1. From: Cardiac Rhythm Management Devices (Part I):Indications, Device Selection, and Function
Anesthes. 2001;95(5):
Figure Legend:
Fig. 2. Depiction of atrial-inhibited pacing, as for sinus bradycardia with intact atrioventricular conduction. In the first beat, the atrium (A) is paced (by convention, an arrow pointing toward the electrocardiogram [ECG] in the atrial timing diagram). The atrial refractory period (ARP) prevents conducted R and ensuing T waves from being interpreted by the device as a P wave and inappropriately resetting the atrial escape interval (AA). After the programmed AA interval, another atrial stimulus occurs and resets the interval. In the third beat, a spontaneous P wave is sensed (by convention, an arrow pointing away from the electrocardiogram in the atrial timing diagram) before the AA interval times out. This resets the AA interval without pacing (the short vertical line in the atrial timing diagram shows where the stimulus would have occurred). In the absence of further sensing, the atrium is paced in the fourth beat when the AA interval times out. This example illustrates a principle that is useful for interpreting a single-chamber pacemaker electrocardiogram. Once the escape interval is known (from the clinical records, device telemetry, or measurement between consecutive paced beats), electrocardiographic interpretation is facilitated by working backward from the last stimulus to identify the sensed event that reset the pacemaker’s escape timing as a P wave (or R wave, as the case may be), and not a spurious signal. Reprinted with permission from Bernstein AD, Parsonnet V: Fundamentals of antibradycardia-pacemaker timing. ACC Educational Highlights 1995; 11:5–9; copyright American College of Cardiology.
Date of download: 10/11/2017
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