Giovanni Leo

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.

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.

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.

Quantitative Magnetic Resonance Imaging Analysis of the Relationship Between Contact Force and Left Atrial Scar Formation After Catheter Ablation of Atrial Fibrillation

Catheter contact force (CF) is an important determinant of radiofrequency (RF) lesion quality during pulmonary vein isolation (PVI). Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) allows good visualization of ablation lesions.

Catheter tip force required for mechanical perforation of porcine cardiac chambers

AIMS Catheter manipulation during ablation procedures can produce injury and tamponade. We evaluated the mechanical forces required to perforate a porcine heart with an ablation catheter. METHODS AND RESULTS A 7 Fr, 3.5 mm irrigated radiofrequency (RF) ablation catheter with a force sensor (FS) within its tip was used to create right atrial (RA) free wall lesions in pigs. The intact heart was removed and the FS-equipped catheter was used to mechanically perforate (without RF delivery) the free walls of both atria and ventricles: directly and through an introducer sheath to prevent catheter shaft buckling. Perforation was also performed through epicardially visible RA lesions and adjacent unablated tissue. Twenty-four RA free wall lesions were created in four pigs. One hundred and forty-four mechanical perforations were performed: 44 RA, 30 left atrial (LA), 37 right ventricular (RV), and 33 left ventricular (LV). The RA and RV perforation force (PF) was lower than through the LA and LV (P<0.0001). The LV perforation time was shorter when the catheter was gripped through an introducer sheath (0.8±0.5 vs. 3.2±3 s, P<0.0001). Perforation force through transmural RA lesions was lower than through unablated RA tissue (172.4±79.1 vs. 300.6±116.8 g, P<0.0002). CONCLUSION The force threshold for mechanical perforation in the porcine heart is lower for right- compared with left-sided chambers, and also lower through recently created RA RF lesions compared with unablated RA tissue. Left ventricular perforation is achieved more rapidly with the ablation catheter in a sheath despite the same PF because the sheath prevents catheter buckling.

Mapping Contact Force during Catheter Ablation for the Treatment of Atrial Fibrillation: New Insights into Ablation Therapy

The distribution of ablation catheter contact force may be important for elucidating the mechanisms of pulmonary vein (PV) reconnection following PV isolation (PVI) for the treatment of paroxysmal atrial fibrillation (PAF). A novel method was developed for the visualisation of tissue contact force on left atrial models derived from segmented MRI data and the approach was tested in 3 patients. The left atrium was automatically segmented from preprocedural whole-heart cardiac magnetic resonance (CMR) scans in three patients undergoing circumferential PVI for catheter ablation of PAF. During the procedure, the CMR shell was overlaid on to real-time fluoroscopy using the EP Navigator (EPN) software (Philips Healthcare, The Netherlands) and registered using the trachea and intracardiac catheters. Using a wide area circumferential approach to encircle ipsilateral pairs of PVs, the position of each radiofrequency (RF) application (25W for 40s) was recorded on the CMR shell using the point tagging feature of EPN. Using a contact force-sensing ablation catheter (TactiCath, Endosense, Switzerland), the contact force-time integral (FTI) for each registered ablation point was recorded. The FTI for each point was then projected on to the CMR shell with a circular diameter of 10mm using custom-made software. This radius of force distribution was chosen to reflect the typical accuracy of location of the mapping catheter and also to take into account the motion of the catheter during the RF application. 4 vein PVI and FTI maps were achieved in all patients (see figure 1 for example). The mean FTI applied to each side of the left atrium was recorded in gram seconds. The total and regional FTIs applied to achieve PVI differed between and within patients respectively, but in an inconsistent manner. The FTI map on the pre-segmented atrial shell provides an intuitive post-procedural assessment of the tissue-contact force achieved during RF delivery. The FTI is less consistent between patients for the RPVs than for the LPVs, perhaps reflecting patient-specific technical challenges. Comparison of FTI maps with post-ablation delayed enhancement, T2W MRI and clinical outcome data may assist in understanding the mechanisms of effective lesion delivery and of PV reconnection after ablation.

Feasibility and safety of intra‐coronary Beta irradiation with 144Ce/Pr for prevention of restenosis after percutaneous transluminal coronary angioplasty of in‐stent restenotic lesions

Background: Endovascular brachytherapy is a proven and efficacious treatment of coronary in‐stent restenosis with established long‐term benefit. Owing to its complexity and logistic inconveniences, brachytherapy did not find wide acceptance, especially in the current drug‐eluting stents era. We conducted a single center, non‐randomized pilot trial with 144Ce/Pr, utilizing a new high‐energy Beta emitting source, for prevention of restenosis after percutaneous treatment of in‐stent restenotic lesions. Methods and Results: Thirty consecutive patients presenting in‐stent restenosis were enrolled in the study. After conventional balloon angioplasty, 144Ce/Pr was applied to the dilated coronary segment at a dose of 21Gy. Technical feasibility, safety and efficacy of 144Ce/Pr at 9 months clinical and angiographic follow‐up were tested. Thirty‐seven arterial segments were irradiated with 100% technical success and no in‐hospital major adverse cardiac events (MACE). Five MACE were observed (13.5% of the treated segments) during 9 months follow‐up, including four target lesion revascularizations and one episode of acute coronary syndrome secondary to sudden late thrombotic occlusion of the irradiated segment. Conclusions: The study confirmed the safety and the feasibility of the intra‐coronary Beta irradiation utilizing the 144Ce/Pr source. It also shows some practical advantages compared to traditional Gamma or other Beta sources. Considering the high‐risk restenosis profile of the selected patients (i.e. diffuse in‐stent restenosis, bifurcation lesions, small vessels) these results are encouraging in terms of restenosis prevention. Late acute thrombosis remains a problem requiring further improvement.