Chromosome compaction and chromatin stiffness enhance diffusive loop extrusion by slip-link proteins

We use Brownian dynamics simulations to study the formation of chromatin loops through diffusive sliding of slip-link-like proteins, mimicking the behaviour of cohesin molecules. We recently proposed that diffusive sliding is sufficient to explain the extrusion of chromatin loops of hundreds of kilo-base-pairs (kbp), which may then be stabilised by interactions between cohesin and CTCF proteins. Here we show that the flexibility of the chromatin fibre strongly affects this dynamical process, and find that diffusive loop extrusion is more efficient on stiffer chromatin regions. We also show that the dynamics of loop formation are faster in confined and collapsed chromatin conformations but that this enhancement is counteracted by the increased crowding. We provide a simple theoretical argument explaining why stiffness and collapsed conformations favour diffusive extrusion. In light of the heterogeneous physical and conformational properties of eukaryotic chromatin, we suggest that our results are relevant to understand the looping and organisation of interphase chromosomes in vivo.

Determination of Nitrate in Forages by Using Selective Ion Electrode: Collaborative Study

Each of 10 collaborating laboratories analyzed 4 blind duplicate pairs of forage samples for nitrate, by using a potentiometric method. Two forage controls and a 100 000 mg KNO3/L standard were also provided. Nitrate was extracted into an aqueous Al2(SO4)3 solution containing 70 mg KNO3/L and quantitated with a nitrate-selective electrode. Standards were prepared using extracting solution as diluent. Nitrate concentrations in forage samples ranged from <0.50 to 4.35% KNO3. Repeatability coefficients of variation (CV0) ranged from 1.74 to 3.61%, and reproducibility coefficients of variation (CV1) ranged from 6.92 to 7.66%. Mean recovery of a 0.55% KNO3 spike was 94.5%. The method has been adopted official first action.

High-Sensitivity Dry Rehydratable Film Method for Enumeration of Coliforms in Dairy Products: Collaborative Study

A dry-film coliform count plate that is inoculated with 5 mL sample was compared with the Violet Red Bile Agar plate method in a collaborative study by 18 laboratories. Products analyzed were 2% milk, chocolate milk, cream, vanilla ice cream, cottage cheese, and cheese. Collaborators tested blind duplicate uninoculated samples and samples inoculated at low, medium, and high level. Significantly (P< 0.05) higher numbers of coliforms were recovered by the dry-film method from 2% milk samples at the 3 inoculum levels, the chocolate milk at the low- and high-inoculum levels, and the cream at the high-inoculum level. Significantly higher counts were obtained by the agar method for cottage cheese samples at the low-inoculum level. The repeatability standard deviation for the dry-film method was significantly higher for the high-inoculum level chocolate milk sample and the medium-inoculum level cottage cheese. The same statistic was significantly higher for the agar method at all 3 inoculum levels in the 2% milk and the medium-inoculum level cream. The high-sensitivity dry rehydratable film method for enumeration of coliforms in dairy products has been adopted first action by AOAC INTERNATIONAL.

SuperCam Calibration Targets: Design and Development

SuperCam is a highly integrated remote-sensing instrumental suite for NASA's Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques (RMI). They provide information on the mineralogy, geochemistry and mineral context around the Perseverance Rover. The calibration of this complex suite is a major challenge. Not only does each technique require its own standards or references, their combination also introduces new requirements to obtain optimal scientific output. Elemental composition, molecular vibrational features, fluorescence, morphology and texture provide a full picture of the sample with spectral information that needs to be co-aligned, correlated, and individually calibrated. The resulting hardware includes different kinds of targets, each one covering different needs of the instrument. Standards for imaging calibration, geological samples for mineral identification and chemometric calculations or spectral references to calibrate and evaluate the health of the instrument, are all included in the SuperCam Calibration Target (SCCT). The system also includes a specifically designed assembly in which the samples are mounted. This hardware allows the targets to survive the harsh environmental conditions of the launch, cruise, landing and operation on Mars during the whole mission. Here we summarize the design, development, integration, verification and functional testing of the SCCT. This work includes some key results obtained to verify the scientific outcome of the SuperCam system.

One Health and Zoonotic Uncertainty in Singapore and Australia: Examining Different Regimes of Precaution in Outbreak Decision-Making

A One Health approach holds great promise for attenuating the risk and burdens of emerging infectious diseases (EIDs) in both human and animal populations. Because the course and costs of EID outbreaks are difficult to predict, One Health policies must deal with scientific uncertainty, whilst addressing the political, economic and ethical dimensions of communication and intervention strategies. Drawing on the outcomes of parallel Delphi surveys conducted with policymakers in Singapore and Australia, we explore the normative dimensions of two different precautionary approaches to EID decision-making—which we call regimes of risk management and organizing uncertainty, respectively. The imperative to act cautiously can be seen as either an epistemic rule or as a decision rule, which has implications for how EID uncertainty is managed. The normative features of each regime, and their implications for One Health approaches to infectious disease risks and outbreaks, are described. As One Health attempts to move upstream to prevent rather than react to emergence of EIDs in humans, we show how the approaches to uncertainty, taken by experts and decision-makers, and their choices about the content and quality of evidence, have implications for who pays the price of precaution, and, thereby, social and global justice.

Apoptotic and Proteolytic Attributes and Metabolomic Changes in Postmortem Muscles from Pigs Subjected to Post-Weaning Transport at Different Seasons

ObjectivesPost-weaning transport of pigs was commonly practiced in the swine industry, however, adversely impact animal growth and well-being due to concurrent stress from weaning and transport. Further, our recent study found that post-weaning transport may have long-term effects on final pork quality attributes in terms of inferior texture and water-holding capacity. Heat shock proteins (HSPs) are anti-apoptotic chaperone proteins, protecting against apoptosis under a variety of cell death stimuli including postmortem muscle conversion process. While a potential role of apoptosis in meat tenderization has been proposed, how early life stress influences apoptotic/proteolytic process and metabolism of postmortem muscles is largely unknown. Thus, the study objective was to evaluate apoptotic and proteolytic attributes and metabolomic changes in postmortem muscles of market weight pigs exposed to early life transport/weaning stress at two seasons.Materials and MethodsTwo repetitions of newly weaned pigs (N = 480) were transported for 12 h in a trailer truck during July 2016 (SUMMER) and April 2017 (SPRING) in north-central Indiana. Upon reaching market weight, 10 animals were randomly chosen from each season and slaughtered in January 2017 and September 2017, respectively. Pairs of longissimus dorsi and psoas major muscles from each carcass were separated at 1d and 7d postmortem. Proteolytic and apoptotic factors including desmin, troponin T, calpain 1, HSP27, and aβ-crystallin were quantified using Western-blot assays, and mitochondria membrane permeability (MMP) was evaluated. Metabolome profiles of 1d samples were analyzed using the GC-TOF-MS/MS platform. Multivariate analyses PCA and PLS-DA were used to determine changes of metabolites. Data were analyzed using PROC MIXED of SAS to compare the traits across season, muscle, and aging effects.ResultsPreviously, SUMMER pigs were reported showing decreased body weight, muscling, and fat deposition, as well as increased shear force and water loss during aging. In the present study, SPRING muscles exhibited increases in calpain 1 autolysis and structural protein degradation, coincided with accelerated apoptosis shown as higher MMP compared to the SUMMER counterparts (P < 0.05). Moreover, PCA and PLS-DA clustering indicated distinct metabolome profiles affected by season and muscle. Seasonal effect mainly altered lipid, glucose, and nitrogen metabolism. A group of 16C to 18C fatty acids were increased in SPRING, probably due to increased lipid anabolism during warm growing/finishing season. Changes of urea, ornithine, aspartic acid, and 5’methylthioadenosine suggested increased amino acid catabolism in SUMMER, corroborating the decreased lean and fat accretion. Seasonal changes of key metabolites related to stress response, including histidine, GABA, and ascorbic acid, suggested increased stress defense in SUMMER pigs, which implied the suppression of apoptotic and proteolytic activities.ConclusionTaken together, SUMMER pigs showed suppressed onset of apoptosis with compromised growth and meat quality, possibly due to alternations in seasonal metabolic response. This may in turn affect the proteolytic potential of early postmortem muscles. Further studies elucidating the involvement of apoptotic process in proteolytic activities in postmortem muscles should be warranted.

Fetal heart rate variability with hypoxemia in an instrumented sheep model

OBJECTIVE

To examine the effect of hypoxemia on fetal heart rate (FHR) variability, using an instrumented pregnant sheep model.

METHODS

In this prospective study, 19 pregnant sheep were instrumented under general anesthesia, at a mean gestational age of 127 days. After a 5-day recovery period, hypoxemia was induced by attaching the mother to a rebreathing circuit. Hypoxemia was sustained for 120 min, following which it was reversed until maternal and fetal partial pressure of oxygen (pO₂ ) returned to baseline. FHR recordings at baseline, after 30 and 120 min of hypoxemia and at recovery were analyzed to calculate short-term variation (STV) in 16 epochs of 3.75 s, every minute. Phase-rectified signal averaging (window length (L) = 10, time (T) = 2 and scale (S) = 2) was used to calculate FHR acceleration (AC) and deceleration (DC) capacities.

RESULTS

At baseline, mean ± SD fetal pO₂ was 2.90 ± 0.38 kPa. Acute hypoxemia was associated with a significant reduction in mean pO₂ at 30 (1.62 ± 0.37 kPa) and 120 (1.51 ± 0.16 kPa) min. Mean ± SD fetal pO₂ at recovery was 2.86 ± 0.32 kPa. At baseline, median STV, AC and DC were 1.307 (interquartile range (IQR), 0.515-2.508) ms, 1.295 (IQR, 0.990-2.685) beats per minute (bpm) and 1.197 (IQR, 0.850-1.836) bpm, respectively. At 30 min of hypoxemia, the values were 1.323 (IQR, 0.753-2.744) ms, 1.696 (IQR, 1.310-3.013) bpm and 1.584 (IQR, 1.217-4.132) bpm, respectively. At 120 min of hypoxemia, they were 1.760 (IQR, 0.928-4.656) ms, 3.098 (IQR, 1.530-5.163) bpm and 3.054 (IQR, 1.508-4.522) bpm, respectively. At recovery, they changed to 0.962 (IQR, 0.703-1.154) ms, 1.228 (IQR, 1.071-2.234) bpm and 1.086 (IQR, 0.873-1.568) bpm, respectively. Hypoxemia for 30 and 120 min was associated with a significant increase in DC compared to baseline (P = 0.014 and 0.017, respectively). The changes in STV and AC were not significant.

CONCLUSION

Acute hypoxemia is associated with a significant increase in the DC of FHR in a fetal sheep model. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Evaluation of the BAX® System for Detection of Salmonella in Selected Foods: Collaborative Study

A multilaboratory study was conducted to compare the automated BAX® System to the standard cultural methods for detection of Salmonella in selected foods. Five food types—frankfurters, raw ground beef, mozzarella cheese, raw frozen tilapia fish, and orange juice—at 3 inoculation levels, were analyzed by each method. A sixth food type, raw ground chicken, was tested using 3 naturally contaminated lots. A total of 16 laboratories representing government and industry participated. In this study, 1386 samples were analyzed, of which 1188 were paired samples and 198 were unpaired samples. Of the 1188 paired samples, 461 were positive by both methods and 404 were negative by both methods. Thirty-seven samples were positive by the BAX System but negative by the standard reference method, and 11 samples were positive by standard cultural method and negative by the BAX System. Of the 198 unpaired samples, 106 were positive by the BAX System and 60 were positive by the standard cultural method. A Chi square analysis of each of the 6 food types, at the 3 inoculation levels tested, was performed. For all foods, the BAX System demonstrated results comparable to those of the standard reference methods based on the Chi square results.

Determination of Fat in Raw and Processed Milks by the Gerber Method: Collaborative Study

The Gerber method is used worldwide as a simple and rapid method for determining fat in raw and processed milks. However, the volume of the test portion used in the method has not been internationally agreed upon. A collaborative study was conducted to evaluate performance of the Gerber method using either a weighed test portion (11.13 g) or by a 10.77 mL test portion delivered by pipet. For each method, laboratories received 10 test samples: 5 raw and 5 pasteurized homogenized milks, 2 of which were blind duplicate pairs. Eleven and 10 laboratories participated in the evaluation of aliquot addition by weight and pipet, respectively. Mojonnier ether extraction (Method 989.05) was used as the reference method. Interlaboratory study statistics were similar between methods of test portion addition and between raw and processed materials; therefore, summary interlaboratory study statistics were pooled. The fat content of milk samples ranged from 0.96 to 5.48%. Absolute reproducibility and repeatability were not affected by fat level, and pooled statistical performance (invalid and outlier data removed) was (g fat/100 g milk) sr = 0.026, sR = 0.047, r = 0.074, and R = 0.132. Relative standard deviations increased with decreasing fat content, and were summarized by fat level: 1–2% fat milk, mean = 1.437, RSDr = 1.809%, RSDR = 3.271%; 2–6% fat milk, mean = 4.156, RSDr = 0.626%, RSDR = 1.131%. Compared with ether extraction, test results by the Gerber method were slightly lower (0.02% fat) using a weighed test portion and significantly lower (0.06% fat) using a 10.77 mL volume addition by pipet. A trend toward underestimating fat content at lower fat concentrations (1–2% fat) was observed with the weighed test portion but not when a pipet was used. The Associate Referee recommends that the Gerber method using a weighed test portion be adopted as First Action with applicability limited to whole milk.

3075Global longitudinal strain and mechanical dispersion in the general population aged 50–64 years – results from the echocardiography study of the Swedish CArdioPulmonary bioImage Study (SCAPIS)

Background

The Swedish CArdioPulmonary bioImage Study (SCAPIS) was initiated to improve understanding of underlying mechanisms in order to prevent cardiovascular and pulmonary disease. 30 000 individuals aged 50–64 years, randomly selected from the general population, were included in the study. Six-thousand-eight-hundred of the individuals underwent transthoracic echocardiography.

Global longitudinal strain (GLS) and mechanical dispersion (MD) are novel echocardiographic measures of left ventricular (LV) systolic function and electrical instability reflecting risk for malignant arrhythmia, respectively. Previous studies suggest that the limit of normal for GLS is −16% and that MD >70 ms may be associated with increased risk for malignant arrhythmias. GLS and MD have, however, not before been investigated in a large population-based study.

Purpose

The purpose of this first project within the SCAPIS echocardiography study is to determine the prevalence of impaired GLS and MD in the general population aged 50–64 years.

Methods

GLS and MD, defined as mean peak longitudinal strain of the 18 LV segments and standard deviation of time-to-peak strain for the 18 LV segments, respectively, were analysed using a commercially available software. For group comparisons, the independent-samples t-test, the Mann-Whitney U-test or One Way Analysis of Variance with the Bonferroni post hoc test were performed. Values are mean±standard deviation.

Results

1850 examinations have so far been reviewed, whereof image quality was considered adequate for strain analysis in 1480 individuals (80%). Image quality, assessed as the number of visually assessable LV segments, was better for the second half of the examinations, as compared to the first half (p<0.001). Of the 1480 individuals where GLS and MD were assessed, 51% were women and mean age was 57±4.4 years with no difference in age between the sexes (p=ns). Mean GLS was −20±2% and men had significantly more negative (p<0.001) GLS values than women (−21±2% vs. −19±2%). There was no significant difference (p=ns) in GLS when comparing individuals aged 50–54, 55–59 or 60–64 years, respectively. GLS values were less negative than −16% in 1.9% of the study population. Mean MD was 41±12 ms with no significant difference (p=ns) between the sexes. MD was significantly lower (p<0.001) among individuals aged 50–54 years, as compared to those aged 55–59 or 60–64 years, respectively. MD was >70 ms in 1.6% of the study population.

Conclusions

These preliminary data from the SCAPIS echocardiography study suggest that, in the general population aged 50–64 years, 1.9% have impaired GLS and 1.6% have increased MD, which is possibly associated with a higher risk for malignant arrhythmias. Men had more negative GLS values than women and MD was lower in the lowest age tertile. Further analyses are ongoing.

Acknowledgement/Funding

The Swedish Heart and Lung Foundation. Grants from Linkoping University. ALF-grants from the Swedish government (LIO-700841).

Extrusion without a motor: a new take on the loop extrusion model of genome organization

Chromatin loop extrusion is a popular model for the formation of CTCF loops and topological domains. Recent HiC data have revealed a strong bias in favour of a particular arrangement of the CTCF binding motifs that stabilize loops, and extrusion is the only model to date which can explain this. However, the model requires a motor to generate the loops, and although cohesin is a strong candidate for the extruding factor, a suitable motor protein (or a motor activity in cohesin itself) has yet to be found. Here we explore a new hypothesis: that there is no motor, and thermal motion within the nucleus drives extrusion. Using theoretical modelling and computer simulations we ask whether such diffusive extrusion could feasibly generate loops. Our simulations uncover an interesting ratchet effect (where an osmotic pressure promotes loop growth), and suggest, by comparison to recent in vitro and in vivo measurements, that diffusive extrusion can in principle generate loops of the size observed in the data. Extra View on : C. A. Brackley, J. Johnson, D. Michieletto, A. N. Morozov, M. Nicodemi, P. R. Cook, and D. Marenduzzo “Non-equilibrium chromosome looping via molecular slip-links”, Physical Review Letters 119 138101 (2017)

Salubrinal enhances eIF2α phosphorylation and improves fertility in a mouse model of Classic Galactosemia

Loss of galactose-1 phosphate uridylyltransferase (GALT) activity in humans results in Classic Galactosemia, and the GalT-deficient (GalT^-/-) mouse mimics the patient condition. GalT^-/- ovaries display elevated endoplasmic reticulum (ER) stress marker, BiP, and downregulated canonical phosphatidylinositol 3-kinase (Pi3k)/protein kinase B (Akt) growth/pro-survival signaling. Numbers of primordial follicles are reduced in the mutants, recapitulating the accelerated ovarian aging seen in human patients. We previously found that oral administration of the compound Salubrinal (an eIF2α phosphatase inhibitor), resulted in reduction of ovarian BiP expression, rescued Pi3k/Akt signaling, and a doubling of primordial follicles in GalT^-/- adults. Here, we further characterized galactosemic stress in GalT^-/- mice versus wild-type (WT) controls, and examined whether Salubrinal treatment improved broader reproductive parameters. We assessed the expression levels of factors of the unfolded protein response (UPR), and found that BiP, phospho-Perk, and phospho-eIF2α were all elevated in GalT^-/- ovaries. However, neither IKK activation (NFκB pathway) nor alternative Xbp1 splicing downstream of ER membrane protein Ire1α activation was induced, suggesting an Xbp1-independent UPR in galactosemic stress. Moreover, Salubrinal treatment significantly increased the number of ovulated eggs in mutant animals after gonadotrophic superovulation. Salubrinal treatment also normalized estrus cycle stage lengths and resulted in significantly larger litter sizes than vehicle-treated mutants. Overall, we show that Salubrinal protects against galactosemia-induced primordial follicle loss in a fashion that includes suppressing the de-phosphorylation of eIF2α, and that intervention in this way significantly improves and extends ovarian function, fertility, and fecundity.

Point-of-care Hepatitis C virus testing and linkage to treatment in an Australian inner-city emergency department

BACKGROUND

In Australia, Hepatitis C Virus (HCV) treatment is declining, despite broad access to direct-acting antiviral medication. People who inject drugs are proportionally over-represented in emergency department presentations. Emergency department assessment of people who have injected drugs for HCV presents an opportunity to engage this marginalised population with treatment. We describe the outcomes of risk-based screening and point-of-care anti-HCV testing for emergency department patients, and linkage to outpatient antiviral treatment.

METHODS

During the three-month study period, consecutive adult patients who presented to the emergency department during the study times were screened for risk factors and offered the OraQuick oral HCV antibody test. Those with reactive results were offered venepuncture in the emergency department for confirmatory testing and direct-acting antiviral treatment in clinic. The main outcome measures were the number and proportion of viremic participants that were linked to the hepatitis clinic, commenced treatment and achieved a sustained viral response. Secondary outcome measures were the proportion (%) of presentations screened that were oral antibody reactive, and the prevalence and type of HCV risk factors.

RESULTS

During the study period, 2408 of the 3931 (61%) presentations to the emergency department were eligible for screening. Of these 2408 patients, 1122 (47%) participated, 307 (13%) declined participation and 977 (41%) could not be approached during their time in the emergency department. Among the 1122 participants, 378 (34%) reported at least one risk factor. Subsequently, 368 (97%) of the 378 participants underwent OraQuick anti-HCV test, and 50 (14%) had a reactive result. A risk factor of ever having injected drugs was present in 44 (88%) of participants who were sero-positive. Of the 45 that had blood tested, 30 (67%) were HCV ribonucleic acid (RNA) positive. Three participants died. Of the 27 remaining participants, 10 (37%) commenced treatment and 7 of these 10 (70%) obtained a cure. There was a high rate of homelessness (24%) among anti-HCV positive participants.

CONCLUSION

Among emergency department participants with a risk factor for HCV, positive serology was common using a rapid point-of-care test. A history of injecting drug use was identified as the risk factor with highest yield for positive HCV serology, and is suitable as a single screening question. However, linkage to care post ED presentation was low in this marginalised population. There is a need for new pathways to improve the care cascade for marginalised individuals living with HCV infection.

Whole-genome sequencing reveals clinically relevant insights into the aetiology of familial breast cancers

BACKGROUND

Whole-genome sequencing (WGS) is a powerful method for revealing the diversity and complexity of the somatic mutation burden of tumours. Here, we investigated the utility of tumour and matched germline WGS for understanding aetiology and treatment opportunities for high-risk individuals with familial breast cancer.

PATIENTS AND METHODS

We carried out WGS on 78 paired germline and tumour DNA samples from individuals carrying pathogenic variants in BRCA1 (n = 26) or BRCA2 (n = 22) or from non-carriers (non-BRCA1/2; n = 30).

RESULTS

Matched germline/tumour WGS and somatic mutational signature analysis revealed patients with unreported, dual pathogenic germline variants in cancer risk genes (BRCA1/BRCA2; BRCA1/MUTYH). The strategy identified that 100% of tumours from BRCA1 carriers and 91% of tumours from BRCA2 carriers exhibited biallelic inactivation of the respective gene, together with somatic mutational signatures suggestive of a functional deficiency in homologous recombination. A set of non-BRCA1/2 tumours also had somatic signatures indicative of BRCA-deficiency, including tumours with BRCA1 promoter methylation, and tumours from carriers of a PALB2 pathogenic germline variant and a BRCA2 variant of uncertain significance. A subset of 13 non-BRCA1/2 tumours from early onset cases were BRCA-proficient, yet displayed complex clustered structural rearrangements associated with the amplification of oncogenes and pathogenic germline variants in TP53, ATM and CHEK2.

CONCLUSIONS

Our study highlights the role that WGS of matched germline/tumour DNA and the somatic mutational signatures can play in the discovery of pathogenic germline variants and for providing supporting evidence for variant pathogenicity. WGS-derived signatures were more robust than germline status and other genomic predictors of homologous recombination deficiency, thus impacting the selection of platinum-based or PARP inhibitor therapy. In this first examination of non-BRCA1/2 tumours by WGS, we illustrate the considerable heterogeneity of these tumour genomes and highlight that complex genomic rearrangements may drive tumourigenesis in a subset of cases.

Self-sharpening induces jet-like structure in seafloor gravity currents

Gravity currents are the primary means by which sediments, solutes and heat are transported across the ocean-floor. Existing theory of gravity current flow employs a statistically-stable model of turbulent diffusion that has been extant since the 1960s. Here we present the first set of detailed spatial data from a gravity current over a rough seafloor that demonstrate that this existing paradigm is not universal. Specifically, in contrast to predictions from turbulent diffusion theory, self-sharpened velocity and concentration profiles and a stable barrier to mixing are observed. Our new observations are explained by statistically-unstable mixing and self-sharpening, by boundary-induced internal gravity waves; as predicted by recent advances in fluid dynamics. Self-sharpening helps explain phenomena such as ultra-long runout of gravity currents and restricted growth of bedforms, and highlights increased geohazard risk to marine infrastructure. These processes likely have broader application, for example to wave-turbulence interaction, and mixing processes in environmental flows.

The current paradigm of material transport across the ocean-floor by gravity currents, is of turbulent flows with mixing processes analogous to rivers. However, uniquely high-resolution field data demonstrate that this paradigm is flawed and that gravity currents are analogous to self-organised atmospheric jets.

Automated analysis of fetal cardiac function using color tissue Doppler imaging in second half of normal pregnancy

OBJECTIVES

Color tissue Doppler imaging (cTDI) is a promising tool for the assessment of fetal cardiac function. However, the analysis of myocardial velocity traces is cumbersome and time-consuming, limiting its application in clinical practice. The aim of this study was to evaluate fetal cardiac function during the second half of pregnancy and to develop reference ranges using an automated method to analyze cTDI recordings from a cardiac four-chamber view.

METHODS

This was a cross-sectional study including 201 normal singleton pregnancies between 18 and 42 weeks of gestation. During fetal echocardiography, a four-chamber view of the heart was visualized and cTDI was performed. Regions of interest were positioned at the level of the atrioventricular plane in the left ventricular (LV), right ventricular (RV) and septal walls of the fetal heart, to obtain myocardial velocity traces that were analyzed offline using the automated algorithm. Peak myocardial velocities during atrial contraction (Am), ventricular ejection (Sm) and rapid ventricular filling, i.e. early diastole (Em), as well as the Em/Am ratio, mechanical cardiac time intervals and myocardial performance index (cMPI) were evaluated, and gestational age-specific reference ranges were constructed.

RESULTS

At 18 weeks of gestation, the peak myocardial velocities, presented as fitted mean with 95% CI, were: LV Am, 3.39 (3.09-3.70) cm/s; LV Sm, 1.62 (1.46-1.79) cm/s; LV Em, 1.95 (1.75-2.15) cm/s; septal Am, 3.07 (2.80-3.36) cm/s; septal Sm, 1.93 (1.81-2.06) cm/s; septal Em, 2.57 (2.32-2.84) cm/s; RV Am, 4.89 (4.59-5.20) cm/s; RV Sm, 2.31 (2.16-2.46) cm/s; and RV Em, 2.94 (2.69-3.21) cm/s. At 42 weeks of gestation, the peak myocardial velocities had increased to: LV Am, 4.25 (3.87-4.65) cm/s; LV Sm, 3.53 (3.19-3.89) cm/s; LV Em, 4.55 (4.18-4.94) cm/s; septal Am, 4.49 (4.17-4.82) cm/s; septal Sm, 3.36 (3.17-3.55) cm/s; septal Em, 3.76 (3.51-4.03) cm/s; RV Am, 6.52 (6.09-6.96) cm/s; RV Sm, 4.95 (4.59-5.32) cm/s; and RV Em, 5.42 (4.99-5.88) cm/s. The mechanical cardiac time intervals generally remained more stable throughout the second half of pregnancy, although, with increased gestational age, there was an increase in duration of septal and RV atrial contraction, LV pre-ejection and septal and RV ventricular ejection, while there was a decrease in duration of septal postejection. Regression equations used for the construction of gestational age-specific reference ranges for peak myocardial velocities, Em/Am ratios, mechanical cardiac time intervals and cMPI are presented.

CONCLUSION

Peak myocardial velocities increase with gestational age, while the mechanical time intervals remain more stable throughout the second half of pregnancy. Using an automated method to analyze cTDI-derived myocardial velocity traces, it was possible to construct reference ranges, which could be used in distinguishing between normal and abnormal fetal cardiac function. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.