  Action potential waves triggering the heart's contractions can be imaged at
high spatial and temporal resolutions across the heart surface using
voltage-sensitive optical mapping. However, for over three decades, optical
mapping has been performed with contraction-inhibited hearts. While it was
recently demonstrated that action potential waves can be imaged on parts of the
three-dimensional deforming ventricular surface using multi-camera optical
mapping, panoramic measurements of action potential waves across the entire
beating heart surface remained elusive. 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 even illumination with excitation light
from all sides in a panoramic fashion. We found that it is possible to image
the entire ventricular surface using 12 cameras with 0.5-1.0 megapixels
combined resolution. The 12 calibrated cameras generate 1.5 gigabytes of video
data per second at imaging speeds of 500 fps, which we process using various
computer vision techniques, including three-dimensional cooperative multi-view
motion tracking, to generate three-dimensional dynamic reconstructions of the
deforming heart surface with corresponding high-resolution voltage-sensitive
optical measurements. With our setup, we measured action potential waves at
unprecedented resolutions on the contracting three-dimensional surface of
rabbit hearts during sinus rhythm, paced rhythm as well as ventricular
fibrillation. 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.
