Key result
Simulated strain markers correlate ~0.8 with electrical activation during ectopic but less in endocardial pacing.
Why the study?
Although local mechanical activation times from noninvasive strain imaging can estimate electrical activation to identify arrhythmia origins or reentrant circuits, their reliability remains to be assessed.
Mechanical activation sequences derived from strain reproduce only qualitative features of electrical activation and may yield wrong excitation sources in complex activation sequences.
Answers are grounded in this paper and cite their sources.
Strain markers may misidentify sources in complex sequences; leaves open validation for clinical activation mapping.
Recent advances in the development of noninvasive cardiac imaging technologies have made it possible to measure longitudinal and circumferential strains at a high spatial resolution also at intramural level. Local mechanical activation times derived from these strains can be used as noninvasive estimates of electrical activation, in order to determine, eg, the origin of premature ectopic beats during focal arrhythmias or the pathway of reentrant circuits. The aim of this work is to assess the reliability of mechanical activation time markers derived from longitudinal and circumferential strains, denoted by AT ell and AT ecc , respectively, by means of three‐dimensional cardiac electromechanical simulations. These markers are compared against the electrical activation time (AT v ), computed from the action potential waveform, and the reference mechanical activation markers derived from the active tension and fiber strain waveforms, denoted by AT ta and AT eff , respectively. Our numerical simulations are based on a strongly coupled electromechanical model, including bidomain representation of the cardiac tissue, mechanoelectric (ie, stretch‐activated channels) and geometric feedbacks, transversely isotropic strain energy function for the description of passive mechanics and detailed membrane and excitation‐contraction coupling models. The results have shown that, during endocardial and epicardial ectopic stimulations, all the mechanical markers considered are highly correlated with AT v , exhibiting correlation coefficients larger than 0.8. However, during multiple endocardial stimulations, mimicking the ventricular sinus rhythm, the mechanical markers are less correlated with the electrical activation time, because of the more complex resulting excitation sequence. Moreover, the inspection of the endocardial and epicardial isochrones has shown that the AT ell and AT ecc mechanical activation sequences reproduce only some qualitative features of the electrical activation sequence, such as the areas of early and late activation, but in some cases, they might yield wrong excitation sources and significantly different isochrones patterns.
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Franzone et al. (2019) studied Cardiac electromechanical coupling (simulation). Electromechanical simulations of mechanical activation markers vs. Electrical activation time (ATv) was evaluated on Correlation coefficient (CC) between mechanical markers and electrical activation time. In 3D electromechanical simulations, mechanical activation markers derived from strains were highly correlated with electrical activation time during ectopic stimulations (CC > 0.8) but less correlated during multiple endocardial stimulations.
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