Introduction: Contact force-sensing catheters are widely used for ablation of cardiac arrhythmias. They allow quantification of catheter-to-tissue contact, which is an important determinant for lesion formation and may reduce the risk of complications. The accuracy of these sensors may vary across the measurement range, catheter-to-tissue angle, and amongst manufacturers and we aim to compare the accuracy and reproducibility of four different force sensing ablation catheters. Methods: A measurement setup containing a heated saline water bath with an integrated force measurement unit was constructed and validated. Subsequently, we investigated four different catheter models, each equipped with a unique measurement technology: Tacticath Quartz (Abbott), AcQBlate Force (Biotronik/Acutus), Stablepoint (Boston Scientific), and Smarttouch SF (Biosense Webster). For each model, the accuracy of three different catheters was measured within the range of 0-60 grams and at contact angles of 0°, 30°, 45°, 60°, and 90°. Results: In total, 6685 measurements were performed using 4x3 catheters (median of 568, IQR 511-606 measurements per catheter). Over the entire measurement-range, the force measured by the catheters deviated from the real force by the following absolute mean values: Tacticath 1.29g ±0.99g, AcQBlate Force 2.87g ±2.37g, Stablepoint 1.38g ±1.29g, and Smarttouch 2.26g ±2.70g. For some models, significant under- and overestimation of >10g were observed at higher forces. Mean absolute errors of all models across the range of 10-40g were <3g. Conclusion: Contact measured by force-sensing catheters is accurate with 1-3g deviation within the range of 10g to 40g. Significant errors can occur at higher forces with potential clinical consequences.

Introduction: Chemical ablation by retrograde infusion of ethanol into the vein of Marshall (VOM-EI) can facilitate achievement of mitral isthmus block. This study sought to describe efficacy and safety of this technique. Methods and Results: Twenty-two consecutive patients (14 male, median age 71 years) with attempted VOM-EI for mitral isthmus ablation were included in the study. VOM-EI was successfully performed with a median of 4 ml of 96% ethanol in 19 patients (86%) and mitral isthmus was successfully blocked in all (100%). Touch up endocardial and/or epicardial ablation after VOM-EI was necessary in 12 patients (63%). Perimitral flutter was present in 12 patients (63%) during VOM-EI and terminated or slowed by VOM-EI in four and three patients, respectively. Low-voltage area of the mitral isthmus region increased from 3.1 cm2 (IQR 0-7.9) before to 13.2 cm2 (IQR 8.2-15.0) after VOM-EI and correlated significantly with the volume of ethanol injected (P = 0.03). Median high-sensitive cardiac troponin-T increased significantly from 330 ng/L (IQR 221-516) the evening of the procedure to 598 ng/L (IQR 382-769; P=0.02) the following morning. A small pericardial effusion occurred in three patients (16%), mild pericarditis in one (5%) and uneventful VOM dissection in two (11%). After a median follow-up of 3.5 months (IQR 3.0-11.0), 10 of 18 patients (56%) with VOM-EI and available follow-up had arrhythmia recurrence. Repeat ablation was performed in five patients (50%) and peri-mitral flutter diagnosed in three (60%). Conclusion: VOM-EI is feasible, safe and effective to achieve acute mitral isthmus block