Dual-chamber implantable cardioverter-defibrillators (ICDs) may improve detection of atrial fibrillation as well as differentiation of tachycardias. However, this advantage is undermined by complications associated with the second electrode, which is required in conventional dual chamber devices. Therefore, BIOTRONIK has developed a new electrode called the LinoxSMART S DX that, when used in conjunction with the Lumax DX ICD, offers dual-chamber detection without the risks associated with the second electrode.
Implantable cardioverter-defibrillators (ICDs) terminate ventricular tachycardia (VT) and ventricular fibrillation (VF) with high efficacy and can protect patients from sudden cardiac death (SCD). However, inappropriate shocks may occur if tachycardias are misdiagnosed. Inappropriate shocks are harmful and impair patient quality of life. The risk of inappropriate therapy increases with lower detection rates programmed in the ICD. Single-chamber detection poses greater risks for misdiagnosis when compared with dual-chamber devices that have the benefit of additional atrial information. However, using a dual-chamber device merely for the sake of detection is generally not accepted, since the risks associated with the second electrode may outweigh the benefits of detection. Therefore, BIOTRONIK developed a ventricular lead called the LinoxSMART S DX, which allows for the detection of atrial signals from two electrodes positioned at the atrial part of the ventricular electrode. This device contains two ring electrodes; one that contacts the atrial wall at the junction of the superior vena cava (SVC) and one positioned at the free floating part of the electrode in the atrium. The excellent signal quality can only be achieved by a special filter setting in the ICD (Lumax 540 and 740 VR-T DX, BIOTRONIK). Here, the ease of implantation of the system will be demonstrated.
1. Introduction
Implantable cardioverter-defibrillators (ICD) prevent sudden cardiac death (SCD) in patients after survived SCD or at risk of SCD due to impaired left ventricular function. However, the danger of inappropriate therapies is high, particularly in single-chamber devices. These superfluous electrical discharges can be harmful and impair patient quality of life. Atrial detection may improve device performance and reduce the risk of inappropriate shock.1,2 However atrial detection requires an atrial electrode which in itself carries a significant associated risk.3 One manufacturer, BIOTRONIK, developed a ventricular single chamber electrode with atrial sensing capabilities. The first electrode was the Kainox A+, which revealed excellent sensing capabilities.4 However, it was not commonly used due to electrode stiffness and large diameter (3.5 mm, 10.5 F). Further developments of this electrode lead to the creation of the Linoxsmart S DX lead, which has a smaller diameter (2.6 mm, 7.8 F) and demonstrates excellent implantation features and sensing capabilities.5 This paper depicts the placement of this electrode, in order to highlight the data from the master study and to demonstrate both the ease of implantation and the excellent sensing capabilities of this electrode.
2. Case Presentation
3. Diagnosis, Assessment, and Plan
4. Implantation Procedure
Implantation of the new LinoxSMART S DX electrode along with the Lumax DX ICD, Biotronik, was as easy as the placement of any single chamber ICD. This experience is supported by data from the unpublished master DX-trial. 5 The LinoxSMART S DX electrode offers the advantage of atrial sensing without the disadvantage of an atrial lead. The atrial signal was stable over time in our patient as has been demonstrated in the DX-trial. 5
Dual-chamber devices have demonstrated superiority over single-chamber detection in only one prospective randomized trial, called the 1+1 trial.1 In this trial, patients with slow VT were implanted with a dual-chamber ICD that was either programmed to dual- or single- chamber detection. The combined endpoint was the number of inappropriate therapies in response to SVTs and VTs below the detection rate. For this endpoint, the 1+1-trial demonstrated the significant superiority of dual-chamber (DCH) detection with a long tachycardia detection interval (TDI) compared with conventionally programmed single-chamber (SCH) detection. This finding was revisited by Deisenhofer et al., who randomly assigned patients to DCH- or SCH ICD implantation. However, their trial did not particularly address patients with slow VTs as the mean tachycardia detection interval was 368 ms, and concluded that single- and dual-chamber devices are equally effective for therapy in life-threatening ventricular tachyarrhythmias. DCH devices were shown have superior rhythm classification but were no different than SCH devices in terms of minimizing inappropriate therapies during SVTs. 6 Despite the advantages of a dual chamber ICD for diagnosis and differentiation of tachycardias, the concept of implanting it merely for the sake of detection is generally not accepted, because the improved detection is counter-balanced by the increased risk of lead complications, as well as increased mortality and morbidity.2,7,8 Therefore, improvement of implantation technique or a VDD-system for dual chamber detection is necessary.9,10. The LinoxSMART S DX electrode combined with the Lumax DX ICD offers this advantage. The sensing facilities are similar to a dual chamber devices and the complication rate is as low as in conventional single chamber ICDs. 5
Conclusion
The Lumax VR-T DX has been proven to reliably sense atrial signals and gather valuable information to allow for early detection of atrial arrhythmias. Furthermore, the device offers AV discrimination with SMART for safe shock reduction. The available atrial IEGM channel diagnoses the appropriateness of ICD detection and therapy, thereby reducing inappropriate shocks and gaining information to optimize device programming.
The authors have nothing to disclose.