Diverse QRS morphology reflecting variations in lead placement for left bundle branch area pacing

AIMS

Left bundle branch area pacing (LBBAP) is a potential alternative to His bundle pacing. This study aimed to investigate the impact of different septal locations of pacing leads on the diversity of QRS morphology during non-selective LBBAP.

METHODS AND RESULTS

Non-selective LBBAP and left ventricular septal pacing (LVSP) were achieved in 50 and 21 patients with atrioventricular block, respectively. The electrophysiological properties of LBBAP and their relationship with the lead location were investigated. QRS morphology and axis showed broad variations during LBBAP. Echocardiography demonstrated a widespread distribution of LBBAP leads in the septum. During non-selective LBBAP, the qR-wave in lead V1 indicated that the primary location for pacing lead was the inferior septum (93%). The non-selective LBBAP lead was deployed deeper than the LVSP lead in the inferior septum. The Qr-wave in lead V1 with the inferior axis in aVF suggested pacing lead placement in the anterior septum. The penetration depth of the non-selective LBBAP lead in the anterior septum was significantly shallower than that in the inferior septum (72 ± 11 and 87 ± 8%, respectively). In lead V6, the deep S-wave indicated the time lag between the R-wave peak and the latest ventricular activation in the coronary sinus trunk, with pacemaker leads deployed closer to the left ventricular apex.

CONCLUSION

Different QRS morphologies and axes were linked to the location of the non-selective LBBAP lead in the septum. Various lead deployments are feasible for LBBAP, allowing diversity in the conduction system capture in patients with atrioventricular block.

Temporal and Spatial Pacemap Parameters for Identification of Cardiac Surfaces with Critical Sites for Ventricular Tachycardia

INTRODUCTION

Multi-surface pacemapping may help identify the surface of interest in scar-related ventricular tachycardia. This study aimed to investigate the performance of pacemap parameters for detecting critical sites through multi-surface mapping.

METHODS AND RESULTS

In 26 patients who underwent scar-related ventricular tachycardia ablation, pacemap parameters including a matching score, the difference between the longest and shortest stimulus-QRS intervals (Δs-QRS), and the distance between the good pacemap sites were measured. The parameters were compared between surfaces with and without critical sites and ablation outcomes. A total of 941 pacemaps at 56 surfaces targeting 35 ventricular tachycardias were analyzed. A greater Δs-QRS (40 vs. 8 ms, P<0.001) and longer distance between two good pacemap sites (24 vs. 13 mm, P<0.001) were observed on the surfaces with critical sites. A similar trend was seen in multi-surface pacemapping for the same ventricular tachycardias (52 vs 18 ms in Δs-QRS, P=0.021; 37 vs. 12 mm in distance, P=0.019), although the best pacemap scores were comparable (94 vs. 87, P=0.295). The Δs-QRS >20 ms and the distance >19 mm showed high positive likelihood ratios (19.8 and 6.1, respectively) for discriminating the surface harboring the critical site. Ablation of ventricular tachycardias fulfilling these parameters was successful on the surfaces, but without the required multi-surface ablation.

CONCLUSION

Temporal (Δs-QRS) and spatial (distance) parameters for good pacemap match sites were excellent markers for detecting the surface harboring critical sites in scar-related ventricular tachycardia. A multi-surface pacemapping can successfully identify the surface of interest. This article is protected by copyright. All rights reserved.

Fluoroscopic Predictors of Acceptable Capture threshold during the Implantation of the Micra Transcatheter Pacing System

Introduction

Few predictors of low capture threshold before the deployment of the Micra transcatheter pacing system (Micra TPS) have been determined. We aimed to identify fluoroscopic predictors of an acceptable capture threshold before Micra TPS deployment.

Methods

Sixty patients were successfully implanted with Micra TPS. Before deployment, gooseneck appearance of the catheter shaft was quantified using the angle between the tangent line of the shaft and the cup during diastole in the right anterior oblique (RAO) view. The direction of the device cup toward the ventricular septum was evaluated using the angle between the cup and the horizontal plane in the left anterior oblique (LAO) view.

Results

Of the 95 deployments we evaluated, 56 achieved an acceptable capture threshold of ≤2.0 V at 0.24 ms. In this acceptable threshold group, the deflection angle of the gooseneck shaft was significantly larger and the device cup was placed more horizontally with a lower elevation angle compared with those in the high threshold group. A deflection angle of ≥6° and an elevation angle of ≤30° were identified as the predictors of an acceptable capture threshold after deployment. An acceptable capture threshold was achieved in 24/31 (77.4%) patients in whom either angle criterion was satisfied at the first deployment.

Conclusions

Diastolic gooseneck appearance of the delivery catheter in the RAO view or near‐horizontal direction in the LAO view predicts an acceptable capture threshold after deployment. The shape of the delivery catheter before deployment should be evaluated using multiple fluoroscopic views to ensure successful implantation of Micra TPS.

Left Atrial Reverse Remodeling Following the Modified Box Isolation with Centerline in Patients with Persistent Atrial Fibrillation

Esophageal injury is a rare but serious complication of atrial fibrillation (AF) ablation. To minimize esophageal injury, our persistent AF (PerAF) protocol involves complete left atrial posterior wall (LAPW) and pulmonary vein (PV) isolation (box isolation), with a centerline away from the esophagus. However, there has been a concern that extensive LA isolation might deteriorate LA function. There has been a paucity of data on LA remodeling after box isolation. Therefore, we compared LA size pre- and post-box isolation with an LAPW centerline in patients with PerAF.Patients who underwent catheter ablation (CA) for PerAF between November 2016 and December 2018 were retrospectively evaluated.The LAPW, including all PVs, was completely isolated in 105 consecutive patients (75 men; mean age: 68 ± 10 years) with PerAF, including 58 patients with long-standing PerAF. During a follow-up of 660 ± 332 days, 76 patients (72%) were arrhythmia-free. The LA dimension (38 ± 6 mm versus 42 ± 7 mm; P < 0.0001) and volume index (38 ± 13 mL/m² versus 47 ± 14 mL/m²; P < 0.0001) at 6 months post-ablation were significantly decreased in patients who maintained sinus rhythm compared to pre-ablation. In patients with recurrent AF/atrial tachycardia (AT), these parameters were also significantly decreased (P < 0.001, respectively).Box isolation with a posterior centerline has no esophageal complications and a high clinical success rate in patients with PerAF. Reverse remodeling could be achieved even when using extensive isolation of the PV and LAPW in patients with PerAF.

Safety of Distal His Bundle Pacing Via the Right Ventricle Backed Up by Adjacent Ventricular Capture

OBJECTIVES

This study investigated the differences between distal His bundle pacing (HBP) via the right ventricle and proximal HBP via the right atrium with regard to pacing and sensing parameters.

BACKGROUND

HBP preserves physiological ventricular activation. The capture threshold of the adjacent ventricle accompanying HBP has not been evaluated after implantation.

METHODS

Fifty patients with bradycardia (58% with atrioventricular block) underwent successful HBP and were followed for 1 year. Precise locations of the lead tips were confirmed using follow-up echocardiography.

RESULTS

HBP leads were fixed via the right atrium or right ventricle (25 patients each). Overall, the local ventricle and HBP thresholds were elevated during follow-up. The distal HBP thresholds did not significantly differ from the proximal HBP thresholds, although local ventricular thresholds of distal HBP were markedly lower than those of proximal HBP. At 6 months, the accepted ventricular threshold (≤2.5 V) was maintained in 39 patients (78%). An amplitude of ventricular electrogram post-fixation of ≥2.0 mV and a capture threshold of ≤1.1 V at implantation were determined to be optimal values for predicting the accepted threshold at 6 months, with areas under the curve of 0.86 and 0.84, respectively. Atrial oversensing was often detected in proximal HBP but not distal HBP.

CONCLUSIONS

Distal HBP via the right ventricle captured the His bundle, similar to proximal HBP via the right atrium, with a superior local ventricular threshold during follow-up. Anatomy and electrophysiological ventricular properties at implantation may be critical for maintaining adjacent ventricle capture to prevent lead revision (Evaluation of Electrophysiological Parameters related to His Bundle Pacing in Patients With Bradyarrhythmias; UMIN000031364).

Conduction slowing area during sinus rhythm harbors ventricular tachycardia isthmus

INTRODUCTION

The voltage map during sinus rhythm (SR) is a cornerstone of substrate mapping (SM) in scar-related ventricular tachycardia (VT) and frequently used with pace mapping (PM). Where to conduct PM is unclear in cases of an extensive or unidentified substrate. Conduction properties are another aspect incorporated by SM, and conduction slowing has gained interest as being related to successful ablation, although its mechanism has not been elucidated. We aimed to investigate the relationship between SR conduction properties and VT isthmuses.

METHODS

Nineteen patients (mean age, 62 years) who underwent VT ablation with voltage mapping and PM were reviewed. Isochronal late activation maps (ILAMs) with eight zones were reconstructed and sequentially named from one to eight according to the SR propagation. Good PM sites were superimposed on ILAMs, and the isthmus was defined using different pacing latencies. ILAM properties harboring isthmuses were investigated.

RESULTS

Twenty-eight ILAMs (13 epicardium, 1 right ventricular [RV], and 14 left ventricular [LV] endocardium) were reviewed. Eighteen isthmuses of 24 target VTs were identified, in which the proximal ends were in a later zone than the distal ends (zone 6 vs 4; P < .001), suggesting a reverse isthmus vector to the SR. The conduction velocity of the zone involving the distal isthmus was significantly lower than that of the SR preceding zone (0.40 vs 1.30 m/s; P < .001). SR conduction velocity decelerated by 69.5% (range 59.7%-74.5%) before propagating into the isthmus area.

CONCLUSION

Conduction slowing area during SR were related with the exit portion of the VT isthmuses.

Complete Atrioventricular Block Associated with Pembrolizumab-induced Acute Myocarditis: The Need for Close Cardiac Monitoring

Pembrolizumab, a humanized monoclonal IgG4 antibody directed against programmed death-1, is an immune checkpoint inhibitor that has been introduced for the treatment of non-small-cell lung cancer. However, immune checkpoint inhibitors may cause severe immune-related adverse events. We herein present a case of lung cancer with complete atrioventricular block associated with acute myocarditis, which developed 16 days after the administration of pembrolizumab. The clinical course of this case suggested a strong need for close cardiac monitoring when pembrolizumab is administered on an outpatient basis.

[Electron microscopic study of an experimental contusion cataract of a Japanese monkey]

The traumatic cataract was experimentally induced in the lens of a Japanese monkey and observed with the electron microscope. The purpose of this study was to shed some light on the origin of the cataract caused by various factors. The clinical examinations of the experimental animal showed the opacity of the posterior subcapsular cortex. Electronmicroscopic investigations revealed that lens fibers within the opaque region increased in number of mitochondrion, rough surfaced endoplasmic reticulum and other organelles when compared with those in the clinically normal region of the lens. Furthermore, the intercellular space in the opaque region increased to such an extent that large extracellular vacuoles were formed. Many of these lens fibers became swollen and decreased the interdigitation. Some swollen cells showed sparse arrangement of their cytoplasmic filaments. These morphological changes showed an acceleration of water absorption of the lens fibers from a relatively early stage of the traumatic contusion cataract. The increase in number of mitochondrion in such swollen (hydropic) fibers may play an important role in this process. The present experiment suggests that the appearance of so-called hydropic cells is an initial change in the cataractous lens.

Experimental central serous chorioretinopathy in monkey eyes: fluorescein angiographic findings

In an adult Japanese monkey (Macaca fuscatus), intravenous injections of adrenalin were repeated daily: 0.125 mg/kg for 7 days and 0.375 mg/kg from the 11th day on. In a cynomolgus monkey (Macaca irus), daily injections were carried out with intravenous adrenalin (0.11 mg/kg for 12 days and a double dose from the 13th day on) and also with intramuscular prednisolone. After the 39th injection in the former and after the 32nd injection in the latter monkey, disciform serous retinal detachment was seen to occur in the posterior pole region, and fluorescein angiography revealed multiple dye leakage spots at the level of the retinal pigment epithelium. Sometimes these changes subsided, but on continuing injections, these changes recurred on new locations. Two types of fluorescein leakage spots were recognized, i.e. ink blot type with progressive simple enlargement with time and the mushroom or jet type showing these patterns during enlargement. No abnormality was found in the optic disc, retinal vessels or in the choroidal circulation. The fluorescein angiographic findings were in close resemblance with those seen in the human central serous chorioretinopathy. It was discussed that these fundus changes of the monkey eye produced by repeated adrenalin injections would serve as a good animal model of the human disease.