Regional Strain Research Articles

Analysis of deformation evolution characteristics of the northern Lajishan fault before the Jishishan MS6.2 earthquake based on GNSS observations

A MS6.2 earthquake struck Jishishan Country in Gansu Province on 18 December 2023. The earthquake occurred on the eastern branch of the Northern Lajishan fault (NLJSF) which has never experienced such a violent seismic event in recorded history. In this study, multiple periods of GNSS campaign observation data and continuous observation data are collected to reveal the crustal deformation evolution characteristics of the eastern branch of the NLJSF before the earthquake, focusing on the dynamic behavior of the causative fault, regional strain parameter features, and the variation of GNSS baselines across the NLJSF. Velocity field data show that the differential movement on both sides of the fault zone before the earthquake accumulated energy for the occurrence of the earthquake. Cross-fault profile analyses indicate a noticeable weakening of horizontal shortening on both fault flanks, suggesting a nearing fault lockup. The baseline time series and strain parameter time series results both show that the study area is mainly NEE-trending compression deformation. In addition, before the earthquake, multiple baseline results and strain parameter time series deviated from the linear trend and gradually flattened, indicating a strain accumulation in the study area. The overall crustal deformation evolution shows a relatively high earthquake risk before the Lajishan earthquake.

Prognostic bone fracture healing simulations in an ovine tibia model validated with in vivo sensors

AbstractBone fracture healing is a complex physiological process influenced by biomechanical and biomolecular factors. Mechanical stability is crucial for successful healing, and disruptions can lead to delayed healing or nonunion. Bone commonly heals itself through secondary fracture healing, which is governed by the mechanical strain at the fracture site. To investigate these phenomena, a validated methodology for capturing the mechanoregulatory process in specimen‐specific models of fracture healing could provide insight into the healing process. This study implemented a prognostic healing simulation framework to predict healing trajectories based on mechanical stimuli. Sixteen sheep were subjected to a 3 mm transverse tibial mid‐shaft osteotomy, stabilized with a custom plate, and equipped with displacement transducer sensors to measure interfragmentary motion over 8 weeks. Computed tomography scans were used to create specimen‐specific bone geometries for finite element analysis. Virtual mechanical testing was performed iteratively to calculate strains in the callus region, which guided tissue differentiation and consequently, healing. The predicted healing outcomes were compared to continuous in vivo sensor data, providing a unique validation data set. Healing times derived from the in vivo sensor and in silico sensor showed no significant differences, suggesting the potential for these predictive models to inform clinical assessments and improve nonunion risk evaluations. This study represents a crucial step towards establishing trustworthy computational models of bone healing and translating these to the preclinical and clinical setting, enhancing our understanding of fracture healing mechanisms.Clinical significance: Prognostic bone fracture healing simulation could assist in non‐union diagnosis and prediction.

Myocardial fibrosis in the posterior myocardium in Fabry disease is associated with global rather than regional longitudinal strain reduction.

Myocardial fibrosis in the posterior myocardium in Fabry disease is associated with global rather than regional longitudinal strain reduction.

Comparison of left atrial and left atrial appendage mechanics in patients with ischaemic strokes of different aetiologies

Abstract Background Left atrial (LA) and left atrial appendage (LAA) mechanical dysfunction account for an increase in cardioembolic stroke risk in atrial fibrillation (AF), and more recently in individuals in sinus rhythm (SR). However, the exact contribution of LA and LAA to the pathogenesis of thromboembolic events is not fully understood. Here, we aimed to assess the alterations of LA and LAA mechanics in different stroke subtypes. Methods We recruited three groups of participants: patients with paroxysmal or persistent AF with a history of stroke (AF-stroke, n=69,respectively), individuals in SR with no history of AF but with acute ischaemic stroke(non-AF stroke,n=46); individuals with no history of AF or stroke(control group,n=17). Patients with AF were further categorized into sinus rhythm group (AF-stroke-SR,n=24) and AF rhythm group(AF-stroke-AF, n=45) according to the rhythm at the time of echocardiography. Using speckle-tracking echocardiography, global longitudinal strain (GLS) and mechanical dispersion (MD) of LA and LAA were measured in all patients. Mechanical dispersion was defined as the standard deviation of the time to peak of the regional strain corrected by R-R interval. Results Patients with AF-stroke demonstrated prominently impaired LA and LAA mechanics(LA GLS: 20±6%(AF-stroke-SR),11±4%(AF-stroke-AF); LA MD: 9±3%,11±3%; LAA GLS: 15±3%,11±4% ; LAA MD: 11±4%,12±3% ,respectively) compare with those with non-AF stroke and controls (LA GLS:35±8%, 41±11%;LA MD,6±2%, 4±2%; LAA GLS:21±5%, 23±7%; LAA MD:8±4%, 7±3%,respectively) (all p<0.01). Interestingly, LA and LAA mechanical function was not significantly different between patients with non-AF strokes and the control group. In multivariable analysis, only AF-strokes were independently associated with LA and LAA GLS after adjusting for age and comorbidities (both P<0.01). Conclusions Mechanical dysfunction of LA and LAA might play a greater role in pathogenesis of strokes related to AF rather than non-AF strokes.

Strain and Deformation Analysis Using 3D Geological Finite Element Modeling with Comparison to Extensometer and Tiltmeter Observations

This study verifies the practicality of using finite element analysis for strain and deformation analysis in regions with sparse GNSS stations. A digital 3D terrain model is constructed using DEM data, and regional rock mass properties are integrated to simulate geological structures, resulting in the development of a 3D geological finite element model (FEM) using the ANSYS Workbench module. Gravity load and thermal constraints are applied to derive directional strain and deformation solutions, and the model results are compared to actual strain and tilt measurements from the Jiujiang Seismic Station (JSS). The results show that temperature variations significantly affect strain and deformation, particularly due to the elevation difference between the mountain base and summit. Higher temperatures increase thermal strain, causing tensile effects, while lower temperatures reduce thermal strain, leading to compressive effects. Strain and deformation patterns are strongly influenced by geological structures, gravity, and topography, with valleys experiencing tensile strain and ridges undergoing compression. The deformation trend indicates a southwestward movement across the study area. A comparison of FEM results with ten years of strain and tiltmeter data from JSS reveals a strong correlation between the model predictions and actual measurements, with correlation coefficients of 0.6 and 0.75 for strain in the NS and EW directions, and 0.8 and 0.9 for deformation in the NS and EW directions, respectively. These findings confirm that the 3D geological FEM is applicable for regional strain and deformation analysis, providing a feasible alternative in areas with limited GNSS monitoring. This method provides valuable insights into crustal deformation in regions with sparse strain and deformation measurement data.

Deep learning improves test-retest reproducibility of regional strain in echocardiography.

The clinical utility of regional strain measurements in echocardiography is challenged by suboptimal reproducibility. In this study, we aimed to evaluate the test-retest reproducibility of regional longitudinal strain (RLS) per coronary artery perfusion territory (RLSTerritory) and basal-to-apical level of the left ventricle (RLSLevel), measured by a novel fully automated deep learning (DL) method based on point tracking. We measured strain in a dual-centre test-retest data set that included 40 controls and 40 patients with suspected non-ST elevation acute coronary syndrome. Two consecutive echocardiograms per subject were recorded by different operators. The reproducibility of RLSTerritory and RLSLevel measured by the DL method and by three experienced observers using semi-automatic software (2D Strain, EchoPAC, GE HealthCare) was evaluated as minimal detectable change (MDC). The DL method had MDC for RLSTerritory and RLSLevel ranging from 3.6 to 4.3%, corresponding to a 33-35% improved reproducibility compared with the inter- and intraobserver scenarios (MDC 5.5-6.4% and 4.9-5.4%). Furthermore, the DL method had a lower variance of test-retest differences for both RLSTerritory and RLSLevel compared with inter- and intraobserver scenarios (all P < 0.001). Bland-Altman analyses demonstrated superior reproducibility by the DL method for the whole range of strain values compared with the best observer scenarios. The feasibility of the DL method was 93% and measurement time was only 1 s per echocardiogram. The novel DL method provided fully automated measurements of RLS, with improved test-retest reproducibility compared with semi-automatic measurements by experienced observers. RLS measured by the DL method has the potential to advance patient care through a more detailed, more efficient, and less user-dependent clinical assessment of myocardial function.

Isolation, Identification and Characterization of the Algicidal Micromycete Penicillium chrysogenum SR–1.3

A novel strain SR–1.3 with algicidal properties and the ability to remove microcystin-LR was isolated from the water of Lake Sestroretskij Razliv during the active cyanobacteria vegetation. Based on the morphological and cultural characteristics and the results of sequencing of the ITS DNA region strain SR–1.3 was identified as Penicillium chrysogenum. The SR–1.3 strain exhibited algicidal activity against cyanobacteria and green algae. A dose-dependent and species-specific nature of the algicidal action of the P. chrysogenum SR–1.3 strain has been established. Cyanobacteria showed the highest sensitivity to strain SR–1.3. The complete lysis (100%) of cyanobacteria cells was observed when 10% (vol.) of the culture liquid or the micromycete filtrate were added to the medium. The algicidal effect of strain SR–1.3 on green algae was 30–70%, depending on the culture. According to the level of sensitivity to the algicidal effect SR–1.3, the test cultures can be arranged in the series Planktothrix agardhii Microcystis aeruginosa Aphanizomenon flos-aquae = Anabaena cylindrica Scenedesmus quadricauda Oocystis parva. The inhibitory effect of the strain SR-1.3 mycelium on the cyanobacteria and green algae growth did not exceed 3–6%. Based on the obtained results a conclusion was made about the indirect mechanism of the algicidal action of P. chrysogenum SR–1.3 by excretion into the medium of metabolites that inhibit and/or lyse cells of cyanobacteria and green algae. When toxigenic strains of M. aeruginosa and P. agardhii were cultivated on a medium containing exometabolites of strain SR–1.3, the concentrations of microcystins in the medium decreased by 3.3 and 1.8 times, respectively, compared with control variants. The ability of P. chrysogenum SR–1.3 to remove highly toxic microcystin-LR from the cultivation medium was revealed. The MC-LR content was found to decrease from 1.2 μg/ml to 0.79 μg/ml over 48 hours during the cultivation of strain SR–1.3 on medium with microcystin.

Late Quaternary slip rate of the strike-slip faults on the eastern margin of the Qaidam Basin on the Tibetan Plateau and its implication on regional strain partitioning

The spatial variation in slip rates of large-scale strike-slip faults provides crucial support for the conceptual models of continental collision. However, the reasons for the decrease in slip rate of the East Kunlun Fault at the eastern margin of the Qaidam Basin on the Tibetan Plateau are still unclear. At the eastern margin of the Qaidam Basin, we identified four active strike-slip faults—two NW-SE−orientated dextral (the Xiariha Fault and Yingdeerkang Fault) and two E-W−orientated sinistral (the Reshui-Taosituohe Fault and Taosituohenan Fault)—and determined their slip rates using uncrewed aerial vehicle-based topography and optically stimulated luminescence dating. For the Xiariha Fault, from north to south slip rates are 1.39 +0.51/−0.34 mm/yr, 1.19 +0.15/−0.14 mm/yr, and 0.9 +0.19/−0.16 mm/yr. The Yingdeerkang Fault slips at 0.66 +0.08/−0.07 mm/yr. The Reshui-Taosituohe Fault, from west to east, slips at 0.95 +0.22/−0.19 mm/yr and 1.20 +0.11/−0.09 mm/yr. The Taosituohenan Fault, west to east, slips at 0.62 +0.12/−0.12 mm/yr to 1.01 +0.21/−0.19 mm/yr and 1.21 +0.43/−0.25 mm/yr. We believe that the gradual decrease in slip rate of the East Kunlun Fault at the Tuosuo Lake segment toward the east is influenced by the activity of the four active strike-slip faults with a slip rate of ∼1 mm/yr along the eastern margin of the Qaidam Basin and the Elashan Fault. The decrease in fault slip rate is not solely attributed to the diverse structural styles of the fault itself but also to the strain absorption by the development of differently oriented faults around its periphery.

Impact of systemic lupus erythematosus on cardiovascular morphologic and functional phenotypes: a Mendelian randomization analysis.

Previous studies have established a correlation between systemic lupus erythematosus (SLE) and cardiovascular health, but the potential causal effects of SLE on heart function and structure remain poorly understood. Cardiovascular magnetic resonance imaging (CMR), a novel non-invasive technique, provides a unique assessment of cardiovascular structure and function, making it an essential tool for evaluating the risk of heart disease. In this study, we performed a Mendelian randomization analysis to determine the causal relationship between SLE and CMR traits. Genetic variants independently linked to SLE were selected from a genome-wide association study (GWAS) containing 5,201 cases and 9,066 controls as instrumental variables. A set of 82 CMR traits was obtained from a recent GWAS, serving as preclinical indicators and providing preliminary insights into the morphology and function of the four cardiac chambers and two aortic segments. Primary analysis employed a two-sample Mendelian randomization study using the inverse-variance weighted method. Heterogeneity testing, sensitivity analyses, and instrumental variable strength assessments confirmed the robustness of the findings. SLE exhibited a correlation with increased stroke volume (βLVSV = 0.007, P = 0.045), regional peak circumferential strain (βEcc_AHA_9 = 0.013, P = 0.002; βEcc_AHA_12 = 0.009, P = 0.043; βEcc_AHA_14 = 0.013, P = 0.006), and global peak circumferential strain of the LV (βEcc_global = 0.010, P = 0.022), as well as decreased regional radial strain (βErr_AHA_11 = -0.010, P = 0.017). This research presents evidence of a potential causal association between traits of SLE and alterations in cardiac function, guiding cardiac examinations and disease prevention in lupus patients.

Comparing Echocardiographic Strain Imaging in Cardiac Amyloid and End-Stage Renal Disease Patients.

Diagnosing cardiac amyloidosis (CA) is difficult due to nonspecific clinical symptoms and echocardiographic findings. Prior studies have suggested that apical sparing strain patterns may be diagnostically useful. With increasing strain usage, it remains unclear how specific this pattern is to diagnose CA. We analyzed strain patterns between CA and end-stage renal disease (ESRD) patient populations. Patients with ESRD proven negative for CA (n=19) were compared to CA patients with CKD stage 3 or less (n=25). The ESRD cohort was stratified based on time on dialysis. Echocardiographic longitudinal strain (LS) parameters were collected, including regional and global LS, echocardiographic, and demographic parameters. Relative apical LS was calculated using the following equation: average apical LS/(average mid LS+average basal LS). No significant differences were found regarding regional strain or relative apical strain. Our study showed a sensitivity of 80% and specificity of 42% when using a relative apical strain ratio of >1. All groups demonstrated an apical sparing strain pattern visually on the bulls-eye plot. ESRD demonstrates significant overlapping findings across various imaging modalities compared to CA. We demonstrated that relative apical sparing strain is nonspecific for CA among patients with ESRD. Our study calls into question the clinical value of relative apical-sparing stain patterns in identifying CA in an ESRD population and suggests that diagnostic evaluation should be driven by strong clinical suspicion and other imaging and demographic variables.

Potential of Soft-Shelled Rugby Headgear to Lower Regional Brain Strain Metrics During Standard Drop Tests

BackgroundThe growing concern for player safety in rugby has led to an increased focus on head impacts. Previous laboratory studies have shown that rugby headgear significantly reduces peak linear and rotational accelerations compared to no headgear. However, these metrics may have limited relevance in assessing the effectiveness of headgear in preventing strain-based brain injuries like concussions. This study used an instantaneous deep-learning brain injury model to quantify regional brain strain mitigation of rugby headgear during drop tests. Tests were conducted on flat and angled impact surfaces across different heights, using a Hybrid III headform and neck.ResultsHeadgear presence generally reduced the peak rotational velocities, with some headgear outperforming others. However, the effect on peak regional brain strains was less consistent. Of the 5 headgear tested, only the newer models that use open cell foams at densities above 45 kg/m3 consistently reduced the peak strain in the cerebrum, corpus callosum, and brainstem. The 3 conventional headgear that use closed cell foams at or below 45 kg/m3 showed no consistent reduction in the peak strain in the cerebrum, corpus callosum, and brainstem.ConclusionsThe presence of rugby headgear may be able to reduce the severity of head impact exposure during rugby. However, to understand how these findings relate to brain strain mitigation in the field, further investigation into the relationship between the impact conditions in this study and those encountered during actual gameplay is necessary.

Right Ventricular Longitudinal Strain-Related Indices in Acute Pulmonary Embolism.

Pulmonary embolism (PE) is correlated with serious morbidity and mortality. Efforts have been made to establish and validate mortality predictive scores based mainly on clinical parameters. Patients with PE and traditional indices of echocardiographic right ventricular (RV) dysfunction or pressure overload have a higher probability of a worse outcome. During the last two decades, studies regarding the use of two-dimensional speckle-tracking echocardiography (2DSTE) and its derived indices in the setting of acute PE have been conducted. In this comprehensive review of the literature, we aimed to summarize these studies. Safe conclusions and comparisons among the reviewed studies are prone to statistical errors, mainly because the studies published were heterogenous in design, different 2DSTE-derived parameters were tested, and different clinical outcomes were used as endpoints. Nonetheless, RV strain indices and, more commonly, regional longitudinal strain of the RV free wall have shown a promising correlation with mortality, assisting in the differential diagnosis between PE and other acute or chronic disorders.

Tunable Out-of-Plane Reconstructions in Moiré Superlattices of Transition Metal Dichalcogenide Heterobilayers.

The reconstructed moiré superlattices of the transition metal chalcogenide (TMD), formed by the combined effects of interlayer coupling and intralayer strain, provide a platform for exploring quantum physics. Here, using scanning tunneling microscopy/spectroscopy, we observe that the strained WSe2/WS2 moiré superlattices undergo various out-of-plane atomically buckled configurations, a phenomenon termed out-of-plane reconstruction. This evolution is attributed to the differentiated response of intralayer strain in high-symmetry stacking regions to external strain. Notably, in larger out-of-plane reconstructions, there is a significant alteration in the local density of states (LDOS) near the Γ point in the valence band, exceeding 300%, with the moiré potential in the valence band surpassing 200 meV. Further, we confirm that the variation in interlayer coupling within high-symmetry stacking regions is the main factor affecting the moiré electronic states rather than the intralayer strain. Our study unveils intrinsic regulating mechanisms of out-of-plane reconstructed moiré superlattices and contributes to the study of reconstructed moiré physics.

Effect of Glenohumeral Abduction on Supraspinatus Tendon Strain: A Cadaveric Study

Objectives Rotator cuff tears are among the most common causes of shoulder pain and loss of function in adults. The supraspinatus tendon plays a crucial role in shoulder abduction, where a better understanding of the mechanical environment could lead to more informed clinical decisions. This study aimed to examine the heterogeneous nature of the supraspinatus tendon to understand the differences in regional strain patterns. Methods Five fresh frozen cadaveric shoulders were abducted from 60° to 90°. The supraspinatus tendon was loaded at 30 newtons to simulate motion in a subject operating at roughly 26% of the maximum glenohumeral abduction force. The surface strain at the supraspinatus tendon insertion, where tears most commonly occur, was evaluated in the tendon’s anterior, middle, and posterior regions to identify the heterogeneous deformation during abduction. Results Surface strain increased with increasing abduction angle (R2 = 0.697, P &lt; 0.001). The posterior regions exhibited larger strains compared to the anterior regions at 70° (P = 0.037), 75° (P = 0.028), and 90° (P = 0.011) of abduction. Conclusion During abduction, the strain on the bursal surface of the supraspinatus tendon insertion increases with increasing abduction angle, and the posterior region experiences the largest strains.

Genomic surveillance reveals low-level circulation of two subtypes of genogroup C coxsackievirus A10 in Nanchang, Jiangxi Province, China, 2015-2023.

In recent years, coxsackievirus (CV) A10 has been associated with increasing sporadic hand, foot, and mouth disease (HFMD) cases and outbreaks globally. In addition to mild symptoms such as pharyngitis and herpangina, CVA10-related complications or even fatality can occur. Currently, systematic phylogenetic studies of CVA10 are limited. In this study, we first explored the epidemiological and genetic characteristics of CVA10 in Nanchang, an inland southeastern city of China, based on the HFMD surveillance network from 2015-2023. Among 3429 enterovirus-positive cases, 110 (3.04%) were associated with CVA10, with a male-to-female ratio of 1.62. The median age of the CVA10 patients was 2.3 years (interquartile range, IQR 1.0-4.0), with 94.55% (104/110) of the patients aged less than 5 years. Phylogenetic analyses using the full-length VP1, 5'UTR, P1, P2, P3 sequences and near full-length genomes indicated that CVA10 strains (n = 57) isolated in Nanchang belonged to genogroup C; two strains identified in 2017 belonged to C1 subtypes clustered with strains from Vietnam, Madagascar, France and Spain; and the others belonged to C2 subtypes interdigitating with CVA10 isolates from mainland China, the United States and Australia. Through extensive analysis, we identified a rare F168Y mutation in epitope 4 of VP1 in a Madagascar strain of genogroup F and a Chinese strain of genogroup C. Based on Bayesian evolutionary analyses, the average nucleotide substitution rate for the VP1 gene of CV10 strains was 3.07×10-3 substitutions/site/year. The most recent common ancestor (tMRCA) of genogroup C was dated 1990.84, and the tMRCA of CVA10 strains from Nanchang was dated approximately 2003.16, similar to strains circulating in other regions of China, suggesting that the viruses were likely introduced and cryptically circulated in China before the establishment of the HFMD surveillance network. Recombination analysis indicated intertypic recombination of the Nanchang strain with the genogroup G strain in the 3D region. Given the shifting dominance of viral genotypes and frequent recombination events, the existing surveillance system needs to be regulated to enhance genomic surveillance efforts on a more diverse spectrum of genotypes in the future.

The effects of myocardial bridging on two-dimensional myocardial strain during dobutamine stress echocardiography.

Myocardial bridging (MB) is a common anatomic variant in coronary arteries with unclear functional significance. We evaluated regional myocardial strain by speckle tracking during dobutamine stress echocardiography (DSE) in patients with MB in the left anterior descending coronary artery (LAD). We studied 11 patients with MB in the LAD and no obstructive coronary artery disease (CAD), 7 patients without MB, but obstructive CAD in the LAD, and 12 controls without MB or obstructive CAD. MB was defined as either > 1mm (superficial) or > 2mm (deep) intramyocardial course of the LAD in coronary CT angiography. Regional longitudinal, radial and circumferential strains and strain rates as well as post-systolic strain index (PSI) were measured at rest, peak stress, and early recovery (1min after stress). Strain parameters during DSE were similar in the myocardium distal to MB and other myocardial regions of the same patients as well as the LAD territory in controls. However, patients with obstructive CAD showed impaired LS and strain rate as well as increased PSI at peak stress. None of the MB was associated with systolic compression in invasive coronary angiography and strain parameters were similar between superficial and deep MB. Stress myocardial blood flow by positron emission tomography correlated with LS and RS at peak stress in the myocardium distal to MB (r = -0.73, p = 0.03, and r = 0.64, p = 0.04, respectively). Myocardial strain is not reduced during DSE in patients with MB in the LAD and no significant systolic compression.

Enclaves as mushy magma strain archives: New perspectives on composite magmatic fabrics in plutons

Mineral fabrics within igneous intrusions can archive both tectonic and magmatic processes. However, whether magmatic state fabrics reflect primary magmatic processes or regional tectonic strain is often ambiguous. To investigate when fabrics are formed, one can compare the mineral fabrics to primary magmatic features, such as the interface between solidified magmas in mingling zones. The monzodioritic Fanad pluton shows a NNE-SSW–aligned petrofabric parallel to the strike of a nearby shear zone, with dioritic enclaves aligned parallel and oblique to this petrofabric. We therefore aimed to test if the enclaves’ internal fabrics are passive and align with enclave morphology or result from progressive overprint by regional tectonic strain. Crystallographic preferred orientation and anisotropy of magnetic susceptibility data from all enclaves and the host monzodiorite revealed a NNE-SSW petrofabric parallel to the regional tectonomagmatic fabric. However, anisotropy of anhysteretic remanent magnetization data within petrofabric-oblique enclaves revealed a primary fabric parallel to the enclave long axis. Therefore, we interpret enclave morphologies to reflect earlier magmatic state deformation, with fabrics being realigned to regional tectonic deformation. These two distinct petrofabrics were interpreted in the context of the magmatic processes and the evolving late Caledonian paleostress field, with earlier magma processes distinguished from subsequent tectonic overprinting occurring in the magmatic state. Our new data show that multiple fabrics are preserved within enclaves even though all fabric development occurred within a magmatic state. Our results also show that enclaves can effectively record successive strain events, providing new insight with which to decipher tectonomagmatic processes.

Evolving cartilage strain with pain progression and gait: a longitudinal study post-ACL reconstruction at six and twelve months.

Anterior cruciate ligament (ACL) injuries are prevalent musculoskeletal conditions often resulting in long-term degenerative outcomes such as osteoarthritis (OA). Despite surgical advances in ACL reconstruction, a significant number of patients develop OA within ten years post-surgery, providing a patient population that may present early markers of cartilage degeneration detectable using noninvasive imaging. This study aims to investigate the temporal evolution of cartilage strain and relaxometry post-ACL reconstruction using displacement under applied loading MRI and quantitative MRI. Specifically, we examined the correlations between MRI metrics and pain, as well as knee loading patterns during gait, to identify early candidate markers of cartilage degeneration. Twenty-five participants (female/male = 15/10; average age = 25.6 yrs) undergoing ACL reconstruction were enrolled in a prospective longitudinal cohort study between 2022 and 2023. MRI scans were conducted at 6- and 12-months post-surgery, assessing T2, T2*, and T1ρ relaxometry values, and intratissue cartilage strain. Changes in pain were evaluated using standard outcome scores, and gait analysis assessed the knee adduction moment (KAM). Regressions were performed to evaluate relationships between MRI metrics in cartilage contact regions, patient-reported pain, and knee loading metrics. Increases in axial and transverse strains in the tibial cartilage were significantly correlated with increased pain, while decreases in shear strain were associated with increased pain. Changes in strain metrics were also significantly related to KAM at12 months. Changes in cartilage strain and relaxometry are related to heightened pain and altered knee loading patterns, indicating potential early markers of osteoarthritis progression. These findings underscore the importance of using advanced MRI for early monitoring in ACL-reconstructed patients to optimize treatment outcomes, while also highlighting KAM as a modifiable intervention through gait retraining that may positively impact the evolution of cartilage health and patient pain. Increased axial and transverse strains in the tibial cartilage from 6 to 12 months post-ACL reconstruction were significantly correlated with increased pain, suggesting evolving changes in cartilage biomechanical properties over time.Decreases in shear strain in inner femoral and central tibial cartilage regions were linked to increased pain, indicating alterations in joint loading patterns.Decreases in shear strain in the inner femoral cartilage were significantly associated with decreased 12-month knee adduction moment (KAM), a surrogate for medial cartilage knee loading during walking.

Regional impairment of left ventricular longitudinal strain in aortic regurgitation

BackgroundAortic regurgitation (AR) has an important impact on myocardial mechanics and recent studies have proved the value of global longitudinal strain (GLS) in the assessment of its severity and prognosis. Our purpose was to assess if the direct impact of the regurgitant jet on the myocardial wall could affect regional longitudinal strain.MethodsEighty patients with chronic moderate/severe AR were retrospectively studied. Patients were considered to have a jet-related longitudinal strain reduction when the myocardial segments directly impacted by the jet had their longitudinal strain reduced by at least 30% compared to nonaffected segments. AR severity, left ventricular (LV) size and function were compared according to the presence/absence of this regional pattern. For those who underwent surgery, postoperative regional and global LV function was also analyzed.ResultsA pattern of regional longitudinal strain impairment was identified in 43% of patients, with a regional reduction (in median) of 10 percentage points in absolute strain values in the segments impacted by the jet, compared to nonaffected segments. In the subgroup who underwent surgery, this pattern became attenuated after surgery. Patients with regional longitudinal strain impairment were less likely to improve GLS after surgery (10% vs. 38% improved GLS by at least 2.5%, P = 0.049).ConclusionsTo our knowledge, this study identifies for the first time, a link between the location of the impact of the regurgitant jet in AR and regional longitudinal strain impairment. The presence of this regional pattern might be associated with worse postoperative LV recovery.

AN UPDATE ON CURRENT STATUS OF ANTIBIOTIC RESISTANCE IN SALMONELLA TYPHI: A RETROSPECTIVE ANALYSIS OF BLOOD CULTURE REPORTS FROM A TERTIARY CARE HOSPITAL

Background: Pakistan bears most of the burden of drug-resistant typhoid, challenging its healthcare systems with substantial cost. This study’s purpose is to investigate resistance in community-acquired salmonella typhi to guide its evidence-based empiric treatment. Methods: This study used retrospective data from the microbiology laboratory, Khyber Teaching Hospital, Peshawar (September 2022-March 2023). Data of routine diagnostic samples for typhoid was retrieved from the database. Kirby–Bauer disk diffusion method was employed to determine the sensitivity of S. Typhi against a panel of 21 selected antibiotic discs (not exclusively for each isolate). Results: Among 1742 suspected patients, 239 (13.92%) were positive for S. Typhi with 212/238 (89.1%), 227/233 (97.4%), and 196/239 (82.0%) isolates resistant to chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole, respectively. High resistance (88.0% to ciprofloxacin) was detected against fluoroquinolones. Third-generation cephalosporins also showed poor activity with 144/158 (91.1%) and 120/136 (88.2%) resistance towards ceftriaxone and cefixime, respectively, except for cefoperazone/sulbactam (2/123, 1.6%). Among 157 tested isolates, 3 (1.9%), 9 (5.7%), and 123 (78.3%) were labeled as non-resistant, MDR, and XDR strains, respectively. XDRs were less resistant to azithromycin (1/114), piperacillin/tazobactam (1/123), carbapenems (0/123), and tigecycline (0/123). Conclusion: XDR S. Typhi was observed as the dominant strain in Peshawar regions for which azithromycin is still the drug of choice. With emerging resistance, azithromycin safety should be ensured through antibiotic stewardship principles. An interesting finding was the enhanced activity of cefoperazone/sulbactam, suggesting future studies. Alternative options are expensive antibiotics which can be used as a last resort. Keywords: Typhoid, Antibiotic resistance, Extensive drug-resistant (XDR) S. Typhi, Pakistan.