Estella Pulse Generators - BIOTRONIK USA - News

54 Estella Pulse Generators Technical Manualinterval the highest amplitude of the peak. After this initial period, thesensing threshold is first set to 50% of the measured peak amplitude.After the step duration of 125 ms the threshold is set to 25% of the peakamplitude (atrium 82 ms) but never below the minimum threshold of 2.0mV in the ventricle (atrium 0.2 mV bipolar and 0.5 mV unipolar).7.5 Timing FeaturesFeatures related to pulse generator timing cycles.7.5.1 Refractory PeriodsImmediately upon sensing or pacing, the pulse generator starts arefractory period in the same channel. During the refractory period,intracardiac signals are ignored. This prevents the pulse generatorfrom responding to the depolarization signal or the repolarization signal(T-wave) that might otherwise result in inappropriate inhibition ortriggering.If the pulse generator is programmed to dual chamber sensing, therefractory periods are independently programmable for each sensingchannel. There are two refractory periods in the atrium:Regular atrial refractory period, which is automatically adjusted by theAuto Aref functionalityPVARP is started with each ventricular pace outside of the AV delay. InDDI mode, PVARP is also started with a regular ventricular sensePVARP after PVC is started after a premature ventricular sensed event(PVC)Far-field protection is activated in the atrium for ventricular sensedand paced events. The pulse generator's ventricular refractory period isalways initiated by a sensed or paced ventricular event.CautionShort Pacing Intervals—Use of short pacing intervals (highpacing rates) with long atrial and/or ventricular refractoryperiods may result in intermittent asynchronous pacing and,therefore, may be contraindicated in some patients.7.5.2 PVARPThe Post Ventricular Atrial Refractory Period (PVARP) is a function inthe pacemaker to help prevent Pacemaker Mediated Tachycardia (PMT),by preventing false classification of a retrograde conduction as an atrialevent.