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 defi ned 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 fe ature of excitable media and describe the relationship between the pro perties of an excitable medium and the VW. We present asymptotic resul ts that reveal the sensitivity of the VW to both the propagation veloc ity of the conditioning wavefront and the recovery process parameters. We also have identified a critical length of medium that must be exci ted in order to reveal vulnerability. Analytical results are in agreem ent with numerical studies.