Background: Action potential waves triggering the heart's contractions can be imaged at high spatial and temporal resolutions on the heart surface using voltage-sensitive optical mapping. However, for over three decades, optical mapping has been performed with non-moving, contraction-inhibited hearts, and was only recently demonstrated with beating hearts. While it was demonstrated that action potential waves can be imaged on parts of the three-dimensional deforming ventricular surface using multi-camera optical mapping, the technique has yet lacked spatial resolution and robustness, and panoramic measurements remained elusive.
Aims: Here, we introduce a high-resolution multi-camera optical mapping system consisting of up to 24 high-speed, low-cost cameras with which it is possible to image action potential waves at high resolutions on the entire, strongly deforming ventricular surface of the heart. We imaged isolated hearts inside a custom-designed soccerball-shaped imaging chamber, which facilitates imaging and illumination with excitation light from all sides in a panoramic fashion.
Methods: While we found that it is possible to image the entire ventricular surface using 12 cameras, the imaging quality and robustness increases with more cameras. The 24 calibrated cameras generate 3 gigabytes of video data per second at imaging speeds of 500fps, which we process and combine using various computer vision techniques, including three-dimensional multi-view motion tracking, to generate three-dimensional reconstructions of the entire deforming ventricular surface with corresponding high-resolution voltage-sensitive optical measurements.
Results: With our setup, we measured action potential waves at unprecedented resolutions on the contracting three-dimensional surface of rabbit hearts during sinus rhythm and paced rhythms as well as during ventricular fibrillation and atrial fibrillation.
Conclusion: Our imaging setup defines a new state-of-the-art in the field, and can be used to study the heart's electromechanical dynamics during health and disease.