The WiCS®-LV system (EBR Systems, Inc.) is a leadless endocardial pacing system for cardiac resynchronization therapy (CRT) that uses ultrasound-based technology to transfer energy acoustically from a subcutaneously implanted pulse generator (transmitter) to a small receiver-electrode implanted on the LV endocardial wall (Figure 1), which then converts the acoustic energy to an electrical pacing pulse. It can be co-implanted with any device capable of performing right ventricular (RV) pacing, achieving synchronous biventricular (BiV) capture by sensing the RV pacing signal. The WiSE-CRT study1 demonstrated the feasibility of this technology, with the preliminary results of the SELECT-LV study2 demonstrating its potential clinical efficacy. The WiCS-LV system received CE mark approval in October 2015.
We recently performed the world’s first commercial implants in three patients with existing right ventricular transvenous defibrillators, who had previously failed conventional coronary sinus left ventricular (LV) implantation due to anatomical limitations. The first patient, a 70-year-old female, had experienced an early LV lead displacement followed by a second unsuccessful procedure; the second patient, a 73-year-old male, had no adequate target veins; and the third patient, a 78-year-old male, had a rare coronary venous anomaly involving atresia of the coronary sinus ostium. All patients had severely impaired left ventricular systolic function (EF <35%) and left bundle branch block (LBBB), and two of the three patients were in longstanding atrial fibrillation (AF).
Implantation of the system was performed as a two-stage procedure. The patients first underwent a minor cardiothoracic operation under general anesthetic to anchor the transmitter within an intercostal space. The location chosen for the transmitter had been pre-selected based on assessment of the optimal acoustic window. The following day, the patients underwent implantation of the endocardial receiver-electrode via right femoral artery access and a retrograde aortic approach as previously described.3
In each of these patients, we targeted our placement of the endocardial electrode to the site of latest mechanical activation defined by Speckle-tracking 2D radial strain echo analysis. This technique has previously been used to guide optimal epicardial LV lead placement in the TARGET4 and STARTER5 trials. The ‘optimal’ segments for pacing in each of our patients were identified as mid anterolateral, basal lateral, and basal posterolateral, respectively (Figure 2).
We were able to deploy the electrode in the target segment in two of the three patients (Figure 3). Although the basal segment was inaccessible in the third patient due to excessive distance and angles between the transmitter and the electrode, it was still possible to implant the electrode within the mid segment of the latest mechanically activated sector.
Biventricular pacing was established immediately after electrode implantation in one patient, which was associated with an instantaneous increase in dP/dt max of 450 mmHg/sec. BiV pacing could not be consistently achieved immediately following implant in the other two patients because of air under the ultrasound transmitter face. However, at one-week follow-up, the air had dissipated and all three patients were consistently BiV paced.
At one-month follow-up, all three patients showed improvement in electrocardiogram, echocardiographic, and functional outcome parameters. QRS duration reduced from a mean of 171 ms to 127 ms. Dyssynchrony parameters normalized (Figure 4), mean LV end-systolic volume (ESV) was reduced by 14%, and mean EF increased by 7%. All three patients experienced a subjective improvement in their heart failure symptoms compatible with one class reduction in their NHYA classification, a 13% increase in their six-minute walk test distance, and 26% reduction in their Minnesota Living with Heart Failure questionnaire score.
Our limited early experience with targeted electrode placement of the WiCS-LV system shows that this approach is feasible and associated with impressive improvements in symptoms and left ventricular function in the short term. Registry data collection is now ongoing to document outcomes in a larger patient population. Clearly, further work is required to examine this and other techniques to guide the optimal electrode placement during implant. Nevertheless, in light of these promising preliminary results, WiSE technology appears to provide an exciting opportunity to deliver CRT to patients in whom conventional epicardial LV lead placement has either not been possible or has proven ineffective.
Disclosures: Dr. Thomas and Dr. James have no conflicts of interest to report regarding the content herein. Dr. Turley and Dr. Owens report honorarium from EBR Systems for the preparation of this article.
- Auricchio A, Delnoy PP, Butter C, et al. Feasibility, safety, and short-term outcome of leadless ultrasound-based endocardial left ventricular resynchronization in heart failure patients: results of the wireless stimulation endocardially for CRT (WiSE-CRT) study. Europace. 2014;16(5):681-688.
- Reddy VY, Riahi S, Soegaard P, et al. Wireless LV endocardial stimulation for CRT: Primary results of the safety and performance of electrodes implanted in the left ventricle (SELECT-LV) study. Late-breaking clinical trial, Heart Rhythm, May 2015.
- Auricchio A, Delnoy PP, Regoli F, Seifert M, Markou T, Butter C, collaborative study group. First-in-man implantation of leadless ultrasound-based cardiac stimulation pacing system: novel endocardial left ventricular resynchronization therapy in heart failure patients. Europace. 2013;15(8):1191-1197.
- Khan FZ, Virdee MS, Palmer CR, et al. Targeted left ventricular lead placement to guide cardiac resynchronization therapy: the TARGET study: a randomized, controlled trial. J Am Coll Cardiol. 2012;59(17):1509-18.
- Saba S, Marek J, Schwartzman D, et al. Echocardiography-guided left ventricular lead placement for cardiac resynchronization therapy: results of the Speckle Tracking Assisted Resynchronization Therapy for Electrode Region trial. Circ Heart Fail. 2013;6(3):427-434.