A 69-year-old man with a 30% LVEF, left bundle branch block, in NYHA functional class III, and recipient of an InSync Sentry CRT-D, was seen for syncope and DC shock.
This tracing illustrates normal function of an ICD. An episode of tachycardia was correctly detected in the VF zone and appropriately treated with an electrical shock. The first function of an ICD is to prevent sudden cardiac death by delivering electrical shocks for VF or polymorphic VT. A cardioversion shock is synchronized to the upstroke of the QRS. During polymorphic VT or VF, synchronization is often precluded by the rhythm instability and low amplitude of the EGM. Several shocks are programmed in the VF zone, all of maximal amplitude. The shock polarity is programmable. In this patient, despite the very rapid rate of the tachycardia, its organization suggests that ATP may have been successful.
Electrical shock delivered for a tachycardia detected in the VF zone; the capacitor charge time is >7 sec and the high voltage lead impedance is 48 Ohms; all episodes detected in the VF zone are automatically considered ventricular in origin.
