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

Comparison of Preoperative ECG Screening and Device-Based Vector Analysis in Patients Receiving a Subcutaneous Implantable Cardioverter-Defibrillator

Background and Objectives: Subcutaneous implantable cardioverter-defibrillators (S-ICDs) provide protection against sudden cardiac death from outside the cardiovascular system. ECG screening is a prerequisite for implantation, but the reproducibility of its results post-operatively in the device is only partial. We aimed to compare the results of ECG screening with device-based sensing vector analysis. Materials and Methods: We screened the hospital records of all S-ICD recipients in our clinic. All of them had pre-operative ECG screening performed (primary, secondary, and alternate vectors). The results were compared with device-based vector analysis to determine the relation of the pre- and post-operative vector availability. Results: Complete ECG screening and device-based vector analysis were obtained for 103 patients. At least two acceptable vectors were found in 97.1% of the patients pre-operatively and in 96.1% post-operatively. When comparing vectors in terms of agreement (OK or FAIL) pre- and post-operatively, in 89.3% of the patients, the result for the primary vector was the same in both situations; for the secondary, it was in 84.5%, and for the alternate, it was in 74.8% of patients, respectively. In 55.3% of patients, all three vectors were labeled the same (OK or FAIL); in 37.9%, two vectors had the same result, and in 6.8%, only one vector had the same result pre- and post-operatively. The number of available vectors was the same pre- and post-operatively in 62.1% of patients, while in 15.5%, it was lower, and in 22.3% of patients, it was higher than observed during screening. Conclusions: Routine clinical pre-operative screening allowed for a good selection of candidates for S-ICD implantation. All patients had at least one vector available post-operatively. The final number of vectors available in the device-based analysis in most patients was at least the same (or higher) than during screening. The repeatability of the positive result for a single vector was high.

Evaluation of subcutaneous implantable cardioverter-defibrillator performance in patients with ion channelopathies from the EFFORTLESS cohort and comparison with a meta-analysis of transvenous ICD outcomes

Background

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an alternative to conventional transvenous ICD (TV-ICD) therapy to reduce lead complications.

Objective

To evaluate outcomes in channelopathy vs patients with structural heart disease in the EFFORTLESS-SICD Registry and with a previously reported TV-ICD meta-analysis in channnelopathies.

Methods

The EFFORTLESS registry includes 199 patients with channelopathies (Brugada syndrome 83, long QT syndrome 24, idiopathic ventricular fibrillation 78, others 14) and 786 patients with structural heart disease.

Results

Channelopathy patients were younger (39 ± 14 years vs 51 ± 17 years; P < .001) with left ventricular ejection fraction 59% ± 9% vs 41% ± 18% (P < .001). The complication rate (follow-up: 3.2 ± 1.5 years vs 3.0 ± 1.5 years) was similar: 13.6% vs 11.2% (P = .42). Appropriate shocks rates were 9.5% vs 10.8% (P = .70), with shocks for monomorphic ventricular tachycardia being 2.0% vs 6.9% (P < .02) and for polymorphic ventricular tachycardia/ventricular fibrillation (VT/VF) 8.0% vs 5.7% (P = .30). Conversion effectiveness of VT/VF episodes was similar: 36 of 37 (97.3%) vs 151 of 155 (97.4%, P = .59). VT/VF storm event (2% vs 0.9%, P = .33) and lower inappropriate shock (IAS) (8.5% vs 12.5%, P = .12) rates were statistically similar between channelopathy and non-channelopathy patients, with 45.5% channelopathy vs 31.4% non-channelopathy patients managed with a conditional zone > 200 beats per minute (P = .0002). Annualized appropriate shock, IAS, and complication rates appear to be lower for the S-ICD vs meta-analysis TV-ICD patients, particularly lead complications.

Conclusion

EFFORTLESS demonstrates similar S-ICD efficacy and a nonsignificant, lower rate of IAS in channelopathy patients as compared to structural heart disease. Comparable IAS rates were achieved with the device programmed to higher rates for channelopathy patients.

Usefulness of subcutaneous implantable cardioverter-defibrillator therapy in patients with Brugada syndrome

Implantable cardioverter-defibrillators (ICDs) are the main therapy to prevent sudden cardiac death in patients with Brugada syndrome (BrS). The subcutaneous ICD (S-ICD) can eliminate lead-associated complications compared with transvenous ICD (TV-ICD). However, S-ICD is susceptible to T-wave oversensing (TWOS) and may result in more frequent inappropriate shocks in patients with BrS. This study aimed to compare inappropriate shocks between TV-ICD and S-ICD in patients with BrS. We enrolled 32 patients with BrS (including one woman; mean age 52 ± 18 years) who were implanted with ICD (23 TV-ICDs and 9 S-ICDs) between January 2002 and November 2018 in Oita University Hospital. We carried out a standard surface electrocardiogram (ECG) screening tests in both supine and standing positions prior to S-ICD implantation. The patients received routine clinical review every month and device monitoring every 4 months. The period of follow-up was 129 ± 51 months. Six patients with BrS and TV-ICDs experienced inappropriate shocks (26%) with their ICD therapy. In contrast, two patients with BrS and S-ICDs experienced inappropriate shocks (22%). There was no significant difference between the two groups (P = 0.82). Although one case in the S-ICD group experienced TWOS-induced inappropriate shock, SMART Pass (new high-pass filter) prevented the subsequent recurrence of inappropriate shocks during ICD therapy. Our results suggest that S-ICD is not inferior to TV-ICD in the incidence of inappropriate shocks. SMART Pass may be a useful tool to prevent inappropriate ICD shocks by TWOS in patients with BrS.