Contact force highlighted at HRS 2013

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Endosense presented new study data validating the importance of several proprietary contact force parameters in cardiac ablation procedures, including its most recently developed Lesion Index (LSI), at Heart Rhythm 2013. The data also demonstrated the ability of the company’s TactiCath ablation catheter to detect excessive contact force during robotic catheter navigation.

Moussa Mansour, director of the Cardiac Electrophysiology Laboratory as well as the Atrial Fibrillation Program at Massachusetts General Hospital, USA, who presented an abstract entitled “Application of contact force guidelines increases durable isolation after pulmonary vein isolation for paroxysmal atrial fibrillation” provided evidence of the value of combining three contact force parameters to improve durability of pulmonary vein isolation (PVI) to treat paroxysmal atrial fibrillation (PAF). These include Endosense’s contact force; Force Time Integral (FTI); and Lesion Index (LSI). Featured in Endosense’s new TactiCath Quartz device, LSI is a sophisticated algorithm that combines radiofrequency power, ablation time and contact force applied to the cardiac tissue in order to estimate lesion formation in real time.


Contact force guidelines were developed from Endosense’s TOCCATA study, a 12-month study completed in 2010 which found that clinical outcomes improve with contact force > 20g; and its later EFFICAS I post-market clinical trial, which not only revealed the value of FTI, but established the clinical practice guideline of an absolute minimum FTI of 400gs per individual ablation lesion. Early results of the TOCCASTAR IDE study presented by Mansour underscored this guidance and showed that, in a subgroup that underwent a redo procedure, subjects treated with the combined contact force guidelines of contact force > 20g, FTI > 400gs and LSI > 5.0 showed the strongest improvement in pulmonary vein isolation rate: 80% when all criteria were fulfilled versus 46% when not all criteria were fulfilled.


“The data has clearly demonstrated the importance of contact force in achieving durable pulmonary vein isolation following the catheter ablation treatment of PAF,” said Dipen Shah, professor of Cardiology at the University Hospital Geneva and co-author of the paper. “I believe these new contact force guidelines have great potential to improve clinical practice and, ultimately, lead to better patient outcomes.”


Christian Sohns, Kings College London, UK, in a paper entitled “Quantitative magnetic resonance imaging analysis of the relationship between contact force and left atrial scar formation after catheter ablation of atrial fibrillation” examined the relationship between contact force achieved during catheter ablation for PAF and late gadolinium enhancement MRI (LGE-MRI) signal intensity as a measure for durable isolation following PVI. He found that increased LGE-MRI signal intensity correlates with increased FTI values, hence an important guidance for long-term isolation.


While low contact force can lead to ineffective lesions, excessive contact force may cause safety concerns. In the abstract, “Complementary techniques and location of excessive contact force detection in the left atrium with robotic catheter navigation,” Sarah K Hussain, University of Virginia, Charlottesville, USA, concluded that in a simulated bench experiment, Endosense’s TactiCath ablation catheter could enhance the capabilities of current robotic catheter systems in detecting excessive contact force wherever it occurs in the left atrium.


In the United States, the TactiCath is an investigational device.