Computer simulation of in-vitro atrioventricular node
    pacing experiments with coverage of the whole parameter
    space.

Corlan Alexandru Dan; Cinteză Mircea; Dorobantu
    Maria; Vinereanu Dragos; Vasilescu Ileana; Bălănescu Serban; Iosifescu Dan; Dimulescu
    Doina; Ioachimescu Octavian; Gherasim Leonida

Computer simulation of in-vitro atrioventricular node pacing experiments with coverage of the whole parameter space.

Corlan Alexandru Dan, Cinteză Mircea, Dorobantu Maria, Vinereanu Dragos, Vasilescu Ileana, Bălănescu Serban, Iosifescu Dan, Dimulescu Doina, Ioachimescu Octavian, Gherasim Leonida,

Eur Heart J 18 (suppl):233-233, 1997

ABSTRACT

BACKGROUND. In in-vitro experiments, pacing the lower right atrium was shown to produce in the AV region: reflection, local reentry, decremental conduction, discontinuous AV nodal curve (sudden rise in the AH interval for a minimal decrease of the AA interval), the gap phenomenon (conduction at shorter AA intervals when longer ones were previously blocked).

PURPOSE. To estimate the theoretical probability of occurence of the above phenomena. To provide a tool for the indirect estimation of the constellation of electrophysiologic (EP) parameters of the cells in the AV region starting from the results of an atrial pacing study.

METHODS. We developed a computer model consisting of a 3D mesh of 910 simulation elements of 1mm³--lower right atrium down to the His bundle: atrial (A) elements, slow (S) and fast (F) elements constituting the atrial inputs, transitional (T) zone (with decremental conduction) and compact (N) zone. For each type of element, we selected ranges of EP parameters, based on literature data, in which we took a set of (n) values:

Region	Slow (n)	Fast(n)	Transitional (n)	Compact (n)
Refractory period (ms)	140--220 (7)	180--240 (3)	230--270 (3)	260--300 (3)
Conduction speed (cm/s)	4.7--21 (11)	10--33 (7)	≥ 6,6	5,0

We generated 306 computer models, one for each combination of parameter values which also obeyed a set of further restrictions (such as the refractory period (RP) of the S elements shorter than the RP the F elements). A protocol of simulated pacing with regular-extrastimulus pairs at coupling intervals decreasing by 10ms in the range of 220--140 ms was applied to each model.

RESULTS. Our simulation program computed electrograms and activation maps for each model. These were inspected by two investigators for the types and numbers of phenomena in each simulation: reflection was found in 136 simulations (44%), local reentry in 128 (41%), sustained reentry in 63 (20%), gap phenomenon in 50 (16%), discontinuous AV nodal curve in 78 (25%).

Despite the simplicity of the cell-type architecture of the region, in many cases conduction or reentry took place via an intricate route, also frequently responsible for the gap phenomenon.

CONCLUSION. As all the above phenomena were observed in a substantial proportion of the EP parameter combinations, they can be explained by the presence of four cell region with different EP properties. Using the results of a large number of scenarios it may be possible to match a simulation result with that of an actual experiment and thus infer the constellation of EP parameters that led to the experimental result.