Key result
Simulated spatial inhomogeneities of acute myocardial ischemia yielded dramatic spatial dispersion of the wavefront and were the origin of mid-frequency intra-QRS components in cardiac signals.
Computer modeling demonstrates that ischemic spatial inhomogeneities cause significant wavefront dispersion and generate mid-frequency intra-QRS components in cardiac signals.
Caution against clinical adoption of intra-QRS markers from simulations alone; leaves open in vivo confirmation of ischemia-induced dispersion.
A two-dimensional modified Luo-Rudy model was created to represent a 40 mm by 40 mm slab of myocardial tissue. An inhomogeneity was introduced to simulate acute myocardial ischemia, with components of hyperkalemia, acidosis and anoxia. Simulations were carried out for various degrees of ischemia, to study both the interaction of the propagation front with the inhomogeneity, and the reconstructed signals. The simulations utilized a modified LR model, with a realistic anisotropy of myocardial tissue. Each cluster (.4 mm ×.4 mm) was given bulk electric properties, R x and R y (25Ω and 250Ω, respectively). The slab was stimulated and the 2D depolarization pattern was computed by numerical integration. To study ischemia, a circular inhomogeneity with concentric regions (r o =12.8 mm{border zone, BZ} , r i =11.2 mm{extreme zone, EZ} ) regions was introduced in the model. From the 2D simulations and the regional action potentials (AP), unipolar and bipolar lead potentials were reconstructed. Time-frequency decomposition was performed on the lead signals by wavelet analysis. Isochrone and (dV/dt) max maps were obtained to study depolarization. Our results indicate that spatial inhomogeneities yield dramatic spatial dispersion of the wavefront and are the origin of mid-frequency intra-QRS components in cardiac signals. Severe APD shortening and spatial distortion of the isochrone and upstroke maps are also observed.
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Shenai et al. (1999) studied Acute myocardial ischemia (simulated). Simulated acute myocardial ischemia (hyperkalemia, acidosis, anoxia) was evaluated on Depolarization pattern and reconstructed signals. Simulated spatial inhomogeneities of acute myocardial ischemia yielded dramatic spatial dispersion of the wavefront and were the origin of mid-frequency intra-QRS components in cardiac signals.
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