Contact Force Sensing Radiofrequency Ablation Catheters
Contact force sensing, the ability to determine the amount of pressure the catheter is exerting on the tissue, is another new development in radiofrequency catheters. Although irrigated catheters reduce the incidence of char formation, they can lead to another complication—steam pops. Steam pops occur when the heat from the radiofrequency catheter causes water inside the tissue to boil and steam. Sometimes so much steam builds up that it bursts through the tissue. Steam pops create craters in the heart tissue. They can lead to a severe complication, cardiac perforation (a rip or tear in the heart).
Contact force is one of the variables that affects transmurality. By monitoring contact force, which is measured in grams, electrophysiologists (EPs) may be able to apply just the right amount of pressure to create transmural lesions while avoiding steam pops.
Here are the main contact force sensing radiofrequency catheters.
TactiCath Quartz Contact Force Ablation Catheter
The TactiCath Quartz Ablation Catheter (Abbott) is a third-generation contact forcing catheter, which received US FDA approval in 2014. This catheter has three optical fibers that emit wavelengths. When the catheter tip touches tissue, the optical fibers bend. TactiCath’s software calculates the changes in the wavelengths between the optical fibers and translates this information into a measurement of how much pressure is being applied to the heart tissue. Then the radiofrequency energy console shows the level of contact force. A small green bubble indicates that little contact force is being used, and a large green bubble denotes a large amount of contact force. The console also displays a numerical read-out of contact pressure and the angle of the catheter.
Data for TactiCath comes from four clinical studies that included 464 patients. The TOCCATA study examined the relationship between contact force and clinical outcomes in 34 patients who underwent ablation of afib. At one year, 80% of patients treated with an average contact force greater than 20 g were free from afib recurrence at 12 months, whereas all patients treated with an average contact force less than 10 g experienced afib recurrence. This study highlights that suboptimal contact force is associated with reduced clinical outcomes. The rate of serious adverse events in the TOCCATA study was 12%.1,2
The EFFICAS clinical studies conducted in Europe were a sequence of studies that examined contact force recommendations in ablation of paroxysmal afib. In EFFICAS I, levels of optimal contact were identified for achieving durable lesions to the pulmonary veins.3 In EFFICAS II, when contact force was adjusted by the operator to use the optimal contact force identified in the EFFICAS I trial, durable lesions were achieved in most patients.4
The TOCCASTAR study included 300 paroxysmal afib patients who were intolerant or unresponsive to antiarrhythmic drugs. They were randomized to radiofrequency catheter ablation with TactiCath or standard of care (a non-contract force catheter). Sixty-eight percent of patients who underwent ablation with the TactiCath achieved freedom from afib and off all antiarrhythmic drugs at 12 months. This compared to 69.4% of patients who were treated with a non-contact force catheter. Thus, the TactiCath catheter achieved similar successful ablation outcomes to those achieved with the standard of care.5
In the TactiCath group, patients who underwent ablation using contact force levels that were deemed optimal achieved greater ablation success (76% free from afib at one year) than those who received non-optimal contact force (58% free from afib at one year). However, similar adverse events were observed in the TactiCath group (7.2%) versus standard of care (non-contact force catheter) (9.1%).
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THERMOCOOL SMARTTOUCH Irrigated Catheter
The THERMOCOOL SMARTTOUCH Catheter (Biosense Webster) received US FDA approval in 2014. This contact force sensing catheter enables direct measurement of contact force during ablation procedures. Near the catheter tip is a spring coil surrounded by a magnetic signal emitter and three magnetic signal sensors. The coil allows the tip to bend in response to pressure applied to the catheter, causing the sensors to change position. The SMARTTOUCH then uses the changes in the position of the sensors to calculate the changes in catheter angle and contact force. If the CARTO 3 electroanatomic mapping system is being used, the data is transmitted to the system to provide real-time graphical feedback.
The SMART-AF study investigated the safety and effectiveness of the THERMOCOOL SMARTTOUCH catheter in paroxysmal afib patients who were intolerant or unresponsive to antiarrhythmic drugs. Seventy-two percent of patients achieved ablation success at one year (defined as freedom from atrial fibrillation/atrial flutter/atrial tachycardia). When the contact force was optimized during 80% of the ablation, patients were 4.25 times more likely to experience successful ablation. There were no reports of major adverse events and few reports of adverse events related to the procedure.6
The THERMOCOOL SMARTTOUCH SF catheter, which was US FDA-approved in 2016, combines the contact force technology of the THERMOCOOL SMARTTOUCH catheter with an irrigated catheter tip design. Compared to standard irrigated catheter tips with six holes, the THERMOCOOL SMARTTOUCH has 56 irrigated holes to improve cooling and reduce fluid delivery.
The SMART-SF trial was conducted at 17 US study sites. It investigated the safety and effectiveness of the THERMOCOOL SMARTTOUCH SF catheter in patients with symptomatic paroxysmal afib who couldn’t take antiarrhythmic drugs. A low rate of adverse events (2.5%) was reported in the study, and all adverse events were resolved or improved within one month. In addition, a 55.2% reduction in total fluoroscopy time was reported in the study; therefore, there was a reduction in radiation exposure to patients.7
Collectively, these recent clinical studies highlight the importance of contact force in ablation procedures and indicate that there are optimal contact force levels that lead to more successful ablation outcomes.
To learn about other advancements in catheter design and alternative energy sources, see Balloon Catheters. To learn about other technology and tools used in catheter ablation, see Mapping and Navigation. To learn more about whether catheter ablation is appropriate for you, see Are You a Candidate for Catheter Ablation.
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