Temporal relationship between atrial fibrillation and ischaemic stroke in a large cohort with continuous rhythm monitoring

Background/Introduction

Atrial fibrillation (AF) increases the risk of ischaemic stroke, but the temporal relationship is uncertain.

Purpose

To assess the temporal relationship between AF episodes and ischaemic stroke in patients with cardiovascular implantable electronic devices (CIED) utilizing a case-crossover analysis.

Methods

We linked a very large U.S. aggregated de-identified electronic health record database (2007–2017), containing claims for ischaemic stroke hospitalizations, to a manufacturer's CIED database with continuous AF monitoring. All stroke patients with ≥120 days of pre-stroke rhythm data were included. For each stroke patient, we compared the presence of a day with ≥5.5 hours of AF (the TRENDS study threshold) in the case period (days 1–30 pre-stroke) to that in the control period (days 91–120 pre-stroke). Matched analyses for dichotomous outcomes generated odds ratios with confidence intervals and p values.

Results

We identified 891 ischaemic stroke patients (71.3±10.5 years, 65% male, 27% pacemakers, 60% defibrillators, 13% insertable cardiac monitors) with continuous monitoring data in the 120 days pre-stroke. The vast majority had either no AF in both the case and control periods (n=682, 77%) or AF in both periods (n=143, 16%), i.e., non-informative records. However, among the 66 patients with informative, discordant arrhythmic states, 52 had AF in the case period versus 14 in the control period, for an odds ratio of 3.71 (95% C.I. 2.06–6.70, p<0.001). Analysed by 5-day periods, stroke risk was markedly increased within 30 days of the AF episode (figure). For days 1–5 following an AF episode, the odds ratio was 9.7 (95% C.I. 5.9–16.1). Risk diminished towards non-AF risk after 30 days.

Conclusion

Our analysis of this largest cohort with continuous rhythm monitoring prior to ischaemic stroke demonstrates that stroke risk is highest within a few days of an episode of AF and diminishes rapidly thereafter. Our findings support a strategy of time-limited anticoagulation for patients with infrequent episodes of AF and available continuous rhythm monitoring.

Funding Acknowledgement

Type of funding source: None

Congenital Pseudarthrosis of the Tibia: Results, at Skeletal Maturity, of the Charnley-Williams Procedure

Background

This study assessed the outcomes, at skeletal maturity, for 34 patients in whom congenital pseudarthrosis of the tibia (CPT) had been treated with intramedullary (IM) rod fixation.

Methods

The results in skeletally mature patients in whom type-4 CPT had been treated with an IM rod at an average of 11.9 years earlier were reviewed. The rod procedures varied according to whether both the tibia and the fibula were resected and both bones (type A) or just the tibia (type B) were fixed with an IM rod or whether only the tibia was resected and the fibula received no surgery (type C). Outcome grading ranged from unequivocal union with brace-free function (grade 1) to a functional limb with residual angulation or cortical defects (grade 2) to a severely impaired extremity with insufficient union or refracture (grade 3).

Results

Thirty-four patients were evaluated at a mean age of 16.9 years, a mean of 11.9 years after their initial surgical procedure. Seventeen patients had a grade-1 result; 11 patients, grade 2; and 6, grade 3. Thus, 82% (28) of the 34 patients had a functional extremity at maturity. All patients with a final grade-3 outcome eventually requested amputation. The final outcomes were not affected by the age at the initial fracture or surgery, the presence of neurofibromatosis-1, or cross-ankle fixation. A total of 58 IM rod procedures were performed in the 34 patients. Twenty-four (73%) of the 33 type-A procedures produced grade-1 or 2 outcomes, as did 14 (88%) of the 16 type-B procedures. Of the 9 type-C procedures, none produced a grade-1 result and 4 produced a grade-2 outcome. The results of types A and B combined were superior to those of type-C procedures (p = 0.03). Refracture occurred in 13 of 33 patients with initial stability/union after rod fixation, with 3 of those fractures remaining ununited at the latest follow-up. A dystrophic fibula had no effect on the eventual achievement of a grade-1 or 2 outcome.

Conclusions

This review, in which all patients had reached skeletal maturity, documents functional (grade-1 or 2) outcomes in 82% of cases of IM rod fixation for CPT. This finding was almost identical to the result in our earlier report and confirms the long-term value of permanent IM rod fixation in maintaining union and function in patients with CPT. Procedures not addressing the fibula produced inferior results. Although 13 patients had a refracture following initial union, only 3 of these fractures failed to heal with additional treatment.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Registry report of the prevalence of ECG abnormalities and their relation to patient characteristics in an asymptomatic population

BACKGROUND

Cardiovascular disease is the leading cause of morbidity and mortality in developed countries. Many patients do not experience symptoms before a first major cardiovascular event. Resting electrocardiogram (ECG) may help identify asymptomatic individuals with a high risk of cardiovascular disease.

OBJECTIVE

We sought to determine the prevalence of ECG abnormalities in an apparently symptom-free adult population within a prospective registry.

METHODS

The registry consisted of 4739 consecutive apparently healthy individuals [age 62.8 ± 6.2 (SD) years; 54% female], referred by their General Practitioners between 2009 and 2013. Patient demographics, and clinical data were obtained, alongside blood tests and a resting ECG.

RESULTS

ECG abnormalities were present in 1509 (31.8%) subjects and were commoner with increasing age (F = 0.161, p = 0.01), systolic (F = 0.134, p = 0.01) and diastolic (F = 0.44, p = 0.01) blood pressure and waist circumference (F = 0.53, p = 0.01). Left ventricular hypertrophy (LVH) was the most common abnormality (n = 281) and was positively associated with systolic (F = 0.12, p = 0.01) and diastolic blood pressure (F = 0.99, p = 0.01) and male gender (X2 = 60.5, p < 0.01). All ECG abnormalities (except for LVH) were associated with an increasing age, while right bundle branch block (F = 0.041, p = 0.01) and atrial fibrillation (n = 29; F = 0.036, p = 0.05) were associated with the presence of diabetes mellitus (n = 211). Only left bundle branch block (n = 50) was associated with angina (F = 0.05, p = 0.01).

CONCLUSIONS

Unrecognized cardiac abnormalities are common in middle-aged men and women with no overt symptoms. ECG offers the potential to identify these abnormalities and provide earlier intervention and treatment, and possibly improve cardiovascular outcome.

Putting patients at the center of kidney care transitions: PREPARE NOW, a cluster randomized controlled trial

Care for patients transitioning from chronic kidney disease to kidney failure often falls short of meeting patients' needs. The PREPARE NOW study is a cluster randomized controlled trial studying the effectiveness of a pragmatic health system intervention, 'Patient Centered Kidney Transition Care,' a multi-component health system intervention designed to improve patients' preparation for kidney failure treatment. Patient-Centered Kidney Transition Care provides a suite of new electronic health information tools (including a disease registry and risk prediction tools) to help providers recognize patients in need of Kidney Transitions Care and focus their attention on patients' values and treatment preferences. Patient-Centered Kidney Transition Care also adds a 'Kidney Transitions Specialist' to the nephrology health care team to facilitate patients' self-management empowerment, shared-decision making, psychosocial support, care navigation, and health care team communication. The PREPARE NOW study is conducted among eight [8] outpatient nephrology clinics at Geisinger, a large integrated health system in rural Pennsylvania. Four randomly selected nephrology clinics employ the Patient Centered Kidney Transitions Care intervention while four clinics employ usual nephrology care. To assess intervention effectiveness, patient reported, biomedical, and health system outcomes are collected annually over a period of 36 months via telephone questionnaires and electronic health records. The PREPARE NOW Study may provide needed evidence on the effectiveness of patient-centered health system interventions to improve nephrology patients' experiences, capabilities, and clinical outcomes, and it will guide the implementation of similar interventions elsewhere.

TRIAL REGISTRATION

NCT02722382.

How confident are physicians in deprescribing for the elderly and what barriers prevent deprescribing?

WHAT IS KNOWN AND OBJECTIVE

Deprescribing is the process of discontinuing or reducing the dosage of medications that are no longer appropriate or aligned with goals of care, which is paramount in elderly patients with multiple comorbidities and polypharmacy. The objective of this study was to assess the perceptions of primary care physicians on deprescribing for elderly patients and potential barriers to deprescribing that physicians experience in the Local Health Authority (LHA) of Parma, Emilia-Romagna, Italy.

METHODS

One hundred and sixty physicians (57% of the total number of primary care physicians in Parma) attended an educational session related to deprescribing and were asked to anonymously complete a paper survey. Participants were asked to assess their level of agreement on nine questions about their perception of deprescribing and potential factors affecting the deprescribing process using a seven-point Likert-type scale. A correlation coefficient was calculated to assess the association between physicians' confidence in deprescribing and attitudes or barriers associated with deprescribing.

RESULTS AND DISCUSSION

Many physicians (72%) reported general confidence in their ability to deprescribe. Most respondents (78%) reported they were comfortable deprescribing preventive medications, yet only half (53%) were comfortable deprescribing guideline-recommended therapies. Lack of evidence on discontinuing preventive medicines and concern about withdrawal side effects were reported to impede deprescribing by more than one-third of physicians. When medications were initially prescribed by another physician, 40% of physicians reported hesitance in deprescribing them. About half of physicians (45%) did not feel comfortable deprescribing when patients/caregivers believed that continuation of the medication was needed. Lack of time and difficulty engaging patients/caregivers in the deprescribing process were cited as barriers by about one in four physicians. There was no strong correlation between physicians' confidence and attitudes or barriers associated with deprescribing.

WHAT IS NEW AND CONCLUSION

The study results show that physicians believe they are generally comfortable with deprescribing, although there are still several factors that hamper their ability to engage in the process. An improved understanding of physicians' views on deprescribing may help guide further research, and policies to help patients remain healthy while streamlining their medication regimen.

[Acute Kidney Failure Due to Urachal Cyst?]

A 34-year-old para V woman was referred to our centre at 35+1 weeks of gestation for an assumed fetal malformation with prenatal renal impairment and anhydramnios. Prenatal ultrasound demonstrated unilateral renal agenesis; the bladder was not detectable. The baby was born by caesarian section at 36+2 weeks of gestation because of placental insufficiency. Postnatal adaptation was uneventful, but the newborn presented external stigmas of trisomy 21 and progressive renal impairment with anuria. Nevertheless, the postnatal ultrasound showed two enlarged kidneys in loco typico with impaired perfusion but without signs of malformations. In the lower abdomen, a rosette-shaped structure of unknown origin was noted. Its origin could not be cleared by imaging including voiding cystourethrography and colon contrast radiography. Explorative laparotomy identified the structure as a persistent urachal cyst with secondary obstruction of the upper urinary tract. After removal of the urachus with reconstruction of the bladder dome, renal function recovered completely while urine was drained continuously via suprapubic catheter. A voiding cystourethrogram 3 weeks later showed a posterior urethral valve as an additional unexpected diagnosis. The valve was slit at the age of 6 months without complications, the renal function remained stable in the further course. In retrospect, the main cause for the renal failure remains unclear. It appears to be the obstruction due to the space-consuming character of the urachal cyst, especially because the megacystis typically associated with urethral valve was not viewable. Alternatively, the additional proximal stenosis may have only masked the typical findings of PUV.

Nuclear Magnetic Resonance Structure of the APOBEC3B Catalytic Domain: Structural Basis for Substrate Binding and DNA Deaminase Activity

Human APOBEC3B (A3B) is a member of the APOBEC3 (A3) family of cytidine deaminases, which function as DNA mutators and restrict viral pathogens and endogenous retrotransposons. Recently, A3B was identified as a major source of genetic heterogeneity in several human cancers. Here, we determined the solution nuclear magnetic resonance structure of the catalytically active C-terminal domain (CTD) of A3B and performed detailed analyses of its deaminase activity. The core of the structure comprises a central five-stranded β-sheet with six surrounding helices, common to all A3 proteins. The structural fold is most similar to that of A3A and A3G-CTD, with the most prominent difference being found in loop 1. The catalytic activity of A3B-CTD is ∼15-fold lower than that of A3A, although both exhibit a similar pH dependence. Interestingly, A3B-CTD with an A3A loop 1 substitution had significantly increased deaminase activity, while a single-residue change (H29R) in A3A loop 1 reduced A3A activity to the level seen with A3B-CTD. This establishes that loop 1 plays an important role in A3-catalyzed deamination by precisely positioning the deamination-targeted C into the active site. Overall, our data provide important insights into the determinants of the activities of individual A3 proteins and facilitate understanding of their biological function.

Sequence and structural determinants of human APOBEC3H deaminase and anti-HIV-1 activities

Background

Human APOBEC3H (A3H) belongs to the A3 family of host restriction factors, which are cytidine deaminases that catalyze conversion of deoxycytidine to deoxyuridine in single-stranded DNA. A3 proteins contain either one (A3A, A3C, A3H) or two (A3B, A3D, A3F, A3G) Zn-binding domains. A3H has seven haplotypes (I-VII) that exhibit diverse biological phenotypes and geographical distribution in the human population. Its single Zn-coordinating deaminase domain belongs to a phylogenetic cluster (Z3) that is different from the Z1- and Z2-type domains in other human A3 proteins. A3H HapII, unlike A3A or A3C, has potent activity against HIV-1. Here, we sought to identify the determinants of A3H HapII deaminase and antiviral activities, using site-directed sequence- and structure-guided mutagenesis together with cell-based, biochemical, and HIV-1 infectivity assays.

Results

We have constructed a homology model of A3H HapII, which is similar to the known structures of other A3 proteins. The model revealed a large cluster of basic residues (not present in A3A or A3C) that are likely to be involved in nucleic acid binding. Indeed, RNase A pretreatment of 293T cell lysates expressing A3H was shown to be required for detection of deaminase activity, indicating that interaction with cellular RNAs inhibits A3H catalytic function. Similar observations have been made with A3G. Analysis of A3H deaminase substrate specificity demonstrated that a 5′ T adjacent to the catalytic C is preferred. Changing the putative nucleic acid binding residues identified by the model resulted in reduction or abrogation of enzymatic activity, while substituting Z3-specific residues in A3H to the corresponding residues in other A3 proteins did not affect enzyme function. As shown for A3G and A3F, some A3H mutants were defective in catalysis, but retained antiviral activity against HIV-1vif (−) virions. Furthermore, endogenous reverse transcription assays demonstrated that the E56A catalytic mutant inhibits HIV-1 DNA synthesis, although not as efficiently as wild type.

Conclusions

The molecular and biological activities of A3H are more similar to those of the double-domain A3 proteins than to those of A3A or A3C. Importantly, A3H appears to use both deaminase-dependent and -independent mechanisms to target reverse transcription and restrict HIV-1 replication.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-014-0130-8) contains supplementary material, which is available to authorized users.

Structural determinants of human APOBEC3A enzymatic and nucleic acid binding properties

Human APOBEC3A (A3A) is a single-domain cytidine deaminase that converts deoxycytidine residues to deoxyuridine in single-stranded DNA (ssDNA). It inhibits a wide range of viruses and endogenous retroelements such as LINE-1, but it can also edit genomic DNA, which may play a role in carcinogenesis. Here, we extend our recent findings on the NMR structure of A3A and report structural, biochemical and cell-based mutagenesis studies to further characterize A3A’s deaminase and nucleic acid binding activities. We find that A3A binds ssRNA, but the RNA and DNA binding interfaces differ and no deamination of ssRNA is detected. Surprisingly, with only one exception (G105A), alanine substitution mutants with changes in residues affected by specific ssDNA binding retain deaminase activity. Furthermore, A3A binds and deaminates ssDNA in a length-dependent manner. Using catalytically active and inactive A3A mutants, we show that the determinants of A3A deaminase activity and anti-LINE-1 activity are not the same. Finally, we demonstrate A3A’s potential to mutate genomic DNA during transient strand separation and show that this process could be counteracted by ssDNA binding proteins. Taken together, our studies provide new insights into the molecular properties of A3A and its role in multiple cellular and antiviral functions.

FACS-sorted particles reduce the data variance in optical tweezers-assisted dynamic force spectroscopy measurements

By combining optical tweezers-assisted dynamic force spectroscopy experiments with fluorescence activated cell sorting (FACS), we demonstrate a new approach to reducing the data variance in measuring receptor-ligand interactions on a single molecule level by ensuring similar coating densities. Therefore, the carboxyfluorescein-labelled monophosphorylated peptide tau226-240[pThr231] is anchored on melamine resin beads and these beads are sorted by FACS to achieve a homogeneous surface coverage. To quantify the impact of the fluorescence dye on the bond parameters between the phosphorylated peptide and the corresponding phosphorylation specific anti-human tau monoclonal antibody HPT-104, we perform dynamic force spectroscopy and compare the results to data using unsorted beads covered with the non-fluorescence peptide analogue. Finally, we demonstrate that the data variance of the relative binding frequency is significantly decreased by a factor of 3.4 using pre-sorted colloids with a homogeneous ligand coating compared to using unsorted colloids.

T-type amino acid transporter TAT1 (Slc16a10) is essential for extracellular aromatic amino acid homeostasis control

The uniporter TAT1 (Slc16a10) mediates the facilitated diffusion of aromatic amino acids (AAAs) across basolateral membranes of kidney, small intestine and liver epithelial cells, and across the plasma membrane of non-epithelial cells like skeletal myocytes. Its role for body AA homeostasis has now been investigated using newly generated TAT1 (Slc16a10) defective mice (tat1(-/-)). These mice grow and reproduce normally, show no gross phenotype and no obvious neurological defect. Histological analysis did not reveal abnormalities and there is no compensatory change in any tested AA transporter mRNA. TAT1 null mice, however, display increased plasma, muscle and kidney AAA concentration under both normal and high protein diet, although this concentration remains normal in the liver. A major aromatic aminoaciduria and a smaller urinary loss of all substrates additionally transported by l-type AA antiporter Lat2-4F2hc (Slc7a8) were revealed under a high protein diet. This suggests an epithelial transport defect as also shown by the accumulation of intravenously injected (123)I-2-I-l-Phe in kidney and l-[(3)H]Phe in ex vivo everted gut sac enterocytes. Taken together, these data indicate that the uniporter TAT1 is required to equilibrate the concentration of AAAs across specific membranes. For instance, it enables hepatocytes to function as a sink that controls the extracellular AAAs concentration. Additionally, it facilitates the release of AAAs across the basolateral membrane of small intestine and proximal kidney tubule epithelial cells, thereby allowing the efflux of other neutral AAs presumably via Lat2-4F2hc.

Defective intestinal amino acid absorption in Ace2 null mice

Mutations in the main intestinal and kidney luminal neutral amino acid transporter B(0)AT1 (Slc6a19) lead to Hartnup disorder, a condition that is characterized by neutral aminoaciduria and in some cases pellagra-like symptoms. These latter symptoms caused by low-niacin are thought to result from defective intestinal absorption of its precursor L-tryptophan. Since Ace2 is necessary for intestinal B(0)AT1 expression, we tested the impact of intestinal B(0)AT1 absence in ace2 null mice. Their weight gain following weaning was decreased, and Na(+)-dependent uptake of B(0)AT1 substrates measured in everted intestinal rings was defective. Additionally, high-affinity Na(+)-dependent transport of L-proline, presumably via SIT1 (Slc6a20), was absent, whereas glucose uptake via SGLT1 (Slc5a1) was not affected. Measurements of small intestine luminal amino acid content following gavage showed that more L-tryptophan than other B(0)AT1 substrates reach the ileum in wild-type mice, which is in line with its known lower apparent affinity. In ace2 null mice, the absorption defect was confirmed by a severalfold increase of L-tryptophan and of other neutral amino acids reaching the ileum lumen. Furthermore, plasma and muscle levels of glycine and L-tryptophan were significantly decreased in ace2 null mice, with other neutral amino acids displaying a similar trend. A low-protein/low-niacin diet challenge led to differential changes in plasma amino acid levels in both wild-type and ace2 null mice, but only in ace2 null mice to a stop in weight gain. Despite the combination of low-niacin with a low-protein diet, plasma niacin concentrations remained normal in ace2 null mice and no pellagra symptoms, such as photosensitive skin rash or ataxia, were observed. In summary, mice lacking Ace2-dependent intestinal amino acid transport display no total niacin deficiency nor clear pellagra symptoms, even under a low-protein and low-niacin diet, despite gross amino acid homeostasis alterations.

[Long-term survival of preterm neonates]

In view of the increased survival rate of very preterm neonates, several longitudinal studies were done to assess the quality of life of the survivors. They revealed a fairly constant rate of 25-30% of sensorineural and/or motor impairment. Beyond those "major handicaps," further problems may arise in every single period of life, which, albeit less severe, add to the burden of prematurity. These include growth retardation and cognitive delay in the school age, affected psychosocial behavior during adolescence, and the "metabolic syndrome" of formerly malnourished fetuses in adulthood. Thus, the epidemiologic studies not only confirmed the role of regionalization in the quality of perinatology, but also supported a more farsighted approach to the sequelae of prematurity. Like in young adults who grew up with congenital heart defects, also in former preterm neonates, appropriate medical care has to be provided for an increasing number of long-term survivors. Moreover, the life-long effects of metabolic imprinting in growth-retarded fetuses underline the primary-preventive role of perinatal medicine, extending far beyond the "baby" stage of human development.