Previous research demonstrated that CF is a major determinant for lesion formation and has a greater effect on lesion size than RF output power [
10]. CF appears to be associated with FTI, lesion size, and procedural success [
10,
11,
14]. Research on pulmonary vein isolation for atrial fibrillation (AF) revealed that the rate of recurrence was associated with the percentage of ablations with very low CFs (<10 g) and predicts recurrence at 12 months. All AF patients who were treated with an average CF of <10 g experienced recurrences, whereas 80 % of the patients treated with a CF of >20 g experienced no AF recurrences [
15]. These data demonstrate that proper catheter-tissue contact is crucial to establish appropriate lesions and avoid conduction recovery [
13,
15,
16]. Previously only surrogate information regarding CF was available during ablation procedures such as tactile feedback, movement of the catheter tip on fluoroscopy, ST elevation in the unipolar electrogram and impedance monitoring [
17,
18]. However, these criteria seemed to be inadequate for estimating real-time CF. [
17,
18] Kuck et al. [
14] demonstrated that tactile feedback during mapping and ablation is not a reliable parameter and dangerous forces could be applied during catheter manipulation. Furthermore, Kumar et al. [
18] found that impedance fall with ablation only has modest predictive value for CF and FTI, and could not accurately differentiate between low and high CFs. Currently, catheters are available that provide direct and continuous feedback regarding CF. The use of this type of catheter has been associated with a decrease in the number of RF applications, which does not result in lesion formation because of insufficient CF [
5].
Another important issue during catheter ablation is intermittent CF due to the continuous movements of the heart and respiratory movements. This may occur if the catheter is not in constant contact with the myocardium. This leads to impaired energy delivery and subsequently inferior lesion formation [
15]. Reddy et al. showed a strong correlation between low CF and intermittent catheter-tissue contact. Continuous CF feedback allows the operator to adapt the CF during applications, therefore improving lesion quality. However, in some regions it is difficult to achieve a good and stable catheter position with sufficient CF, as we experienced as well during our ablation procedures. Shah et al. [
11] demonstrated that FTI is strongly and linearly correlated with lesion depth and volume. Therefore, the operator could compensate low CF by varying RF power and duration of an application.