Image Integration to Guide Wireless Endocardial LV Electrode Implantation for CRT

Suboptimal left ventricular (LV) lead placement in myocardial scar (fibrosis) is associated with cardiac resynchronization therapy (CRT) nonresponse (1). Image guidance (echocardiography and cardiac magnetic resonance [CMR]) avoiding fibrosis and targeting late mechanical activation may improve response (2). LV endocardial stimulation delivers effective CRT with rapid, physiological conduction and greater electrical and hemodynamic effects (3). Endocardial access without the constraints of the coronary sinus enables access to the optimal stimulation site (3). Leadless LV endocardial stimulation with a transcatheter-delivered electrode synchronously stimulates the LV in conjunction with a pre-existing pacing system (WiCS-LV, EBR Systems, Sunnyvale, California) (4). We describe wireless LV electrode implantation using our in-house, purpose built, multimodality imaging guidance platform (Department of Imaging Sciences, King’s College London and Siemens Healthineers, London, United Kingdom). This enables rapid processing, analysis, and overlay of CMR sequences displaying myocardial fibrosis and mechanical dyssynchrony onto a 3-dimensional shell merged with fluoroscopy for real-time guidance (Siemens Magnetom Aera 1.5-T magnetic resonance imaging scanner and Artis-Q biplane Combi Suite, Siemens Healthcare, Erlangen, Germany). This was integrated with LV endocardial voltage mapping for corroboration of myocardial scar (Figure 1).

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

Multimodality Imaging Platform to Guide LV Endocardial Electrode Implantation

(A) Custom-built guide cardiac resynchronization therapy software platform detailing distribution, burden and transmurality of cardiac magnetic resonance (CMR)–derived myocardial fibrosis demonstrating full thickness of anteroseptal infarct. Segments with >50% scar burden or transmurality are colored red and those with <50% scar burden or transmurality are green. (B) CMR-derived scar mask (left, purple) alongside a contact bipolar voltage scar map (low voltage in red or yellow as per scale) with excellent agreement (both in left anterior oblique view). (C) CMR-derived 3-dimensional shell split into 16 American Heart Association segments, overlaid onto fluoroscopy in real time to facilitate WiCS-LV (EBR Systems, Sunnyvale, California) delivery. Colors correspond to those in the bullseye plot entitled scar distribution (A). (D) Final position of the WiCS-LV electrode in the anterolateral position (orange tag on CARTO 3 [Biosense Webster, Diamond Bar, California] map) (B). LVEDV = left ventricular end-diastolic volume; LVEF = left ventricular ejection fraction; LVESV = left ventricular end-systolic volume; SDI = systolic dys-synchrony index.

A 61-year-old man with prior anterior myocardial infarction complicated by severe mitral regurgitation underwent surgical revascularization and mitral valve repair but remained breathless (New York Heart Association functional class III) with severely depressed LV function (echocardiographic LV ejection fraction 23%). Electrocardiography demonstrated bifascicular block (right bundle branch block and left anterior fascicular block) with QRS duration 168 ms. CMR LV ejection fraction was 15% with >50% transmural, late gadolinium enhancement in the basal to apical anterior and septal segments. He underwent CRT-defibrillator implantation but due to LV lead displacement was approved for the WiCS-LV system. Contact mapping was performed identifying regions of low voltage (bipolar scar map) and electrical latency (local activation time) using CARTO 3 (Biosense Webster, Diamond Bar, California). A scar mask from pre-procedural CMR merged with the voltage map demonstrated excellent visual agreement (Figure 1B). Acute hemodynamic response (AHR) (dP/dt_max) measured with a RADI (RADI Medical Systems, St. Jude Medical, Sylmar, California) pressure wire in the LV compared biventricular to baseline AAI pacing in addition to electrical latency and paced QRS (pQRS) duration. Two anteroseptal sites in scar (American Heart Association [AHA] segments 2 and 8) demonstrated electrical latency (83 and 153 ms); capture was achieved only at 10 V with a worsened AHR (–4% and –3%) and prolonged pQRS duration (200 ms). Four sites out of scar on the anterolateral, inferolateral, and inferior endocardial surface (AHA segments 6, 11, 4, 10) had more favorable electric and hemodynamic properties; the anterolateral site was optimal with electrical latency of 101 ms, capture threshold 3 V, improved AHR of 8%, and pQRS duration of 120 ms (Figure 1B, orange tag). The WiCS-LV electrode was implanted in this region (Figure 1C and 1D). Procedure duration was 180 min, radiation dose was 2,012 cGy cm², and fluoroscopy time was 19 min. It was complicated by a femoral artery pseudoaneurysm (12-F access, closure with Perclose ProGlide suture system, Abbott Vascular, Abbott Park, Illinois) requiring surgical repair. Despite extensive myocardial infarction, the patient remodeled with improvement of echocardiographic LV ejection fraction to 35%. This demonstrates integration of advanced imaging data to guide delivery of a wireless LV electrode for CRT. This was the second of 8 cases completed at our institution; we employ this approach where pre-procedural CMR is available. Future work will refine and streamline this process to identify the optimal LV endocardial pacing site.

• 2017 The Authors