Patient: 35-year-old female with old anterolateral myocardial wall infarction, left ventricular ejection fraction 0.35, restrictive dilated cardiomyopathy, QRS width 140 ms. Patient had a history of persistent atrial fibrillation.
Index arrhythmia: sustained monomorphic ventricular tachycardia, cycle length 270 ms.
Complaint: ICD delivered shocks. Electrogram
ICD pulse generator: Contak CD (Guidant Inc, St Paul, MN, USA).
Discrimination: onset = 16%; stability = 40 ms; Afib threshold = 200/min; V > A = ON.
Therapy: VF = shock; VT = antitachycardia pacing and cardioversion.
Bradycardia settings Mode: DDD 60-120 bpm.
1. Presence of tachyarrhythmia?: Yes.
2. Assessment of the onset of the tachyarrhythmia triggering the device: the ventricular and shock electrogram demonstrate biventricular pacing, depicted as 1 in the electrogram. After a ventricular premature beat (depicted as 2 in the electrogram), a tachyarrhythmia is initiated (depicted as 3 in the electrogram).
3. Comparison between atrial and ventricular rate: rate branch VV < AA.
4. Description of the atrial rhythm: the atrial electrogram shows large as well as small deflections. The small deflection represents far-field sensing of the ventricular activity. The large deflection represents an atrial rhythm with a cycle length «600ms with a consistent morphology. The atrial electrogram demonstrates sinus tachycardia.
5. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular and shock electrogram during tachycardia (3) changed as compared to the baseline rhythm (1). The tachycardia has a ventricular cycle length of «400 ms, with a stability of «10 ms. The atrial rate is not affected during the tachyarrhythmia, and there is no consistent atrioventricular relation. Each ventricular event during the tachyarrhythmia is sensed twice, which is confirmed by the marker annotations. As a result, a stable monomorphic ventricular tachycardia will be detected in the fibrillation detection window.
Diagnosis: ventricular double-counting during ventricular tachycardia.
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