COMPUTER MODELS OF DEPOLARIZATION ALTERATIONS INDUCED BY MYOCARDIAL ISCHEMIA: THE EFFECT OF SUPERIMPOSED ISCHEMIC INHOMOGENEITIES ON PROPAGATION IN SPACE AND TIME-FREQUENCY DOMAINS

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, Rx and Ry (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 (ro=12.8 mm{border zone, BZ} , ri=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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High arrhythmic risk in antero-septal acute myocardial ischemia is explained by increased transmural reentry occurrence

Scientific Reports ◽

10.1038/s41598-019-53221-2 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Hector Martinez-Navarro ◽

Ana Mincholé ◽

Alfonso Bueno-Orovio ◽

Blanca Rodriguez

Keyword(s):

Myocardial Ischemia ◽

High Performance ◽

Acute Myocardial Ischemia ◽

Border Zone ◽

Apical Region ◽

Efficacy Evaluation ◽

Detailed Model ◽

Subendocardial Ischemia ◽

Ischemic Region ◽

The Impact

AbstractAcute myocardial ischemia is a precursor of sudden arrhythmic death. Variability in its manifestation hampers understanding of arrhythmia mechanisms and challenges risk stratification. Our aim is to unravel the mechanisms underlying how size, transmural extent and location of ischemia determine arrhythmia vulnerability and ECG alterations. High performance computing simulations using a human torso/biventricular biophysically-detailed model were conducted to quantify the impact of varying ischemic region properties, including location (LAD/LCX occlusion), transmural/subendocardial ischemia, size, and normal/slow myocardial propagation. ECG biomarkers and vulnerability window for reentry were computed in over 400 simulations for 18 cases evaluated. Two distinct mechanisms explained larger vulnerability to reentry in transmural versus subendocardial ischemia. Macro-reentry around the ischemic region was the primary mechanism increasing arrhythmic risk in transmural versus subendocardial ischemia, for both LAD and LCX occlusion. Transmural micro-reentry at the ischemic border zone explained arrhythmic vulnerability in subendocardial ischemia, especially in LAD occlusion, as reentries were favoured by the ischemic region intersecting the septo-apical region. ST elevation reflected ischemic extent in transmural ischemia for LCX and LAD occlusion but not in subendocardial ischemia (associated with mild ST depression). The technology and results presented can inform safety and efficacy evaluation of anti-arrhythmic therapy in acute myocardial ischemia.

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The border zone in acute myocardial ischemia in the dog. A histochemical, biochemical and ultrastructural study.

Japanese Circulation Journal ◽

10.1253/jcj.48.18 ◽

1984 ◽

Vol 48 (1) ◽

pp. 18-31 ◽

Cited By ~ 1

Author(s):

KENICHI MITSUNAMI ◽

TAKEHISA FUKUHARA ◽

SHOTARO KATO ◽

KEIZO BITO ◽

MASAHIKO KINOSHITA ◽

...

Keyword(s):

Myocardial Ischemia ◽

Ultrastructural Study ◽

Acute Myocardial Ischemia ◽

Border Zone

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Electroacupuncture Ameliorates Acute Myocardial Ischemia: A Potential Role of the Locus Coeruleus

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2020/4298657 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Xin Wu ◽

Kun Wang ◽

Shuai Cui ◽

Shengbing Wu ◽

Guoqi Zhu ◽

...

Keyword(s):

Myocardial Ischemia ◽

Cardiac Function ◽

Locus Coeruleus ◽

Serum Levels ◽

Acute Myocardial Ischemia ◽

Inflammatory Factors ◽

Neuron Activity ◽

Myocardial Tissue ◽

Hs Crp

The locus coeruleus (LC) is closely linked with cardiovascular disease. However, whether it mediates the alleviating effect of electroacupuncture (EA) on acute myocardial ischemia (AMI) remains unclear. A rat model of myocardial ischemia was established through occlusion of the left anterior descending coronary artery. Multichannel in vivo recording and other techniques were used to assess neurons in the LC, norepinephrine (NE) and dopamine (DA) levels in central and myocardial tissue, serum levels of inflammatory factors, and cardiac function. After induction of AMI, LC neuron activity increased and the central NE concentrations increased, while those of DA decreased. Moreover, the serum levels of high-sensitivity C-reactive protein (hs-CRP) increased, whereas those of interleukin-10 (IL-10) decreased. However, these effects were reversed by EA. Additionally, LC lesioning affected NE and DA levels in myocardial tissue and weakened the antimyocardial ischemic effect of EA. Collectively, our results indicated that LC is closely related to AMI and plays an important role in the antimyocardial ischemic effect of EA. This mechanism may be related to inhibition of LC neuron activity by EA, which inhibits the release of large amounts of hs-CRP and promotes that of IL-10 in the serum. Besides, after LC lesioning, EA may improve cardiac function by inhibiting the release of large amounts of NE and promoting the release of DA in myocardial tissue.

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Simulation study of action potentials during acute myocardial ischemia

Computers in Cardiology 1997 ◽

10.1109/cic.1997.648148 ◽

2002 ◽

Cited By ~ 1

Author(s):

J.M. Ferrero ◽

V. Torres ◽

J. Saiz ◽

M. Monserrat ◽

J.M. Ferrero ◽

...

Keyword(s):

Myocardial Ischemia ◽

Simulation Study ◽

Action Potentials ◽

Acute Myocardial Ischemia

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FEATURE EXTRACTION OF RADAR MULTIPLE-TARGET ECHOES USING WAVELET PACKET TRANSFORM WITH THE BEST BASES

International Journal of Pattern Recognition and Artificial Intelligence ◽

10.1142/s0218001403002253 ◽

2003 ◽

Vol 17 (01) ◽

pp. 127-150 ◽

Cited By ~ 3

Author(s):

SHOUYONG WANG ◽

GUANGXI ZHU ◽

YUAN Y. TANG

Keyword(s):

Wavelet Packet ◽

Wavelet Packet Transform ◽

Time Varying ◽

Multiple Target ◽

Time Frequency ◽

Frequency Decomposition ◽

Frequency Domains ◽

Stationary Signals ◽

Entropy Criterion ◽

Positive Results

Extraction of effective features plays a key role in pattern recognition. A large number of patterns, such as speech, radar signals, earthquake signals, handwriting, etc. are of non-stationary signals or exhibit time-varying behavior. The features of these patterns are often located in both the time and frequency domains. The traditional methods fail to extract such kind of features. Fortunately, wavelet packet transform (WPT) can provide an arbitrary time-frequency decomposition for the signals, because a wavelet packet (WP) library contains many WP bases, which can handle the different components of a signal. Therefore, by selecting a suitable basis, which is called "best basis", the effective features can be extracted. In this paper, three criteria are used to select the best WPT basis, namely: (1) distance criterion, (2) divergence criterion and (3) entropy criterion. Three algorithms to implement the above criteria are also provided. Experiments are conducted and the positive results are obtained.

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