Contact force sensing in atrial fibrillation catheter ablation

Atrial fibrillation affects roughly 460,000 Australians and accounts for over 60,000 hospital admissions every year, driving stroke and heart failure and placing a heavy load on emergency departments from Perth to Brisbane. As the population ages, EP labs are receiving referrals for more longstanding and persistent cases than ever before.

Catheter ablation has shifted from a niche intervention to a mainstream rhythm-control option discussed in Australian cardiology clinics every week. Pulmonary vein isolation remains the cornerstone of treatment, yet producing durable lesions without injuring adjacent oesophageal or phrenic structures has long been a difficult balance. The arrival of catheters that measure the force applied to the beating atrial wall has changed the way operators approach the procedure, allowing energy to be titrated in real time rather than estimated from indirect signals alone.

The Journal of Arrhythmia publishes work from the Asia-Pacific region alongside international cohorts, including themed collections that place Australian registry findings next to data from Japan, Korea and Europe. The following sections explore how contact force sensing has reshaped AF ablation, what the evidence base shows, and how Australian centres are integrating the technology into daily workflows.

The clinical case for measuring catheter-tissue contact

Before force-sensing catheters, operators relied on tactile feedback, fluoroscopic motion and indirect signals such as impedance change to judge apposition to the myocardium. In the thin-walled left atrium, particularly along the ridge between the left pulmonary veins and the left atrial appendage, even experienced operators sometimes delivered insufficient energy to form a transmural lesion or excessive energy that risked steam pop and collateral injury. These uncertainties drove variable single-procedure success and a meaningful burden of redo procedures, with downstream effects on waiting lists at busy public hospitals such as Royal Prince Alfred and The Alfred.

Contact force sensing rests on the link between lesion depth and three variables: power, duration and tip-to-tissue force. Force that is too low risks non-transmural scarring that re-conducts; force that is too high raises barotrauma risk. By giving a real-time gram reading, the technology lets each lesion be tailored to local anatomy.

This shift has practical implications beyond the lab. Better first-pass lesion quality reduces procedure time, fluoroscopy exposure and redo admissions, which matters in a system where Medicare rebates do not fully cover complex ablation and where private funds negotiate tightly with hospitals on device reimbursement. For trainees in Australian fellowships, exposure to force-guided ablation has moved from advanced niche to routine expectation, with recent CSANZ curriculum updates reflecting that change.

How the technology captures and displays force

Two catheter families dominate Australian practice: the ThermoCool SmartTouch, with a spring-mounted tip and three optical fibre Bragg gratings, and the TactiCath, with a force-sensitive triaxial spring and three magnetic sensors. The EnSite Contact system offers a complementary navigation environment, and all three show real-time force vectors, numerical gram readings and colour-coded bars on the mapping screen.

The most useful parameter during ablation is not absolute force but the force-time integral (FTI) in gram-seconds, and increasingly the lesion size index and ablation index, which combine power, duration and force into a single number targeting a defined lesion depth. Australian operators typically aim for an FTI of at least 400 gram-seconds anteriorly and 350 gram-seconds posteriorly, although published targets vary. Continuous display of force alongside impedance and temperature allows a dynamic response to catheter migration, respiratory excursion and beat-to-beat variation in atrial coupling.

Force-sensing catheters do not remove the need for careful handling. Catheter orientation, respiratory phase and angle of contact all influence the displayed force, and over-reliance on a green "in-range" indicator can be misleading when the tip rests against a fibrous ridge. Senior electrophysiologists at Royal Melbourne Hospital emphasise to their fellows that the force number is a guide, not a guarantee, and that integration with intracardiac echocardiography and high-density mapping remains essential for safe and effective pulmonary vein isolation.

Pivotal trial evidence and Australian real-world data

The first major prospective evaluation, the TOCCATA study, demonstrated a clear relationship between average contact force and freedom from atrial tachyarrhythmia at 12 months, with operators averaging less than 10 g producing markedly worse outcomes. EFFICAS and EFFICAS II showed that minimum force per lesion and the proportion of contiguous low-force applications were strong predictors of late gap formation. SMART-AF confirmed that operators could be trained to target a specific force range, with single-procedure success above 70 percent in paroxysmal AF when targets were met.

For persistent AF, where outcomes remain more modest, the PRECEPT and CIRCA-DOSE studies suggested that force-guided workflows combined with ablation index targets offer better lesion contiguity and reduced reconnection rates. These findings have been broadly adopted in Australian labs, where persistent AF cases typically include posterior wall isolation, roof line and anterior line ablation alongside pulmonary vein isolation, all benefiting from reproducible lesion creation. Multiple registries have confirmed a low rate of steam pop and oesophageal injury when force-sensing workflows are followed carefully.

Local experience mirrors these international findings. The Victorian Cardiac Outcomes Registry and site-based audits at tertiary centres in New South Wales and Queensland report single-procedure freedom from atrial tachyarrhythmia in the 65 to 75 percent range at one year for paroxysmal patients, with low major complication rates. This audit work has informed ongoing discussion within CSANZ about minimum operator volumes and credentialing standards, an area where Australia has historically played a leading role in defining competency benchmarks for catheter ablation.

Optimising lesion formation in Australian workflows

In routine Australian practice, operators standardise on ablation index targets of 400 to 450 anteriorly and 350 posteriorly, with power at 25 to 35 W depending on habitus. Posterior wall energy is usually limited to 25 W with routine oesophageal temperature monitoring. Public tertiary hospitals often run one or two all-day EP lists weekly, while private providers such as Ramsay Health Care deliver higher catheter lab throughput, yet both environments have integrated force-sensing into routine care.

Public fellowships often rotate trainees through complex ablation cases including adult congenital arrhythmia substrate modification, a topic addressed in the adult congenital arrhythmia guide, giving registrars exposure to non-standard anatomy that benefits from precise lesion control.

General anaesthesia is favoured by many Australian labs, including for paroxysmal cases, partly because controlled ventilation reduces respiratory excursion of the catheter and improves the consistency of force measurements. This contrasts with deep sedation workflows used at some overseas centres and reflects local anaesthetic preference and theatre staffing models aimed at minimising patient movement during long procedures.

Safety considerations and complication avoidance

Contact force sensing has improved safety in two main ways. First, keeping average force below roughly 20 g substantially reduces steam pop risk, with contemporary series reporting rates well below one percent. Second, lower power on the posterior wall guided by FTI targets has reduced endoscopically detected oesophageal lesions, though not to zero. Australian centres contribute to international registries on oesophageal injury and continue to refine their protocols, including routine post-procedural upper endoscopy in selected research protocols.

Tamponade remains the most feared mechanical complication, and force-sensing catheters have not eliminated it. Transseptal access under intracardiac echocardiography is now standard at most Australian centres, and force-sensing catheters are not a substitute for careful transseptal technique. Operators also watch for catheter char formation, particularly on the coumadin ridge adjacent to the left atrial appendage where high force with low flow can cause coagulum.

Beyond the periprocedural period, late complications such as stiff left atrium syndrome, pulmonary vein stenosis and atrio-oesophageal fistula remain rare but important. Ongoing education through the journal's themed collections helps Australian clinicians stay current on rare event recognition, including the increasingly recognised overlap between arrhythmias and systemic diseases such as cardiac amyloidosis. Readers interested in this adjacent area will find the article on arrhythmias in cardiac amyloidosis recognition and palliative management a useful complement to ablation-focused material.

Patient selection and shared decision-making

AF ablation does not suit every patient, and Australian guidelines emphasise shared decision-making, particularly within the first three years after diagnosis where early ablation may offer the greatest benefit on hard endpoints such as heart failure admissions. The EAST-AFNET 4 trial influenced local practice by supporting early rhythm control in selected patients with recently diagnosed AF and cardiovascular comorbidities, and force-guided ablation has made this strategy more deliverable in routine care.

Referral in Australia typically begins with a GP review, initial rate or rhythm management, then onward referral to a cardiologist, with electrophysiologist consultation reserved for symptomatic or refractory cases. Public waiting lists remain long outside metropolitan areas, and regional or remote patients commonly travel to Sydney, Melbourne, Adelaide or Perth. Some private insurers cover ablation where medical criteria are met, while others require higher thresholds documented by tools such as the EHRA score.

Pre-procedural assessment routinely includes left atrial imaging by cardiac CT or MRI, transthoracic echocardiography, anticoagulation review and increasingly screening for sleep apnoea, which is highly prevalent among Australian adults. Patients with cardiac amyloidosis, hypertrophic cardiomyopathy or adult congenital substrates require specialised protocols, and the resources linked above provide additional context for non-standard ablation scenarios.

Pulsed field ablation is set to complement, rather than replace, contact force sensing, since lesion formation strategies and safety monitoring remain relevant regardless of the energy source. Artificial intelligence integration that predicts lesion transmurality from real-time signals is under active development, and Australian centres are likely to be among the early adopters given existing expertise in high-density mapping and registry participation. The Journal of Arrhythmia will continue to cover these advances through its themed collections, original research and invited reviews, with submissions on novel aspects of contact force technology, comparative workflows or Australian registry data welcomed through the journal's online portal where the editorial team offers rapid peer review and open-access publication across the Asia-Pacific region.