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-Atrial rate -Ventricular rate -AV conduction pattern -AV dissociation -AA interval stability -A-EGM morphology -V-EGM morphology -Sudden onset -Chamber of origin

Figure 4.7. Available information blocks with relevant data in dual chamber devices; application in relation to the relative rate of atria and ventricles. VV and AA stand for the cycle length or interval, not for rate.

Electro Cardio Gram With Pacemaker Strip

Figure 4.8. Stored bipolar electrograms showing ventricular tachycardia (VT). Rhythm strip from top to bottom: atrial, ventricular, and shock electrogram. A ventricular premature beat (1) initiates VT (2) with regular ventricular intervals detected in the programmed tachycardia detection zone. During VT, the ventricular rate is faster than the atrial rate. Markers: AS = atrial sensing; PVC = premature ventricular complex; VP = ventricular pacing; VT = ventricular tachycardia window. (Guidant Prizm DR, model 1861)

Figure 4.8. Stored bipolar electrograms showing ventricular tachycardia (VT). Rhythm strip from top to bottom: atrial, ventricular, and shock electrogram. A ventricular premature beat (1) initiates VT (2) with regular ventricular intervals detected in the programmed tachycardia detection zone. During VT, the ventricular rate is faster than the atrial rate. Markers: AS = atrial sensing; PVC = premature ventricular complex; VP = ventricular pacing; VT = ventricular tachycardia window. (Guidant Prizm DR, model 1861)

Guidant Stored Electrogram

Figure 4.9. Stored bipolar electrograms demonstrating double tachycardia, which is ventricular tachycardia (VT) during atrial fibrillation (AF). Rhythm strip from top to bottom: atrial, ventricular, and shock electrogram. The atrial electrogram shows atrial fibrillation. A ventricular premature beat (2) initiates VT (3). During VT, the morphology of the ventricular and shock electrograms change as compared to baseline rhythm (1). Markers: AF = atrial fibrillation window; AS = atrial sensing; VP-FB = ventricular pacing, fallback; VS = ventricular sensing; VT = ventricular tachycardia window. (Guidant, Renewal II, model H155)

Figure 4.9. Stored bipolar electrograms demonstrating double tachycardia, which is ventricular tachycardia (VT) during atrial fibrillation (AF). Rhythm strip from top to bottom: atrial, ventricular, and shock electrogram. The atrial electrogram shows atrial fibrillation. A ventricular premature beat (2) initiates VT (3). During VT, the morphology of the ventricular and shock electrograms change as compared to baseline rhythm (1). Markers: AF = atrial fibrillation window; AS = atrial sensing; VP-FB = ventricular pacing, fallback; VS = ventricular sensing; VT = ventricular tachycardia window. (Guidant, Renewal II, model H155)

known as "double tachycardia", most often atrial fibrillation and ventricular tachycardia. On the atrial level, the blocks "atrial rate", "AA interval stability", and "AV conduction pattern" can be used to identify the type of atrial tachyarrhythmia. A regular atrial rhythm is usually found during atrial flutter or tachycardia.

For the identification of ventricular tachycardia, combinations of blocks "AV dissociation", "VV interval stability", and "ventricular electrogram morphology" are used (Figure 4.9). The ventricular electrogram morphology and stability of ventricular intervals are applicable for identification of ventricular tachycardia during atrial fibrillation. The blocks "AV dissociation" and "ventricular electrogram morphology" are suitable for identification of ventricular tachycardia during atrial flutter or tachycardia. Atrial flutter or tachycardia with stable N:1 AV conduction have a consistent AV conduction pattern. This AV conduction pattern will change when ventricular tachycardia is present (Figure 4.10). The physiologic block "VV interval stability" is not applicable during atrial tachyarrhythmias with stable N:1 AV conduction as the ventricular response is regular.

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