Validation of the measurement setup
The accuracy of the setup for measuring the force applied to the platform was validated in the air by measuring standard weights, which were put on the platform. The validation procedure is detailed further in the online supplement.

Ablation catheter models

Four ablation catheter models were investigated. Each model was used in conjunction with the corresponding equipment needed to read out the force sensor. Tacticath™ Quartz, Smarttouch®, and Stablepoint™ must all be paired with a specific 3D mapping system while the AcQBlate® Force can be used as a standalone solution. An overview of additional technical details can be found in table 1.
All four catheter models provide a force sensing tip, temperature measurement, irrigation, and catheter deflection. However, the force sensing technology is different for each model and described in the following section as well in Figure 2:

Tacticath Quartz (Abbott, Abbott Park, IL, USA):

A beam of light is emitted by the TactySys system and travels through three optical fibers towards the catheter’s tip into a complex, deformable 3-D structure incorporating three Fabry-Pérot interferometers made of two semi-reflective parallel surfaces. When a force is applied to the catheter tip, the flexible titanium-alloy structure deforms, changing its length and, therefore, the reflected interference pattern. By knowing the deformation characteristics, both the magnitude and orientation of the acting contact force can be computed.

AcQBlate® Force (Biotronik, Berlin, Germany):

The tip is suspended by a Z-Axis (In-axis to the catheter) sensor that is realized by a deformable parallelogram, sensitive to axial forces on the catheter. Additionally, separate X- and Y-Axis sensors are located more proximally along the shaft. They are sensitive to lateral forces only. One single optical fiber, incorporating a fiber Bragg grating (FBG) runs through the deformable sensors. At each sensor, a different wavelength is reflected. As soon as the catheter tip is exposed to a force, the fiber changes its length at the respective section, therefore shifting the reflected wavelength along the spectrum. Knowing the forces along all axes, the acting force vector can be calculated.