Enrico Adornato, Elena Maria Fernanda Adornato, Pasquale Monea, Antonio Pangallo, Virgilio Pennisi.
Divisione di Cardiologia, Azienda Ospedaliera “Bianchi-Melacrino-Morelli”, Reggio Calabria, Italy
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The assessment of the cardiac events
initiating ICD therapy and the results of the delivered antitachycardia therapy
(pacing/shock) is of great importance during the follow-up of ICD patients.
Unfortunately, patient’s clinical history is not always diagnostic in hemodynamically
well tolerated VT treated by ATP for the lack of symptoms and also in VF immediately
terminated by shock before the appearance of symptoms; on the other hand,
inappropriate shock discharge over atrial fibrillation may provoke dizziness or
syncope1,2. Whereas, advances in ICD technology have allowed the implementation
of sophisticated diagnostic functions which may provide a better identification of
both atrial and ventricular deflections and an accurate interpretation of the arrhythmic
events occurring after ICD implantation.
The second ICD generation has been utilizing, for the arrhythmia diagnosis, the
analysis of RR intervals which were associated with the rhythm that led to the
detection of the arrhythmic event and/or documented, just before and after, the
device therapy. However, RR interval information may be inadequate for identifying
the real rhythm in a significant number of patients; e.g., in presence of an atrial
fibrillation with rapid ventricular response and small variations in RR intervals,
suggesting an episode of VT; or in presence of VT with marked RR interval variability
at its onset, suggesting an episode of atrial fibrillation; finally, when the pathological
tachycardia starts in the context of a sinus tachycardia and no difference exists
between RR intervals during VT and sinus tachycardia. The present generation of
ICDs is capable of stored intracardiac electrograms (EGMs) during arrhythmic events,
providing a wide variety of information for the identification of cardiac rhythm leading
to ICD therapy, the assessment of the ICD operation in detection and termination of VTs,
the evaluation of the ICD problems encountered during the patient follow-up, and
finally, the knowledge of the mechanism of sudden cardiac death3-5.
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