Changing place, changing future: Repositioning a subcutaneous implantable cardioverter-defibrillator can resolve inappropriate shocks secondary to myopotential oversensing

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.

Pooled Analysis of Complications with Transvenous ICD Compared to Subcutaneous ICD in Patients with Catecholaminergic Polymorphic Ventricular Arrhythmia

Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is associated with arrhythmic events which may lead to sudden cardiac death (SCD). A leading therapy for CPVT besides medical treatment with beta-blockers is the use of an implantable cardioverter-defibrillator (ICD). For this paper we compared data from a pooled analysis to get further evidence about the complications of transvenous and subcutaneous ICDs. Methods: We gathered data from a search of PubMed, Web of Science, Cochrane Library and Cinahl. For our analysis, we chose 30 studies with a total number of 784 patients. We compared the data regarding complications caused by different ICD device types. Results: During a mean follow up of 38.9 months for the patients with ICD implantation (n = 337), data showed a complication rate of 101 (30%). A total of 330 (98%) of them received a transvenous-ICD (T-ICD) and 7 (2%) a subcutaneous-ICD (S-ICD). A total of 97 (29.4%) of the T-ICD patients and 4 (57.1%) of the S-ICD patients had at least one complication. Of the 234 complications that occurred in T-ICD patients 152 (65%) were inappropriate shocks due to supraventricular arrhythmias, T/R-wave oversensing or electrode defect, 26 (11.1%) lead fracture/failure, 1 (0.4%) electrode defect, 46 were (19.7%) events of electrical storms, 1 (0.4%) thromboembolic event, 2 (0.8%) cases of endocarditis and 6 (2.6%) infections of the ICD-pocket. Ten (100%) of the complications for the four patients with the S-ICD were an event of an inappropriate shock due to supraventricular arrhythmias, T/R-wave oversensing or electrode defect. Conclusion: Subcutaneous ICDs (S-ICD) show a certain advantage over T-ICDs regarding lead-related complications. Nevertheless, they still show problems with inappropriate shocks and other ICD related complications. Therefore, a case-by-case decision is advised, but the continuous improvement of S-ICD might make it an overall advantageous therapy option in the future.

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.

Incidence of myopotential induction in subcutaneous implantable cardioverter-defibrillator patients: Is the oversensing issue really solved?

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has established its role in the prevention of sudden cardiac death in a defined population. Inappropriate shocks and device malfunction in S-ICD therapy may be caused by myopotential (MP) oversensing.

OBJECTIVE

The purpose of this study was to systematically evaluate a cohort of consecutive S-ICD patients for MP inducibility.

METHODS

After S-ICD implantation, all vectors (primary [PrimV], secondary [SecV], alternative [AltV]) were analyzed during isometric chest press (ICP), lifting and holding a 20-kg weight, and side plank exercise (SPE), supporting the body weight on the left arm. When MPs were induced, signal classification was assessed: adequate noise detection, induced undersensing (R waves classified as noise), and oversensing (noise annotated as R waves). In case of noise induction in the current vector, device reprogramming to a noise-free vector was done.

RESULTS

We systematically assessed 41 patients. In nearly all patients (90.2%), MPs were inducible. ICP was the most potent inductor of MPs. Whereas SecV (70.7%) and AltV (75.6%) were most vulnerable during ICP, PrimV was most affected during SPE (51.2%). In only a few cases did the S-ICD software distinguish correctly between MPs and QRS. MPs predominantly led to undersensing (up to 65.9%), but in up to 22% of patients MP-induced oversensing occurred but did not lead to tachycardia detection. No relation was seen between S-ICD lead and generator position and MP inducibility.

CONCLUSION

Induction of MPs during physical exercise was observed frequently. Although in most cases MP noise led to undersensing, oversensing events were commonly observed.

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.

Change of sensing vector in the subcutaneous ICD during follow-up and after device replacement

BACKGROUND

The subcutaneous implantable cardioverter defibrillator (S-ICD) has been established as a valuable alternative to transvenous ICD for prevention of sudden cardiac death. The system automatically chooses the optimal sensing vector. However, during follow-up and especially after device replacement we observed a change of the suggested sensing vector in automatic setup. Therefore, we analyzed frequency and reasons of vector change and its impact on inappropriate shocks (IAS).

MATERIAL AND METHODS

Between June 2010 and December 2017, a total of 216 patients with S-ICD^® were included in this analysis. In all patients sensing vectors at the time of implantation, during follow-up, and after device replacement were investigated. Median follow-up time was 27.3 ± 25.3 months.

RESULTS

A change of the initial vector was seen in 77 patients (35.7%). The most frequent reason for vector change was the postoperative setup in supine and erect position in 54 patients (70.1%). In 12 patients (15.5%), the vector was manually changed due to inappropriate sensing and/or therapies. Routine setup during follow-up led to automatic vector change in 10 cases (13.0%). In only 1 patient the vector was manually changed due to oversensing in an exercise treadmill test. In 27 patients, the device was replaced due to battery depletion and in 6 of these patients the sensing vector was changed by the automatic setup. Vector change did not have an impact for inappropriate therapies in the follow-up; only 1 patient received an IAS due to an inadvertent vector change after device replacement.

CONCLUSION

In the present study, a significant number of S-ICD^® patients had a manual or automatic vector change during follow-up and after device replacement. The study underlines the importance of a thoroughly performed screening and at least two valuable sensing vectors preimplant. Further studies are needed to evaluate the necessity of a routine automatic setup during follow-up.