Fail of detection a life threatening sustained ventricular tachycardia; a case report

M. Khair Alsaad (Bielefeld)1, A. Tego (Bielefeld)1, F. Drevinja (Bielefeld)1, S. Schulze Lammers (Bielefeld)1, M. Lafi (Bielefeld)1, C. Stellbrink (Bielefeld)1

1Universitätsklinikum OWL Klinik für Kardiologie und intern. Intensivmedizin Bielefeld, Deutschland


Background: An implantable cardioverter defibrillator (ICD) is a lifesaving therapy when experiencing a sustained ventricular tachycardia (VT) and/or a ventricular fibrillation (VF). Failure to detect VT or VF due to misclassification as supraventricular tachycardia (SVT) is possible in ICD patients depending on the device discrimination algorithm and can be potentially fatal.

Case summary and patients’ history: A 69 years old man, with a history of coronary artery disease. He underwent a coronary bypass surgery in 2010 with a LIMA graft to the LAD and two venous grafts to the RCA and the LCX. He had also undergone 2 PCI with implantation of 4 drug eluting stents in the RCA in 2009 and 2017 due to 2 inferior myocardial infarctions. In addition he suffered from a terminal kidney disease due to hereditary tubulointerstitial nephritis.

In 2009 he underwent implantation of a single chamber ICD (Medtronic; Evera MRI S VR) for secondary prevention after recurrent sustained VT. In 2018 he underwent elective ICD replacement for battery depletion. No further VT episodes occurred until admission to our hospital in 2022.

During a routine visit at the dialysis center, he experienced dizziness and chest pain and collapsed shortly thereafter. A single lead monitor electrocardiogram (ECG) monitor on site showed a wide QRS complex tachycardia consistent with VT. Resuscitation was immediately initiated and external defibrillation applied because no ICD therapy delivery was observed. VT was terminated, and stable sinus rhythm successfully reestablished. After rapid return of spontaneous circulation the pt was immediately transferred to our intensive care unit where an immediate device interrogation was performed.

The interrogation revealed intact device electrode and battery function. Stored intracardiac electrograms showed several detected tachycardia episodes with a cycle length of 320 to 350 ms (Figure 1). The tachycardia was classified as SVT and ICD therapy withheld (Figure 2). Both discriminators onset and stability had remainded activated after device replacement in 2018. As a consequence we deactivated both criteria according to current recommendations in 2019 while switching the wavelet feature of the device on. Addditionally, we reduced the VT zone to 300ms. The patient stayed then for few days in our department to observe and investigate the cause of the VT. He didn’t experience any other episodes during that time and could be discharged.


The activated onset feature, which normally functions to distinguish between rapid and gradually onset of fast ventricular rhythms led to the failure of detection the initially slow VT episodes in our patient. The stability feature, which examines the tachycardia cycle length for variation, will cause the VT not to be detected if an R-R interval short enough to fall within the VT zone is detected, such is in the case of our patient. Since the VT zone was programmed at 340 ms, many of our patient's tachycardia episodes fall within the VT zone but the cycle length varied by more than the programmed value in ms and that’s why the algorithm let the VT interval counter to be reset.

Conclusion: Individual-oriented programming of an ICD according to current manufacturer-specific recommendations is indispensable. Reevaluation and actualization of the programmed features after device battery replacement is vitally important and should be emphasized.

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