Patent ID: 7561913

Claim:
A method of controlling a therapy in an implantable medical device, comprising: setting a refractory period upper limit; setting a lower limit for the refractory period; initializing a refractory period to the refractory period upper limit; sensing a cardiac signal other than during the refractory period and determining whether to deliver a therapy in response to the cardiac signal; determining whether an R-wave synchronization criteria for delivering the therapy are met; and then if the R-wave synchronization criteria are met, delivering the therapy and returning to the sensing step; and if the R-wave synchronization criteria are not met, automatically adjusting the refractory period to be less than the refractory period upper limit and return to the sensing step; determining whether the refractory period, as adjusted, is less than the lower limit; terminating the method in response to the refractory period, as adjusted, being less than the lower limit; determining, in response to the refractory period, as adjusted, not being less than the lower limit, whether the R-wave synchronization criteria corresponding to the refractory period, as adjusted, are met for a subsequently sensed cardiac signal; delivering the therapy in response to the R-wave synchronization criteria being met for the subsequently sensed cardiac signals; and automatically adjusting the refractory period, as adjusted, in response to the R-wave synchronization criteria not being met.