Catheter ablation of the cavo-tricuspid isthmus (CTI) is the curative first-line therapy for typical atrial flutter. Currently, two approaches are used in clinical practice. In contrast to the conventional linear ablation approach, the Maximum voltage-guided (MVG) strategy aims to limit ablation to high voltage areas (HVAs) representing the detectable correlate of relevant conducting bundles. Data from registries show that the MVG technique is sufficient to reach comparable clinical outcome with significantly shorter ablation duration when compared to the conventional linear strategy. Despite growing evidence, however, data from properly powered prospective randomized trials are lacking and the linear approach still remains standard. In addition, data on radiation exposure are controversial. As a substrate-based approach, the MVG strategy requires detailed mapping and signal analysis for identification of the individual architecture and exactly targeted energy application. However, the spatial mapping resolution of large tip catheters is limited. The use of the MicroFidelity catheter technology (IntellaMiFi) with high resolution mini-electrodes at the 8 mm catheter tip can be expected to further improve the feasibility of a voltage-guided approach. In addition, the MVG approach theoretically may encompass an increased risk for clinically inapparent reconduction. A prospective study with predefined invasive re-evaluation of persistent CTI block is needed to further evaluate this issue. Objective of this prospective randomized study is evaluate the performance of the micro-sensor technology for zero-fluoroscopy voltage-guided ablation of typical atrial flutter (AFL) compared with a population undergoing conventional linear ablation including a predefined invasive re-evaluation of persistent CTI block in addition to clinical follow-up. The study has been approved by the responsible ethics committee.