PMT Intervention Feature
A pacemaker mediated tachycardia (PMT) may result in ventricular pacing at the Upper Tracking Rate when retrograde P waves (due to the loss of AV synchrony) are sensed and tracked in an atrial tracking mode. PMT Intervention provides an automatic way to detect and interrupt a pacemaker defined PMT. If PMT Intervention is successful, physiologic tracking of the sinus node will resume.
PMT is nominally programmed Off and it operates in atrial tracking modes DDD, DDDR, VDD, and VDDR.
To program this feature in pacemakers, go to Params -> Additional Features.
To program this feature in ICDs, go to Pacing -> Params -> Additional Features.
Programming for pacemakers (excluding Advisa DR™ MRI, Revo MRI™ and EnRhythm™)
Programming for ICDs (and Advisa DR MRI, Revo MRI and EnRhythm)
A PMT may occur when retrograde P waves (caused by a loss of AV synchrony) are sensed and tracked. This can only occur in an atrial tracking mode (DDD, DDDR, VDD, VDDR). The PMT Intervention feature provides an automatic way for the device to detect and interrupt pacemaker-defined PMTs.
When PMT Intervention is programmed On, the device monitors for a PMT when eight consecutive VA intervals are detected that meet the following conditions:
- Duration less than 400 milliseconds.
- Start with ventricular paced event.
- End with atrial sensed event.
If a pacemaker-defined PMT is detected, the PVARP will be forced to 400 milliseconds for one cycle after the ninth paced ventricular event. The next atrial event will fall within the 400 millisecond PVARP becoming an atrial refractory (AR) event (refractory events are not tracked by the ventricle).
Note that after a PMT Intervention, this feature is automatically suspended for 90 seconds until PMT monitoring resumes.
This diagram summarizes PMT Intervention.
The strip below displays PMT Intervention in action. The pacemaker is tracking retrograde P waves, which can be seen in the beginning of the strip. PMT Intervention extends the PVARP after the ninth beat to mask the retrograde P wave, which breaks the PMT.
Sources: Medtronic Adapta™/Versa™/Sensia™ Reference Guide; Medtronic Consulta™ CRT-P Clinician Manual;Medtronic Protecta™ XT DR Clinician Manual; Medtronic Protecta™ XT CRT-D Clinician Manual.