Four-Dimensional Imaging of Cardiac Trabeculae Contracting In Vitro Using Gated OCT

Abstract

Cardiac trabeculae are widely used as experimental muscle preparations for studying heart muscle. However, their geometry (diameter, length, and shape) can vary not only among samples, but also within a sample, leading to inaccuracies in estimating their stress production, volumetric energy output, and/or oxygen consumption. Hence, it is desirable to have a system that can accurately image each trabecula in vitro during an experiment. To this end, we constructed an optical coherence tomography system and implemented a gated imaging procedure to image actively contracting trabeculae and reconstruct their time-varying geometry. By imaging a single cross section while monitoring the developed force, we found that gated stimulation of the muscle was sufficiently repeatable to allow us to reconstruct multiple contractions to form a four-dimensional representation of a single muscle contraction cycle. The complete muscle was imaged at various lengths and the cross-sectional area along the muscle was quantified during the contraction cycle. The variation of cross-sectional area along the length during a contraction tended to increase as the muscle was contracting, and this increase was greater at longer muscle lengths. To our knowledge, this is the first system that is able to measure the geometric change of cardiac trabeculae in vitro during a contraction, allowing cross-sectional stress and other volume-dependent parameters to be estimated with greater accuracy.

Work-loop contractions reveal that the afterload-dependent time course of cardiac Ca2+ transients is modulated by preload

“…In total, seven trabeculae were studied. Their cross-sectional area was measured using spectral-domain optical coherence tomography as described previously ( 26 ). Briefly, a broadband (100 nm) low-coherence superluminescent diode with a central wavelength of 840 nm was split into a measurement and reference path.…”

Passive myocardial mechanical properties: meaning, measurement, models

“…One way to monitor deformation in native tissue is based on the implantation of high-density beads that can be tracked echocardiographically (Ashikaga et al 2004). Other techniques allow strain tracking on and within cardiac tissue by imaging intrinsic tissue features, using modalities such as brightfield microscopy, confocal imaging, speckle tracking ultrasound, magnetic resonance imaging (MRI, Odening et al 2013;Brado et al 2017;Cheuk et al 2021) or optical coherence tomography (Cheuk et al 2017).…”

Simultaneous Brightfield, Fluorescence, and Optical Coherence Tomographic Imaging of Contracting Cardiac Trabeculae <em>Ex Vivo</em>

“…By steering the laser in a single axis, one can construct a cross-section of the sample of interest (Bscan) and, similarly, by repeating the process in a stepwise pattern in the remaining axis, a three-dimensional image can be generated (C-scan). By extension, one can collect a series of B-scans at a single slice for a repeating time-varying subject based on an external trigger and repeat to generate a three-dimensional scan, representing a time-varying planar image 10 .…”