Inappropriate shock for myopotential over-sensing in a patient with subcutaneous ICD

Lights and shadows of subcutaneous implantable cardioverter-defibrillator in Brugada syndrome

Currently the cornerstone of therapy for ventricular arrhythmic complications and sudden cardiac death prevention in Brugada syndrome (BrS) is an implantable cardioverter-defibrillator (ICD). BrS patient population differs from the majority of patients with an ICD implanted for structural heart disease, and as widely known, transvenous ICD (TV-ICD) systems have been associated with high complication rates in patients with BrS. Technological evolution of these devices has certainly reduced complications due to the device itself, but a careful preimplant screening of these patients is still essential. To date, criteria for an adequate screening process to select suitable candidates for a subcutaneous implantable cardioverter-defibrillator (S-ICD) from patients with BrS are sometimes nonstandardized and often lack important precautions that are instead fundamental to select the most suitable type of ICD for these patients. To better select suitable candidates for an S-ICD from patients with BrS, a full screening process should include screening during or immediately after an exercise test and after a drug provocation challenge test. We report an analysis of the "lights and shadows" of S-ICD for a correct use of this device in patients with BrS.

Clinical impact of ECG change on oversensing of subcutaneous implantable cardioverter-defibrillators

BACKGROUND

Inappropriate shocks delivered from subcutaneous implantable cardioverter-defibrillators (S-ICD) are most frequently caused by cardiac oversensing. However, the predictors for oversensing of S-ICD remain unclear.

OBJECTIVE

We aimed to investigate the predictors for oversensing of S-ICD, especially clinical impact of ECG change.

METHODS

We retrospectively enrolled 99 consecutive patients who underwent S-ICD implantation between 2013 and 2021. Oversensing events were defined as inappropriate charge of the capacitors induced by cardiac or noncardiac signals other than tachycardia.

RESULTS

During a median 34 month (IQR 20-50 months) of the follow-up period, 11 of the 99 patients experienced 34 oversensing events and 4 patients received inappropriate shocks during their events. Six patients exhibited ECG changes (bundle branch block, 3; ventricular pacing, 1; inverted T wave, 1; poor R progression, 1) during follow-up period. Oversensing events were observed in four of the six patients with ECG changes (67%), and three patients underwent S-ICD removal because of inevitable shock. Contrastingly, among the remaining patients without ECG change, all 7 patients who experienced oversensing events could continue using S-ICD with reprogramming sensing vector and/or restriction of excessive exercise. Logistic regression analysis showed lower voltage of Sokolow-Lyon ECG (V₁S+V₅R) was the predictor of oversensing event among the patients without ECG change. When the cut off value was 2.1mV, the sensitivity, specificity, positive predictive value, and negative predictive value were 85.7%, 62.7%, 15.7%, and 98.1%, respectively.

CONCLUSION

Unavoidable oversensing resulting in S-ICD removal is caused by ECG changes. Oversensing in patients without ECG change can be managed.

Safety and Efficacy of Magnet Use to Temporarily Inhibit Inappropriate Subcutaneous Implantable Cardioverter Defibrillator Therapy in Emergency Situations: A Case Report

Introduction: The subcutaneous implantable cardioverter defibrillator (S-ICD) represents a major advancement in ICD technology. Inappropriate shocks (IAS) occur in more than 3.1% of the population with S-ICD each year and are usually followed by admission to the emergency department (ED). In this setting, the disabling of IAS is mandatory during a pseudo-electrical storm (ES). This report describes the strategies that can be followed in order to temporarily inhibit IAS in critical care settings with the use of magnets.

Case presentation: An S-ICD was implanted more than 6 weeks prior to presentation in a 68-year-old man with hypertrophic cardiomyopathy. In the ED, the patient experienced 3 IAS in the last hour. A Medtronic magnet was applied to stop IAS, as the specific programmer was not available. The maneuver interrupted the IAS. In order to verify the universal magnetic response of the S-ICD, six different magnets and one smartphone with MagSafe technology were tested. All magnet models suspended arrhythmia detection and IAS, while the smartphone did not cause magnet interferences.

Conclusions: This report demonstrates the safety and efficacy of all clinical magnet models in inhibiting IAS. In case of pseudo-ES, any type of magnet allows ED providers to easily and rapidly disable the functionality of the devices when appropriate.

Sensing and Detection Functions in Implantable Cardioverter Defibrillators: The Good, the Bad and the Ugly

Implantable cardioverter defibrillators are small devices that have been proven to be beneficial by preventing sudden cardiac death, whether in primary or secondary prevention. Appropriate functioning of implantable cardioverter defibrillators is mainly dependent on the "good" sensing of ventricular electrogram waves, allowing for the adequate detection of ventricular arrhythmias in order to deliver appropriate therapy of either antitachycardia pacing or by delivering a shock according to the detected rhythm. Basic sensing function in defibrillators is based on detection rate and detection duration; additional parameters that are involved in the process of adequate detection include ventricular electrogram sensing, auto-adjusting sensitivity, supraventricular arrhythmia discrimination criteria, noise detection, and various dedicated algorithms. Defective sensing may result in the delivery of inappropriate therapy (oversensing) or inappropriate withholding of therapy (undersensing); the latter of which may lead to sudden cardiac death. This paper describes different clinical scenarios and programming tips to avoid abnormal or critical clinical situations.

S-ICD lead dislodgement in a young isometric athlete: A rare complication

The subcutaneous implantable cardioverter defibrillator (S-ICD) is an alternative to transvenous ICD in patients who do not need cardiac pacing. We report the case of a young isometric athlete who received S-ICD for primary prevention of sudden death. Lead dislodgement and myopotential noise oversensing during isometric training led to inappropriate shock, and a surgical revision was performed. During the procedure, strong fibrous adhesions were found, requiring polytetrafluoroethylene dilator sheaths. The S-ICD was finally reimplanted. Despite continued isometric training, no more myopotential oversensing occurred after 1-year follow-up. The present case highlights the possible higher risks of lead complication in an isometric athlete and the uncommon effort in removing an old-generation subcutaneous defibrillator lead.

Subcutaneous Implantable Cardioverter-Defibrillator in Patients With Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: A Transatlantic Experience

Background Despite growing use of the subcutaneous implantable cardioverter-defibrillator (S- ICD ), its clinical role in arrhythmogenic right ventricular cardiomyopathy/dysplasia ( ARVC /D) patients remains undefined. We aim to elucidate the cardiac phenotype, implant characteristics, and long-term efficacy regarding appropriate therapy and complications in ARVC /D patients with an S- ICD implant. Methods and Results A transatlantic cohort of ARVC /D patients who underwent S- ICD implantation was analyzed for clinical characteristics, S- ICD therapy, and long-term outcome including device-related complications. The cohort included 29 patients (52% male, 76% probands, 59% with ARVC /D-associated mutation, 59% primary prevention [no prior sustained ventricular arrhythmias], and 45% first-generation S- ICD devices). At implant, all inducible patients (27/29) had conversion of induced ventricular fibrillation. Two patients (7%) had superficial infections of the incision site that were treated conservatively. Over a median follow-up of 3.16 years (interquartile range: 2.21-4.51 years), all episodes (6 patients, 4% per year) of sustained ventricular arrhythmias were appropriately detected and treated. Six patients (21%) experienced 39 inappropriate shocks, with 3 requiring device explantation. Oversensing of noncardiac signal (n=4; especially myopotentials) and cardiac signal (n=4) was the most frequent etiology. No lead or device dislodgement, infection, skin erosion, or explantation related to need for antitachycardia pacing was noted. Conclusions S- ICD can effectively treat both induced and spontaneous ventricular arrhythmias in patients with ARVC /D. The rate of inappropriate shocks, although considerable, is comparable to that in ARVC /D patients treated with transvenous ICD s. When they occurred, inappropriate shocks were primarily due to cardiac and, uniquely, noncardiac oversensing. We suggest potential strategies for minimizing inappropriate therapy.

Subcutaneous Implantable Cardioverter Defibrillator Lead Repositioning for Preventing Inappropriate Shocks Due to Myopotential Oversensing in a Post-Fulminant Myocarditis Patient

A 28-year-old female presented with fulminant lymphocytic myocarditis. She developed cardiogenic shock, frequent sustained ventricular tachycardia, and fibrillation (VT and VF). The left ventricular ejection fraction improved from 5% to 40% after medical therapy, but the right ventricular systolic dysfunction and enlargement persisted. In addition, sustained VTs, requiring direct current cardioversion, occurred during oral administration of amiodarone following intravenous amiodarone, even after percutaneous stellate ganglion block. Standard body surface electrocardiogram (ECG) screening for an implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD) (EMBLEM™ S-ICD, Boston Scientific, Marlborough, MA, USA) demonstrated that two of the three sensing vectors were eligible in spite of very low-amplitude QRS complexes in the body surface ECGs. After implantation of the S-ICD, the patient experienced repetitive, inappropriate shocks due to pectoral myopotential oversensing, which could not be resolved by reprogramming the device settings. Thus, the S-ICD lead was changed from the standard left parasternal position to the midline of the sternum to reduce muscular noise due to myopotentials. Thereafter, the patient experienced appropriate ICD shocks for sustained VT and VF but no inappropriate ICD sensing or shocks. Lead repositioning may be one of the feasible solutions in S-ICD patients with low-amplitude QRS complexes and inappropriate shocks due to myopotential oversensing which cannot be resolved by reprogramming the device settings.

An "UninTENSional" Subcutaneous Implantable Cardioverter-defibrillator Shock

Subcutaneous implantable cardioverter-defibrillators (ICDs) (S-ICDs) are advantageous because they eliminate the need for transvenous leads. However, just like in the case of traditional ICDs, inappropriate shocks are an unwanted complication that may result following their placement. In this case, we discuss the mechanism of an inappropriate shock in a patient with an S-ICD.