4/25/2023 0 Comments Slowing a velocity vector code![]() If the notional CV of a single cell membrane could be measured, this would be much faster than that of a series of cells (due to ‘delays’ in conduction at cell–cell connections). Additionally, CV is, at the scales relevant to cardiac measurements, an emergent property reflecting the interaction of multiple activation paths at smaller scales. Furthermore, since the heart is orthotropic, ideally, multiple CVs are measured, reflecting longitudinal and transverse (relative to locally prevailing cell orientation) CV (CV l and CV t), meaning more than two measurement points are necessary. However, the curved surface of the heart, transmural (volume conduction) effects, and issues accessing the heart render measurement of cardiac CV non-trivial. ![]() The basis for measuring CV is relatively simple: either one measures the time required for an electrical impulse to travel a certain distance or the distance traveled in a predefined period of time. In short, a reduced wavelength means that re-entry can occur over a smaller distance, thus increasing the likelihood of self-sustained arrhythmias.įor the study of arrhythmias and the mechanisms of electrical remodeling, precise measurement of CV is an important factor. As the wavelength shortens (through slowed CV and/or accelerated repolarization), it becomes possible that multiple excitation waves can co-exist, re-exciting tissue multiple times without initiation of a new sinus excitation. It was first discussed in 1913, with the idea that in a healthy heart, the ‘wave of excitation’ was sufficiently broad (long wavelength) and fast (large CV) that the ventricle activated once each sinus beat. This concept is formally defined as the wavelength of the heart, which is equal to the CV multiplied by the refractory period. For re-entry to occur, the tissue must no longer be refractory by the time the excitation wave returns to a given point. Re-entrant activity occurs when excitation fails to stop following the normal cardiac sequence and instead re-excites regions of the heart in advance of the next sinus beat. Re-entry typically underlies tachyarrhythmias and fibrillation. CV is of particular interest in understanding determinants of re-entrant arrhythmias.
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