Atrial fibrillation (AF) is the most common sustained rhythm disorder, and its treatment has been revolutionised during the past 20 years. This includes improved detection (Apple watch etc), better anticoagulation (DOAC), left atrial appendage management and catheter ablation.
The first hybrid surgical and catheter AF ablation program (HyCASA = Hybrid catheter and surgical ablation) of its kind in the Southern Hemisphere has been established in Perth and is now a global education centre for this procedure.
Since catheter ablation of AF was first described in 1998, the use of this intervention has increased exponentially, and its annual growth rate exceeds other cardiac interventions. This increased use of catheter ablation in AF management is supported by randomised controlled trials and clinical guidelines and has also been driven by major technological advances.
There has been increasing incidence of AF in all industrialised populations with an increase of 1.2% per annum seen in Western Australia between 1995 and 2010. Catheter ablation alone is highly effective in patients with a small left atrium and paroxysmal AF, though challenges remain for those patients with a large left atrium and persistent AF.
Technological advances have greatly improved our accuracy of energy titration during catheter ablation. This avoids excessive energy delivery reducing the risk of tamponade, phrenic nerve palsy and oesophageal injury and also avoids inadequate energy delivery thereby reducing risk of repeat procedures. Many recent advances have occurred because practical application of high-performance computing in the catheterisation laboratory allows rapid computation of location, cardiac signals, and catheter contact ‘on the fly’.
The challenge is to achieve better results in persistent AF, particularly in patients failing endocardial catheter ablation and, so far, most randomised controlled trials of additional catheter ablation strategies have been disappointing.
The Converge study is one of the few positive RCT in patients with persistent AF demonstrating superior outcomes by additional ablation, in this case comparing HyCASA (pulmonary vein isolation plus surgical thoracoscopic posterior LA ablation) with catheter ablation (pulmonary vein isolation plus linear ablation across the LA roof) in persistent AF patients.
HyCASA ablation strategy
This comprises epicardial surgical and endocardial ablation components. The ablation target is the posterior left atrial wall between the four pulmonary veins.
This area is targeted in patients with non-pulmonary vein mediated AF because a high percentage of non-PV sources originate from this anatomical region which shares the same embryologic origin (and therefore electrophysiology) as the pulmonary veins.
An endocardial catheter-only approach to posterior LA wall ablation is challenging due to risk of thermal injury to the oesophagus, which potentially leads to the extremely rare but devastating complication of atrial-oesophageal fistula (estimated 80% mortality).
Furthermore, endocardial-only posterior wall ablation frequently fails because of complex muscle fibre orientation on the posterior LA wall and complexity of endo-epicardial connections. Epicardial posterior left atrium ablation avoids oesophageal injury because energy is directed away from the oesophagus by clever engineering and catheter design.
The HyCASA approach depends upon a team-based approach with close collaboration between a cardiothoracic surgeon and cardiac electrophysiologist. The surgical component is beating heart and entirely thoracoscopic by access via one sub-xyphoid and three axillary ports.
The surgical and catheter components are separated by six months (surgical ablation first then catheter ablation). The delay is designed to ensure complete resolution of post ablation inflammation and oedema before commencing consolidation ablation by endocardial mapping and ablation.
In addition, my team has chosen to add Atriclip left atrial appendage occlusion in all cases because this removes additional potential AF sources from the appendage and obviates the need for long-term anticoagulation in the majority of patients.
Potential complications of surgical HyCASA include cardiac perforation or injury (<1%), pericarditis (almost universal usually settles before discharge), stroke (< 1 in 500) and incisional hernia (< 1%)
Endocardial catheter ablation remains the mainstay of invasive AF treatment. The HyCASA approach is reserved for the most difficult and recalcitrant AF cases. Our approach is to offer a patient HyCASA if they have failed two previous catheter ablation attempts and if the patient remains highly symptomatic.
Considering the highly selected patient population (difficult recalcitrant AF cases), the success rate has been: 82% of the 75 treated patients achieving successful AF suppression. These patients would otherwise have failed AF ablation and been only considered for pace and ablate or rate control only.
Key messages
- The first hybrid surgical and catheter AF ablation programme (HyCASA) of its kind in the Southern Hemisphere was established in Perth and is now a global education centre for this procedure
- HyCASA ablation strategy comprises both epicardial surgical and endocardial ablation components
- Consider referral for HyCASA when patients have failed catheter ablation and remain symptomatic as an alternative to the pace and ablate or other rate control strategies.
Author competing interests – Heart Rhythm Clinic of WA is the only practice currently offering this treatment in Australia.