ECG predictors of T wave oversensing in subcutaneous implantable cardioverter defibrillators
Introduction
The S-ICD has a proven track record in delivering lifesaving and effective shock therapy for patients with lethal arrhythmias [1]. The S-ICD performs well in a head-to-comparison with transvenous implantable cardioverter defibrillators in discriminating supraventricular tachyarrhythmias from ventricular tachyarrhythmias [2], though results of a randomised trial comparing S-ICD to transvenous ICDs have yet to be published. Clinical experience has demonstrated that the S-ICD has limited sensing specificity due to failure to appropriately discriminate/sense electrical signals unrelated to supraventricular tachycardia [1], [3]. Indeed, registry data have reported rates of inappropriate therapy of approximately 7% per annum, mostly due to T wave oversensing and undersensing of the cardiac signal [2], [3], [4]. This rate is considerably higher than rates of inappropriate shocks reported in contemporary TV-ICD device [5].
The pre-implant ECG screen is an integral part of selecting potential S-ICD recipients and excluding patients whose QRS-T wave morphology does not satisfy the screening tool. As the S-ICD employs an ECG morphology-based sensing algorithm, we hypothesise that ECG markers may prove be useful predictors of T wave oversensing.
Section snippets
Methods
Patients who had successfully passed the pre-implant ECG screen and had an S-ICD implanted at two UK centres were studied. The study group comprised patients who had experienced TWOS and had received an inappropriate shock due to TWOS. Patients with oversensing of the cardiac signal were excluded if they had experienced oversensing due to noise, a change in QRS morphology (e.g. monomorphic ventricular tachycardia or aberrantly conducted beats). Patients who had not received an inappropriate
Results
Complete datasets could be recorded in 101 patients, 10 (9.9%) of whom were not enrolled in the EFFORTLESS registry. The mean age of the population was 58.6 ± 18 years and the S-ICD was implanted for a primary prevention indication in 75 (75%). Mean follow-up was 19.5 months. In total, 93% had dual zone programming, the most frequent setting being conditional zone 200 bpm and shock zone of 220 bpm in 54/94 (57.4%). The primary vector was programmed in 49 (48.5%), the secondary vector in 44 (43.6%)
Discussion
In this study, 5.9% of patients experienced TWOS over a median follow up of 19.5 months with a mean of 1.8 shocks per patient with TWOS. This incidence is similar to that for inappropriate shocks reported in the Effortless registry [1], [3], [4], [6]. Patients who experienced TWOS had significantly broader QRS complexes, lower R:T ratios, and greater time to peak T wave amplitude and QTc. On analysis using a univariate statistical model, all these parameters were predictive of TWOS. With
Conclusion
In this study, the ECG parameters that predict TWOS are QRS duration, time to peak T wave, QT interval and R:T ratio with time to pTc being the most powerful predictor of TWOS on multivariate analysis. These findings need to be validated in a larger cohort of S-ICD patients.
Author contributions
DW: Concept and study design, data collection, data analysis and data interpretation, drafting article, statistics, and approval of article.
GL: Data collection, critical revision of article and approval of article.
CB: Funding secured by CB, critical revision of article and approval of article.
JMM: Drafting article critical revision of article and approval of article.
Funding source
DGW was supported by an educational grant from Medtronic, Inc. Funding for the study was provided by the Russells Hall Cardiac Rhythm Management Research Fund.
Conflicts of interest
DW has received an educational grant from Medtronic UK.
JM has received Honoraria and research grants from Medtronic, St Jude, Sorin, and Boston Scientific.
JM is now the senior medical director for Boston Scientific.
Acknowledgments
The National Research Ethics Service committee for the East of England approved the study (14/EE/0197) and the study has therefore been performed with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
References (14)
- et al.
Safety and efficacy of the totally subcutaneous implantable defibrillator: 2-year results from a pooled analysis of the IDE study and EFFORTLESS Registry
J. Am. Coll. Cardiol.
(2015) - et al.
Inappropriate shocks in the subcutaneous ICD: incidence, predictors and management
Int. J. Cardiol.
(2015) - et al.
Use of a discrimination algorithm to reduce inappropriate shocks with a subcutaneous implantable cardioverter-defibrillator
Heart Rhythm.
(2014) - et al.
Anasarca-mediated attenuation of the amplitude of electrocardiogram complexes: a description of a heretofore unrecognized phenomenon
J. Am. Coll. Cardiol.
(2001) - et al.
Prognostic importance of change in QRS duration over time associated with left ventricular dysfunction in patients with congestive heart failure: the DIAMOND study
J. Card. Fail.
(2008) - et al.
Increased T wave complexity can indicate subclinical myocardial ischemia in asymptomatic adults
J. Electrocardiol.
(2011) - et al.
T-wave axis deviation and left ventricular hypertrophy interaction in diabetes and hypertension
J. Electrocardiol.
(2013)
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This author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.