How to map WFDB_Annotation().getTime() to actual timestamps?

Question

I'm trying to link some arterial blood pressure beats that I extracted from the MIMIC waveform database to events in the MIMIC clinical database. I obtained the arterial blood pressure beats using WFDB to get the beat onsets. For the beginning of a beat, I call WFDB_Annotation().getTime() to get the sample number to which the annotation "points". How can I map it to an actual timestamp (e.g. 2015-05-24 17:47:59) so that I can link it to events in the MIMIC clinical database?

Assume that the sampling frequency is 125 Hz, and that the waveform record started at timestamp 2567-03-30 17:47:59 (which I believe we can see in the waveform header, e.g. s00020-2567-03-30-17-47.hea) for patient s00020: if WFDB_Annotation().getTime() returns 65133, is the actual timestamp 65133/125 + 2567-03-30 17:47:59?

Answer 1

I believe (based on work in June 2015 using MIMIC II v2.6) that the waveforms and the EMR were time-shifted separately, meaning that while some of the patient IDs have been matched, you cannot match timestamps (e.g. you know the waveform is for that patient but you do not know what stay or when during their stay the waveform was recorded).