cornerstone, and contemporary series report single-procedure freedom from atrial arrhythmia in roughly 50–70% of patients at one to two years, with higher rates after repeat procedures. Success depends heavily on left atrial size, AF duration, and the extent of low-voltage substrate identified on high-density mapping. Patients with paroxysmal AF, modest atrial dilatation, and limited comorbidity consistently do better, which is why many Australian electrophysiologists now offer ablation earlier in the disease course rather than after years of failed drug therapy.

Advanced techniques, including posterior wall isolation, roof line, and targeting of low-voltage areas identified by late-gadolinium cardiac MRI, are increasingly used in the larger Australian centres such as Royal Prince Alfred, The Alfred, and the Royal Adelaide. Cryoballoon and radiofrequency point-by-point platforms are both reimbursed through private insurers and selected public hospital funding models, though waiting lists in the public system can stretch beyond six months in some states. Hybrid approaches combining surgical and catheter ablation remain restricted to a few quaternary centres and are generally reserved for refractory cases.

Complication rates in HCM are not higher than in non-HCM cohorts, although pericardial effusion and vascular access issues are worth noting in patients on chronic anticoagulation. Restoration of sinus rhythm translates into measurable gains in exercise capacity, NT-proBNP levels, and quality of life, which matters for patients whose daily activities are constrained by HCM-related dyspnoea. Long-term stroke reduction is more difficult to demonstrate, and lifelong anticoagulation is still recommended in most HCM patients with a history of AF, regardless of apparent rhythm stability.

Australian realities that shape the choice

The decision between ablation and rate control in Australia is not made in a vacuum. Medicare supports specialist consultations and standard ablation procedures, but gap payments in private rooms can be substantial, and rural patients often shoulder the cost of travel, accommodation, and time off work. The Australian Heart Rhythm Society, alongside the Cardiac Society of Australia and New Zealand, has published consensus documents that help clinicians navigate these choices, and local arrhythmia multidisciplinary teams in hospitals like Fiona Stanley or the Royal Melbourne regularly discuss borderline cases by videoconference.

Cultural context also matters. Aboriginal and Torres Strait Islander patients with HCM face a higher burden of cardiovascular comorbidity and may experience additional barriers to procedural care. Outreach cardiology services in Western Australia and Queensland, combined with culturally safe communication, help ensure that ablation is offered equitably rather than reserved for patients living near a major city. Shared decision-making tools that weigh the burden of lifelong medication, the procedural risks of ablation, and the patient's own goals of care remain an essential part of the conversation.

For clinicians seeking to keep pace with the rapidly evolving evidence base, the journal continues to publish original research, themed collections, and case-based discussion relevant to everyday practice. Readers can explore the latest issue and submitted manuscripts through the Journal of Arrhythmia homepage and consider how emerging technologies might soon refine the calculus between rate and rhythm control in this complex patient group.