Undetected ventricular fibrillation in a single-chamber implantable cardioverter-defibrillator: When the far-field channel sees more than the intraventricular channel

Rate disparity of near‐field versus far‐field ICD electrograms: A clue to the diagnosis of dissimilar ventricular rhythms

“…This VF, however, remained undetected by the ICD because RR intervals on the RV EGM stayed prolonged at 400 ms, longer than the programmed tachycardia intervention interval. Other published case reports described virtually identical findings with the FF EGM in VF faster than the organized RV EGM except one that documented an organized tachycardia in the FF ECG where it was faster than the near‐field EGM . Documented termination of arrhythmias involved substantial ICD delay in shock delivery, and need for manual activation of an ICD shock, or external defibrillation …”

Interventricular Differences in Action Potential Duration Restitution Contribute to Dissimilar Ventricular Rhythms in ex vivo Perfused Hearts

“…A recent case report by Kubickova et al highlights the potential serious clinical implications of dissimilar ventricular rhythms and ventricular rates. During VF sensitivity checks in an implantable cardioverter defibrillator (ICD) implant, the device failed to shock a patient in VF due to a slower concomitant RV VT below the treatment threshold zone (18). In this study, we were able to elicit dissimilar rates in VT and showed that in keeping with this case report, the RV rate was always slower.…”

Commentary: Interventricular Differences in Action Potential Duration Restitution Contribute to Dissimilar Ventricular Rhythms in ex vivo Perfused Hearts

“…However, it can only be a possible concept in CRT-D devices. It is unfortunately not applicable in the single- or dual-chamber ICDs because of the absence of LV sensing (3, 4). Further technical investigations in favor of a functioning hemodynamic sensor are possibly more promising as this would be applicable in all types of ICDs.…”