Elsevier

Heart Rhythm

Volume 16, Issue 6, June 2019, Pages 913-920
Heart Rhythm

Clinical
Devices
Effect of diurnal variations in the QRS complex and T waves on the eligibility for subcutaneous implantable cardioverter-defibrillators

https://doi.org/10.1016/j.hrthm.2019.01.004Get rights and content

Background

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are an established therapy for preventing sudden cardiac death. However, a considerable number of patients still undergo inappropriate shocks even after conventional preimplantation electrocardiographic (ECG) screening.

Objective

This study aimed to elucidate the additional effect of diurnal variations in the QRS complex and T waves of 24-hour Holter screening on S-ICD eligibility.

Methods

Patients with transvenous ICDs who did not need pacing were selected for the study. The ECG was recorded by placing the electrodes to simulate the 3 sensing vectors of the S-ICD, with the patient in the standing and supine positions (conventional), during exercise, and during 24-hour Holter screening. We investigated the additional discrimination of diurnal variations in patients ineligible for S-ICDs as well as characteristics of those patients.

Results

Of the 86 patients (82% men; mean age 54±16 years) analyzed by all 3 screenings, 2 (2.3%) and 3 (3.4%) were considered ineligible by conventional and exercise screening, respectively. An additional 21 patients (24.4%) were found ineligible through Holter screening. A multivariate logistic regression analysis demonstrated that Brugada syndrome and an increased QRS duration per millisecond were associated with ineligibility (odds ratio 5.74; 95% confidence interval 1.74–20.2; P = .003 and odds ratio 1.04; 95% confidence interval 1.01–1.07; P = .007, respectively). T-wave oversensing was mostly observed during 0–6 AM, but no significant diurnal variations were observed in the incorrect QRS profiles.

Conclusion

The detection of diurnal variations through Holter monitoring in addition to conventional screening is expected to be useful for determining S-ICD eligibility.

Introduction

The placement of transvenous implantable cardioverter-defibrillators (TV-ICDs) is an established therapy to prevent sudden cardiac death (SCD).1, 2 Placing subcutaneous ICDs (S-ICDs) has recently become an attractive therapeutic option for patients who do not need pacing therapy, avoiding the important complications associated with transvenous leads.3 Some previous studies reported that inappropriate shocks (IASs) are associated with a reduced quality of life and increased mortality.4, 5 The propensity score matching of S-ICDs and TV-ICDs in SIMPLE and EFFORTLESS registries demonstrated similar outcomes regarding IASs at 3-year follow-up (11.9% from S-ICD vs 8.9% from TV-ICD; P = .07).6 The IDE and EFFORTLESS pooled analysis reported that IASs from S-ICDs were 24%, 39%, and 21% due to supraventricular tachyarrhythmias, T-wave oversensing (TWOS), and low-amplitude signals, respectively.7

Manufacturers have developed surface electrocardiographic (ECG) screening templates to detect incorrect QRS profile/TWOS and avoid IASs. In several previous reports, an increased body weight, increased QRS duration, right bundle branch block (RBBB), QRS-T discordance in all 3 leads (I, II, and aVF), presence of hypertrophic cardiomyopathy (HCM), and Brugada syndrome (BrS) predicted screening failure.8, 9, 10, 11, 12, 13 A previous study proposed a routine exercise screening test to reduce IASs.14 However, exercise screening cannot analyze the daily fluctuations in the QRS-T complex, which usually occur from evening to early morning, especially in patients with BrS, coronary spastic angina (CSA), and early repolarization syndrome.15, 16 Few data exist on the most frequent time of IASs from S-ICDs and the clinical effect of diurnal variations in the QRS complex and T waves on S-ICD eligibility. This study aimed to elucidate the additional effect of diurnal variations in the QRS complex and T waves using 24-hour Holter monitoring on S-ICD eligibility as well as characteristics of ineligible patients.

Section snippets

Study subjects

This analysis included data from a prospective, multicenter, observational study performed at the Japanese Red Cross Musashino Hospital and National Disaster Medical Center. We assessed consecutive patients with TV-ICDs implanted for primary or secondary prevention of SCD who attended routine follow-ups at the ICD clinics between January 2016 and January 2018. Most patients had primary cardiomyopathy, including inherited primary arrhythmia syndromes. The remaining patients presented with

Results

During the study period, all patients (n = 204) implanted with TV-ICDs were screened for inclusion in the study. We excluded patients who were older than 80 years (n = 12), were pacemaker dependent, had an indication for pacing during implantation (n = 78) or resynchronization pacing (n = 18), or had failed to complete the exercise test (n = 10) (Figure 3). Three of 6 patients with long QT syndrome were excluded because they developed bradycardia on β-blockers or we needed to perform atrial

Discussion

To our knowledge, this is the first attempt to systematically evaluate the extent to which the Holter ECG can be used to assess the eligibility for S-ICD in patients with prior TV-ICD implantation who do not need bradycardia pacing. The main findings of this study were as follows:

  • 1.

    Through Holter screening, we found an additional 24.4% of patients with TV-ICDs who were ineligible for S-ICD implantation.

  • 2.

    Regarding TWOS, the number of vectors failing screening was the largest during 0–6 AM for each

Conclusion

This prospective multicenter study firstly evaluated the effect of diurnal variations in the QRS complex and T waves on the eligibility for S-ICD. A quarter of patients with TV-ICDs, who initially appeared eligible by conventional and exercise screening ECGs, became ineligible during Holter screening. The detection of a diurnal variation through Holter monitoring and an optimized vector selection might be useful in improving the discrimination capability to determine the ineligibility for S-ICD

Acknowledgments

We thank John Martin, for providing English language editing services.

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