The role of entirely subcutaneous ICD™ systems in patients with dilated cardiomyopathy

Opportunities and drawbacks of the subcutaneous defibrillator across different clinical settings

INTRODUCTION

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an established therapy for the prevention of sudden cardiac death (SCD) and an alternative to a transvenous implantable cardioverter-defibrillator system in selected patients. Beyond randomized clinical trials, many observational studies have described the clinical performance of S-ICD across different subgroups of patients.

AREAS COVERED

Our review aimed to describe the opportunities and drawbacks of the S-ICD, focusing on their use in special populations and across different clinical settings.

EXPERT OPINION

The choice to implant S-ICD should be based on the patient's tailored approach, which takes into account the adequate S-ICD screening at rest or during stress, the infective risk, the ventricular arrhythmia susceptibility, the progressive nature of the underlying disease, the work or sports activity, and the risk of lead-related complications.

Usefulness of the MADIT-ICD Benefit Score in a Large Mixed Patient Cohort of Primary Prevention of Sudden Cardiac Death

Background: Decision-making in primary prevention is not always trivial and many clinical scenarios are not reflected in current guidelines. To help evaluate a patient’s individual risk, a new score to predict the benefit of an implantable defibrillator (ICD) for primary prevention, the MADIT-ICD benefit score, has recently been proposed. The score tries to predict occurrence of ventricular arrhythmias and non-arrhythmic death based on data from four previous MADIT trials. We aimed at examining its usefulness in a large single-center register of S-ICD patients with various underlying cardiomyopathies. Methods and results: All S-ICD patients with a primary preventive indication for ICD implantation from our large single-center database were included in the analysis (n = 173). During a follow-up of 1227 ± 978 days, 27 patients developed sustained ventricular arrhythmias, while 6 patients died for non-arrhythmic reasons. There was a significant correlation for patients with ischemic cardiomyopathy (ICM) (n = 29, p = 0.04) to the occurrence of ventricular arrhythmia. However, the occurrence of ventricular arrhythmias could not sufficiently be predicted by the MADIT-ICD VT/VF score (p = 0.3) in patients with (n = 142, p = 0.19) as well as patients without structural heart disease (n = 31, p = 0.88) and patients with LV-EF < 35%. Of the risk factors included in the risk score calculation, only non-sustained ventricular tachycardias were significantly associated with sustained ventricular arrhythmias (p = 0.02). Of note, non-arrhythmic death could effectively be predicted by the proposed non-arrhythmic mortality score as part of the benefit score (p = 0.001, r = 0.3) also mainly driven by ICM patients. Age, diabetes mellitus, and a BMI < 23 kg/m2 were key predictors of non-arrhythmic death implemented in the score. Conclusion: The MADIT-ICD benefit score adds a new option to evaluate expected benefit of ICD implantation for primary prevention. In a large S-ICD cohort of primary prevention, the value of the score was limited to patients with ischemic cardiomyopathy. Future research should evaluate the performance of the score in different subgroups and compare it to other risk scores to assess its value for daily clinical practice.

Implantable Cardioverter Defibrillator Therapy in Patients with Acute Decompensated Heart Failure with Reduced Ejection Fraction: An Observation from the KCHF Registry

BACKGROUND

It remains unclear the clinical characteristics and prognosis of implantable cardioverter defibrillator (ICD) on prevention for sudden cardiac death (SCD) in Japanese patients with acute decompensated heart failure (ADHF) and reduced left ventricular ejection fraction (LVEF). We investigated the prevalence, clinical characteristics, and clinical outcomes in a contemporary large-scale Japanese ADHF registry.

METHODS

Among the consecutive 3785 patients hospitalized for ADHF and discharged alive in the Kyoto Congestive Heart Failure registry, we identified 1409 patients with reduced LVEF (ICD: N = 115, non-ICD: N = 1294).

RESULTS

Patients in the ICD group were younger (69.3 ± 12.9/74.2 ± 13.6 years; p < 0.001), more likely to be men (84%/65%), and more often had a history of heart failure hospitalization (70%/36%; p = 0.001), cardiomyopathy as the underlying heart disease (51%/27%; p < 0.001), and previous serious ventricular arrhythmia (57%/3.8%; p < 0.001), and had lower LVEF (25.4±7.4%/29.5±6.9%; p < 0.001), and estimated glomerular filtration rate (43.0±19.7/47.8±23.4 mL/min/1.73m2; p = 0.04) than those in the non-ICD group. The cumulative 1-year incidence of the primary arrhythmic composite endpoint of SCD, arrhythmic death, or resuscitated cardiac arrest trended to be lower in the ICD group than in the non-ICD group (0.0% versus 3.4%, p = 0.053), and the lower adjusted risk of the ICD group relative to the non-ICD group was significant for the primary arrhythmic endpoint (HR 0.10, 95% CI, 0.01-0.53; p = 0.003). However, there were no differences in the cumulative incidences of all-cause death between the ICD and non-ICD groups (17.3% versus 17.5%, p = 0.68), and the adjusted risk of the ICD group relative to the non-ICD group remained insignificant for all-cause death (HR, 0.85; 95%CI, 0.52-1.36, p = 0.51).

CONCLUSIONS

This study elucidated the real-world features of ADHF patients between those with ICD and those without. ICD use in patients with ADHF and reduced LVEF as compared with non-ICD use was associated with significant risk reduction for arrhythmic events, but not for mortality.

Pitfalls of the S-ICD therapy: experiences from a large tertiary centre

Aim

The subcutaneous ICD (S-ICD) has evolved to a potential first option for many patients who have to be protected from sudden cardiac death. Many trials have underlined a similar performance regarding its effectiveness in relation to transvenous ICDs and have shown the expected benefits concerning infective endocarditis and lead failure. However, there have also been problems due to the peculiarities of the device, such as oversensing and myopotentials. In this study, we present patients from a large tertiary centre suffering from complications with an S-ICD and propose possible solutions.

Methods and results

All S-ICD patients who experienced complications related to the device (n = 40) of our large-scale single-centre S-ICD registry (n = 351 patients) were included in this study. Baseline characteristics, complications occurring and solutions to these problems were documented over a mean follow-up of 50 months. In most cases (n = 23), patients suffered from oversensing (18 cases with T wave or P wave oversensing, 5 due to myopotentials). Re-programming successfully prevented further oversensing episode in 13/23 patients. In 9 patients, generator or lead-related complications, mostly due to infectious reasons (5/9), occurred. Further problems consisted of ineffective shocks in one patient and need for antibradycardia stimulation in 2 patients and indication for CRT in 2 other patients. In total, the S-ICD had to be extracted in 10 patients. 7 of them received a tv-ICD subsequently, 3 patients refused re-implantation of any ICD. One other patient kept the ICD but had antitachycardic therapy deactivated due to inappropriate shocks for myopotential oversensing.

Conclusion

The S-ICD is a valuable option for many patients for the prevention of sudden cardiac death. Nonetheless, certain problems are immanent to the S-ICD (limited re-programming options, size of the generator) and should be addressed in future generations of the S-ICD.

Graphic abstract