the length of the blanking period the rp_interval is defined as the time between the terminal marker for the abnormal interval and the different cardiac event for example the time between atrial marker 312 and ventricular marker 318 if the average interval is greater than this quantity indicating that the point falls outside the noise window the processor branches to process block 406 where it places the synthetic marker a predetermined distance for example 46 milliseconds after the marker for the different cardiac event in this embodiment placing the synthetic marker 46 milliseconds after the marker for the different cardiac event is equivalent to placing the marker at the start of the noise window however if the average interval is not greater than the abnormal interval less the length of the cross chamber blanking period execution continues to decision block 408 in block 408 the processor determines whether the average interval is greater than the rp_interval less some predetermined period such as 86 milliseconds the length of the exemplary cross chamber blanking period if the average interval is greater than this quantity the processor branches to block 410 placing the synthetic marker one average interval before the terminal marker of the abnormal interval on the other hand if the average interval is less than this quantity the processor places the synthetic marker a predetermined time such as 86 milliseconds after the marker for the different cardiac event as indicated in process block 412 if there is no noise marker at decision block 402.