An inappropriately-appropriate ICD therapy: What is the mechanism and what interventions can be done?

Key Clinical Message

R-wave double counting is a rare cause of ventricular oversensing that can lead to inappropriate shocks. Optimizing device programming is essential for the avoidance of subsequent inappropriate therapies.

Abstract

R-wave double counting is a rare cause of ventricular oversensing that can lead to inappropriate shocks. We present the case of a female patient, 52-years-old with a history of end-stage hypertrophic cardiomyopathy. The patient suffered an implantable cardioverter-defibrillator (ICD) shock. Cardiac device interrogation revealed ventricular tachycardia (VT) with a cycle length of 420 ms that was misclassified in the ventricular fibrillation (VF) zone owing to R-wave double counting. Optimizing device programming is essential for the avoidance of subsequent inappropriate therapies. Possible therapeutic options are briefly presented in the case.

EHRA expert consensus statement and practical guide on optimal implantation technique for conventional pacemakers and implantable cardioverter-defibrillators: endorsed by the Heart Rhythm Society (HRS), the Asia Pacific Heart Rhythm Society (APHRS), and the Latin-American Heart Rhythm Society (LAHRS)

With the global increase in device implantations, there is a growing need to train physicians to implant pacemakers and implantable cardioverter-defibrillators. Although there are international recommendations for device indications and programming, there is no consensus to date regarding implantation technique. This document is founded on a systematic literature search and review, and on consensus from an international task force. It aims to fill the gap by setting standards for device implantation.

Development of ventricular fibrillation after implantation of a biventricular implantable cardioverter defibrillator: what is the mechanism?

Syncopal spells in heart failure patient with cardiovascular implantable electronic devices (CIED) require multiple assessments. T‐wave oversensing is a well‐described phenomenon that remains significant in modern implantable cardioverter defibrillators (ICD) systems. It can lead to inappropriate therapies and loss of biventricular pacing in those with cardiac resynchronization devices. Strategies to overcome this problem are important.

Two cases of inappropriate implantable cardioverter-defibrillator therapies due to T wave oversensing induced by body twisting

T wave oversensing (TWOS) is a common cause of inappropriate implantable cardioverter-defibrillator (ICD) therapies. Various algorithms to avoid inappropriate ICD therapy are available; however, they are not helpful to avoid TWOS. Although the reproduction of TWOS is useful to resolve the problem of TWOS, it is sometimes difficult to reproduce TWOS. We report two cases of inappropriate ICD therapy due to TWOS, which were induced only by body twisting. We can successfully manage the device based on the evidence of reproduced TWOS.

Early failure of the Biotronik Linox implantable cardioverter defibrillator lead

INTRODUCTION

The Linox and Durata implantable cardioverter defibrillator (ICD) leads were introduced to British Columbia (BC) in 2008. We determined their performance and the potential risk factors for lead failure in a large population-based patient registry.

METHODS AND RESULTS

We used the BC Cardiac Registry, a mandatory Governmental database of ICD implants, to identify all recipients of Linox and Durata leads in BC between October 2008 and April 2012, and those subsequently undergoing reoperation. Lead failure was defined as recurrent nonphysiological high-rate sensing unrelated to external electromagnetic interference or T-wave oversensing; a sudden rise in impedance unrelated to perforation or lead dislodgement; or abnormal lead parameters with definite evidence of lead fracture or insulation failure. We determined the estimated cumulative lead survival by the Kaplan-Meier method, and the risk factors for lead failure in a proportional hazards model. Over a median of 39 (27-50) months, the Linox failed more frequently than the Durata (16/477 [3.4%] vs. 4/838 [0.4%]; P < 0.001), and had a significantly lower estimated cumulative survival (91.6 [80.6-96.5]% vs. 99.4 [98.4-99.8]% at 5 years; P < 0.0001). Linox failure was characterized by high-rate nonphysiological sensing (11 cases), and/or a sudden impedance rise (7 cases). Insulation failure was clearly confirmed in 6 cases of Linox failure. Female sex was a significant risk factor for Linox failure (adjusted HR = 2.1[1.3-3.4]; P = 0.004).

CONCLUSIONS

This multicenter registry indicates a high rate of Linox lead failure, particularly in female patients. Ongoing surveillance of the Linox ICD lead performance is recommended.

Introduction of new industry standards for cardiac implantable electronic devices: balancing benefits and unexpected risks

The DF-4 connector is a novel industry standard for the connection of a defibrillator lead to the generator. It aims at reducing the bulk created by two or three pins at the proximal end of the defibrillator lead and its corresponding ports at the header of the device. Having only one connection port between the lead and the device reduces the material in the pocket, the risk of lead-to-port mismatch, may lower the risk of lead abrasion, and probably makes the implantation procedure a little easier since only one set screw is required. However, all these conceived benefits are related to convenience rather than to a medical need.

After the recent experiences with the possible negative clinical impact of ‘minor’ changes like simply downsizing a defibrillator lead, a word of caution is warranted. The lead is the weakest part of the defibrillator system, complex in design and undergoing constant stress through movement. It is very hard to predict which issues may evolve over time with the changes in lead design. Does the perceived benefit really outweigh an unpredictable risk in a sensitive medical product like a defibrillator? This article tries to address the possible issues of the new spring contacts instead of set screws, the proximity of the low- and high-voltage connections as well as the inability of adding a pace/sense or an additional shock lead without a special adaptor, and advocates a measured speed in the introduction of this technology.

In vitro tests of electromagnetic interference of electromagnetic navigational bronchoscopy to implantable cardioverter defibrillators

AIMS

To characterize the electromagnetic field emitted by the electromagnetic navigational bronchoscopy (ENB) superDimension(®) Bronchus system (SDBS) and to determine whether current implantable cardioverter defibrillator (ICD) systems are suitable for use in conjunction with SDBS.

METHODS AND RESULTS

The electromagnetic emission of the SDBS location board were measured using a field strength meter connected to a low-frequency (5 Hz-100 kHz) electric and magnetic field analyser; the static magnetic field was measured using a three-axis Tesla meter. A human torso simulator was used in the in vitro experiment: a polyethylene plastic box (61 cm length × 43 cm depth × 16.5 cm height) was filled with a semisolid gel and a 0.45% saline solution to provide electric conductance similar to tissue. The ICDs were immersed 1 cm into the gel and connected with a dual-coil integrated bipolar pacing/sensing/shock lead. Tip and right ventricular coil of the lead were connected to an arrhythmia simulator using low-impedance cables. The system transmits electromagnetic waves of 2.5, 3.0, and 3.5 kHz frequency. The maximum magnetic fields measured were B = 53 and 12 µT at location board plane and at ICD plane, respectively. Corresponding figures for the electric field were E = 16.6 and 4.4 V/m. None of the tested ICDs recorded any noise signal during the period in which the location board was switched-on. Stored electrogram analysis confirmed the correct detection of simulated tachyarrhythmia and therapy delivery by every tested ICD.

CONCLUSION

The results of this study demonstrated that tested ICDs are compatible with ENB performed with SDBS. They also suggest that these results may be extended to all ICDs manufactured in compliance with current EN regulations.