Pacemaker Learning Package
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| Atrial escaped interval
The interval from a paced or sensed ventricular event to the next scheduled paced atrial event. Figure 15: Intervals and timing in DDD mode. Core Pace Module 6. Single and Dual Pacemaker timing ppt presentation 2003 12 DDD Examples The Four Faces of DDD • Atrial and ventricular pacing – Atrial pace re-starts the lower rate timer and triggers an AV delay timer (PAV) • The PAV expires without being inhibited by a ventricular sense, resulting in a ventricular pace A P A P V P V P On this slide, we see AV sequential or dual chamber pacing. Both the atrium and the ventricles are being paced, first the atrium and then the ventricle. Looking at the 2 complexes shown: The pacemaker begins by pacing in the atrium. 2 timers are started: • The lower rate timer • The AV Interval timer Liverpool Hospital Intensive Care: Learning Packages Intensive Care Unit Pacemaker Learning Package LH_ICU2016_Learning_Package_Pacemaker_Learning_Package 23 | P a g e The AV Interval timer expires WITHOUT BEING INHIBITED by a ventricular sense – so the pacemaker paces in the ventricle. The lower rate timer continues. If it expires without being inhibited by an atrial event (as shown above), the pacemaker paces in the atrium, and the cycle begins again. IN SUMMARY Intervals and timing can be a hard concept to understand, but fortunately the pacemaker calculates all these intervals for us. It is important to know how pacing works using its sensing, output and timing mechanisms as it helps with troubleshooting. For example: looking at the above slide and DDD mode • Why does the pacemaker’s AV interval timer expire without being inhibited? Perhaps the patient has a heart block Perhaps the patient has delayed AV conduction — the patient’s PR interval is longer than the PAV programmed into the pacemaker • Why does the pacemaker’s atrial escape interval expire? The patient’s sinus rate is less than the pacemaker’s programmed rate (i.e. sinus bradycardia) |