Catheter-tissue Contact Force Research Articles

Local impedance technology for effective PVI with a novel ablation catheter: results from a large, international, multicenter registry

Abstract Funding Acknowledgements Type of funding sources: None. Background Highly localized impedance (LI) measurements in combination with a catheter-tissue contact force (CF) during atrial fibrillation (AF) ablation may improve tissue characterization and lesion prediction during pulmonary vein isolation (PVI). Purpose This analysis explores the relationship between LI parameters, ablation spot locations and procedural success during ablation of PVs in a large population of consecutive AF patients. Methods Two-hundred twelve consecutive patients from 16 European centers undergoing de novo AF radiofrequency (RF) catheter ablation with a novel open-irrigated tip catheter enabled by CF and LI measurement capabilities (Stablepoint) were included. Ablation was guided by the magnitude and time-course of LI drop during RF delivery. The interlesion distance between each ablation spot was set ≤6 mm. First pass isolation (FPI) was defined as successful PVI at or before completion of the first encircling lesion set regardless of visual gaps. Procedural endpoint was the achievement of the PVI as assessed by entrance and exit block. Data are reported as mean±SD. Results A total of 13891 ablation spots performed around PVs were analyzed (baseline LI=161.2±19 Ω; LI drop=21.9±9 Ω; LI drop rate=3.1±2 Ω/s; RF Delivery time=9.2±4 s; CF=12.5±7 g). LI drop was predicted by baseline LI (r=0.56, 95%CI:0.55 to 0.57, p<0.0001). A total of 80 PV gaps were detected, mostly at the right pairs of the PV (63.7%, p=0.013). The FPI rate per vein was 93.3% resulting from 180 patients (84.9%) with FPI. PV gaps were located at anterior (31.3%), posterior (31%), and carina (16%) sites after the FPI evaluation. At successful ablation spots, both baseline LI and LI drop were larger than at PV gap spots (161.4Ω vs 153.0Ω, p<0.0001 for baseline LI; 22.1Ω vs 14.4Ω, p<0.0001 for LI drop), whereas RF delivery time was shorter (9.1s at successful ablation spots vs 10.1s at PV gap spots, p<0.0001). CF values seem to be higher at successful ablation spot that at PV gap spots (12.5g vs 11.4g, p=0.0592). On the basis of the receiver-operating characteristic curve (ROC) analysis, the best LI drop that predicts successful ablation spots was >20Ω (Sensitivity=56.8%, Specificity=93.2%, PPV=99.7%, Area under the ROC curve=0.7841, p<0.0001). Optimal LI drops were identified by left atrial region and were >21Ω at anterior sites and >18Ω at posterior sites. No steam pops or complications were reported during the procedures. All PVs were successfully isolated in all study patients Conclusions In a large, international population of consecutive de novo AF cases, an ablation strategy guided by LI and CF information results in a very high first pass isolation rate. LI drop is predictive of PV segment isolation. A regional approach to RF ablation guided by LI information may be useful in patients with AF.

Is catheter-tissue contact force value important for ablation of ventricular arrhythmias originating from the left ventricular papillary muscles?

Good catheter-tissue contact is mandatory to create effective ablation lesions. The minimal contact force value for ablation of arrhythmias originating from the left ventricle is 8.0-10.0 grams but is not known for arrhythmias arising from papillary muscles. To analyze contact force values during successful ablation procedures of arrhythmias originating from the left ventricular papillary muscles. 24 consecutive patients (mean age 57.9 ± 11.9 years, 16 males) underwent ablation of premature ventricular complexes originating from left ventricular papillary muscles with the use of CARTO electro-anatomical system and intracardiac echocardiography. Acute complete abolition of ventricular ectopy was obtained in 23 (96%) patients. The fluoroscopy time was 3.9 ± 3.5 min and procedure duration - 114.8 ± 37.9 min. The mean contact force during successful ablations was 3.0 ± 1.1 grams and 3.18 ± 1.8 grams for antero-lateral and postero-medial papillary muscle, respectively (NS). The mean contact force during a single unsuccessful ablation was 3.0 grams. At control Holter ECG, the mean Ectopy Burden was Reduced in the Antero-Lateral Papillary Muscle Group from 18.0% ± 7.9% to 2.6% ± 2.9% (p = 0.005415) and in the Postero-Medial Papillary Muscle Group - from 34.8% ± 13.7%-1.7% ± 1.3% (p = 0.012694). During Median 27 (IQR: 17-34) Months of Follow-up There one Recurrence of Arrhythmia. The values of contact force for successful ablation of ventricular ectopy originating from the left ventricular papillary muscles may be much lower than those for ablation of other foci which questions the role of contact force measurement when ablating these arrhythmias.

Abstract 9064: The Increase of Tissue Echogenicity as the Pre-State of Steam Pops During Radiofrequency Catheter Ablation

Introduction: Steam pops (SPs) during radiofrequency catheter ablation (RFA) using force sensing catheters are infrequent but represent a potential severe complication such as embolic stroke, cardiac perforation. SPs remains unpredictable, and unclear in detailed phenomenon. Methods: In an ex vivo, we set the bovine myocardium to 36 °C in a constant temperature bath and performed an experiment in a water tank that generated a non-pulsatile flow. RFA using irrigation catheter was applied at catheter-tissue contact force (CF) 5, 10, 20g, 30g, 40g, and 50g for 30sec. The increase of tissue echogenicity (increased echo brightness) observed by intracardiac echocardiographic images using ViewFlex™ Xtra and impedance during RFA were evaluated with and without SPs. Results: SPs phenomenon appeared in 48 out of 137 sites (35%), and the increased echo brightness during RFA was observed in 89 lesions (65%). All lesions with SPs showed increased echo brightness before SPs (6.4±6.1sec before SPs). Sites with SPs showed stronger CF (30.8±14.8g vs. 22.9±15.9g, p=0.0047), higher initial impedance (78±12Ω vs. 73±9Ω, p=0.0063), greater impedance drops in 5 seconds after the beginning of RFA (13±7Ω, vs. 6±5Ω, p<0.0001), and earlier appearance of increased echo brightness (9.7±6.2 vs 17.4±6.3 sec, p<0.0001). Among 89 lesions with increased echo brightness, sites with SPs showed greater impedance drops in 5 seconds after the beginning of RFA (13±7Ω, vs. 7±6Ω, P<0.0001). In ROC curve analysis of the impedance drops in 5 seconds after the beginning of RFA (AUC, 0.81; sensitivity, 85%; specificity, 71%), optimal cut-off value of SPs was 7.6Ω, and SPs were not observed in lesions with the impedance drops of 3Ω or less. (Figure) Conclusions: The increase of tissue echogenicity observed by ICE images show the pre-state of all steam pops during RFA. Steam pops could be avoided by checking the impedance drop at the initial stage of RFA under ICE monitoring.

Catheter-related complications and mortality of atrial fibrillation ablation following introduction of contact force-sensing technology

ObjectivesContact force-sensing catheters allow real-time catheter-tissue contact force monitoring during atrial fibrillation. These catheters were rapidly adopted into clinical practice following market introduction in 2014, but concerns have been raised...

Impact of catheter-tissue contact force on lesion size during right ventricular outflow tract ablation in a swine model.

BackgroundThe catheter-tissue contact force (CF) is one of the significant determinants of lesion size and thus has a considerable impact on the effectiveness of ablation procedures. This study aimed to evaluate the impact of CF on the lesion size during right ventricular outflow tract (RVOT) ablation in a swine model.MethodsTwelve Guangxi Bama miniature male pigs weighing 40 to 50 kg were studied. After general anesthesia, a ThermoCool SmartTouch contact-sensing ablation catheter was introduced to the RVOT via the femoral vein under the guidance of the CARTO 3 system. The local ventricular voltage amplitude and impedance were measured using different CF levels. We randomly divided the animals into the following four groups according to the different CF levels: group A (3–9 g); group B (10–19 g); group C (20–29 g); and group D (30–39 g). Radiofrequency ablations were performed at three points in the free wall and septum of the RVOT in power control mode at 30 W for 30 s while maintaining the saline irrigation rate at 17 mL/min. At the end of the procedures, the maximum depth, surface diameter, and lesion volume were measured and recorded. A linear regression analysis was performed to determine the relationship between continuous variables.ResultsA total of 72 ablation lesions were created in the RVOT of the 12 Bama pigs. The maximum depth, surface diameter, and volume of the lesions measured were well correlated with the CF (free wall: β = 0.105, β = 0.162, β = 3.355, respectively, P < 0.001; septum: β = 0.093, β = 0.150, β = 3.712, respectively, P < 0.001). The regional ventricular bipolar voltage amplitude, unipolar voltage amplitude, and impedance were weakly positively associated with the CF (β = 0.065, β = 0.125, and β = 1.054, respectively, P < 0.001). There was a significant difference in the incidence of steam pops among groups A, B, C, and D (free wall: F = 7.3, P = 0.032; septum: F = 10.5, P = 0.009); and steam pops occurred only when the CF exceeded 20 g. Trans-mural lesions were observed when the CF exceeded 10 g in the free wall, while the lesions in the septum were non-trans-mural even though the CF reached 30 g.ConclusionsCF seems to be a leading predictive factor for the size of formed lesions in RVOT ablation. Maintaining the CF value between 3 and 10 g may be reasonable and effective for creating the necessary lesion size and reducing the risk of complications, such as steam pops and perforations.

Eliminating the effects of motion during radiofrequency lesion delivery using a novel contact-force controller.

Catheter-tissue contact force is a determinant of radiofrequency (RF) ablation lesion effectiveness. However, ablation on a beating heart is subject to force variability, making it difficult to optimally deliver consistently durable and transmural lesions. This work evaluates improvements in contact force stability and lesion reproducibility by using a catheter contact-force controller (CFC) during lesion delivery in vitro and in vivo. Using a sheath and force-sensing catheter, an experienced operator attempted to maintain a constant force of 20 g at targets within the atria and left ventricle of a pig manually and using the CFC; the average force and contact-force variation (CFV) achieved using each approach were compared. Ablation lesions (20 W, 30 seconds, 17 mL/min irrigation) were created in bovine tissue samples mounted on a platform programmed to reproduce clinically relevant motion. CFC-assisted lesions were delivered to stationary and moving tissue with forces of 5 to 35 g. Mimicking manual intervention, lesions were also delivered to moving tissue while the CFC was disabled. Resultant lesion volumes were compared using two-way analysis of variance. When using the CFC, the average force was within 1 g of the set level, with a CFV less than 5 g, during both in vitro and in vivo experiments. Reproducible and statistically identical (P = .82) lesion volumes proportional to the set force were achieved in both stationary and moving tissue when the CFC was used. CFC assistance maintains constant force in vivo and removes effect of motion on lesion volume during RF lesion delivery.

P300Characterization of catheter tissue contact force in treating premature ventricular complexes arising from the aortic root

P300Characterization of catheter tissue contact force in treating premature ventricular complexes arising from the aortic root

Design and Evaluation of a Catheter Contact-Force Controller for Cardiac Ablation Therapy.

Maintaining a constant contact force (CF) of an ablation catheter during cardiac catheter ablation therapy is clinically challenging due to inherent myocardial motion, often resulting in poor ablation of arrhythmogenic substrates. To enable a prescribed contact force to be applied during ablation, a catheter contact force controller (CCFC) was developed. The system includes a hand-held device attached to a commercial catheter and steerable sheath. A compact linear motor assembly attaches to an ablation catheter and autonomously controls its relative position within the shaft of the steerable sheath. A closed-loop control system is implemented within embedded electronics to enable real-time catheter-tissue contact force control. To evaluate the performance of the CCFC, a linear motion phantom was used to impose a series of physiological CF profiles; lesion CF was controlled at prescribed levels ranging from 15 to 40g. For a prescribed CF of 25g, the CCFC was able to regulate the CF with a root mean squared error of 3.7 ± 0.7g. The ability of the CCFC to retract the catheter upon sudden changes in tissue motion, which may have caused tissue damage, was also demonstrated. Finally, the device was able to regulate the CF for a predetermined amount of time according to a force-time integral model. The developed CCFC is capable of regulating catheter-tissue CF in a laboratory setting that mimics clinical ablation therapy. Catheter-tissue CF control promises to improve the precision and success of ablation lesion delivery.

Abstract 15618: Anatomy Does Matter: The Relationship Between Catheter-Tissue Contact Force and Anatomical Variations of Left Atrium

Background: Adequate catheter-to-myocardial contact force (CF) and catheter stability are important to create transmural lesions during catheter ablation of atrial fibrillation (AF). It is known that there are anatomical variations in left atrium (LA) and it is related to the outcome after the ablation. We tested any relationship between the CF and LA anatomical variations. Methods: Consecutive patients undergoing radiofrequency-based extensive encircling pulmonary vein (PV) isolation for the treatment of paroxysmal AF were dichotomized according to the LA anatomical variations; patients who had a PV-bifurcation region of LA ridge that was steep enough to enable a stable catheter-tip contact or a left common PV (group 1, the red arrows in Figure 1), or those who had neither (group 2, the blue arrows in Figure 1). The blinded operators carried out the procedure with the use of CARTO system, and the following VisiTag™ module setting was applied; a minimum time spent in an area of 5 seconds, a maximum distance the catheter has moved of 4mm, a force over time of 25%, and a minimum force of 10g. Low-CF tags was defined as ablation tags on CARTO map located at anterior aspect of left PVs that did not fulfill the pre-determined VisiTag™ criteria. The endpoints were the number of low-CF tags and freedom from AF 1 year after the ablation. Results: Patients in group 1 (n=31) had a smaller number of low-CF tags than those in group 2 (n=55, 2.8±2.1 vs. 5.9±3.8; p=0.013). Freedom from AF was more common in group 1 compared to group 2 (80.6% vs. 60%; p=0.04), and was independently associated with the number of low-CF of &lt;3 (hazard ratio 2.4, confidence interval 1.12-6.87; p=0.026). Conclusions: Contact of the catheter-tip with the tissue may predict outcome after AF ablation, and it may depend on LA anatomical variations.

Open-irrigated laser catheter ablation: influence of catheter–tissue contact force on lesion formation

Catheter-tissue contact force (CF) is a major determinant for radiofrequency (RF) ablation lesion size and quality. We sought to test the influence of catheter CF on lesion formation by using an open-irrigated electrode-laser mapping and ablation (ELMA) catheter. With the ELMA catheter in a stable vertical position, continuous wave 1064 nm laser impacts at 15 W (9.5 W/mm(2)), 30 s (285 J/mm(2)), irrigation flow 30 mL/min, were aimed at the endocardial surface of bovine myocardium in heparinized stagnant blood (ACT >350 s) at room temperature (18 °C). Lesions were produced with CFs of 100 g, 10 g, in contact but without pressure, with the catheter tip 2.0 mm, and 5.0 mm away (n = 10, each). Lesions were evaluated morphometrically and were compared by the unpaired t tests. There were no significant differences between volumes of lesions achieved with catheter-tissue CF of 100 g, 10 g, and in contact without pressure: 297 ± 56.0 vs. 300 ± 39 vs. 320 ± 24, respectively (p > 0.05). However, volumes of lesions produced at a distance of 2 mm (95 ± 14 mm(3)) were significantly smaller (p < 0.0001), whereas at a distance of 5.0 mm, no lesions were produced. No steam-pop with crater or thrombus formation occurred. By using an open-irrigated ELMA catheter, catheter-tissue CF is not a determinant for laser ablation lesion size and quality. Maximum sizes of lesions can be achieved with the catheter in intimate endocardial contact without pressure. However, lesions can be produced also at a catheter-tissue distance of 2.0 mm. Noticeably, there is no thrombus formation during laser application with the free floating ELMA catheter in the stagnant blood.

Augmented Reality for Improving Catheterization in Magnetic Resonance Imaging-Guided Cardiac Electrophysiology Therapy1

Augmented Reality for Improving Catheterization in Magnetic Resonance Imaging-Guided Cardiac Electrophysiology Therapy1

MRI-conditional catheter sensor for contact force and temperature monitoring during cardiac electrophysiological procedures

Background MR-guided cardiac electrophysiological (EP) ablations has drawn increasing attention from both the MRI and EP communities, as high-contrast MR images provide images that couple anatomical information with lesion efficacy [1]. Catheter manipulation can be challenging for cardiac electrophysiologists as conventional electroanatomical maps, frequently include false space. Perforation of heart vessels and chambers by catheters is an uncommon, but devastating, complication during EP procedures arising from either excessive force or vaporization of tissue. Ultimately, these complications arise from an inability to adequately determine catheter-tissue Contact Force (CF) at the catheter tip [2]. Accurate catheter temperature control is of importance during EP Radiofrequency Ablation (RFA) for determining lesion efficacy. We hypothesized that a novel optical sensor design, attachable to a conventional ablation catheter, could allow simultaneous CF and temperature monitoring, providing useful information to the EP physician during the procedure. Methods

MRI-based visual and haptic catheter feedback: simulating a novel system's contribution to efficient and safe MRI-guided cardiac electrophysiology procedures

Background MRI-guided Electrophysiology (EP) procedures integrate real-time MRI images with catheter position during Radiofrequency Ablation (RFA) of arrhythmias [1]. Using simultaneous MR catheter tracking and imaging [2], this technology can both guide catheter manipulation and provide dynamic assessment of lesion efficacy [3]. Despite advances in MRI-guided EP, maneuvering catheters to the desired location and ensuring appropriate tissue contact is still challenging inside an MRI due to two issues: (1) inconsistent catheter-tissue contact force (CTCF); and (2) visual-motor disorientation arising from differences between manipulation of the catheter’s proximal controlling handle and visualization of the catheter-tissue interface. Both issues can increase the risk of cardiac perforation during catheter manipulation. We hypothesized that a technique based on MR imaging to generate force and vibrotactile alarms, as well as the presentation of a reproducible endoscopic view to the catheter operator, could facilitate precise application of RF energy, thereby increasing efficacy and reducing complications.

Catheter-tissue contact force for pulmonary veins isolation: a pilot multicentre study on effect on procedure and fluoroscopy time

AimsCatheter–tissue contact is critical for effective lesion creation in radiofrequency catheter ablation (RFCA). In a multicentre prospective study, we assessed the effect of direct contact force (CF) measurement on acute procedural parameters during RFCA of atrial fibrillation (AF).Methods and resultsA new open-irrigated tip catheter with CF sensing (SmartTouch™, Biosense Webster Inc.) was used. All the patients underwent the first ablation procedure for paroxysmal AF with antral pulmonary vein (PV) isolation, aiming at entry and exit conduction block in all PVs. Ninety-five patients were enroled in nine centres and successfully underwent ablation. Overall procedure time, fluoroscopy time, and ablation time were 138.0 ± 67.0, 14.3 ± 11.2, and 33.8 ± 19.4 min, respectively. The mean CF value during ablation was 12.2 ± 3.9 g. Force time integral (FTI) analysis showed that patients achieving a value below the median of 543.0gs required longer procedural (158.0 ± 74.0 vs. 117.0 ± 52.0 min, P = 0.004) and fluoroscopy (17.5 ± 13.0 vs. 11.0 ± 7.7 min, P = 0.007) times as compared with those in whom FTI was above this value. Patients in whom the mean CF during ablation was >20 g required shorter procedural time (92.0 ± 23.0 vs. 160.0 ± 67.0 min, P = 0.01) as compared with patients in whom this value was <10 g. Four groin haematomas were the only complications observed.ConclusionContact force during RFCA for PV isolation affects procedural parameters, in particular procedural and fluoroscopy times, without increasing complications.

Characterization of the impact of catheter-tissue contact force in lesion formation during cavo-tricuspid isthmus ablation in an experimental swine model

Catheter-tissue contact is critical for effective lesion creation. The objective of this study was to determine in an experimental swine model the pathological effects of cavo-tricuspid isthmus ablation using two systems that provide reliable measures of the pressure at the catheter tip during radiofrequency ablation procedures. We performed the procedure in eight pigs in our experimental electrophysiology laboratory after right femoral vein dissection and insertion of a 12 Fr. introducer during general anaesthesia and endotracheal intubation. The target contact force during the applications was <10 grs. (axial or lateral), 10-20, 20-30, and >30 grs. in two pigs each. The power was set at 40 W and maximum target temperature at 45°C. We performed a radiofrequency line dragging from the tricuspid valve to the inferior vena cava in the eight pigs. Euthanasia of the animals was carried out a week after the procedure and a pathological examination of the lesions was performed. In the endocardial macroscopic analysis the extent of lesions, presence of thrombus, transmurality, and endothelial rupture was assessed. External surface was examined searching for transmural lesions. The mean contact force applied was 18.7 ± 8.4 grs. and the mean depth of the lesions was 3.6 ± 2 mm. Lesions were never transmural with average forces <10 grs., and the mean depth was very low (0.75 mm). To achieve transmural lesions contact forces of at least 20 grs. were required. We found a positive correlation (r = 0.85, P < 0.05) between the average force during the applications and depth of the lesions. When ablating the cavo-tricuspid isthmus in a swine model, contact forces of at least 20 grs. are required to achieve transmural lesions. Catheter-tissue contact is critical for effective lesion creation. This information is important for improving ablation efficacy.

Initial impedance decrease as an indicator of good catheter contact: Insights from radiofrequency ablation with force sensing catheters

Good catheter-tissue contact force (CF) is critical for transmural and durable lesion formation during radiofrequency (RF) ablation but is difficult to assess in clinical practice. Tissue heating during RF application results in an impedance decrease at the catheter tip. The purpose of this study was to correlate achieved CF and initial impedance decreases during atrial fibrillation (AF) ablation. We correlated achieved CF and initial impedance decreases in patients undergoing ablation for AF with two novel open-irrigated CF-sensing RF catheters (Biosense Webster SmartTouch, n = 647 RF applications; and Endosense TactiCath, n = 637 RF applications). We then compared those impedance decreases to 691 RF applications with a standard open-irrigated RF catheter (Biosense Webster ThermoCool). When RF applications with the CF-sensing catheters were analyzed according to an achieved average CF <5 g, 5-10 g, 10-20 g, and >20 g, the initial impedance decreases during ablation were larger with greater CF. Corresponding median values at 20 seconds were 5 Ω (interquartile range [IQR] 2-7), 8 Ω (4-11), 10 Ω (7-16), and 14 Ω (10-19) with the SmartTouch and n/a, 4 Ω (0-10), 8 Ω (5-12), and 13 Ω (8-18) with the TactiCath (P <.001 between categories for both catheters). When RF applications with the SmartTouch (CF-sensing catheter, median achieved CF 12 g) and ThermoCool (standard catheter) were compared, the initial impedance decrease was significantly greater in the CF-sensing group with median decreases of 10 Ω (6-14 Ω) vs 5 Ω (2-10 Ω) at 20 seconds (P <.001 between catheters). The initial impedance decrease during RF applications in AF ablations is larger when greater catheter contact is achieved. Monitoring of the initial impedance decrease is a widely available indicator of catheter contact and may help to improve formation of durable ablation lesions.

Characterization of Catheter–Tissue Contact Force During Epicardial Radiofrequency Ablation in an Ovine Model

Contact force (CF) during radiofrequency ablation (RFA) is an important determinant of endocardial lesion size with limited data on epicardial RFA and CF. We evaluated CF characteristics using irrigated RFA on the epicardium in an ovine model. In 12 sheep, a 7-F irrigated RFA catheter with CF sensor was introduced via a pericardial incision onto/in parallel with ventricular epicardium. RFA (30 W per 30 second duration) was applied at 5g, 10g, 20g, 40g, and 70g: (1) over left and right ventricular myocardium with or without fat, (2) either directly over or adjacent to a coronary artery, or directly over the phrenic nerve. Force-time integral, lesion dimensions, and coronary artery/phrenic nerve injury were recorded. Lesion size, volume, and force-time integral progressively increased with higher CF (P<0.05). Steam pops occurred with high CF. Epicardial fat had an attenuating effect on RF penetration into myocardium (P<0.05); however, myocardial RF lesions could be created at sites with >3.5 mm epicardial fat. At sites with epicardial fat, each 10g increment in CF led to a 0.6 mm increase in lesion depth, whereas each 1 mm of fat reduced lesion depth into underlying myocardium by 0.7 mm. Extent of acute coronary injury with direct and indirect RFA and phrenic nerve palsy occurrence was proportional to CF. CF is a determinant of epicardial RF lesion size, steam pops, acute coronary artery injury, and phrenic nerve injury. Although epicardial fat limits lesion size, RFA with high CF can produce small myocardial RF lesions at sites of thick epicardial fat.

Initial impedance decrease as an indicator of good catheter contact: insights from radiofrequency ablation with two different force sensing catheters

Background: Good catheter-tissue contact force (CF) is critical for transmural and durable lesion formation during radiofrequency (RF) ablation, but difficult to assess in clinical practice. CF-sensing catheters have been developed recently. Tissue heating during RF-application results in an impedance decrease at the catheter tip. Methods: We correlated initial impedance decreases with the achieved CF during RF applications in atrial fibrillation ablations with a CF-sensing RF-catheter with stable catheter position and CF during the first 20 seconds. We analyzed 642 RF-applications in 12 patients undergoing ablation with the Tacticath catheter (Endosense) and 562 RF-applications in 21 patients undergoing ablation with the SmartTouch catheter (Biosense-Webster). Results: When RF-applications were analyzed according to an achieved average CF of 20g, starting impedance levels were 152Ω, 150Ω and 155Ω with the Tacticath catheter (p=0.12), and 124Ω, 126Ω and 131Ω with the SmartTouch catheter (p=0.001). The initial impedance decreases were significantly larger when greater CF was achieved. The corresponding median values were 3Ω (IQR -3-7), 7Ω (4-11) and 11Ω (7-16) at 10 seconds, and 4Ω (-4-10), 8Ω (4-12) and 13Ω (7-18) at 20 seconds with the Tacticath (p<0.001 between categories), and 6Ω (IQR 3-9), 9Ω (6-13) and 11Ω (7-16) at 10 seconds, and 7Ω (3-11), 10Ω (7-16) and 14Ω (10-19) at 20 seconds with the SmartTouch (p=0.001 between categories). ![Figure][1] Figure 1 Conclusions: The initial impedance decrease during RF-application is larger when greater catheter contact is achieved, with findings very consistent between two CF-sensing catheters. Monitoring of the initial impedance decrease is a widely available indicator of catheter contact and may help to improve formation of durable ablation lesions. [1]: pending:yes

Predictive value of impedance changes for real-time contact force measurements during catheter ablation of atrial arrhythmias in humans

Catheter-tissue contact force (CF) determines radiofrequency (RF) ablation lesion size. Impedance changes during RF delivery are used as surrogate markers for CF. The relationship between impedance and real-time CF in humans remains unknown. To determine whether impedance changes have predictive value for real-time CF during catheter ablation of atrial arrhythmias. Real-time CF, force-time integral, and impedance were measured in 2265 RF lesions for atrial fibrillation or flutter in 34 patients. Operators were blinded to CF measurements. Impedance preablation, at 5-second intervals for 30 seconds after the RF onset, maximal impedance fall and time to impedance plateau during RF were correlated with CF. Average CF was divided into low (≤20 g), intermediate (21-60 g), and high (>60 g) categories. Preablation impedance poorly correlated with preablation CF (R = .07). Maximal impedance fall modestly correlated with average CF and force-time integral (R = .32 and .37, respectively). There was a large degree of overlap in impedance fall between different CF categories. A maximal impedance fall of 10 Ω could predict average CF of >20 g, with a sensitivity and specificity of 71% and 53% and a positive and negative predictive value of 51% and 49%, respectively. Impedance fall was only able to differentiate between different CF categories ≥15 seconds after the RF onset. Higher CFs moderately correlated with delayed plateau in impedance (R = .41). Impedance measurements (both baseline and impedance fall) are, at best, moderately efficacious as surrogate markers for predicting real-time catheter-tissue CF. These findings highlight the importance of real-time CF measurements, rather than impedance changes to optimize ablation efficacy.

Marked Variation in Catheter-Tissue Contact Force During Cavotricuspid Isthmus Ablation Using Traditional Markers of Good Contact

Marked Variation in Catheter-Tissue Contact Force During Cavotricuspid Isthmus Ablation Using Traditional Markers of Good Contact