Usefulness of a standard 12-lead electrocardiogram to predict the eligibility for a subcutaneous defibrillator

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.

Pre-implant predictors of inappropriate shocks with the third-generation subcutaneous implantable cardioverter defibrillator

AIMS

Despite recent improvements, inappropriate shocks emitted by implanted subcutaneous implantable cardioverter defibrillators (S-ICDs) remain a challenge in 'real-life' practice. We aimed to study the pre-implant factors associated with inappropriate shocks for the latest generation of S-ICDs.

METHODS AND RESULTS

Three-hundred patients implanted with the third-generation S-ICD system for primary or secondary prevention between January 2017 and March 2020 were included in this multicentre retrospective observational study. A follow-up of at least 6 months and pre-implant screening procedure data were mandatory for inclusion. During a mean follow-up of 22.8 (±11.4) months, 37 patients (12.3%) received appropriate S-ICD shock therapy, whereas 26 patients (8.7%) experienced inappropriate shocks (incidence 4.9 per 100 patient years). The total number of inappropriate shock episodes was 48, with nine patients experiencing multiple episodes. The causes of inappropriate shocks included supraventricular arrhythmias (34.6%) and cardiac (30.7%) or extra-cardiac noise (38.4%) oversensing. Using multivariate analysis, we explored the independent factors associated with inappropriate shocks. These were the availability of less than three sensing vectors during pre-implant screening [hazard ratio (HR), 0.33; 95% confidence interval (CI), 0.11-0.93; P = 0.035], low QRS/T wave ratio in Lead I (for a threshold <3; HR, 4.79; 95% CI, 2.00-11.49; P < 0.001), history of supraventricular tachycardia (HR, 8.67; 95% CI, 2.80-26.7; P < 0.001), and being overweight (body mass index > 25; HR, 2.66; 95% CI, 1.10-6.45; P = 0.03).

CONCLUSION

Automatic pre-implant screening data are a useful quantitative predictor of inappropriate shocks. Electrocardiogram features should be taken into consideration along with other clinical factors to identify patients at high risk of inappropriate shocks.

Predicting inappropriate S-ICD® episodes by simple 12-lead surface ECG parameters

AIMS

The present study aims at analyzing the role of a preimplantation 12-lead electrocardiogram (ECG) on the prediction of inappropriate S-ICD® episodes.

METHODS

N=116 screened patients (pts) with an S-ICD® and a follow-up of at least 6 months were included. A preimplantation 12-lead ECG (50 mm/s, 10 mm/mV) was analyzed with regard to QRS and T-wave amplitude, T wave concordance or discordance and QRS/T wave ratio in all 12 leads. To ensure an exact determination of parameters Datinf® Measure software was used. Results were correlated to the occurrence of oversensing of cardiac signals during follow-up.

RESULTS

N = 116 pts. (63,8% male, mean age 40,9 ± 15,5 years) were included (primary prevention in 47.4% of pts). The most frequent cardiac diseases were hypertrophic cardiomyopathy (HCM) in n = 25 (21,6%), electrical heart disease in n = 20 (17,2%), and dilated cardiomyopathy in n = 17 (14,7%). Mean follow-up was 740 ± 549 days. During follow- up n = 17 (14.7%) pts. experienced n = 27 inappropriate episodes due to T-wave oversensing. Besides HCM (OR 6.16, CI 1.79-21.15, p = 0.004) a discordance of QRS to T-wave in lead I (OR 6.5, CI 1.86-22.67, p = 0.003) was found to be a strong predictor for inappropriate shocks. In multivariate analysis the pts. with a combination of both had an 8.4-fold higher risk of misclassification of intracardiac signals (p = 0.003) with consecutive inappropriate therapy.

CONCLUSION

A discordance of QRS to T-wave in lead I turned out to be a strong predictor for future inappropriate shocks in a typical S-ICD® cohort with special impact on HCM pts.