• cardiac arrhythmias
• biophysics
• Real-time

Current optical methodologies, combined with highly specialized genetic manipulation, have provided exceptional novel insights into the biological world. The last decade lead to the birth of optogenetics, a technique which combines optics and genetics to achieve precise control on specific cells of living samples. Recently, optogenetics has provided
interesting understaning of the electro-dynamical mechanisms underlying the cardiovascular system, leading to cardiac pacing, re-synchronization therapy and cardioversion. Although these interventions have clearly proven the feasibility and efficiency of cardiac pathway manipulation, optical stimulation has been somehow applied in a mechanistic, relatively unspecific way, rather than directly driven by the cardiac electrical dynamics: this aspect limits the full potential of such a new technology. Here, an all-optical platform was implemented and characterized: a complementar integrated, newly developed software was designed to perform a real-time monitoring and control of whole mouse heart electrical activity. The system combines an ultrafast wide-field mesoscope with a digital micro-mirror device, capable of drawing arbitrarily-chosen patterns, thus allowing optogenetic activation. After implementing the stimulation path, the system has been aligned, calibrated and characterized in terms of optical coupling, resolution, and optogenetic photoefficiency. Cardiac functionality can be manipulated either in free-run mode with sub-millisecond temporal resolution or in a closed-loop fashion: an ad hoc hardware and software platform has been developed to provide a real-time intervention capable of reacting to threatening anomalous electrical
signaling within 2 ms. The methodology has been tested in exemplicative applications, both in healthy and simulated pathological conditions. First, it was exploited to restore atrioventricular block, by triggering the optical stimulation of the ventricle according to optically mapped atrial activity. Furthermore, real-time intra-ventricular manipulation of the propagating electrical wave-front has been demonstrated, opening the
prospect for real-time resynchronization therapy and cardiac defibrillation. The development of this innovative optical methodology provides the first proof-of-concept that a real-time, self-sustaining, optical-based stimulation can efficiently control cardiac rhythm in normal and abnormal conditions, promising a new approach to the investigation of cardiac pathophysiology.