Optical mapping of the pig heart in situ under artificial blood circulation

Abstract

The emergence of optical imaging has revolutionized the investigation of cardiac electrical activity and associated disorders in various cardiac pathologies. The electrical signals of the heart and the propagation pathways are crucial for elucidating the mechanisms of various cardiac pathological conditions, including arrhythmia. The synthesis of near-infrared voltage-sensitive dyes and the voltage sensitivity of the FDA-approved dye Cardiogreen have increased the importance of optical mapping (OM) as a prospective tool in clinical practice. We aimed to develop a method for the high-spatiotemporal-resolution OM of the large animal hearts in situ using di-4-ANBDQBS and Cardiogreen under patho/physiological conditions. OM was adapted to monitor cardiac electrical behaviour in an open-chest pig heart model with physiological or artificial blood circulation. We detail the methods and display the OM data obtained using di-4-ANBDQBS and Cardiogreen. Activation time, action potential duration, repolarization time and conduction velocity maps were constructed. The technique was applied to track cardiac electrical activity during regional ischaemia and arrhythmia. Our study is the first to apply high-spatiotemporal-resolution OM in the pig heart in situ to record cardiac electrical activity qualitatively under artificial blood perfusion. The use of an FDA-approved voltage-sensitive dye and artificial blood perfusion in a swine model, which is generally accepted as a valuable pre-clinical model, demonstrates the promise of OM for clinical application.

Cardiac Optical Mapping in Situ in Swine Models: A View of the Current Situation

“…Moreover, the use of uncouplers, such as blebbistatin, may induce side effects on electrophysiological parameters of the heart [ 3 , 9 ]. Our study [ 4 ], in agreement with others [ 10 , 11 , 12 ], revealed no significant effect of blebbistatin on the electrophysiological parameters of pig hearts in situ. However, in terms of clinical application, the lack of detailed information on the toxicity of this uncoupler is still a limiting factor in its usage for eliminating contraction artefacts during OM under artificial blood circulation.…”

“…The study by our group presents data obtained by using a custom-made frame (glued to the epicardial surface in a special procedure) that enabled us to record optical signals from a 40 × 40 mm area of the pig heart in situ under physiological blood circulation with applied stimulation (500 ms cycle length) or ventricular fibrillation. However, our data revealed that mechanical motion arrest using a frame partially restricts the field of view and does not fully eliminate motion artefacts [ 4 ]. Thus, OM under physiological blood circulation, for which the heart must function as a pump, is easy to create in principle, but complicated to apply for qualitative registration at high spatiotemporal resolution.…”

“…Artificial blood perfusion, a routine procedure applied in clinical open-heart surgery, ensures controlled conditions and allows an electromechanical uncoupler to be applied. As our study suggests, it is a promising mode of circulation for the registration of cardiac electrical activity using OM [ 4 ]. However, artificial blood circulation requires additional equipment and advanced specialists.…”

“…Different voltage-sensitive dyes were used in our study and that of Lee et al: di-4-ANBDQBS [ 3 , 4 ], di-4-ANEQ(F)PTEA [ 3 ], and Cardiogreen [ 4 ]. Di-4-ANBDQBS is a near-infrared fluorescent dye that has been commonly used in OM studies since the demonstration of its high voltage sensitivity and suitability for use in the blood-perfused myocardium [ 13 ].…”

“…However, due to possible technical challenges, the development of OM in large animal models in situ has long remained uninvestigated. Very recently, Lee et al [ 3 ] and our group [ 4 ] published studies of OM approaches for the pig heart in situ (in vivo), likely advancing the methodological capacity to perform complex electrophysiological investigations of the heart. Both studies had the same aim, i.e., to develop high-spatiotemporal-resolution OM suitable for registering the electrical activity of the pig heart in situ, but different methods were chosen.…”