Index arrhythmia: out-of-hospital arrest, ventricular fibrillation.
Complaint: admission one month after implantation because of several consecutive shocks. After defibrillator implantation, pharmacological treatment consisted of 80 mg furosemide, 250 ^g digoxine, 10 mg fosinopril, and 25 mg spironolacton, in combination with 200 mg amiodarone.
ICD pulse generator: Ventak Mini IV (Guidant Inc, St Paul, MN, USA).
Discrimination: onset = 16%; stability = 30 ms.
Therapy: VF = shock; VT = antitachycardia pacing and cardioversion.
Mode: VVI 40bpm.
Electrogram interpretation (See Figure 6.4b)
1. Presence of tachyarrhythmia?: Yes.
2. Assessment of the onset of the tachyarrhythmia triggering device therapy: the stored bipolar shock electrogram demonstrates ventricular premature beats (*) during sinus rhythm, in bigeminy. After a third ventricular premature beat, a fast polymorphic ventricular tachycardia (arrow) is initiated.
3. Characteristics of the ventricular electrogram during the tachyarrhythmia: the morphology of the ventricular activity is polymorphic during tachycardia. The morphology of the shock electrogram during tachycardia changed as compared to the baseline rhythm. The tachycardia has a ventricular cycle length of « 250 ms, with a stability of «10 ms.
Diagnosis: ventricular bigeminy, late coupled ventricular premature beat, inducing polymorphic ventricular tachycardia.
Action: Analysis of electrolytes; potassium was 2.4 mg/L; surface ECG.
Figure 6.4c. The electrocardiogram after adjustment of electrolytes, and after correction of polypharmacia. Lead II still shows a QT interval of 462 ms, with an RR interval of 723 ms and a QTc of 501 ms.
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