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Figure 6.20b.

1. Tachycardia: probably not.

2. Comparison between atrial and ventricular rate: VV < AA.

3. Description of the atrial rhythm: the atrial electrogram shows a regular, paced rhythm transitioning to an atrial rhythm which remains stable, and with the same morphology throughout the recording.

4. Assessment of the onset of the tachyarrhythmia: the onset is characterized by a premature beat in the ventricle, and several ventricular events with an extremely short coupling, sometimes with a high frequency.

5. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular abnormal activity is different from the conducted beats. When using a caliper, it is possible to see that a normal QRS is seen after every atrial activity, with a normal AV interval. The events do not reset the atrial activity.

6. The atrioventricular relationship is unclear (see above).

7. The shock (HV) does not restore normality.

Figure 6.20c. Lead V4. Atrial pacing; no ventricular arrhythmia; tiny bumps/spikes are observed in the precordial leads; the relation with the intracardiac signals is not clear.

Suspected: noise at ventricular level, almost 2 years after implantation. Lead problem?

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1. Measurement of the pacing and sensing characteristics - no changes vs before.

2. Shock delivery and measurement of shock lead impedance - no change of impedance after 0.1 J shock (40 ohm, as was previously known).

3. Local manipulation to provoke the abnormal electrograms (electrogram below).

Figure 6.20d. This was easy - saturation of the amplifiers was evident (overflow to the atrial electrogram). The impedance did not change during this shock (39 ohm).

Conclusion: damage to the lead, not evident during assessment. Caused by action sports? Replacement of the lead.

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