Long-term results of first-generation S-ICD systems: strong from the start and through the threats of time

The advent of the subcutaneous implantable cardioverter defibrillator (S-ICD) in clinical practice was meant to provide the well-established traditional transvenous implantable cardioverter defibrillator (TV-ICD) with potentially advantageous solutions. Among them were an easier implantation technique, a simpler algorithm for life-threatening event detection only, and no need for placement of ICD components in the heart and circulation. These solutions would, in the inventors’ view, simplify the task of delivering life-saving therapy while removing some redundant technology in TV-ICDs.

Awareness of unfavourable implications of redundant TV-ICD technology was consistently raised after publication of MADIT-RIT,1 a study showing that simplification of programming and intervention reduced inappropriate therapy and mortality. The results of MADIT-RIT opened the way to new standards of TV-ICD treatment2 and created a favourable context in which a closer alignment between TV-ICD and S-ICD programming could be investigated.

The S-ICD implantation technique consists of subcutaneous or submuscular placement of the generator in the left midaxillary line at the level of the fifth and sixth intercostal spaces. and subcutaneous placement of the tunnelled lead from the generator pocket to the left of the sternum. Because the S-ICD requires accurate discrimination between the QRS complex and the T-wave (sensing analysis), pre-implant ECG screening is recommended to prevent implantation in patients at risk of oversensing. In addition, due to the lack of pacing capability, the S-ICD is precluded in patients requiring bradycardia, tachycardia, or biventricular pacing at the time of implantation.


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