The intra-operative real-time assessment of tissue viability can potentially improve therapy delivery and clinical outcome in cardiovascular therapies. Cardiac ablation therapy for the treatment of supraventricular or ventricular arrhythmia continues to be done without being able to assess if the intended lesion and lesion size have been achieved. Here, we report a method for continuous measurements of cardiac muscle microcirculation to provide an instrument for realtime ablation monitoring. We performed two acute open chest animal studies to assess the ability to perform real-time monitoring of creation and size of ablation lesion using a standard RF irrigated catheter. Radiofrequency ablation and laser Doppler were applied to different endocardial areas of alive open-chest pig. We performed two experiments at three different RF ablation energy setting and different ablation times. Perfusion signals before and after ablation were found extensively and distinctively different. By increasing the ablation energy and time, the perfusion signal was decreasing. In vivo assessing the local microcirculation during RF ablation by laser Doppler can potentially be useful to differentiate between viable and nonviable ablated beating heart in real time.