Case 38 Slowing of the Heart Rhythm Followed by a Shock

Patient: 84-year-old male patient.

Index arrhythmia: monomorphic sustained ventricular tachycardia, CL 330 ms. Complaint: patient experienced a shock. Interval plot

Figure 6.38a.

ICD pulse generator: Lexos VR-T (Biotronik Inc, Berlin, Germany). Epicardial lead system.

Tachycardia settings

Detection: VF = 300 ms; VT = 370 ms. Discrimination: onset = 16%; stability = 40 ms.

Therapy: VF = shock; VT = antitachycardia pacing and cardioversion.

Bradycardia settings Mode: VVI 50bpm.

Electrogram (See Figure 6.38b) Interpretation

1. Presence of tachyarrhythmia?: Yes.

2. Assessment of the onset of the tachyarrhythmia triggering the device: a premature beat (1) initiates a fast tachyarrhythmia (2).

Figure 6.38b. From top to bottom: marker channel, near-field ventricular electrogram, and wide-band ventricular electrogram. Markers: VF = sense in ventricular fibrillation window; VP = ventricular pace; VS = ventricular sense.

3. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular activity is consistent during tachycardia. The morphology of the ventricular electrogram changed as compared to the baseline rhythm, which is clearly in the wide-band ventricular electrogram. The tachycardia has a cycle length of ~ 280 ms, with a stability of ~ 10 ms.

Diagnosis: monomorphic ventricular tachycardia. The initiation is related to a paced beat, occurring after a pause.

Action: reprogrammation of the tachycardia detection zone to provide antitachycardia pacing as first therapy to terminate the arrhythmia. It is tempting to change the pacing mode to AAI, but this is evidently impossible.

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