Unidirectional block in a computer model of partially coupled segments of cardiac Purkinje tissue |
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Authors: | Candido Cabo Roger C Barr |
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Institution: | (1) Departments of Biomedical Engineering and Pediatrics, Duke University, 136 Engineering Building, 27706 Durham, NC |
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Abstract: | The initiation of a reentrant circuit requires a zone of slow conduction and a zone of unidirectional block. This study used
computer model conditions under which partial coupling between segments of cardiac Purkinje tissue resulted in unidirectional
block. The structure used was one-dimensional and divided into three segments: a middle segment of variable length coupled
to two long (semi-infinite in concept) segments. The DiFrancesco-Noble equations represented the ionic currents of the membrane.
The results show that the possibility of unidirectional block depends on the size of the middle segment and the coupling resistances
between the segments. No combination of coupling resistances allowed unidirectional block for middle segments with a length
of two space constants (4 mm) or longer. Unidirectional block occurred for many combinations of coupling resistances as the
length of the middle segment decreased to around half a space constant (1 mm). The number of length combinations that caused
unidirectional block decreased again as segment length further decreased. These results provide a possible mechanism of unidirectional
block for situations where islands of viable tissue are connected through nonviable tissue, such as in a healed myocardial
infarction. |
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Keywords: | Unidirectional block Reentry DiFrancesco-Noble model |
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