Results

We acquired a total of 6685 measurements using 12 catheters, three for each of the 4 models. For each catheter, a median of 107 (IQR 100-128) measurements was taken at each of the five specific angles. The overall correlation between measured force and real force was high with 𝜌𝑆𝑝𝑒𝑎𝑟𝑚𝑎𝑛 ≥ 0.98 for all models. The results of all measurements are displayed in Figure 3. The mean absolute error for each model, across the full range, was 1.29g ±0.99g for Tacticath, 2.87g ±2.37g for AcQBlate® Force, 1.38g ±1.29g for Stablepoint, and 2.26g ±2.70g for Smarttouch®. However, for some combinations of a catheter, angle, and applied force, overestimation and underestimation of the real force were higher with a maximum of 6.5g / -5.6g for Tacticath, 11g / -11.6 for AcQblate® Force, 7.4g / -5.6g for Stablepoint, and 8.5 / -22.6g for Smarttouch®.
In the clinical range of 10-40g, all catheters had a lower absolute mean error with 1.19g ±0.88g for Tacticath, 2.86g ±2.08g for AcQBlate® Force, 1.02g ±0.77g for Stablepoint, and 1.52g ±1.17g for Smarttouch® (figure 4).
In the high force range, overestimation of more than 10g was observed for the AcQblate® Force catheter at 90°, while both Smarttouch® and AcQblate® Force underestimated forces by more than 10g at angles of 30° and 45°. The Stablepoint catheter overestimated higher contact forces at 0° and 30°. Finally, the Tacticath did not over- nor underestimate forces by more than 5g at all angles.
AcQBlate® Force and Smarttouch®showed a higher variance between individual catheters (figure 3, second and fourth row). In addition, when fitting the data using a local estimate function (figure 3), the measurement errors of two models seem to scatter a bit more: The residual standard errors are numerically higher for AcQBlate® Force (14.5g) and Smarttouch® (14.0g), compared to Tacticath (12.3g) and Stablepoint(10.1g).