VULNERABILITY IN ONE-DIMENSIONAL EXCITABLE MEDIA

Potentially life-threatening cardiac arrhythmias can be initiated with stimuli timed to occur during the ''vulnerable window (VW)''. We defined VW as the time interval between the ''conditioning'' and ''test'' stimuli following in sequence, during which the test stimulus response propagates in only one direction. We show that the VW is a geneTiC feature of excitable media and describe the relationship between the properties of an excitable medium and the VW. We present asymptotic results that reveal the sensitivity of the VW to both the propagation velocity of the conditioning wavefront and the recovery process parameters. We also have identified a critical length of medium that must be excited in order to reveal vulnerability. Analytical results are in agreement with numerical studies.