Medtronic PROTECTA XT DR D314DRG, Clinician Manual

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After delivering a therapy, the device must evaluate the effectiveness of the therapy and
deliver additional therapy if the arrhythmia persists. Following episode termination, the
device must continue to monitor for recurrence of the tachyarrhythmia. If an arrhythmia
terminates spontaneously following detection, or if a fast ventricular rate is due to
oversensing, therapy should be withheld.
8.2.1 System solution: VT/VF detection
Ventricular tachyarrhythmia detection is an ongoing process of classifying sensed
ventricular events for tachyarrhythmia episode detection. Based on the results of the
detection process, the device may deliver programmed therapy to the patient or withhold
therapy from the patient. After delivering a therapy, the device continues to monitor the
patient’s rhythm to determine whether the tachyarrhythmia has terminated or whether it
persists or changes. The device can be programmed to monitor for slower,
non-life-threatening VTs without providing therapy.
8.2.2 Operation of VT/VF detection
Figure 142. Overview of VT/VF detection
VT/VF event
classification
Initial VT/VF
episode
detection
Termination
Termination
Therapy
Therapy
VT/VF
episode
redetection
The device classifies the patient’s heart rhythm by measuring each interval and counting
the number of tachyarrhythmia events that occur within programmed tachyarrhythmia
“detection zones”. There are 4 programmable detection zones: VF, Fast VT, VT, and
Monitor. If the number of tachyarrhythmia events in a zone exceeds a programmed
threshold, the device detects a ventricular tachyarrhythmia episode. Upon detection, the
device may deliver a scheduled therapy, after which it reevaluates the patient’s heart rhythm
for episode termination or redetection.
Medtronic PROTECTA™ XT DR D314DRG
Clinician Manual 305