Case 10 Tachycardia after Antiarrhythmic Drugs

Patient: neonate at age of 3 years.

Index arrhythmia: out-of-hospital cardiac arrest, ventricular fibrillation due to LQT3.

Complaint: recurrent shocks. Electrogram

413 415 4 IS 403 153 155 1-50 165

Ep=d

Figure 6.10a. From top to bottom: atrial electrogram, near-field and wide-band ventricular electrogram, and markers. Markers: AS = atrial sensing; Epsd = episode; VF = ventricular fibrillation; VS = ventricular sensing.

413 415 4 IS 403 153 155 1-50 165

Ep=d

Figure 6.10a. From top to bottom: atrial electrogram, near-field and wide-band ventricular electrogram, and markers. Markers: AS = atrial sensing; Epsd = episode; VF = ventricular fibrillation; VS = ventricular sensing.

ICD pulse generator: Prizm DR 1853 HE (Guidant Inc, St Paul, MN, USA); epicardial sense/pace leads and epicardial defibrillation patch.

Tachycardia settings

Bradycardia settings

Mode: AAI 70bpm.

86 6. Clinical Case Studies Electrogram interpretation

Figure 6.10b. From top to bottom: atrial electrogram (A), near-field and wide-band ventricular electrogram (splitted in V and V').

1. Comparison between atrial and ventricular rate: rate branch VV = AA.

2. Description of the atrial rhythm: the atrial electrogram shows a fast atrial rhythm with cycle length «415 ms with a consistent atrial morphology. The atrial electrogram demonstrates sinus tachycardia.

Figure 6.10c. Wide-band electrogram and marker channel. Markers: AS = atrial sensing; Epsd = episode; VF = ventricular fibrillation; VS = ventricular sensing.

3. Assessment of the onset of the tachyarrhythmia triggering device therapy: the marker channel demonstrates sensed activations in the ventricular fibrillation window (*). These sensed activations have a consistent sequence of a short (155 ms) and a long interval (250 ms) for each ventricular depolarization.

4. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular and shock electrogram during tachycardia is stable with a consistent atrioventricular relation. The PR (A-V) interval measured between the electrograms is 180 ms; the split bipolar ventricular and wide band ventricular electrogram width measure «230 ms! The tachycardia has a ventricular cycle length of « 415 ms.

Diagnosis: double counting of ventricular depolarization due to increased dosage of flecainide as antiarrhythmic drug treatment.

Further action: lower dose of flecainide.

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