Specifications

Refractory Periods
Overview
A refractory period is an interval during which an intrinsic event sensed on
a particular lead channel cannot start certain timing intervals. Each
refractory period begins with a blanking period, during which no sensing
occurs. During the unblanked portion of a refractory period, sensing occurs,
but sensed events may not directly affect timing operations. Refractory
periods are intended to prevent certain timing intervals from being started
by inappropriate signals such as retrograde P-waves, far-field R-waves, or
electrical noise.
Though they may not start timing intervals, refractory sensed events are
monitored by the pacemaker, and they affect the operation of Mode Switch,
Rate Adaptive AV operation, Non-Competitive Atrial Pacing (NCAP), and
pacemaker-defined PVC for which the periodicity or number of sensed
events are pertinent. Refractory sensed events are included on Marker
Channel recordings and Marker Channel Diagrams.
12-16 Understanding Pacemaker Operations
9879EN-12_9501043EN/CTC.qxd 5/10/99 11:27 Page 12-16
7 x 9 inches (178 mm x 229 mm)
Medtronic Confidential
Refer to the “Reference man.” category in doc#163256 for Printing
Instructions.
196407001 Rev A