Cardiovascular disease is a significant public health issue accounting for almost 17 million deaths per year globally. According to estimates, 40-50% of them are sudden cardiac deaths. Approximately six million sudden cardiac deaths are caused by ventricular tachyarrhythmias.
The implantable cardioverter-defibrillator (ICD) device detects and terminates these life-threatening ventricular tachyarrhythmias. Based on evidence from several trials, clinical practice guidelines of different European cardiological societies recommend the ICD in patients at high risk of developing ventricular tachyarrhythmia (primary prevention), or in patients who have experienced a prior episode of life-threatening ventricular tachyarrhythmias (secondary prevention).
Recently, the subcutaneous implantable ICD emerged as a promising alternative to the established transvenous ICD to overcome short- and long-term complications associated with the implantation of transvenous leads and direct contact with the heart. Specifically, such difficulties are pneumothorax, cardiac perforation, lead fracture, lead-dysfunction, infections (e.g. lead endocarditis) and venous thrombosis. The subcutaneous ICD leaves the heart and vascular system untouched. It is important to note, however, that the subcutaneous ICD is restricted to patient populations who are not dependent on pacing therapy for bradycardia, anti-tachycardia (ATP), or resynchronization (CRT). Based on NICE (National Institute for Health and Care Excellence) guidance document, the current evidence on the efficacy and safety of subcutaneous ICD for preventing sudden cardiac death is adequate to support the use of this procedure.
The authors have performed a systematic literature review to evaluate the effectiveness and safety of the subcutaneous ICD compared to the conventional transvenous ICD in patients at an increased risk for sudden cardiac death due to an underlying acquired or congenital cardiac condition. Medline, EMBASE, Cochrane Library and CRD-database were searched for relevant literature, together with clinical trial registries. No new meta-analysis was performed.
The authors have included seven (7) observational studies (n=6,916; one study provides 5,760 patients) that compare the subcutaneous ICD with the conventional transvenous ICD. Furthermore, one (1) systematic review and one (1) meta-analysis with the results of the five (5) aforementioned studies were identified. Two independent reviewers have marked three (3) of these studies as high-biased, while the other four (4) were characterized as medium-biased.
Regarding clinical effectiveness, the authors have concluded that there are no statistically significant differences between subcutaneous ICDs or transvenous ICDs when comparing the criteria (overall mortality, the rate of appropriate shock and mental quality of life). However, the quality of this evidence is meagre.
Regarding safety, the authors have concluded that there are no statistically significant differences between subcutaneous ICDs or transvenous ICDs when comparing the criteria (inappropriate shocks, infections and haematomas, yet less lead complications with subcutaneous ICD). However, the quality of this evidence is very low, too.
In conclusion, the identified literature is insufficient to make conclusions about the comparative effectiveness of subcutaneous and transvenous ICDs. However, a substantially lower risk for lead complications in patients treated with subcutaneous ICD.
See the full report in English (with summary in German) here.
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