Panoramic voltage-sensitive optical mapping of contracting hearts using cooperative multiview motion tracking with 12 cameras.

Voltage-sensitive fluorescence imaging is widely used to image action potential waves in the heart. However, although the electrical waves trigger mechanical contraction, imaging needs to be performed with pharmacologically contraction-inhibited hearts, limiting studies of the coupling between cardiac electrophysiology and tissue mechanics. Here, we introduce a multiple-camera optical mapping system with which we image action potential waves at high resolutions across the entire ventricular surface of the beating and strongly deforming heart. We imaged intact isolated rabbit hearts inside a soccer-ball shaped imaging chamber, facilitating even illumination and panoramic imaging. Using 12 high-speed cameras, ratiometric voltage-sensitive imaging, and three-dimensional (3D) multiview motion tracking, we reconstructed the entire 3D deforming ventricular surface and performed corresponding voltage-sensitive measurements during sinus rhythm, paced rhythm and ventricular fibrillation (VF). Our imaging setup defines a new state-of-the-art in the field and can be used to study the heart's electromechanical physiology during health and disease at unprecedented resolutions. For example, we measured action potential duration and contractile changes in response to pharmacological blockage of potassium ion channels during sinus rhythm, measured electrical activation times and observed mechanical strain waves following electrical activation fronts during pacing, and observed electromechanical vortices during VF. KEY POINTS: The heartbeat is controlled by electrical impulse phenomena that trigger contractile motion. Optical mapping uses fluorescent dyes to measure electrical impulse phenomena in cardiac muscle tissue. It is an important tool for studying cardiac electrophysiology and rhythm abnormalities. With current optical mapping techniques, it is not possible to image beating hearts. Hearts need to be contraction-inhibited using pharmacological agents. This limits optical mapping studies to measurements of electrical activation patterns and action potentials. Tissue strain and contractile motion cannot be assessed simultaneously. A novel 3D optical mapping system is presented that enables panoramic imaging of action potential waves across the surface of strongly contracting isolated hearts. With this system, it is possible to measure electrical activation and action potential waves simultaneously with deformation and strain.