A 66-year-old man with valvular heart disease and depressed left ventricular ejection fraction underwent implantation of a dual chamber Virtuoso DR defibrillator for secondary prevention. VF was induced by T wave shock at the end of the procedure.
VF is induced at the end of procedure to verify:
1) the integrity of the defibrillation circuit and the connection between the leads and the pulse generator;
2) the accurate sensing of VF by the device; a close scrutiny of the tracings is necessary to identify deficiencies in the detection function;
3) that the VF episode is terminated by a shock delivered by the device; the “defibrillation threshold” is rarely measured, as most operators confirm the presence of a “safe margin” of defibrillation; Note : the tachycardia is not VF, though is treated as such by the ICD, as the rate in inside the programmed VF zone
Induced VF, followed by a successful 19.8 J shock requiring a >3 sec charge time; the shock impedance is 47 ohms. These are standard programmed parameters of induction (single detection zone >176 bpm and therapy; ventricular sensing to 1.2 mV).
