Pacemaker Systems (Last Updated - 4/12/2006)

-5 letter system (but usually only first 3 letters are used)

-1st Position:
     -Indicates the chambers PACED:
          -A: Atrial pacing only
          -V: Ventricular pacing only
          -D: Dual-Chamber pacing (both atrium & ventricle)
-2nd Position:
     -Indicates the chambers SENSED:
          -A: Atrial sensing only
          -V: Ventricular sensing only
          -D: Dual-Chamber sensing (both atrium & ventricle)
          -O: Absence of sensing --> the device will pace automatically @ the specified rate & will ignore any intrinsic rhythm
-3rd Position:
     -Indicates the RESPONSE to a sensed event:
          -I: Sensed event inhibits the output pulse & causes the pacer to recylce
          -T: Output pulse is triggered
          -D: Dual modes of response
               -Restricted to dual-chamber pacers
               -An event sensed in the atrium inhibits atrial output but triggers ventricular output then there is a delay between the sensed atrial event & the triggered ventricular output (to mimic the PR interval)
               -If the ventricular sensor senses a NATIVE ventricular event during the delay, then ventricular output is inhibited
          -O: No response to sensed input
               -Used most commonly w/ an absence of sensing (O in the 2nd position)
-4th Position:
     -Indicates RATE MODULATION (Rate Responsive or Rate Adaptive Pacing):
          -R: Indicates that the pacer has rate modulation & incorporates a sensor to adjust the paced rate in response to patient activity
          -O: Indicates that rate modulation is either unavailable or disabled (usually omitted --> Ex.) DDD is DDDO)
-5th Position:
     -Indicates MULTISITE PACING --> stimulation sites in both atria, ventricles, multiple sites w/in any one chamber (atria or ventricle) or any combo of these (this feature is uncommon except in biventricular pacing for management of heart failure):
          -O: Multisite pacing not available
          -A: Multisite pacing in the atrium or atria
          -V: Multisite pacing in the ventricle or ventricles
          -D: Dual multisite pacing in both atrium and ventricle

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