Guided implantation of a leadless left ventricular endocardial electrode and acoustic transmitter using computed tomography anatomy, dynamic perfusion and mechanics, and predicted activation pattern

Abstract

Background: The WiSE-CRT System (EBR systems, Sunnyvale, CA) permits leadless left ventricular pacing. Currently, no intraprocedural guidance is used to target optimal electrode placement while simultaneously guiding acoustic transmitter placement in close proximity to the electrode to ensure adequate power delivery.

Objective: The purpose of this study was to assess the use of computed tomography (CT) anatomy, dynamic perfusion and mechanics, and predicted activation pattern to identify both the optimal electrode and transmitter locations.

Methods: A novel CT protocol was developed using preprocedural imaging and simulation to identify target segments (TSs) for electrode implantation, with late electrical and mechanical activation, with ≥5 mm wall thickness without perfusion defects. Modeling of the acoustic intensity from different transmitter implantation sites to the TSs was used to identify the optimal transmitter location. During implantation, TSs were overlaid on fluoroscopy to guide optimal electrode location that were evaluated by acute hemodynamic response (AHR) by measuring the maximal rate of left ventricular pressure rise with biventricular pacing.

Results: Ten patients underwent the implantation procedure. The transmitter could be implanted within the recommended site on the basis of preprocedural analysis in all patients. CT identified a mean of 4.8 ± 3.5 segments per patient with wall thickness < 5 mm. During electrode implantation, biventricular pacing within TSs resulted in a significant improvement in AHR vs non-TSs (25.5% ± 8.8% vs 12.9% ± 8.6%; P < .001). Pacing in CT-identified scar resulted in either failure to capture or minimal AHR improvement. The electrode was targeted to the TSs in all patients and was implanted in the TSs in 80%.

Conclusion: Preprocedural imaging and modeling data with intraprocedural guidance can successfully guide WiSE-CRT electrode and transmitter implantation to allow optimal AHR and adequate power delivery.

Keywords: Cardiac resynchronization therapy; Endocardial pacing; Guiding endocardial pacing; Hemodynamic assessment; WiSE-CRT.

Graphical abstract

Figure 1

Target segments for electrode implantation. Thinning of the apical anterior and inferior segments are in shown in (A), with the corresponding reduced myocardial blood flow in (B) and late iodine enhancement in (C). Myocardial perfusion (D: myocardial blood flow; E: perfused capillary blood volume; F: average enhancement) showed significant hypoperfusion in the basal to apical anteroseptal, anterior, and inferior segments. Mechanical activation is shown in (G) and (H), with the latest time to peak contraction in the mid inferior and inferolateral segments. Panel (I) shows that the latest electrical activating segment was between the basal to mid inferolateral segments. Combining this information together predicted the target segments of the basal to mid inferolateral segments. The left ventricular wall thickness was ≥0.5 cm.

Figure 2

Acoustic intensity. The acoustic intensity of the transmitter when placed onto the viable intercostal space (ICS) was modeled. A transmitter was placed onto a 3-dimensional reconstruction of the rib cage, and the corresponding acoustic intensity was shown on a 16-segment bull’s-eye plot. This patient had 3 available ICSs. White areas had no power coverage, and blue areas had the greatest acoustic intensity likely to yield reliable biventricular pacing. If the target segment was basal anterolateral, then the sixth ICS should not be used, as this would not provide biventricular pacing.

Figure 3

Flowchart of the planning protocol. CRT = cardiac resynchronization therapy; CT = computed tomography; US = ultrasound.

Figure 4

Box and whisker plot showing absolute improvement in the maximal rate of left ventricular pressure rise (dP/dt_max) with biventricular pacing in target and nontarget segments.