2.5. Study group

In the study group, the QDOT MICRO® catheter was utilized. The QDOT MICRO® allows for vHP-SD ablation mode (QMODE+, 90 W, 4 s) and a conventional temperature controlled ablation mode (QMODE, 50 W maximum), where the system adjusts the irrigation flow rate and power based on the measured temperature to stabilize the catheter tip temperature [1], [2]. In the QMODE+ mode only the power is adapted to achieve the target temperature [1], [2]. After additional mapping via the QDOT MICRO® catheter utilizing the microelectrodes RF ablation was performed at the site of earliest activation or the best pacemap. The initial approach was to use QMODE+, with a target temperature of 60 °C and a CF range of 10–40 g for 5–10 RF applications. If the QMODE+ ablation was not effective, the mode was changed to QMODE and the RF delivery was continued in the same area utilizing 30–40 W for up to 60–120 s. Fig. 1 provides an example of PVC ablation within the LVOT utilizing the QDOT MICRO®.

A: Electroanatomic map of the left ventricle utilizing CARTO 3, V7 (Biosense Webster) and COHERENT mapping (study group). Left side RAO view, right side superior view. CS = coronary sinus catheter placed distal in the coronary sinus. White arrow = location of earliest activation with very high-power short duration application (red-white dot) at the LV-summit. RAO = right anterior oblique, SUP = superior view. B: Surface and intracardiac electrocardiograms with the QDOT MICRO ablation catheter at the location of earliest activation of the PVC within LVOT. Please note the potentials on the micro-electrodes (pointed out by white arrows). MAP M1-M2 = distal electrodes on the map catheter. MAP M3-M4 = proximal electrodes on the map catheter. MAP u1-u2, MAP u2-u3, MAP u1-u3 = micro-electrodes. Speed 200 mm/s.