Hendrik Lambert

Novel Contact Force Sensor Incorporated in Irrigated Radiofrequency Ablation Catheter Predicts Lesion Size and Incidence of Steam Pop and Thrombus

Background—An open-irrigated radiofrequency (RF) ablation catheter was developed to measure contact force (CF). Three optical fibers measure microdeformation of the catheter tip. The purpose of this study was to (1) validate the accuracy of CF sensor (CFS) (bench test); and (2) determine the relationship between CF and tissue temperatures, lesion size, steam pop, and thrombus during RF ablation using a canine thigh muscle preparation. Methods and Results—CFS measurements (total 1409) from 2 catheters in 3 angles (perpendicular, parallel, and 45°) were compared with a certified balance (range, 0 to 50 g). CFS measurements correlated highly (R2≥0.988; mean error, ≤1.0 g). In 10 anesthetized dogs, a skin cradle over the thigh muscle was superfused with heparinized blood at 37°C. A 7F catheter with 3.5-mm saline-irrigated electrode and CFS (Endosense) was held perpendicular to the muscle at CF of 2, 10, 20, 30, and 40 g. RF was delivered (n=100) for 60 seconds at 30 or 50 W (irrigation 17 or 30 mL/min). Tissue temperature (3 and 7 mm depths), lesion size, thrombus, and steam pop increased significantly with increasing CF at each RF power. Lesion size was greater with applications of lower power (30 W) and greater CF (30 to 40 g) than at high power (50 W) with lower CF (2 to 10 g). Conclusions—This novel ablation catheter, which accurately measures CF, confirmed CF is a major determinant of RF lesion size. Steam pop and thrombus incidence also increases with CF. CFS in an open-irrigated ablation catheter that may optimize the selection of RF power and application time to maximize lesion formation and reduce the risk of steam pop and thrombus.

A novel radiofrequency ablation catheter using contact force sensing: Toccata study

OBJECTIVES The aim of this multicenter study was to evaluate the device- and procedure-related safety of a novel force-sensing radiofrequency (RF) ablation catheter capable of measuring the real-time contact force (CF) and to present CF data and its possible implications on patient safety. BACKGROUND The clinical outcome of RF ablation for the treatment of cardiac arrhythmias may be affected by the CF between the catheter tip and the tissue. Insufficient CF may result in an ineffective lesion, whereas excessive CF may result in complications. METHODS Seventy-seven patients (43 with right-sided supraventricular tachycardia [SVT] and 34 with atrial fibrillation [AF]) received percutaneous ablation with the novel studied catheter. The CF applied and safety events related to the procedure were reported. RESULTS CF values at mapping ranged from 8 ± 8 to 60 ± 35 g and from 12 ± 10 to 39 ± 29 g in the SVT group and the LA group, respectively, showing a significant interinvestigator variability (P < .0001). High transient CFs (>100 g) were noted in 27 patients (79%) of the LA group. One device-related complication (tamponade, 3%) occurred in the AF group. CONCLUSIONS Catheter ablation using real-time CF technology is safe for the treatment of SVT and AF. High CFs may occur during catheter manipulation and not just during ablation, suggesting that measuring CF may provide additional useful information to the operator for safe catheter manipulation. In the future, CF-sensing catheters may also increase the effectiveness of RF ablations by allowing better control of the RF lesion size.

Importance of catheter contact force during irrigated radiofrequency ablation: evaluation in a porcine ex vivo model using a force-sensing catheter.

Effect of Ablation Electrode Contact Force. Introduction: Ablation electrode–tissue contact has been shown to be an important determinant of lesion size and safety during nonirrigated ablation but little data are available during irrigated ablation. We aimed to determine the importance of contact force during irrigated‐tip ablation.

Electrical reconnection after pulmonary vein isolation is contingent on contact force during initial treatment: results from the EFFICAS I study

Background—Pulmonary vein isolation is the most prevalent approach for catheter ablation of paroxysmal atrial fibrillation. Long-term success of the procedure is diminished by arrhythmia recurrences occurring predominantly because of reconnections in previously isolated pulmonary veins. The aim of the EFFICAS I multicenter study was to demonstrate the correlation between contact force (CF) parameters during initial procedure and the incidence of isolation gaps (gap) at 3-month follow-up. Method and Results—A radiofrequency ablation catheter with integrated CF sensor (TactiCath, Endosense, Geneva, Switzerland) was used to perform pulmonary vein isolation in 46 patients with paroxysmal atrial fibrillation. During the ablation procedure, the operator was blinded to CF information. At follow-up, an interventional diagnostic procedure was performed to assess gap location as correlated to index procedure ablation parameters. At follow-up, 65% (26/40) of patients showed ≥1 gaps. Ablations with minimum Force–Time Integral (FTI) <400 gs showed increased likelihood for reconnection (P<0.001). Reconnection correlated strongly with minimum CF (P<0.0001) and minimum FTI (P=0.0007) at the site of gap. Gap occurrence showed a strong trend with lower average CF and average FTI. CF and FTI are generally higher on the right side, although the left anterior segment presents a unique challenge to achieve stable position with good CF. Conclusions—Minimum CF and minimum FTI values are strong predictors of gap formation. Optimal CF parameter recommendations are a target CF of 20 g and a minimum FTI of 400 gs for each new lesion.

Area Under the Real-Time Contact Force Curve (Force–Time Integral) Predicts Radiofrequency Lesion Size in an In Vitro Contractile Model

FTI Predicts RF Lesion Size in Contractile Model. Introduction: Electrode tissue contact, radiofrequency (RF) power and duration are major determinants of RF lesion size. Since contact forces (CF) vary in the beating heart, we evaluated contact force–time integral (FTI) as a predictor of lesion size at constant RF power in a contractile bench model simulating the beating heart.

Electrical Reconnection After Pulmonary Vein Isolation Is Contingent on Contact Force During Initial TreatmentClinical Perspective

Background—Pulmonary vein isolation is the most prevalent approach for catheter ablation of paroxysmal atrial fibrillation. Long-term success of the procedure is diminished by arrhythmia recurrences occurring predominantly because of reconnections in previously isolated pulmonary veins. The aim of the EFFICAS I multicenter study was to demonstrate the correlation between contact force (CF) parameters during initial procedure and the incidence of isolation gaps (gap) at 3-month follow-up. Method and Results—A radiofrequency ablation catheter with integrated CF sensor (TactiCath, Endosense, Geneva, Switzerland) was used to perform pulmonary vein isolation in 46 patients with paroxysmal atrial fibrillation. During the ablation procedure, the operator was blinded to CF information. At follow-up, an interventional diagnostic procedure was performed to assess gap location as correlated to index procedure ablation parameters. At follow-up, 65% (26/40) of patients showed ≥1 gaps. Ablations with minimum Force–Time Integral (FTI) <400 gs showed increased likelihood for reconnection (P<0.001). Reconnection correlated strongly with minimum CF (P<0.0001) and minimum FTI (P=0.0007) at the site of gap. Gap occurrence showed a strong trend with lower average CF and average FTI. CF and FTI are generally higher on the right side, although the left anterior segment presents a unique challenge to achieve stable position with good CF. Conclusions—Minimum CF and minimum FTI values are strong predictors of gap formation. Optimal CF parameter recommendations are a target CF of 20 g and a minimum FTI of 400 gs for each new lesion.

Randomized, Controlled Trial of the Safety and Effectiveness of a Contact Force-Sensing Irrigated Catheter for Ablation of Paroxysmal Atrial Fibrillation: Results of the TactiCath Contact Force Ablation Catheter Study for Atrial Fibrillation (TOCCASTAR) Study.

Background— Contact force (CF) is a major determinant of lesion size and transmurality and has the potential to improve efficacy of atrial fibrillation ablation. This study sought to evaluate the safety and effectiveness of a novel irrigated radiofrequency ablation catheter that measures real-time CF in the treatment of patients with paroxysmal atrial fibrillation. Methods and Results— A total of 300 patients with symptomatic, drug-refractory, paroxysmal atrial fibrillation were enrolled in a prospective, multicenter, randomized, controlled trial and randomized to radiofrequency ablation with either a novel CF-sensing catheter or a non-CF catheter (control). The primary effectiveness end point consisted of acute electrical isolation of all pulmonary veins and freedom from recurrent symptomatic atrial arrhythmia off all antiarrhythmic drugs at 12 months. The primary safety end point included device-related serious adverse events. End points were powered to show noninferiority. All pulmonary veins were isolated in both groups. Effectiveness was achieved in 67.8% and 69.4% of subjects in the CF and control arms, respectively (absolute difference, −1.6%; lower limit of 1-sided 95% confidence interval, −10.7%; P=0.0073 for noninferiority). When the CF arm was stratified into optimal CF (≥90% ablations with ≥10 g) and nonoptimal CF groups, effectiveness was achieved in 75.9% versus 58.1%, respectively (P=0.018). The primary safety end point occurred in 1.97% and 1.40% of CF patients and control subjects, respectively (absolute difference, 0.57%; upper limit of 1-sided 95% confidence interval, 3.61%; P=0.0004 for noninferiority). Conclusions— The CF ablation catheter met the primary safety and effectiveness end points. Additionally, optimal CF was associated with improved effectiveness. Clinical Trial Registration— http://www.clinicaltrials.gov. Unique identifier: NCT01278953.

EFFICAS II: optimization of catheter contact force improves outcome of pulmonary vein isolation for paroxysmal atrial fibrillation

Aims A challenge of pulmonary vein isolation (PVI) in catheter ablation for paroxysmal atrial fibrillation (PAF) is electrical reconnection of the PV. EFFICAS I showed correlation between contact force (CF) parameters and PV durable isolation but no prospective evaluation was made. EFFICAS II was a multicentre study to prospectively assess the impact of CF guidance for an effective reduction of PVI gaps. Methods and results Pulmonary vein isolation using a radiofrequency (RF) ablation catheter with an integrated force sensor (TactiCath™) was performed in patients with PAF. Operators were provided EFFICAS I-based CF guidelines [target 20 g, range 10–30 g, minimum 400 g s force-time integral (FTI)]. Conduction gaps were assessed by remapping of PVs after 3 months, and gap rate was compared with EFFICAS I outcome. At follow up, 24 patients had 85% of PVs remaining isolated, compared with 72% in EFFICAS I (P = 0.037) in which CF guidelines were not used. The remaining 15% of gaps correlated to the number of catheter moves at creating the PVI line, quantified as Continuity Index. For PV lines with contiguous lesions and low catheter moves, durable isolation was 81% in EFFICAS I and 98% in EFFICAS II (P = 0.005). At index procedure, the number of lesions was reduced by 15% in EFFICAS II vs. EFFICAS I. Conclusion The use of CF with the above guidelines and contiguous deployment of RF lesions in EFFICAS II study resulted in more durable PVI in catheter ablation of PAF.

A Randomized Controlled Trial of the Safety and Effectiveness of a Contact Force Sensing Irrigated Catheter for Ablation of Paroxysmal Atrial Fibrillation: Results of the TOCCASTAR Study

Background— Contact force (CF) is a major determinant of lesion size and transmurality and has the potential to improve efficacy of atrial fibrillation ablation. This study sought to evaluate the safety and effectiveness of a novel irrigated radiofrequency ablation catheter that measures real-time CF in the treatment of patients with paroxysmal atrial fibrillation. Methods and Results— A total of 300 patients with symptomatic, drug-refractory, paroxysmal atrial fibrillation were enrolled in a prospective, multicenter, randomized, controlled trial and randomized to radiofrequency ablation with either a novel CF-sensing catheter or a non-CF catheter (control). The primary effectiveness end point consisted of acute electrical isolation of all pulmonary veins and freedom from recurrent symptomatic atrial arrhythmia off all antiarrhythmic drugs at 12 months. The primary safety end point included device-related serious adverse events. End points were powered to show noninferiority. All pulmonary veins were isolated in both groups. Effectiveness was achieved in 67.8% and 69.4% of subjects in the CF and control arms, respectively (absolute difference, −1.6%; lower limit of 1-sided 95% confidence interval, −10.7%; P=0.0073 for noninferiority). When the CF arm was stratified into optimal CF (≥90% ablations with ≥10 g) and nonoptimal CF groups, effectiveness was achieved in 75.9% versus 58.1%, respectively (P=0.018). The primary safety end point occurred in 1.97% and 1.40% of CF patients and control subjects, respectively (absolute difference, 0.57%; upper limit of 1-sided 95% confidence interval, 3.61%; P=0.0004 for noninferiority). Conclusions— The CF ablation catheter met the primary safety and effectiveness end points. Additionally, optimal CF was associated with improved effectiveness. Clinical Trial Registration— http://www.clinicaltrials.gov. Unique identifier: NCT01278953.

Relationship Between Catheter Contact Force and Radiofrequency Lesion Size and Incidence of Steam Pop in the Beating Canine Heart Electrogram Amplitude, Impedance, and Electrode Temperature Are Poor Predictors of Electrode-Tissue Contact Force and Lesion Size

Background—Electrode-tissue contact force (CF) is believed to be a major factor in radiofrequency lesion size. The purpose of this study was to determine, in the beating canine heart, the relationship between CF and radiofrequency lesion size and the accuracy of predicting CF and lesion size by measuring electrogram amplitude, impedance, and electrode temperature. Methods and Results—Eight dogs were studied closed chest. Using a 7F catheter with a 3.5 mm irrigated electrode and CF sensor (TactiCath, St. Jude Medical), radiofrequency applications were delivered to 3 separate sites in the right ventricle (30 W, 60 seconds, 17 mL/min irrigation) and 3 sites in the left ventricle (40 W, 60 seconds, 30 mL/min irrigation) at (1) low CF (median 8 g); (2) moderate CF (median 21 g); and (3) high CF (median 60 g). Dogs were euthanized and lesion size was measured. At constant radiofrequency and time, lesion size increased significantly with increasing CF (P<0.01). The incidence of a steam pop increased with both increasing CF and higher power. Peak electrode temperature correlated poorly with lesion size. The decrease in impedance during the radiofrequency application correlated well with lesion size for lesions in the left ventricle but less well for lesions in the right ventricle. There was a poor relationship between CF and the amplitude of the bipolar or unipolar ventricular electrogram, unipolar injury current, and impedance. Conclusions—Radiofrequencylesion size and the incidence of steam pop increase strikingly with increasing CF. Electrogram parameters and initial impedance are poor predictors of CF for radiofrequency ablation.