Abstract 9781: Electromechanical Optical Mapping in Beating, in Situ Swine Hearts

Abstract

Introduction: Optical mapping is a powerful method for imaging cardiac propagation but is traditionally limited to motion-arrested, ex vivo preparations. Extending the method to beating, in situ preparations will enable study of bidirectional electromechanical interactions and physiological coupling between the heart and the animal. Challenges in adapting optical mapping to this setting include motion artifact, loading of voltage sensitive dye (VSD), and absorption of excitation and emission light by blood. Here, we outline a system to simultaneously image electrical propagation and contraction of intact beating hearts in an in vivo swine model. Methods: Fifteen pigs weighting 25-35 kg were anesthetized. Hearts were exposed via median sternotomy. We glued 20-30 fiducial markers (2 mm, ~1 cm spacing) to the anterior LV epicardium. We injected 14 ml of 50 uM di-4-ANEQ(F)PTEA into a catheter placed in the LAD. Blood flow in the artery was blocked during and for 1 min following the injection. This VSD works at longer wavelengths than commonly used VSDs and is therefore less affected by blood. Fluorescence was excited with alternating amber (602 nm) and green (526 nm) LEDs. Emission was long pass filtered (>700 nm) and recorded at 750 Hz with a pair of video cameras (SciMedia MiCAM03-N256) fitted with 35 mm, f/1.4 lenses . We analyzed marker motion to (1) quantify contraction and (2) partially correct motion artifact in membrane potential ( Vm ) signals. We also computed the ratio of green- to amber-elicited fluorescence on alternate frames to further correct motion artifact. Results and Conclusions: The method successfully images Vm and deformation. The figure shows an isochronal activation map of a paced beat (A), bars aligned with systolic principal strain (B), and Vm and shortening strain signals from selected sites (C). The method can be used to investigate coupled electromechanics and arrhythmogenesis in a more physiologically realistic setting than previous techniques.