Interval Plots Tachograms

The interval plot is a graphical presentation of the detected intervals (ms) plotted versus time (sec). The detected intervals preceding arrhythmia detection, during the arrhythmia, and after delivered ICD therapy are displayed. The plot shows V-V and A-A intervals with different symbols (e.g. closed circles "•" or open squares "□"). In the interval plot, the

Electrogram Ventricular Tachycardia
Figure 3.10. Application of rate branches in relation to interval plots (Medtronic devices). With VV and AA, intervals are shown, not rate.

programmed rate cutoffs for the detection zones are displayed as horizontal lines and their values are printed at the top of the interval plot. The time "0" seconds represents the fulfilled tachycardia detection.

By analyzing the relationship of atrial and ventricular activities, the interpretation of the interval plot can provide a fast diagnosis of the arrhythmia triggering device therapy, especially in dual-chamber defibrillators. Based on the comparison of atrial and ventricular intervals, tachyarrhythmias can be roughly divided into three rate branches: ventricular rate > atrial rate (VV < AA), ventricular rate < atrial rate (VV > AA), and ventricular rate = atrial rate (VV = AA). Figure 3.10 shows the application of the different branches in relation to interval plots. The majority of ventricular tachyarrhythmias have ventricular rates faster than the atrial rate (branch VV < AA). This dissociated atrioventricular conduction is characterized by two separate tracks of the atrial and ventricular rate/interval.

Figure 3.11. Interval plot of ventricular fibrillation with the accompanying electrogram. During the initial rhythm, the interval plot shows that each ventricular activity is preceded by an atrial activity. The ventricular intervals have a cycle length of ^ 600 ms. At the onset of the tachyarrhythmia, there is a sudden decrease of ventricular intervals, while the atrial intervals remain constant. The ventricular intervals have a mean cycle length of ^ 170 ms, the atrial intervals of ^ 600 ms.

Figure 3.11. Interval plot of ventricular fibrillation with the accompanying electrogram. During the initial rhythm, the interval plot shows that each ventricular activity is preceded by an atrial activity. The ventricular intervals have a cycle length of ^ 600 ms. At the onset of the tachyarrhythmia, there is a sudden decrease of ventricular intervals, while the atrial intervals remain constant. The ventricular intervals have a mean cycle length of ^ 170 ms, the atrial intervals of ^ 600 ms.

Figure 3.12. Interval plot of ventricular tachycardia with 1:1 retrograde atrioventricular conduction, and the accompanying electrogram. During the initial rhythm, the interval plot shows that each ventricular activity is preceded by an atrial activity. The ventricular intervals have a cycle length of ^ 700 ms. At the onset of tachyarrhythmia, there is a sudden decrease of the ventricular intervals followed by a decrease in atrial intervals. During the tachyarrhythmia, each ventricular activity is followed by an atrial activity. The ventricular intervals have a mean cycle length of ^ 360 ms.

Figure 3.12. Interval plot of ventricular tachycardia with 1:1 retrograde atrioventricular conduction, and the accompanying electrogram. During the initial rhythm, the interval plot shows that each ventricular activity is preceded by an atrial activity. The ventricular intervals have a cycle length of ^ 700 ms. At the onset of tachyarrhythmia, there is a sudden decrease of the ventricular intervals followed by a decrease in atrial intervals. During the tachyarrhythmia, each ventricular activity is followed by an atrial activity. The ventricular intervals have a mean cycle length of ^ 360 ms.

Some examples of interval plots of arrhythmias recorded in dual-chamber devices are shown in Figures 3.11-3.16.

Event Markers, Marker Channels™, Status Channel

With third-generation devices, it became possible to display real-time data and stored data using several tabular or graphical options. One interesting, simple, and easy-to-use option is to show timing events (for pacing, sensing of normal beats, sensing of arrhythmias - tachycardia, fast tachycardia, fibrillation-, the starting of capacitor charging, the delivery of therapy -ATP or shocks-). These events can be displayed as single, double, or multiple lines above and/or below a baseline, with different calibrations according to the event. Figure 3.17 shows the different calibrations for ELA-Medical defibrillators.

Figure 3.13. Interval plot of ventricular tachycardia during atrial fibrillation, and the accompanying electrogram. The initial rhythm is sensed atrial, ventricular paced with a cycle length of ^ 600 ms. At the onset of the tachyarrhythmia, there is a sudden decrease of ventricular cycle length (^ 260 ms), and the ventricular intervals are stable during the tachyarrhythmia. The delivered shock terminates the ventricular tachycardia, and restores sinus rhythm as well.

Figure 3.13. Interval plot of ventricular tachycardia during atrial fibrillation, and the accompanying electrogram. The initial rhythm is sensed atrial, ventricular paced with a cycle length of ^ 600 ms. At the onset of the tachyarrhythmia, there is a sudden decrease of ventricular cycle length (^ 260 ms), and the ventricular intervals are stable during the tachyarrhythmia. The delivered shock terminates the ventricular tachycardia, and restores sinus rhythm as well.

In the majority of current devices, the device activity is annotated by markers (Table 3.1). The markers represent the ICD's classification for each detected event by letter symbols.

Table 3.1. Most important marker annotations for normal rhythm and for tachyarrhythmias. Device activity markers are summarised for Biotronik, Guidant, Medtronic, and St Jude Medical ICDs.

Manufacturer

Table 3.1. Most important marker annotations for normal rhythm and for tachyarrhythmias. Device activity markers are summarised for Biotronik, Guidant, Medtronic, and St Jude Medical ICDs.

Manufacturer

Was this article helpful?

0 0

Post a comment