Stratos LV/LV-T Technical Manual 89

Reversion back to the programmed pacing mode occurs in a similarly programmable manner. If a programmable number of atrial intervals (Z) out of 8 consecutive atrial intervals (p-p) are slower than the programmed mode switch intervention rate (Z out of 8), the device will revert back to the permanently programmed parameters. Z is programmable from 3 to 8. The device will also revert back to the permanent program if 2 atrial-paced events occur or if no atrial paced or sensed events have occurred for at least 2 seconds. Each occurrence of mode switching resets the corresponding counter (X or Z) to a value of zero.

Mode Switch Events are recorded in memory and are available to the user through the following diagnostics:

IEGM Recordings

Tachy Episode Trends

Mode Switch Trends

Mode Switch Histogram

Mode Switch Counter

Mode Switching is temporarily suspended during magnet application and are inactive during ERI.

2.9PMT Management

A PMT is defined as a tachycardia caused by inadvertently tracking the retrograde P-waves. The PMT management feature includes PMT Protection/Termination and a programmable PMT detection and termination algorithm.

2.9.1 Protection

Pacemaker-mediated tachycardia (PMT) is normally triggered by ventricular depolarizations that are not synchronized with atrial depolarizations (e.g., VES). The tachycardia is maintained in a retrograde direction by intrinsic VA conduction of the stimulated ventricular depolarization and in an antegrade direction by ventricular pacing of the pacemaker that is triggered by P-waves. It is the objective of the atrial PMT protection interval to not use retrogradely conducted atrial sensed events for pacemaker timing, but only to statistically evaluate them for detection of atrial tachycardia incidents.