This 60-year-old man presenting with hypertrophic cardiomyopathy received a Current dual chamber ICD for secondary prevention of VT. He was seen after he had sustained 2 episodes of syncope complicated by physical injury.
Main programmed parameters
Narrative
The text confirmed the occurrence of 3 VT/VF episodes; the analyzed episode was detected in the VF zone, was non-sustained and lasted 12 sec; the shock therapy was aborted.
Tracing
This tracing also raises the issue of the delays that are observed between onset of fast ventricular arrhythmias and delivery of electrical shocks. In the VT zone, ATP sequences are delivered immediately after the initial detection phase. In the VF zone, the capacitor charge time is added before delivery of the shock. This programming must be flawless, in the VF zone particularly, because even a short delay in the treatment of a very fast ventricular tachyarrhythmia can be the cause of devastating symptoms. Conversely, as illustrated on the previous tracing, the programming of an excessively short detection time causes unnecessary and energy wasting charge of the capacitors for non-sustained tachyarrhythmias. In this patient, the rate of the ventricular arrhythmia was above 300 bpm and rapidly caused syncope. This leaves 2 choices: 1) leave the programming unchanged and the arrhythmia end spontaneously, with a risk of syncope, fall and physical injury, or 2) shorten the delay between the onset of arrhythmia and the shock delivery, which might prevent the loss of consciousness. Abbreviating this delay by shortening the detection time does not seem feasible. However, the strength of the first shock can be decreased, shortening the charge time and hastening its delivery. On the other hand, if the shock is too weak and ineffective, a second, stronger shock will be needed, the charge time of which is added to the redetection delay, lengthening the overall arrhythmia duration.
