Catheter ablation of atrioventricular nodal reentrant tachycardia with an irrigated contact-force sensing radiofrequency ablation catheter.

INTRODUCTION: Radiofrequency ablation (RFA) slow pathway modification for catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) is traditionally performed using a 4-mm nonirrigated (NI) RF ablation catheter. Slow pathway modification using irrigated, contact-force sensing (ICFS) RFA catheters has been described in case reports, but the outcomes have not been systematically evaluated. METHODS: Acute procedural outcomes of 200 consecutive patients undergoing slow pathway modification for AVNRT were analyzed. A 3.5-mm ICFS RFA catheter (ThermoCool SmartTouch STSF, Biosense Webster, Inc.) was utilized in 134 patients, and a 4-mm NI RFA catheter (EZ Steer, Biosense Webster, Inc.) was utilized in 66 patients. Electroanatomic maps were retrospectively analyzed in a blinded fashion to determine the proximity of ablation lesions to the His region. RESULTS: The baseline characteristics of patients in both groups were similar. Total RF time was significantly lower in the ICFS group compared to the NI group (5.53 ± 4.6 vs. 6.24 ± 4.9 min, p = 0.03). Median procedure time was similar in both groups (ICFS, 108.0 (87.5-131.5) min vs. NI, 100.0 (85.0-125.0) min; p = 0.2). Ablation was required in closer proximity to the His region in the NI group compared to the ICFS group (14.4 ± 5.9 vs. 16.7 ± 6.4 mm, respectively, p = 0.01). AVNRT was rendered noninducible in all patients, and there was no arrhythmia recurrence during follow-up in both groups. Catheter ablation was complicated by AV block in one patient in the NI group. CONCLUSION: Slow pathway modification for catheter ablation of AVNRT using an ICFS RFA catheter is feasible, safe, and may facilitate shorter duration ablation while avoiding ablation in close proximity to the His region.

Temporal trends in atrial fibrillation ablation procedures at an academic medical center: 2011-2021.

INTRODUCTION: Radiofrequency ablation technology for treating atrial fibrillation (AF) has evolved rapidly over the past decade. We investigated the impact of technological and procedural advances on procedure times and ablation outcomes at a major academic medical center over a 10-year period. METHODS: Clinical data was collected from patients who presented to NYU Langone Health between 2011 and 2021 for a first-time AF ablation. Time to redo AF ablation or direct current cardioversion (DCCV) for recurrent AF during a 3-year follow-up period was determined and correlated with ablation technology and practices, antiarrhythmic medications, and patient comorbid conditions. RESULTS: From 2011 to 2021, the cardiac electrophysiology lab adopted irrigated-contact force ablation catheters, high-power short duration ablation lesions, steady-pacing, jet ventilation, and eliminated stepwise linear ablation for AF ablation. During this time the number of first time AF ablations increased from 403 to 1074, the percentage of patients requiring repeat AF-related intervention within 3-years of the index procedure dropped from 22% to 14%, mean procedure time decreased from 271 ± 65 to 135 ± 36 min, and mean annual major adverse event rate remained constant at 1.1 ± 0.5%. Patient comorbid conditions increased during this time period and antiarrhythmic use was unchanged. CONCLUSION: Rates of redo-AF ablation or DCCV following an initial AF ablation at a single center decreased 36% over a 10-year period. Procedural and technological changes likely contributed to this improvement, despite increased AF related comorbidities.

Outcomes and atrial substrate analysis in patients with HIV undergoing atrial fibrillation ablation.

INTRODUCTION: Patients with HIV infection have increased risk of atrial fibrillation, but the pathophysiologic mechanisms and the utility of catheter ablation in this population are not well-studied. We aimed to characterize outcomes of atrial fibrillation ablation and left atrial substrate in patients with HIV. METHODS: The study was a retrospective propensity score-matched analysis of patients with and without HIV undergoing atrial fibrillation ablation. A search was performed in the electronic medical record for all patients with HIV who received initial atrial fibrillation ablation from 2011 to 2020. After calculating propensity scores for HIV, matching was performed with patients without HIV by using nearest-neighbor matching without replacement in a 1:2 ratio. The primary outcome was freedom from atrial arrhythmia and secondary outcomes were freedom from atrial fibrillation, freedom from atrial tachycardia, and freedom from repeat ablation, compared by log-rank analysis. The procedures of patients with HIV who underwent repeat ablation at our institution were further analyzed for etiology of recurrence. To further characterize the left atrial substrate, a subsequent case-control analysis was then performed for a set of randomly chosen 10 patients with HIV matched with 10 without HIV to compare minimum and maximum voltage at nine pre-specified regions of the left atrium. RESULTS: Twenty-seven patients with HIV were identified. All were prescribed antiretroviral therapy at time of ablation. These patients were matched with 54 patients without HIV by propensity score. 86.4% of patients with HIV and 76.9% of controls were free of atrial fibrillation or atrial tachycardia at 1 year (p = .509). Log-rank analysis showed no difference in freedom from atrial arrhythmia (p value .971), atrial fibrillation (p-value .346), atrial tachycardia (p value .306), or repeat ablation (p value .401) after initial atrial fibrillation ablation in patients with HIV compared to patients without HIV. In patients with HIV with recurrent atrial fibrillation, the majority had pulmonary vein reconnection (67%). There were no significant differences in minimum or maximum voltage at any of the nine left atrial regions between the matched patients with and without HIV. CONCLUSIONS: Ablation to treat atrial fibrillation in patients with HIV, but without overt AIDS is frequently successful therapy. The majority of patients with recurrence of atrial fibrillation had pulmonary vein reconnection, suggesting infrequent nonpulmonary vein substrate. In this population, the left atrial voltage in patients with HIV is similar to that of patients without HIV. These findings suggest that the pulmonary veins remain a critical component to the initiation and maintenance of atrial fibrillation in patients with HIV.

Self-Ordering of Buckling, Bending, and Bumping Beams.

A collection of thin structures buckle, bend, and bump into each other when confined. This contact can lead to the formation of patterns: hair will self-organize in curls; DNA strands will layer into cell nuclei; paper, when crumpled, will fold in on itself, forming a maze of interleaved sheets. This pattern formation changes how densely the structures can pack, as well as the mechanical properties of the system. How and when these patterns form, as well as the force required to pack these structures is not currently understood. Here we study the emergence of order in a canonical example of packing in slender structures, i.e., a system of parallel confined elastic beams. Using tabletop experiments, simulations, and standard theory from statistical mechanics, we predict the amount of confinement (growth or compression) of the beams that will guarantee a global system order, which depends only on the initial geometry of the system. Furthermore, we find that the compressive stiffness and stored bending energy of this metamaterial are directly proportional to the number of beams that are geometrically frustrated at any given point. We expect these results to elucidate the mechanisms leading to pattern formation in these kinds of systems and to provide a new mechanical metamaterial, with a tunable resistance to compressive force.

Novel chairside spectrometer-trained system for measuring the irradiance of light-curing units.

The purpose of this study was to compare the performances of 5 different instruments in measuring the irradiance of light-curing units (LCUs). A novel spectrometer-trained radiometer (CheckUp), 2 conventional chairside radiometers (Bluephase Meter I and Bluephase Meter II), and 2 devices considered to be gold standards for measuring irradiance (an integrating sphere spectrometer and a thermopile sensor) were used to evaluate 7 LCUs. The irradiance of each LCU was measured 10 times with each meter. Data were analyzed using linear regression analysis and a 1-way analysis of variance with Tukey post hoc test (α = 0.05). The mean irradiance values of the LCUs differed significantly depending on which meter was used for measurement (P < 0.05). Bivariate regression analysis demonstrated that the highest correlations in the irradiance values were found between the CheckUp meter and both the integrating sphere (r2 = 0.980) and the thermopile (r2 = 0.933). The absolute mean (SD) percentage deviation between irradiance measured by the CheckUp instrument and irradiance measured by the other meters was 7.2% (2.0%) for the integrating sphere, 7.0% (3.6%) for the thermopile, 21.5% (16.1%) for Bluephase Meter I, and 13.1% (7.1%) for Bluephase Meter II. Compared with the 2 conventional chairside radiometers, the CheckUp meter provided the highest correlation with and lowest absolute percentage deviation from the irradiance measured by the gold standard spectrometers.

Outcomes of posterior wall isolation with pulmonary vein isolation for paroxysmal atrial fibrillation.

INTRODUCTION: Prior studies have shown that addition of posterior wall isolation (PWI) may reduce atrial fibrillation recurrence in patients with persistent atrial fibrillation. No data on PWI in paroxysmal AF (pAF) patients with normal left atrial voltage is available, to date. OBJECTIVE: This study sought to evaluate the efficacy of PWI in addition to pulmonary vein isolation (PVI) in patients presenting with pAF and normal left atrial voltage. METHODS: Consecutive patient registry analysis was performed on all patients with pAF and normal left atrial voltage undergoing initial radiofrequency ablation from November 1, 2018 to November 15, 2019. Primary endpoint was recurrence of atrial arrhythmia including AF, atrial tachycardia (AT), or atrial flutter (AFL). RESULTS: A total of 321 patients were studied, 214 in the PVI group and 107 in the PWI + PVI group. Recurrence of any atrial arrhythmia occurred in 18.2% of patients in the PVI group and 16.8% in the PVI + PWI cohort (p = 0.58). At 1 year, recurrence was 14.0% in the PVI group and 15.0% in the PWI + PVI group (p = 0.96). There was a lower AT/AFL recurrence in the PVI + PWI group, not reaching significance (3.7% in the PWI + PVI group vs. 7.9% in PVI group, p = 0.31). Need for carina lesions predicted recurrence in the PVI-only group. CONCLUSIONS: Addition of PWI to PVI in pAF patients undergoing their first ablation did not reduce the frequency of atrial arrhythmia recurrence. This warrants further study in a prospective trial.

Elastogranular columns and beams.

String and grains can be combined to create structures capable of bearing significant loads. In this work, we prepare columns and beams through a layer-by-layer deposition of granular matter and loops of fiber strings, and characterize their mechanical properties. The loops cause the grains to jam, and the inter-grain contact leads to a Hertzian-like constitutive response. Initially, one force chain that propagates vertically through the column bears most of the compressive load. As the magnitude of the load is increased, more force chains form in the column, which act in parallel to increase its stiffness, akin to a "super-Hertzian" regime. Applying a compressive prestress enables the structures to withstand shear, enabling the fabrication of cantilevered beams. This work provides a mechanical framework to use elastogranular jamming to create rapid, reusable infrastructure components, such as columns, beams, and arches from inexpensive, commonplace materials, such as rocks and string.

Efficient snap-through of spherical caps by applying a localized curvature stimulus.

In bistable actuators and other engineered devices, a homogeneous stimulus (e.g., mechanical, chemical, thermal, or magnetic) is often applied to an entire shell to initiate a snap-through instability. In this work, we demonstrate that restricting the active area to the shell boundary allows for a large reduction in its size, thereby decreasing the energy input required to actuate the shell. To do so, we combine theory with 1D finite element simulations of spherical caps with a non-homogeneous distribution of stimulus-responsive material. We rely on the effective curvature stimulus, i.e., the natural curvature induced by the non-mechanical stimulus, which ensures that our results are entirely stimulus-agnostic. To validate our numerics and demonstrate this generality, we also perform two sets of experiments, wherein we use residual swelling of bilayer silicone elastomers-a process that mimics differential growth-as well as a magneto-elastomer to induce curvatures that cause snap-through. Our results elucidate the underlying mechanics, offering an intuitive route to optimal design for efficient snap-through.

Elastic Instabilities Govern the Morphogenesis of the Optic Cup.

Because the normal operation of the eye depends on sensitive morphogenetic processes for its eventual shape, developmental flaws can lead to wide-ranging ocular defects. However, the physical processes and mechanisms governing ocular morphogenesis are not well understood. Here, using analytical theory and nonlinear shell finite-element simulations, we show, for optic vesicles experiencing matrix-constrained growth, that elastic instabilities govern the optic cup morphogenesis. By capturing the stress amplification owing to mass increase during growth, we show that the morphogenesis is driven by two elastic instabilities analogous to the snap through in spherical shells, where the second instability is sensitive to the optic cup geometry. In particular, if the optic vesicle is too slender, it will buckle and break axisymmetry, thus, preventing normal development. Our results shed light on the morphogenetic mechanisms governing the formation of a functional biological system and the role of elastic instabilities in the shape selection of soft biological structures.

Emergence of structure in columns of grains and elastic loops.

It is possible to build free-standing, load-bearing structures using only rocks and loops of elastic material. We investigate how these structures emerge, and find that the necessary maximum loop spacing (the critical spacing) is a function of the frictional properties of the grains and the elasticity of the confining material. We derive a model to understand both of these relationships, which depends on a simplification of the behavior of the grains at the edge of a structure. We find that higher friction leads to larger stable grain-grain and grain-loop contact angles resulting in a simple function for the frictional critical spacing, which depends linearly on friction to first order. On the other hand, a higher bending rigidity enables the loops to better contain the hydrostatic pressure of the grains, which we understand using a hydroelastic scale. These findings will illuminate the stabilization of dirt by plant roots, and potentially enable the construction of simple adhesion-less structures using only granular material and fiber.

Quantitative analysis of ablation technique predicts arrhythmia recurrence following atrial fibrillation ablation.

BACKGROUND: Optimal ablation technique, including catheter-tissue contact during atrial fibrillation (AF) radiofrequency (RF) ablation, is associated with improved procedural outcomes. We used a custom developed software to analyze high-frequency catheter position data to study the interaction between catheter excursion during lesion placement, lesion-set sequentiality, and arrhythmia recurrence. METHODS: A total of 100 consecutive patients undergoing first-time RF ablation for paroxysmal AF were analyzed. Spatial positioning of the ablation catheter sampled at 60 Hz during RF application was extracted from the CARTO3 system (Biosense Webster Inc, USA) and analyzed using custom-developed MATLAB software to determine precise catheter spatial 3D excursion during RF ablation. The primary end point was freedom from atrial arrhythmia lasting longer than 30 seconds after a single ablation procedure. RESULTS: At 1 year, 86% of patients were free from recurrent arrhythmia. There was no significant difference in clinical, echocardiographic, or ablation characteristics between patients with and without recurrent arrhythmia. Analyzing 15,356,998 position data points revealed that lesion-set sequentiality and mean lesion catheter excursion were predictors of arrhythmia recurrence. Analyzing arrhythmia recurrence by mean single-lesion catheter excursion (excursion >2.81 mm) and by sequentiality (using 46% of lesions with interlesion distance >6 mm as cutoff) revealed significantly increased arrhythmia recurrence in the higher excursion group (23% vs 6%, P = .03) and in the less sequential group (24% vs 4%, P = .02). CONCLUSIONS: Ablation lesion sequentiality measured by catheter interlesion distance and catheter stability measured by catheter excursion during lesion placement are potentially modifiable factors affecting arrhythmia recurrence after RF ablation for AF.

Early ICD lead failure in defibrillator systems with multiple leads via cephalic access.

INTRODUCTION: Implantable cardioverter defibrillators (ICDs) are proven to prevent sudden death in patients at elevated risk for sustained ventricular tachycardia or fibrillation. Complications related to ICD failure can stem from lead dysfunction, manufacturing defects, patient characteristics, or implantation technique. We conducted a review of all ICD leads implanted at our center from 2011 to 2017 to determine risk factors for premature lead failure. METHODS: We conducted a retrospective review of patients of all ICD leads implanted from December 2011 to June 2017 at our institution. A total of 660 patients (Biotronik Linox S/SD, n = 281; Sprint Quatro, n = 207; Durata, n = 121; Endotak, n = 51) underwent ICD implantations. Patient and lead characteristics, procedural outcomes and complications were recorded. Lead failure was defined per Heart Rhythm Society lead-management consensus as a lack of procedural or clinical success, thus requiring an extraction of the lead. Patient and lead outcomes were recorded and variables associated with lead failure were assessed by the Kaplan-Meier method. RESULTS: Overall failure rate was similar for all leads: Linox S/SD-0.29%/year; Sprint Quattro-0.21%/year, Durata-0.39%/year and Endotak Reliance-0.0% (P = .769). No difference was found in overall survival when comparing all ICD manufacturers during the study period. Subgroup analysis revealed the risk of premature lead failure was particularly pronounced in multi-lead ICD systems implanted via cephalic access (P < .001). The estimated failure rate of Linox leads implanted via cephalic access in multi-lead systems was 19%/year. The estimated failure rate of non-Linox leads implanted via cephalic access in multi-lead systems was 11%/year. Neither age, nor gender were risk factors for lead failure in the Linox, or non-Linox cohorts. CONCLUSION: All analyzed ICD leads were found to have a similar overall risk of premature failure. ICD lead implantation via cephalic access in multilead ICD systems may be a previously unidentified risk factor for premature ICD lead failure, although these findings require further validation.

Direct autotransfusion following emergency pericardiocentesis in patients undergoing cardiac electrophysiology procedures.

INTRODUCTION: Acute hemopericardium during cardiac electrophysiology (EP) procedures may result in significant blood loss and is the most common cause of procedure-related death. Matched allogeneic blood is often not immediately available. The feasibility and safety of direct autotransfusion in cardiac electrophysiology patients requiring emergency pericardiocentesis is unknown. METHODS: We retrospectively analyzed records of patients undergoing EP procedures at a single, tertiary care medical center who had procedure-related acute hemopericardium requiring emergency pericardiocentesis during a 3-year period. Procedure details, transfusion volumes, and clinical outcomes of patients who received direct autotransfusion of aspirated pericardial blood via a femoral venous sheath were compared to those of patients who did not receive direct autotransfusion. RESULTS: During the study period, 10 patients received direct autotransfusion (group 1) and outcomes were compared with those of 14 control patients who did not receive direct autotransfusion (group 2). The volume of aspirated pericardial blood was similar in groups 1 and 2 (1.6 ± 0.7 L vs 1.3 ± 1.0 L, respectively; P = .52). Amongst patients with aspirated volumes <1 L, group 1 patients (n = 4) were less likely than group 2 patients (n = 8) to require allotransfusion (0% vs 75%, P = .02). Amongst patients with aspirated volume ≥1 L, group 1 patients (n = 6) required fewer units of red cell allotransfusion than group 2 patients (n = 6) (1.5 ± 0.8 units vs 4.3 ± 2.0 units, P = .01). No procedural complications related to direct autotransfusion occurred. CONCLUSIONS: Direct autotransfusion following emergency pericardiocentesis during electrophysiology procedures requiring systemic anticoagulation is feasible and safe. The utilization of direct autotransfusion may eliminate or reduce the need for allotransfusion.

Multiple procedure outcomes for nonparoxysmal atrial fibrillation: Left atrial posterior wall isolation versus stepwise ablation.

OBJECTIVE: To compare multiple-procedure catheter ablation outcomes of a stepwise approach versus left atrial posterior wall isolation (LA PWI) in patients undergoing nonparoxysmal atrial fibrillation (NPAF) ablation. BACKGROUND: Unfavorable outcomes for stepwise ablation of NPAF in large clinical trials may be attributable to proarrhythmic effects of incomplete ablation lines. It is unknown if a more extensive initial ablation strategy results in improved outcomes following multiple ablation procedures. METHODS: Two hundred twenty two consecutive patients with NPAF underwent first-time ablation using a contact-force sensing ablation catheter utilizing either a stepwise (Group 1, n = 111) or LA PWI (Group 2, n = 111) approach. The duration of follow-up was 36 months. The primary endpoint was freedom from atrial arrhythmia >30 s. Secondary endpoints were freedom from persistent arrhythmia, repeat ablation, and recurrent arrhythmia after repeat ablation. RESULTS: There was similar freedom from atrial arrhythmias after index ablation for both stepwise and LA PWI groups at 36 months (60% vs. 69%, p = .1). The stepwise group was more likely to present with persistent recurrent arrhythmia (29% vs. 14%, p = .005) and more likely to undergo second catheter ablation (32% vs. 12%, p < .001) compared to LA PWI patients. Recurrent arrhythmia after repeat ablation was more likely in the stepwise group compared to the LA PWI group (15% vs. 4%, p = .003). CONCLUSIONS: Compared to a stepwise approach, LA PWI for patients with NPAF resulted in a similar incidence of any atrial arrhythmia, lower incidence of persistent arrhythmia, and fewer repeat ablations. Results for repeat ablation were not improved with a more extensive initial approach.

Rapid pacing and high-frequency jet ventilation additively improve catheter stability during atrial fibrillation ablation.

INTRODUCTION: Catheter stability during atrial fibrillation ablation is associated with higher ablation success rates. Rapid cardiac pacing and high-frequency jet ventilation (HFJV) independently improve catheter stability. Simultaneous modulation of cardiac and respiratory motion has not been previously studied. The objective of this study was to determine the effect of simultaneous heart rate and respiratory rate modulation on catheter stability. METHODS: Forty patients undergoing paroxysmal atrial fibrillation ablation received ablation lesions at 15 prespecified locations (12 left atria, 3 right atria). Patients were randomly assigned to undergo rapid atrial pacing for either the first or the second half of each lesion. Within each group, half of the patients received HFJV and the other half standard ventilation. Contact force and ablation data for all lesions were compared among the study groups. Standard deviation of contact force was the primary endpoint defined to examine contact force variability. RESULTS: Lesions with no pacing and standard ventilation had the greatest contact force standard deviation (5.86 ± 3.08 g), compared to lesions with pacing and standard ventilation (5.45 ± 3.28 g; P < .01) or to lesions with no pacing and HFJV (4.92 ± 3.00 g; P < .01). Lesions with both pacing and HFJV had the greatest reduction in contact force standard deviation (4.35 ± 2.81 g; P < .01), confirming an additive benefit of each maneuver. Pacing and HFJV together was also associated with a reduction in the proportion of lesions with excessive maximum contact force (P < .001). DISCUSSION: Rapid pacing and HFJV additively improve catheter stability. Simultaneous pacing with HFJV further improves catheter stability over pacing or HFJV alone to optimize ablation lesions.

Packing transitions in the elastogranular confinement of a slender loop.

Confined thin structures are ubiquitous in nature. Spatial and length constraints have led to a number of novel packing strategies at both the micro-scale, as when DNA packages inside a capsid, and the macro-scale, seen in plant root development and the arrangement of the human intestinal tract. Here, we investigate the resulting packing behaviors between a growing slender structure constrained by deformable boundaries. Experimentally, we vary the arc length of an elastic loop injected into an array of soft, spherical grains at various initial number densities. At low initial packing fractions, the elastic loop deforms as though it were hitting a flat surface by periodically folding into the array. Above a critical packing fraction φc, local re-orientations within the granular medium create an effectively curved surface leading to the emergence of a distinct circular packing morphology. These results bring new insights into the packing behavior of wires and thin sheets, and will be relevant to modeling plant root morphogenesis, burrowing and locomotive strategies of vertebrates & invertebrates, and developing smart, steerable needles.

Buckling of geometrically confined shells.

We study the periodic buckling patterns that emerge when elastic shells are subjected to geometric confinement. Residual swelling provides access to range of shapes (saddles, rolled sheets, cylinders, and spherical sections) which vary in their extrinsic and intrinsic curvatures. Our experimental and numerical data show that when these moderately thick structures are radially confined, a single geometric parameter - the ratio of the total shell radius to the amount of unconstrained material - predicts the number of lobes formed. We present a model that interprets this scaling as the competition between radial and circumferential bending. Next, we show that reducing the transverse confinement of saddles causes the lobe number to decrease with a similar scaling analysis. Hence, one geometric parameter captures the wave number through a wide range of radial and transverse confinement, connecting the shell shape to the shape of the boundary that confines it. We expect these results to be relevant for an expanse of shell shapes, and thus applicable to the design of shape-shifting materials and the swelling and growth of soft structures.

Evolution of critical buckling conditions in imperfect bilayer shells through residual swelling.

We propose and investigate a minimal mechanism that makes use of differential swelling to modify the critical buckling conditions of elastic bilayer shells, as measured by the knockdown factor. Our shells contain an engineered defect at the north pole and are made of two layers of different crosslinked polymers that exchange free molecular chains. Depending on the size of the defect and the extent of swelling, we can observe either a decreasing or increasing knockdown factor. FEM simulations are performed using a reduced model for the swelling process to aid us in rationalizing the underlying mechanism, providing a qualitative agreement with experiments. We believe that the working principle of our mechanism can be extended to bimetallic shells undergoing variations in temperature and to shells made of pH-responsive gels, where the change in knockdown factor could be changed dynamically.

Factors predicting persistence of AV nodal block in post-TAVR patients following permanent pacemaker implantation.

INTRODUCTION: A common complication of transcatheter aortic valve repair (TAVR) is development of conduction defects requiring pacemaker (PPM) implantation. These defects are not universally permanent. OBJECTIVE: To determine the incidence and predictors of persistent device dependency in patients with PPM implantation following TAVR with a self-expanding prosthesis. METHODS: Records of patients who underwent post-TAVR PPM implantation were reviewed. Patients with persistent complete AV block (AVBIII) one month post-TAVR were compared to those regaining conduction. RESULTS: Between September 2014 and March 2017, 485 patients underwent TAVR with a self-expanding prosthesis; 77 (15.9%) underwent PPM implantation for AVBIII. Device interrogation at one month was available for 61 patients (79%): 22 (36.1%) had resolution of AVBIII while 39 (63.9%) remained pacemaker-dependent. Pre-TAVR right bundle branch block was more frequent in device-dependent patients (19 of 38, 50% vs 4 of 22, 18%; RR 2.75; P = .01). Device-dependence was associated with AVBIII as the first postprocedural rhythm (37 of 39, 95% vs 12 of 22, 55%; RR 1.74; P < .0001), earlier implantation (median 1d, IQR: 0-1.5d vs 2d, IQR: 1.0-4.0d, P = .0004), and a shorter duration of hospitalization (median 3d, IQR: 2-3.5d vs 4d, IQR: 2-5.75d, P = .03). Pacemaker dependence was also associated with a higher prosthesis-to left ventricular outflow tract (LVOT) diameter (1.45 ± 0.11 vs 1.39 ± 0.07; P = .02) and the lack of prior aortic valvuloplasty (5 of 39, 13% vs 8 of 22, 36%; RR 0.35; P = .03). CONCLUSIONS: In patients receiving a PPM following self-expanding TAVR, a long-term pacing requirement can be predicted from the timing of AV block, existing conduction-system disease, larger prosthesis-to-LVOT diameter, and the lack of aortic valvuloplasty.

Elastogranular Mechanics: Buckling, Jamming, and Structure Formation.

Confinement of a slender body into a granular array induces stress localization in the geometrically nonlinear structure, and jamming, reordering, and vertical dislodging of the surrounding granular medium. By varying the initial packing density of grains and the length of a confined elastica, we identify the critical length necessary to induce jamming, and demonstrate how folds couple with the granular medium to localize along grain boundaries. Above the jamming threshold, the characteristic length of elastica deformation is shown to diverge in a manner that is coupled with the motion and rearrangement of the grains, suggesting the ordering of the granular array governs the deformation of the slender structure. However, overconfinement of the elastica will vertically dislodge grains, a form of stress relaxation in the granular medium that illustrates the intricate coupling in elastogranular interactions.