Radiofrequency (RF) ablation is becoming a standard of care for atrial fibrillation (AF) management. However, a relatively high incidence of recurrence after acutely successful procedures persists, a problem connected to non-transmural necrosis and gaps in linear lesions. This work reports an innovative catheter for RF ablation guided by polarization-sensitive optical coherence reflectometry, a powerful technique offering three main capabilities: (i) Feedback on contact and catheter-tissue orientation through intensity measurements. (ii) Identification of healthy or ablated tissue related to loss of birefringence caused by denaturation of oriented collagen in myocardium, as quantified by polarization sensitive detection. (iii) Real-time lesion formation monitoring through quantitative analysis of collagen fibers shrinkage during heating based on the normalized cross-correlation of intensity signals. Endocardial experiments have been carried out in-vitro and using a percutaneous femoral access in an in-vivo swine model. This novel integrated catheter design opens a new path to better clinical outcomes by providing the electrophysiologist complete control over the procedure, including local navigation between lesions to ensure continuity, information about catheter-tissue contact, safe and effective energy delivery, and real-time estimation of lesion size. Fig. 1 Left: Structural (intensity-based) M-scan showing lack of contact (B), myocardium soft contact (M-SC) and myocardium hard contact (M-HC). Middle: Mean phase retardation (MPR) images showing contrast between healthy and ablated tissue as necrosis occurs. Right: Evolution of normalized cross-correlation related to tissue thermal deformation for different tissue depths, from the endocardial surface to 1.2 mm deep.