The development of the extravascular defibrillator with substernal lead placement: A new Frontier for device-based treatment of sudden cardiac arrest

Abstract

Introduction: The extravascular implantable cardioverter-defibrillato (EV ICD) system with substernal lead placement is a novel nontransvenous alternative to current commercially available ICD systems. The EV ICD provides defibrillation and pacing therapies without the potential long-term complications of endovascular lead placement but requires a new procedure for implantation with a safety profile under evaluation.

Methods: This paper summarizes the development of the EV ICD, including the preclinical and clinical evaluations that have contributed to the system and procedural refinements to date.

Results: Extensive preclinical research evaluations and four human clinical studies with >140 combined acute and chronic implants have enabled the development and refinement of the EV ICD system, currently in worldwide pivotal study.

Conclusion: The EV ICD may represent a clinically valuable solution in protecting patients from sudden cardiac death while avoiding the long-term consequences of transvenous hardware. The EV ICD offers advantages over transvenous and subcutaneous systems by avoiding placement in the heart and vasculature; relative to subcutaneous systems, EV ICD requires less energy for defibrillation, enabling a smaller device, and provides pacing features such as antitachycardia and asystole pacing in a single system.

Keywords: ICD; anterior mediastinum; arrhythmia; extravascular; substernal.

Figure 1

Modeling‐predicted defibrillation threshold. Modeling predictions of defibrillation threshold for transvenous, substernal, and subcutaneous leads.

Figure 2

Implanted extravascular ICD (EV ICD) system. Representative X‐ray images of the implanted EV ICD system from a patient in the supine position.

Figure 3

Preprocedural chest markings. The lateral edges of the sternum (dotted lines) and sternal midline (solid line) are denoted. In this example, a cutaneous patch electrode is positioned on the left midaxillary line to emulate an ICD can.

Figure 4

Extravascular ICD (EV ICD) system placement and lead design. EV ICD system with epsilon‐shaped lead implanted within the substernal space and the device positioned on the patient's left midaxillary line (left image). The defibrillation coil segments (Coil 1 and Coil 2) are each 4 cm in length and oriented toward the patient's right; the ring electrodes (Ring 1 and Ring 2) are nearer the cardiac center of mass (right image).

Figure 5

Sternal tunneling tool. A 9‐French introducer sheath is backloaded onto the malleable tunneling rod and introduced into the anterior mediastinum. Subsequently, the sternal tunneling tool is removed, and the lead is inserted through the retained introducer sheath.

Figure 6

Transverse tunneling tool. The transverse tunneling tool is used to create a tunneling path from the xiphoid incision site to the left midaxillary tissue pocket. Once the tunnel is created, the handle is removed and the lead connector pin is inserted into the tunneling tool channel. The lead connector pin is pulled through the tunneling tract to the pocket for connection to the ICD generator.