Implanted defibrillators in trouble: initial device misclassification leads to correct diagnosis-a case series.

Aims: Supraventricular tachycardia, mistakenly diagnosed as ventricular tachycardia, may lead to inappropriate ICD therapy. Inappropriate ICD therapy associates with increased morbidity and mortality. A reduction of inappropriate therapy is therefore desired.

Methods and results: We present three different cases that beautifully illustrate the diagnostic possibilities of stored electrograms. Initial differential diagnoses in all three patients included ventricular tachycardia, focal atrial tachycardia, atrio-ventricular re-entry tachycardia, and atrio-ventricular nodal re-entry tachycardia. The first case was diagnosed as atrio-ventricular nodal re-entry tachycardia. In the second case, atrio-ventricular re-entry tachycardia was revealed. Ectopic atrial tachycardia was the reason for inappropriate therapy in the third patient.

Conclusion: Thorough analysis of stored electrograms yielded correct diagnosis in all cases, which subsequently was confirmed by electrophysiological study.