Bol

Figure 3.2. Example of event counters. The first column displays device performance since the last interrogation. The last column displays the total performance since implantation.

In current devices, interval tables are still available. They can provide additional information to assess the outcome of delivered antitachycardia pacing or shock therapies (Figure 3.1).

ICD diagnostics include information on the battery status, energy consumption, lead impedance, and the integrity of the high-voltage shock circuit. Event counters can help to assess the overall performance of the device. The counters provide information on pacemaker function such as the percentage of paced and sensed events. For tachyarrhythmias, the event counters provide the number of delivered therapies, and aborted or inhibited therapies (Figures 3.2 and 3.3).

Electrograms

With third-generation devices, the most significant advance in diagnostic information was the storage of intracardiac electrogram recordings. This diagnostic information included recording of RR intervals preceding and following device therapy, and stored electrograms with real-time markers of arrhythmias triggering device therapy. The current generation of devices can be programmed to record events from different electrogram sources. The electrograms can be recorded from the pair of electrodes used for rate sensing (near-field), the defibrillation coils (far-field or wide-band), or both. Both

Arrhythmia / Therapy statistics

Last treated episode: VT OT/Feb/2006 10:22

Total number of shocks since beginning of life (without EPS) : 6

ARRHYTHMIAS FV j Fast VT VT SlowVT Others

Detection 2 6 0 0

THERAPIES FV / Fast VT VT SiowVT Others

Delivered(%effective) 2 9 0 0

34J shock 0 0 0 0

Unsuccessful ATP on Fast VT : 0

Pacing I Sensing Statistic PMT : 0 Time in MS : 09h 09min ModeSwitCh : 6

RR PaceSens. PAC RR Pace Sens. PVC Atrial Ventricular

Figure 3.3. Example of event counters with separate statistics for arrhythmia therapy and pacemaker performance.

RR PaceSens. PAC RR Pace Sens. PVC Atrial Ventricular

Figure 3.3. Example of event counters with separate statistics for arrhythmia therapy and pacemaker performance.

Figure 3.4. Stored bipolar far-field ventricular electrogram demonstrating a change in electrogram morphology during ventricular tachycardia as compared to the supraventricular baseline rhythm. The atrial activity is reflected on the far-field ventricular electrogram.

Figure 3.5. Real-time registration in a single-chamber device. From top to bottom, surface electrocardiogram lead II, device activity channel with marker annotations, and near-field ventricular electrogram. Note the subtle change in the near-field ventricular electrogram morphology: the first negative peak is more pronounced during VT compared to sinus rhythm.

electrogram sources have advantages and disadvantages. Near-field ventricular electrograms show no atrial activity, which could result in an inability to diagnose the arrhythmia triggering the device. However, they can provide information on detection problems such as the presence of over- or under-sensing of signals. In contrast, far-field electrograms have the advantage that they resemble the conventional surface electrocardiogram. The far-field electrogram can reflect atrial activity and ventricular electrogram morphology changes, which both can be helpful for arrhythmia diagnosis by the physician (Figure 3.4).

Figure 3.6. Real-time registration in a single-chamber device. From top to bottom, surface electrocardiogram lead II, device activity channel with marker annotations, near-field ventricular electrogram, and far-field ventricular electrogram. The atrial activity is reflected on the far-field ventricular electrogram. Two ventricular premature beats, the 4th and 6th beat, show a subtle change in the far-field electrogram. The amplitude of the electrogram is increased as compared to the baseline ventricular electrogram during sinus rhythm. The morphology of the ventricular premature beat has a "QRS" pattern in the near-field ventricular electrogram, while the ventricular electrogram morphology has a "Rs" pattern during sinus rhythm.

Figure 3.6. Real-time registration in a single-chamber device. From top to bottom, surface electrocardiogram lead II, device activity channel with marker annotations, near-field ventricular electrogram, and far-field ventricular electrogram. The atrial activity is reflected on the far-field ventricular electrogram. Two ventricular premature beats, the 4th and 6th beat, show a subtle change in the far-field electrogram. The amplitude of the electrogram is increased as compared to the baseline ventricular electrogram during sinus rhythm. The morphology of the ventricular premature beat has a "QRS" pattern in the near-field ventricular electrogram, while the ventricular electrogram morphology has a "Rs" pattern during sinus rhythm.

Figure 3.7. Real-time registration in a dual-chamber device. From top to bottom, surface electrocardiogram lead II, device activity channel with marker annotations, atrial electrogram, and near-field ventricular electrogram. The real-time registration shows sinus rhythm.

The correlation of electrograms with markers, rate characteristics, and RR-interval stability improves the understanding of electrograms to diagnose the arrhythmia triggering the device. The presence of device activity markers allows the physician to analyze how the device interacts with arrhythmias.

Electrograms can be displayed online (in real time) on the programmer (with a printer) or can be recorded on a conventional ECG recorder. Some examples of online electrograms are shown in Figures 3.5-3.8.

If electrograms are stored in the ICD, they can improve the retrospective analysis of events. To save energy, only a limited number of episodes are completely shown, and sometimes only short strips ("snapshots") can be obtained. Today, it is possible to retrieve the electrogram remotely from the patient, via a GSM, or the Internet. This form of telemedicine will certainly change our attitude and possibilities for follow-up (Figure 3.9).

Figure 3.8. Real-time registration in a dual-chamber device. From top to bottom, surface electrocardiogram lead II, device activity channel with marker annotations, atrial electrogram, and near-field ventricular electrogram. The atrial electrogram shows multiple events. The real-time registration shows atrial fibrillation and ventricular pacing.

Figure 3.8. Real-time registration in a dual-chamber device. From top to bottom, surface electrocardiogram lead II, device activity channel with marker annotations, atrial electrogram, and near-field ventricular electrogram. The atrial electrogram shows multiple events. The real-time registration shows atrial fibrillation and ventricular pacing.

Figure 3.9. Example of a transtelephonically transmitted stored ventricular electrogram with the accompanying electrogram, which was obtained at interrogation of the device (surface and far-field). The transmitted electrogram shows a snapshot of ventricular fibrillation during intra-operative testing of defibrillation efficacy. The transmitted electrogram resembles the stored far-field electrogram as obtained during intra-operative testing.

Figure 3.9. Example of a transtelephonically transmitted stored ventricular electrogram with the accompanying electrogram, which was obtained at interrogation of the device (surface and far-field). The transmitted electrogram shows a snapshot of ventricular fibrillation during intra-operative testing of defibrillation efficacy. The transmitted electrogram resembles the stored far-field electrogram as obtained during intra-operative testing.

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