Real-time lesion formation and gap detection during ablation: DURABLE-I follow-up

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Evgeny Pokushalov

One-year results from the Dielectric Unravveling of RAdiofrequency ABLation Effectiveness (DURABLE-I) clinical trial have shown that the KODEX (Navix International Limited) system help to improve effectiveness by detecting gaps in real time during the index ablation procedure. The results were presented for the first time by principal investigator Evgeny A Pokushalov, Novosibirsk State Research Institute of Circulation Pathology, Novosibirsk, Russia, at the AF Symposium (11–13 January, Orlando, USA).

The trial showed that in most cases the EP Dynamics D700 electro-magnetic system detected gaps in real time during the index ablation procedure. The data suggests that if these gaps were treated before oedema formation, the rate of durable, contiuous and permanent pulmonary vein isolation (PVI), could potentially reach 75% compared to the conventional 25% success rate. A three-fold increase in success rate. Catheter ablation for symptomatic atrial fibrillation (AF) has moved from being an experimental procedure into a widely used therapy. It offers a safe and effective treatment option. A prerequisite for PVI are transmural and contiguous circumferential lesions around the pulmonary veins in the heart. However, electrical reconnection of initially isolated pulmonary veins remains a primary concern and is a dominant factor for arrhythmia recurrence during long-term follow up.

“We know from a lot of studies that the reason for reoccurrence of AF is gaps,” said Pokushalov. “We know this especially from the Gap-AF and PRESSURE randomised trials. Gaps are present in 70% of patients, meaning early reintervention could be considered a reasonable strategy for improving outcomes”. He continued, “Currently pulmonary vein reconnection is prevalent and while wsurrogate measurements like contact-force decrease this rate but do not eliminate it completely. There is still no real-time tool to assess the gaps directly.”

The scope of current electro-anatomical mapping system technologies is limited but the system used in this study, KODEX, has additional features. Unlike other commercially available electro-anatomical mapping systems that use a hybrid localisation technology and require specialty catheters, the KODEX system can operate with any standard sensor-less electrophysiology (EP) catheters.

KODEX is based on real time–wide-band electro-magnetic measurements. This is a new approach for navigation and ablation. These measurements enable high-precision navigation, high-definition real-time anatomical imaging, tissue imaging (wall thickness, scar, fibrosis, inflammation and oedema among others) and physical property imaging (e.g. contact-force, blood flow), real-time treatment monitoring.

“Very importantly these measurements allowed us to get outcome imaging,” said Pokushalov, “We set out to test whether this system is capable of identifying gaps that will only become apparent following oedema resolution.”

The dielectric unravelling of radiofrequency ablation effectiveness (DURABLE-I) clinical trial was a single centre (Meshalkin Institute, Novosibirsk, Russia) non-randomised trial, involving 36 consecutive persistent atrial fibrillation patients. All patients underwent Carto 3-guided conservative PVI using a Smarttouch ablation catheter (Biosense Webster) and lesion characteristics were recorded concomitantly by the dielectric system. PVI durability was fully validated by both electrical and adenosine tests. The patients were revisited by the same operator one month after ablation.

The patients were, on average, 58.5±7.6 years old with 16 of them being male and 20 being female. Of the patients, 25 (70%) had arterial hypertension and five (14%) had diabetes mellitus. They had an average CHAD2 score of 1.8±1.1 and the time from diagnosis to ablation was 46±33 months. The average left atrium diameter was 5.2±0.7.

The procedures had a total of 2,520 ablation points, with an average of 67±2 per patient. The points had an average contact force of 12.8±7.4 grams

At the follow-up procedure, one month post ablation, 61 gaps were identified with 27 (75%) of patients having gaps. The average number of gaps per patient was 2.64±1.96. At follow-up 16 (59%) of patients were symptomatic and, of those patients, six (37.5%) were documented as having arrhythmia. The same number of gaps were encountered on both the right and left PVI rings and there was no clear dominance of a specific segment. The dielectric system’s gap measurement accuracy was 83%.

At the end of the study the long-term outcome of the patients was good. Over a period of 12±2 (5–14) months post re-study, AF did not recur in any of the patients who had durable PVI at one month and only a single patient who underwent re-isolation is still in AF.

Pokushalov concluded by saying, “Despite state-of-the-art performance of ablation procedure together with strict electrical and pharmacological validation tests, 75% of the patients had reconduction one month later. This trial showed that the electro-magnetic system detected gaps in real time during the index ablation procedure in 18 out of the 27 patients. If these gaps were treated before oedema formation, the rate of durable, contiguous and permanent PVI, could potentially reach 75% compared to the conventional 25% success rate, which is a three-fold increase of success rate”.

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