Defect engineering of BCZT-based piezoelectric ceramics with high piezoelectric properties

The intrinsic conduction mechanism and optimal sintering atmosphere of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) ceramics were regulated by Mn-doping element in this work. By Hall and impedance analysis, the undoped BCZT ceramics exhibit a typical n-type conduction mechanism, and the electron concentration decreases with the increasing oxygen partial pressure. Therefore, the undoped ceramics exhibit best electrical properties (piezoelectrical constant d33 = 585 pC·N−1, electro-mechanical coupling factor kp = 56%) in O2. A handful of Mn-doping element would transfer the conduction mechanism from n-type into p-type. And the hole concentration reduces with the decreasing oxygen partial pressure for Mn-doped BCZT ceramics. Therefore, the Mn-doped ceramics sintered in N2 have the highest insulation resistance and best piezoelectric properties (d33 = 505 pC·N−1, kp = 50%). The experimental results demonstrate that the Mn-doping element can effectively adjust the intrinsic conduction mechanism and then predict the optimal atmosphere.

Defect Engineering of BCZT–based Piezoelectric Ceramics with High Piezoelectric Properties

The intrinsic conduction mechanism and optimal sintering atmosphere of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) ceramics was regulated by doping Mn element in this work. By Hall and impedance analysis, the undoped BCZT ceramics exhibit a typical n–type conduction mechanism, and the electron concentration decreases with the increasing oxygen partial pressure. Therefore, the undoped ceramics exhibit best electrical properties (d33 = 585 pC/N, kp = 56%) in O2. A handful of Mn doping element would transfer the conduction mechanism from n-type into p–type. And the hole concentration reduces with the decreasing oxygen partial pressure for Mn-doped BCZT ceramics. Therefore, the Mn-doped ceramics sintered in N2 have the highest insulation resistance and best piezoelectric properties (d33 = 505 pC/N, kp = 50%). The experimental results demonstrate that the doping Mn element can effectively adjusts the intrinsic conduction mechanism and then predicts the optimal atmosphere.

Impact of pacing configuration and right ventricular lead location on dynamic atrioventricular delay optimization

Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Introduction Automatic adjustment of atrioventricular delay (AVD) with SyncAV has been shown to improve electrical synchronization. However, the effect of pacing configuration and right ventricular (RV) lead location on SyncAV programming is unknown. Purpose Evaluate the effect of pacing configuration and lead location on SyncAV optimization during biventricular (BiV) and LV-only pacing, with and without MultiPoint Pacing (MPP). Methods Patients with LBBB and QRS duration (QRSd) ≥ 150 ms scheduled for CRT-P/D device implantation with quadripolar LV lead were enrolled in this prospective study. RV lead location was classified at implant by the operator via fluoroscopy. QRSd was measured post-implant from 12-lead surface ECG by blinded experts during the following pacing modes: intrinsic conduction, BiV (BiV = RV + LV1), MPP (MPP = RV + LV1 + LV2), LV-only single-site (LVSS = LV1 only), and LV-only MPP (LVMPP = LV1 + LV2). For each mode, SyncAV was enabled (e.g. BiV + SyncAV) with the patient-tailored SyncAV offset that minimized QRSd. For BiV and LVSS, LV1 was the latest activating LV cathode; for MPP and LVMPP, LV1 + LV2 were the two LV cathodes with the widest possible separation (≥30mm). All modes used minimal RV-LV and LV1-LV2 delays. Results Fifty-three patients (68% male, 36% ischemic, 26% ejection fraction, 169 ms intrinsic QRSd) completed device implant and QRSd assessment. RV leads were implanted in either the septum (48%) or apex (52%), according to implanting physician preference. Relative to intrinsic conduction, BiV + SyncAV and MPP + SyncAV reduced QRSd by 23% and 27%, respectively (p < 0.01). LVSS + SyncAV reduced QRSd by 22% (p < 0.01 vs BiV + SyncAV), and LVMPP + SyncAV reduced QRSd by 25% (p < 0.05 vs MPP + SyncAV). RV apex or septum lead location did not have a significant impact on QRS reduction for each pacing configuration. As a percent of PR interval, optimal SyncAV offsets were similar for BiV + SyncAV and MPP + SyncAV (16% vs 13%, p = 0.05), and for LVSS + SyncAV and LVMPP + SyncAV (18% vs 21%, p = 0.46), but were significantly higher for LV-only settings vs. corresponding BiV/MPP settings (p < 0.05 for both pairs). For BiV + SyncAV, apical vs septal RV leads required greater SyncAV offsets (22% vs 11%, p < 0.05). SyncAV offsets also tended to be higher in apical vs septal RV leads for MPP (21% vs 11%), LVSS (20% vs 15%), and LVMPP (25% vs 16%), but without statistical significance. Conclusion SyncAV improves acute electrical synchronization in CRT patients with LBBB, particularly with patient-specific SyncAV programming. Pacing configuration (RV + LV or LV only, with or without MPP) and RV lead location (apex or septum) could potentially influence optimal SyncAV programming. Abstract Figure.

Comparison of QRSarea and left ventricular activation time during left bundle branch pacing and left ventricular septal pacing

Funding Acknowledgements Type of funding sources: None. Background Left bundle branch area pacing (LBBAP) has recently been introduced as a novel physiological pacing strategy. Within LBBAP, distinction is made between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP, no left bundle capture). Objective To compare acute electrocardiographic (ECG) and vectorcardiographic (VCG) effects of LBBP and LVSP as compared to intrinsic conduction. Methods In 50 patients with normal cardiac function and pacemaker indication for bradycardia, ECG characteristics of LBBP and LVSP were evaluated during RVSP and pacing at various depths in the septum: starting at the RV side of the septum: the last position with QS morphology, the first position with r’ morphology, LVSP and – in patients where LBB capture was achieved – LBBP. From the ECG’s QRS duration and QRS morphology in V1, and the stimulus-LVAT interval were measured. After conversion of the ECG into VCG (Kors conversion matrix), QRS area was calculated. Results In LVSP, QRS area significantly decreased from 82 ± 29 µVs during RVSP to 46 ± 12 µVs during LVSP. In patients where LBB capture was achieved QRS area significantly decreased from 78 ± 23 µVs to 38 ± 15 µVs in LBBP. In patients with LBB capture, QRS area was significantly smaller during LBBP compared to LVSP (figure A), but LVAT was not significantly different (figure B, p = 0.138). In patients with normal ventricular activation where LBBP was achieved (n = 20), QRS area was significantly larger during LVSP (48 ± 17) compared to LBBP (37 ± 16), the latter being not significantly different from normal intrinsic ventricular activation (35 ± 19 µVs). Conclusions ECG and VCG indices demonstrate that ventricular dyssynchrony is comparable but slightly more synchronous during LBBP compared to LVSP. Abstract Figure. QRS area and S-LVAT in LVSP and LBBP

862Syncav with multipoint pacing improves acute left ventricular hemodynamics

Funding Acknowledgements Abbott Introduction SyncAV has been shown to improve electrical synchronization by automatically adjusting atrioventricular delay (AVD) according to the intrinsic atrioventricular conduction time. Additional incremental electrical synchronization may be gained by the addition of second left ventricular (LV) pulse with MultiPoint Pacing (MPP). While the electrical synchronization benefits of SyncAV have been previously explored, there has been no assessment of the acute hemodynamic impact of SyncAV with or without MPP. Objective Evaluate the acute LV hemodynamic impact of SyncAV with and without MPP. Methods Heart failure patients with LBBB and QRS duration (QRSd) > 140 ms undergoing CRT-P/D implant with a quadripolar LV lead were enrolled in this prospective study. A guidewire or catheter with pressure transducer was placed in the LV chamber and the maximum pressure change (dP/dtmax) was recorded during the following pacing modes: intrinsic conduction, conventional biventricular pacing with SyncAV (BiV + SyncAV), and MPP with SyncAV (MPP + SyncAV). Twelve-lead surface ECG was used to determine the patient-tailored SyncAV offset that minimized QRSd. Results Twenty-seven patients (67% male, 44% ischemic, 30 ± 7% ejection fraction) completed the acute recordings. Relative to the intrinsic QRSd of 163 ms, BiV + SyncAV reduced QRSd by 21.5% to 124 ms (p < 0.001 vs. intrinsic) and MPP + SyncAV reduced QRSd by 26.6% to 120 ms (p < 0.05 vs. BiV + SyncAV). Beyond electrical synchronization, SyncAV significantly improved acute hemodynamics. Relative to the intrinsic dP/dtmax of 842 mmHg/s, BiV + SyncAV elevated dP/dtmax by 6.3% to 900 mmHg/s (p < 0.001 vs. intrinsic) and MPP + SyncAV elevated dP/dtmax by 8.8% to 926 mmHg/s (p < 0.005 vs. BiV + SyncAV). Despite both QRSd and dP/dtmax improvement with SyncAV and MPP, correlation between electrical and hemodynamic measurements was poor (R2 = 0.0 for BiV + SyncAV, R2 = 0.1 for MPP + SyncAV). Conclusion SyncAV may significantly improve acute LV hemodynamics in addition to electrical synchrony in LBBB patients. Further incremental improvement was achieved by combining SyncAV with MPP. Abstract Figure.

43Dynamic atrioventricular delay achieves superior electrical synchrony when pacing both ventricles rather than left ventricle alone

Funding Acknowledgements Abbott Introduction Automatic adjustment of atrioventricular delay (AVD) with SyncAV has been shown to improve electrical synchronization when pacing one or two sites in the left ventricle together with the right ventricle. However, it is unknown if the same benefit can be gained by using SyncAV while pacing only the left ventricle without right ventricular pacing. Purpose Evaluate the acute improvement in electrical synchrony provided by SyncAV with and without MultiPoint Pacing (MPP) during biventricular (BiV) and LV only pacing. Methods Patients with LBBB and QRS duration (QRSd) ≥ 150 ms scheduled for CRT-P/D device implantation with quadripolar LV lead were enrolled in this prospective study. QRSd was measured post-implant from 12-lead surface electrograms by blinded experts during the following pacing configurations: intrinsic conduction, conventional BiV (BiV = RV + LV1), MPP (MPP = RV + LV1 + LV2), LV-only single-site (LVSS = LV1 only), and LV-only MPP (LVMPP = LV1 + LV2). For each pacing mode, SyncAV was enabled (e.g. BiV + SyncAV) with the patient-tailored SyncAV offset that minimized QRSd. As an additional reference, QRSd during BiV was also measured using the nominal static AVD (paced/sensed AVD = 140/110 ms). BiV and LVSS pacing used the latest activating LV cathode, whereas MPP and LVMPP used the two LV cathodes with the widest possible separation (>30mm). All configurations used the minimum programmable RV-LV and LV1-LV2 delays. Results Thirty-five patients (78% male, 33% ischemic, 26% ejection fraction, 165 ms intrinsic QRSd) completed device implant and QRSd assessment. Relative to intrinsic conduction, BiV with nominal AVD reduced the QRSd by 17.5% (p < 0.001 vs intrinsic). Enabling SyncAV with a patient-optimized offset significantly improved QRSd reduction. BiV + SyncAV reduced QRSd by 25.2% (p < 0.001 vs. BiV). The greatest QRSd reduction of 28.9% was achieved by MPP + SyncAV (p < 0.01 vs. BiV + SyncAV). Single- and multi-site LV-only pacing reduced QRSd significantly less than corresponding biventricular modes. LVSS + SyncAV reduced QRSd by 22.5% (p < 0.05 vs. BiV + SyncAV), and LVMPP + SyncAV reduced QRSd by 24.3% (p < 0.05 vs. MPP + SyncAV). As a percent of PR interval, optimal SyncAV offsets were similar for BiV + SyncAV (median: 13%, mean: 17%) vs. MPP + SyncAV (median: 13%, mean 16%, p = 0.35 vs. BiV + SyncAV), and similar for LVSS + SyncAV (median: 20%, mean: 28%) and LVMPP + SyncAV (median: 23%, mean: 26%, p = 0.35 vs. LVSS + SyncAV), but were significantly higher for LV-only settings vs. corresponding BiV/MPP settings (p < 0.01 for both pairs). Conclusion: Greater improvement in electrical synchrony using SyncAV was observed when right ventricular pacing was included with left ventricular pacing. Additional benefit was gained by the addition of a second left ventricular pacing site with MPP in combination with SyncAV in both biventricular and LV only pacing modes. Abstract Figure.

P1236Revealing cardiac mechanics with CMR whilst CRT is active: the first step

Introduction Cardiac resynchronisation therapy (CRT) is a routine treatment for heart failure with reduced ejection fraction and conduction delay to improve symptoms and prognosis. Technological advancements both in cardiac magnetic resonance (CMR) and devices (MRI-conditional modes) now enable investigation of the haemodynamic response to CRT over a range of heart rates. Methods Patients with a CRT-D device were enrolled from heart failure clinics at a single tertiary centre. A complete device system assessment and baseline device check was conducted to ensure MRI compatibility and suitability. Left ventricular (LV) volumes and systolic blood pressure were measured at baseline and heart rates of 75, 90, 100, 115, 125, and 140 bpm (randomised order) with CRT active and intrinsic conduction (AOO). MRI conditional mode parameters were replicated through standard parameter modification to ensure biventricular pacing during CRT active scans. All scans were conducted using a 3.0 T Siemens Prisma MRI scanner with analysis on commercially available software. Contractility was derived from the systolic blood pressure and left ventricular end systolic volume. A post scan device and lead assessment was conducted to assess for scanning safety. Results Scanning was conducted in 22 patients (safety cohort). Post scan battery voltage reduced by 2.9±1.0%. Mean change in atrial, right ventricular and left ventricular lead impedance was 0.5±0.06%, 3.0±0.04% and −1.7±0.05% respectively. Mean change in atrial, right ventricular and left ventricular pacing threshold was 0.0±0.3%, 8.3±0.3% and 5.6±0.3%. No patient experienced symptoms related to scanning or device failure. Preliminary data for patients with CRT on and off have been analysed (paired analysis cohort, n=8, 6 men). Mean age was 71.1±8.2, aetiology was primarily ischaemic (62.5%) with the remainder dilated cardiomyopathy. The mean LV ejection fraction at baseline was 29.4±12.9%. Biventricular pacing led to acute improvements in ejection fraction (p=0.005), left ventricular cardiac output (p<0.0001) and contractility (p=0.05) over the entire range of heart rates studied. We also noted an improvement in the force frequency relationship during biventricular pacing with a higher peak contractility (p=0.05), a higher heart rate at which this occurred (HR=130) and a generally up sloping relationship when compared with intrinsic conduction. Conclusion We have demonstrated for the first time, the mechanistic improvements in cardiac contractility consequent to CRT using CMR and also that MRI scans of conditional devices can be safe with CRT active. Acknowledgement/Funding Dr A Koshy is conducting a PhD supported by grant from Medtronic. Dr Klaus Witte has received honoraria from Medtronic