Macromolecular condensation organizes nucleolar sub-phases to set up a pH gradient

Nucleoli are multicomponent condensates defined by coexisting sub-phases. We identified distinct intrinsically disordered regions (IDRs), including acidic (D/E) tracts and K-blocks interspersed by E-rich regions, as defining features of nucleolar proteins. We show that the localization preferences of nucleolar proteins are determined by their IDRs and the types of RNA or DNA binding domains they encompass. In vitro reconstitutions and studies in cells showed how condensation, which combines binding and complex coacervation of nucleolar components, contributes to nucleolar organization. D/E tracts of nucleolar proteins contribute to lowering the pH of co-condensates formed with nucleolar RNAs in vitro. In cells, this sets up a pH gradient between nucleoli and the nucleoplasm. By contrast, juxta-nucleolar bodies, which have different macromolecular compositions, featuring protein IDRs with very different charge profiles, have pH values that are equivalent to or higher than the nucleoplasm. Our findings show that distinct compositional specificities generate distinct physicochemical properties for condensates.

Dominance Analysis: A formalism to uncover dominant energetic contributions to biomolecular condensate formation in multicomponent systems

Phase separation in aqueous solutions of macromolecules is thought to underlie the generation of biomolecular condensates in cells. Condensates are membraneless bodies, representing dense, macromolecule-rich phases that coexist with the dilute, macromolecule-deficient phase. In cells, condensates comprise hundreds of different macromolecular and small molecule solutes. Do all components contribute equally or very differently to the driving forces for phase separation? Currently, we lack a coherent formalism to answer this question, a gap we remedy in this work through the introduction of a formalism we term energy dominance analysis. This approach rests on model-free analysis of shapes of the dilute arms of phase boundaries, slopes of tie lines, and changes to dilute phase concentrations in response to perturbations of concentrations of different solutes. We present the formalism that underlies dominance analysis, and establish its accuracy and flexibility by deploying it to analyse phase spaces probed in silico, in vitro , and in cellulo .

Metastable condensates suppress conversion to amyloid fibrils

Stress granules form via co-condensation of RNA binding proteins with prion-like low complexity domains (PLCDs) and RNA molecules released by stress-induced polysomal runoff. Homotypic interactions among PLCDs can drive amyloid fibril formation and this is enhanced by ALS-associated mutations. We find that homotypic interactions that drive condensation versus fibril formation are separable for A1-LCD, the PLCD of hnRNPA1. These separable interactions lead to condensates that are metastable versus fibrils that are globally stable. Metastable condensates suppress fibril formation, and ALS-associated mutations enhance fibril formation by weakening condensate metastability. Mutations designed to enhance A1-LCD condensate metastability restore wild-type behaviors of stress granules in cells even when ALS-associated mutations are present. This suggests that fibril formation can be suppressed by enhancing condensate metastability through condensate-driving interactions.

Sequence-specific interactions determine viscoelasticity and aging dynamics of protein condensates

Biomolecular condensates are viscoelastic materials. Here, we report results from investigations into molecular-scale determinants of sequence-encoded and age-dependent viscoelasticity of condensates formed by prion-like low-complexity domains (PLCDs). The terminally viscous forms of PLCD condensates are Maxwell fluids. Measured viscoelastic moduli of these condensates are reproducible using a Rouse-Zimm model that accounts for the network-like organization engendered by reversible physical crosslinks among PLCDs in the dense phase. Measurements and computations show that the strengths of aromatic inter-sticker interactions determine the sequence-specific amplitudes of elastic and viscous moduli as well as the timescales over which elastic properties dominate. PLCD condensates also undergo physical aging on sequence-specific timescales. This is driven by mutations to spacer residues that weaken the metastability of terminally viscous phases. The aging of PLCD condensates is accompanied by disorder-to-order transitions, leading to the formation of non-fibrillar, beta-sheet-containing, semi-crystalline, terminally elastic, Kelvin-Voigt solids. Our results suggest that sequence grammars, which refer to the identities of stickers versus spacers in PLCDs, have evolved to afford control over the metastabilities of terminally viscous fluid phases of condensates. This selection can, in some cases, render barriers for conversion from metastable fluids to globally stable solids to be insurmountable on functionally relevant timescales.

Single fluorogen imaging reveals distinct environmental and structural features of biomolecular condensates

Recent computations suggest that biomolecular condensates that form via macromolecular phase separation are network fluids featuring spatially inhomogeneous organization of the underlying molecules. Computations also point to unique conformations of molecules at condensate interfaces. Here, we test these predictions using high-resolution structural characterizations of condensates formed by intrinsically disordered prion-like low complexity domains (PLCDs). We leveraged the localization and orientational preferences of freely diffusing fluorogens and the solvatochromic effect whereby specific fluorogens are turned on in response to the physic-chemical properties of condensate microenvironments to facilitate single-molecule tracking and super-resolution imaging. We deployed three different fluorogens to probe internal microenvironments and molecular organization of PLCD condensates. The spatiotemporal resolution and environmental sensitivity afforded by single-fluorogen imaging shows that the internal environments of condensates are more hydrophobic than coexisting dilute phases. Molecules within condensates are organized in a spatially inhomogeneous manner featuring slow-moving nanoscale molecular clusters or hubs that coexist with fast-moving molecules. Finally, molecules at interfaces of condensates are found to have distinct orientational preferences when compared to the interiors. Our findings, which affirm computational predictions, help provide a structural basis for condensate viscoelasticity and dispel the notion of protein condensates being isotropic liquids defined by uniform internal densities.

A Deep Learning-Based Approach to Estimate Paneth Cell Granule Area in Celiac Disease

CONTEXT.—

Changes in Paneth cell numbers can be associated with chronic inflammatory diseases of the gastrointestinal tract. So far, no consensus has been achieved on the number of Paneth cells and their relevance to celiac disease (CD).

OBJECTIVES.—

To compare crypt and Paneth cell granule areas between patients with CD and without CD (non-CD) using an artificial intelligence-based solution.

DESIGN.—

Hematoxylin-eosin-stained sections of duodenal biopsies from 349 patients at the McGill University Health Centre were analyzed. Of these, 185 had a history of CD and 164 were controls. Slides were digitized and NoCodeSeg, a code-free workflow using open-source software (QuPath, DeepMIB), was implemented to train deep learning models to segment crypts and Paneth cell granules. The total area of the entire analyzed tissue, epithelium, crypts, and Paneth cell granules was documented for all slides, and comparisons were performed.

RESULTS.—

A mean intersection-over-union score of 88.76% and 91.30% was achieved for crypt areas and Paneth cell granule segmentations, respectively. On normalization to total tissue area, the crypt to total tissue area in CD was increased and Paneth cell granule area to total tissue area decreased when compared to non-CD controls.

CONCLUSIONS.—

Crypt hyperplasia was confirmed in CD compared to non-CD controls. The area of Paneth cell granules, an indirect measure of Paneth cell function, decreased with increasing severity of CD. More importantly, our study analyzed complete hematoxylin-eosin slide sections using an efficient and easy to use coding-free artificial intelligence workflow.

Establishment of persistent enteric mycobacterial infection following streptomycin pre-treatment

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis, a chronic gastrointestinal disease affecting ruminants. This disease remains widespread in part due to the limitations of available diagnostics and vaccines. A representative small animal model of disease could act as a valuable tool for studying its pathogenesis and to develop new methods for paratuberculosis control, but current models are lacking. Streptomycin pre-treatment can reduce colonization resistance and has previously been shown to improve enteric infection in a Salmonella model. Here, we investigated whether streptomycin pre-treatment of mice followed by MAP gavage could act as a model of paratuberculosis which mimics the natural route of infection and disease development in ruminants. The infection outcomes of MAP were compared to M. avium subsp. hominissuis (MAH), an environmental mycobacterium, and M. bovis and M. orygis, two tuberculous mycobacteria. Streptomycin pre-treatment was shown to consistently improve bacterial infection post-oral inoculation. This model led to chronic MAP infection of the intestines and mesenteric lymph nodes (MLNs) up to 24-weeks post-gavage, however there was no evidence of inflammation or disease. These infection outcomes were found to be specific to MAP. When the model was applied to a bacterium of lesser virulence MAH, the infection was comparatively transient. Mice infected with bacteria of greater virulence, M. bovis or M. orygis, developed chronic intestinal and MLN infection with pulmonary disease similar to zoonotic TB. Our findings suggest that a streptomycin pre-treatment mouse model could be applied to future studies to improve enteric infection with MAP and to investigate other modifications underlying MAP enteritis.

Phase separation of protein mixtures is driven by the interplay of homotypic and heterotypic interactions

Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via phase separation coupled to percolation. Intracellular condensates often encompass numerous distinct proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA-binding proteins, hnRNPA1 and FUS. Using simulations and experiments, we find that 1:1 mixtures of A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own due to complementary electrostatic interactions. Tie line analysis reveals that stoichiometric ratios of different components and their sequence-encoded interactions contribute jointly to the driving forces for condensate formation. Simulations also show that the spatial organization of PLCDs within condensates is governed by relative strengths of homotypic versus heterotypic interactions. We uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins.

Early versus Delayed Surgery in Patients with Left-Sided Infective Endocarditis and Stroke

BACKGROUND

Timing of surgery remains controversial in patients with infective endocarditis and stroke. Guidelines on infective endocarditis suggest delaying surgery for up to 4 weeks. However, with early heart failure due to progression of the infection or recurrent septic embolism, urgent surgery becomes imperative.

METHODS

Out of 688 patients who were surgically treated for left-sided infective endocarditis, 187 presented with preoperative neurological events. The date of cerebral stroke onset was documented in 147 patients. The patients were stratified according to timing of surgery: 61 in the early group (0-7 days) vs. 86 in the delayed group (>7 days). Postoperative neurological outcome was assessed by the modified Rankin Scale.

RESULTS

Preoperative sepsis was more prevalent in patients with preoperative neurological complications (46.0% vs. 29.5%, p < 0.001). Patients with haemorrhagic stroke were operated on later (19.8% vs. 3.3%, p = 0.003). Postoperative cerebrovascular accidents were comparable between both groups (p = 0.13). Overall, we observed good neurological outcomes (p = 0.80) and a high recovery rate, with only 5% of cases showing neurological deterioration after surgery (p = 0.29). In-hospital mortality and long-term survival were not significantly different in the early and delayed surgery groups (log-rank, p = 0.22).

CONCLUSIONS

Early valve surgery in high-risk patients with infective endocarditis and stroke can be performed safely and is not associated with worse outcomes.

FIREBALL: A tool to fit protein phase diagrams based on mean-field theories for polymer solutions

Biomolecular condensates form via phase transitions of condensate-specific biomacromolecules. Intrinsically disordered regions (IDRs) featuring the appropriate sequence grammar can contribute homotypic and heterotypic interactions to the driving forces for phase separation of multivalent proteins. Experiments and computations have matured to the point where the concentrations of coexisting dense and dilute phases can be measured or computed for individual IDRs in complex milieus. For a macromolecule such as a disordered protein in a solvent, the locus of points that connects concentrations of the two coexisting phases defines a phase boundary or binodal. Often, only a few points along the binodal are accessible via measurements. In such cases and for quantitative and comparative analysis of parameters that describe the driving forces for phase separation, it is useful to fit measured or computed binodals to well-known mean-field free energies for polymer solutions. The non-linearity of the underlying free energy functions makes it challenging to put mean-field theories into practice. Here, we present FIREBALL, a suite of computational tools designed to enable efficient construction, analysis, and fitting to experimental or computed data of binodals. We show that depending on the theory being used, one can also extract information regarding coil-to-globule transitions of individual macromolecules. Statement of Significance Macromolecular phase separation drives the assembly of membraneless bodies known as biomolecular condensates. Measurements and computer simulations are being brought to bear to quantify how the concentrations of macromolecules in coexisting dilute and dense phases vary with changes to solution conditions. These mappings can be fit to analytical expressions for free energies of solution to extract information regarding parameters that enable comparative assessments of the balance of macromolecule-solvent interactions across different systems. The underlying free energies are non-linear and fitting them to data can become non-trivial. To enable comparative numerical analyses, we introduce FIREBALL, a user-friendly suite of computational tools that allows one to generate, analyze, and fit phase diagrams and coil-to-globule transitions using well-known theories.

Phase Separation in Mixtures of Prion-Like Low Complexity Domains is Driven by the Interplay of Homotypic and Heterotypic Interactions

Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via coupled associative and segregative phase transitions. We previously deciphered how evolutionarily conserved sequence features drive phase separation of PLCDs through homotypic interactions. However, condensates typically encompass a diverse mixture of proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA binding proteins namely, hnRNPA1 and FUS. We find that 1:1 mixtures of the A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own. The enhanced driving forces for phase separation of mixtures of A1-LCD and FUS-LCD arise partly from complementary electrostatic interactions between the two proteins. This complex coacervation-like mechanism adds to complementary interactions among aromatic residues. Further, tie line analysis shows that stoichiometric ratios of different components and their sequence-encoded interactions jointly contribute to the driving forces for condensate formation. These results highlight how expression levels might be tuned to regulate the driving forces for condensate formation in vivo . Simulations also show that the organization of PLCDs within condensates deviates from expectations based on random mixture models. Instead, spatial organization within condensates will reflect the relative strengths of homotypic versus heterotypic interactions. We also uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins. Overall, our findings emphasize the network-like organization of molecules within multicomponent condensates, and the distinctive, composition-specific conformational features of condensate interfaces.

Programmable synthetic biomolecular condensates for cellular control

The formation of biomolecular condensates mediated by a coupling of associative and segregative phase transitions plays a critical role in controlling diverse cellular functions in nature. This has inspired the use of phase transitions to design synthetic systems. While design rules of phase transitions have been established for many synthetic intrinsically disordered proteins, most efforts have focused on investigating their phase behaviors in a test tube. Here, we present a rational engineering approach to program the formation and physical properties of synthetic condensates to achieve intended cellular functions. We demonstrate this approach through targeted plasmid sequestration and transcription regulation in bacteria and modulation of a protein circuit in mammalian cells. Our approach lays the foundation for engineering designer condensates for synthetic biology applications.

FIREBALL: A tool to fit protein phase diagrams based on mean-field theories for polymer solutions

Biomolecular condensates form via phase transitions of condensate-specific biomacromolecules. Intrinsically disordered regions (IDRs) featuring the appropriate sequence grammar can contribute homotypic and heterotypic interactions to the driving forces for phase separation of multivalent proteins. At this juncture, experiments and computations have matured to the point where the concentrations of coexisting dense and dilute phases can be quantified for individual IDRs in complex milieus both in vitro and in vivo . For a macromolecule such as a disordered protein in a solvent, the locus of points that connects concentrations of the two coexisting phases defines a phase boundary or binodal. Often, only a few points along the binodal, especially in the dense phase, are accessible for measurement. In such cases and for quantitative and comparative analysis of parameters that describe the driving forces for phase separation, it is useful to fit measured or computed binodals to well-known mean-field free energies for polymer solutions. Unfortunately, the non-linearity of the underlying free energy functions makes it challenging to put mean-field theories into practice. Here, we present FIREBALL, a suite of computational tools designed to enable efficient construction, analysis, and fitting to experimental or computed data of binodals. We show that depending on the theory being used, one can also extract information regarding coil-to-globule transitions of individual macromolecules. Here, we emphasize the ease-of-use and utility of FIREBALL using examples based on data for two different IDRs.

Statement of Significance

Macromolecular phase separation drives the assembly of membraneless bodies known as biomolecular condensates. Measurements and computer simulations can now be brought to bear to quantify how the concentrations of macromolecules in coexisting dilute and dense phases vary with changes to solution conditions. These mappings can be fit to analytical expressions for free energies of solution to extract information regarding parameters that enable comparative assessments of the balance of macromolecule-solvent interactions across different systems. However, the underlying free energies are non-linear and fitting them to actual data is non-trivial. To enable comparative numerical analyses, we introduce FIREBALL, a user-friendly suite of computational tools that allows one to generate, analyze, and fit phase diagrams and coil-to-globule transitions using well-known theories.

Phase Separation in Mixtures of Prion-Like Low Complexity Domains is Driven by the Interplay of Homotypic and Heterotypic Interactions

Prion-like low-complexity domains (PLCDs) are involved in the formation and regulation of distinct biomolecular condensates that form via coupled associative and segregative phase transitions. We previously deciphered how evolutionarily conserved sequence features drive phase separation of PLCDs through homotypic interactions. However, condensates typically encompass a diverse mixture of proteins with PLCDs. Here, we combine simulations and experiments to study mixtures of PLCDs from two RNA binding proteins namely, hnRNPA1 and FUS. We find that 1:1 mixtures of the A1-LCD and FUS-LCD undergo phase separation more readily than either of the PLCDs on their own. The enhanced driving forces for phase separation of mixtures of A1-LCD and FUS-LCD arise partly from complementary electrostatic interactions between the two proteins. This complex coacervation-like mechanism adds to complementary interactions among aromatic residues. Further, tie line analysis shows that stoichiometric ratios of different components and their sequence-encoded interactions jointly contribute to the driving forces for condensate formation. These results highlight how expression levels might be tuned to regulate the driving forces for condensate formation in vivo . Simulations also show that the organization of PLCDs within condensates deviates from expectations based on random mixture models. Instead, spatial organization within condensates will reflect the relative strengths of homotypic versus heterotypic interactions. We also uncover rules for how interaction strengths and sequence lengths modulate conformational preferences of molecules at interfaces of condensates formed by mixtures of proteins. Overall, our findings emphasize the network-like organization of molecules within multicomponent condensates, and the distinctive, composition-specific conformational features of condensate interfaces.

Significance Statement

Biomolecular condensates are mixtures of different protein and nucleic acid molecules that organize biochemical reactions in cells. Much of what we know about how condensates form comes from studies of phase transitions of individual components of condensates. Here, we report results from studies of phase transitions of mixtures of archetypal protein domains that feature in distinct condensates. Our investigations, aided by a blend of computations and experiments, show that the phase transitions of mixtures are governed by a complex interplay of homotypic and heterotypic interactions. The results point to how expression levels of different protein components can be tuned in cells to modulate internal structures, compositions, and interfaces of condensates, thus affording distinct ways to control the functions of condensates.

Phase Transitions of Associative Biomacromolecules

Multivalent proteins and nucleic acids, collectively referred to as multivalent associative biomacromolecules, provide the driving forces for the formation and compositional regulation of biomolecular condensates. Here, we review the key concepts of phase transitions of aqueous solutions of associative biomacromolecules, specifically proteins that include folded domains and intrinsically disordered regions. The phase transitions of these systems come under the rubric of coupled associative and segregative transitions. The concepts underlying these processes are presented, and their relevance to biomolecular condensates is discussed.

Condensates formed by prion-like low-complexity domains have small-world network structures and interfaces defined by expanded conformations

Biomolecular condensates form via coupled associative and segregative phase transitions of multivalent associative macromolecules. Phase separation coupled to percolation is one example of such transitions. Here, we characterize molecular and mesoscale structural descriptions of condensates formed by intrinsically disordered prion-like low complexity domains (PLCDs). These systems conform to sticker-and-spacers architectures. Stickers are cohesive motifs that drive associative interactions through reversible crosslinking and spacers affect the cooperativity of crosslinking and overall macromolecular solubility. Our computations reproduce experimentally measured sequence-specific phase behaviors of PLCDs. Within simulated condensates, networks of reversible inter-sticker crosslinks organize PLCDs into small-world topologies. The overall dimensions of PLCDs vary with spatial location, being most expanded at and preferring to be oriented perpendicular to the interface. Our results demonstrate that even simple condensates with one type of macromolecule feature inhomogeneous spatial organizations of molecules and interfacial features that likely prime them for biochemical activity.

Quantifying Coexistence Concentrations in Multi-Component Phase-Separating Systems Using Analytical HPLC

Over the last decade, evidence has accumulated to suggest that numerous instances of cellular compartmentalization can be explained by the phenomenon of phase separation. This is a process by which a macromolecular solution separates spontaneously into dense and dilute coexisting phases. Semi-quantitative, in vitro approaches for measuring phase boundaries have proven very useful in determining some key features of biomolecular condensates, but these methods often lack the precision necessary for generating quantitative models. Therefore, there is a clear need for techniques that allow quantitation of coexisting dilute and dense phase concentrations of phase-separating biomolecules, especially in systems with more than one type of macromolecule. Here, we report the design and deployment of analytical High-Performance Liquid Chromatography (HPLC) for in vitro separation and quantification of distinct biomolecules that allows us to measure dilute and dense phase concentrations needed to reconstruct coexistence curves in multicomponent mixtures. This approach is label-free, detects lower amounts of material than is accessible with classic UV-spectrophotometers, is applicable to a broad range of macromolecules of interest, is a semi-high-throughput technique, and if needed, the macromolecules can be recovered for further use. The approach promises to provide quantitative insights into the balance of homotypic and heterotypic interactions in multicomponent phase-separating systems.

Relationship between coronary stenosis severity and high shear thrombosis assessment in vitro

Funding Acknowledgements

Type of funding sources: None.

Among stable outpatients presenting with suspected coronary artery disease, the presence and extent of coronary artery calcification (CAC) and the severity of disease on CT coronary angiography (CTCA) has been shown to be predictive of future major adverse cardiovascular events (MACE) including myocardial infarction (MI). In stable patients, high on-treatment platelet reactivity has also been shown to relate to an increased risk of MACE including MI. The relationship between thrombotic markers in peripheral blood and the extent of CAC and coronary disease severity, is unknown.

It was the aim of this pilot study to assess the relationship between thrombotic status and the extent of CAC and severity of coronary stenosis on CT.

Subjects with suspected coronary disease undergoing CTCA and CAC were invited to participate in this observational study. Venous blood was obtained to assess platelet reactivity to high shear (occlusion time, OT) and endogenous fibrinolysis (lysis time, LT) using the Global Thrombosis Test, and related to CAC and to maximum stenosis in any main coronary artery on CTCA.

Eighty patients were recruited, specifically 20 patients from each CAC quartile (adjusted for age, gender and ethnicity), 58% were male, aged 61±10 y. Groups were matched for age, sex, diabetes, and hs-CRP. The median Agatson CAC score was 27 [interquartile range (IQR) 0.5-125.5] and in each quartile (Q) as follows: Q1 0[0-0]; Q2 17[6-51.5]; Q3 70.25[26-111.5] and Q4 192.6[70.5-413.5].

Patients were divided into 4 groups according to maximal severity of coronary stenosis on CTCA (0%, 1-49%, 50-69%, &gt;70%). With increasing stenosis severity, we found patients exhibited less efficient endogenous fibrinolysis (longer LT) (LT 1728s[1512-2102] vs. 2028s[1687-2288] vs. 1728s[1634-1927] vs. 2524s[2425-2623] respectively, p=0.040) whilst platelet reactivity appeared unrelated to severity of coronary stenosis (438s[341-479] vs. 415s[357-484] vs. 444s[384-504] vs. 391s[357-425], p=0.907).

Platelet reactivity (OT 430s[339-477] vs. 458s[391-499] vs. 409s[351-488] vs. 413s[354-496], p=0.76) and spontaneous fibrinolysis (LT 1754s[1548-2162] vs. 1809s[1635-2291] vs. 2111s[1838-2312] vs. 1846s[1666-2090], p=0.253) were similar between the quartiles. Furthermore, there was no difference in platelet reactivity (430s[339-477] vs. 413s[354-496], p=0.830) or spontaneous fibrinolysis (1754s[1548-2162] vs. 1846s[1666-2090], p=0.561) when comparing patients within the lowest and the highest quartiles of CAC.

The severity of maximal coronary stenosis, but not the extent of CAC, is related to the effectiveness of spontaneous fibrinolysis at high shear in vitro, with patients with more severe stenoses exhibiting less efficient fibrinolysis. Further studies are required to investigate whether the extent of in vivo coronary shear (related to plaque morphology) can be reflected by the assessment of thrombosis and fibrinolysis in response to high shear in vitro.

Diurnal Variation in thrombolytic status in patients presenting with STEMI

Funding Acknowledgements

Type of funding sources: None.

Background

Prior studies mainly in healthy volunteers and patients with stable coronary artery disease (CAD) indicate circadian variation in spontaneous fibrinolytic activity. This is predominantly attributable to changes plasminogen activator inhibitor-1 (PAI-1) levels peaking between midnight and 06:00 hr, with a nadir at 18:00 hr. Whether circadian variation in spontaneous fibrinolysis exists amongst patients with ST-elevation myocardial infarction (STEMI) is unknown.

Purpose

It was our aim to assess circadian variation in fibrinolytic status in the acute setting in patients presenting with STEMI.

Methods

A prospective, observational study was conducted in patients presenting with STEMI for primary percutaneous coronary intervention (PPCI). Blood was tested on arrival pre-PPCI, after aspirin and P2Y12 inhibitor administration, but before any anticoagulant or antithrombotic agent administration in the cardiac cath lab. Venous blood was assessed to determine endogenous fibrinolysis using the Global Thrombosis Test, which utilises non-anticoagulated blood to assess the formation of an occlusive thrombus under high shear and the time taken for spontaneous restart of flow as a measure of endogenous fibrinolysis (lysis time, LT).

Results

A total of 527 patients were included, aged 64±13 years and 78% were male. 304 (58%) patients presented within working hours (08:00-17:00) with peak presentation between 11:00-12:00 and trough between 03:00 to 05:00 hrs.

Lysis time was not related to time of presentation. Time of presentation was divided into 4 groups (A 00:00-05:59, B 06:00-11:59, C 12:00-17:59, D 18:00-23:59 hrs). There was no significant difference in LT between patients presenting at the 4 timepoints (median 1362s [interquartile range IQR 1077-1808] vs 1503s [1182-2056] vs 1440s [1164-1998] vs. 1420s [1125-1820], respectively, p=0.340). When comparing Group A to C, the LT was not significantly different (1362s [1077-1808] vs. 1440 [1164-1998], p=0.413). The presentation time of patients with impaired endogenous fibrinolysis (LT&gt;3000 sec) did not differ significantly from patients with normal endogenous fibrinolysis. The hourly variation was similar in diabetics and non-diabetics, but the variation in lysis time appeared blunted in patients taking long term aspirin prior to presentation compared to non-aspirin takers.

Conclusion

In contrast to the known circadian variation in fibrinolysis in normal volunteers, and stable CAD, in our large cohort of STEMI patients, there appears to be no relationship between time of presentation/onset of STEMI and the effectiveness spontaneous fibrinolysis. This is reflected in our observation, supported by most contemporary studies, that peak time of STEMI presentation is during the late morning, and this does not relate to known circadian variation in fibrinolysis markers in CAD.

Indications, Complications, and Outcomes of Cardiac Surgery After Heart Transplantation: Results From the Cash Study

Background

Allograft pathologies, such as valvular, coronary artery, or aortic disease, may occur early and late after cardiac transplantation. Cardiac surgery after heart transplantation (CASH) may be an option to improve quality of life and allograft function and prolong survival. Experience with CASH, however, has been limited to single-center reports.

Methods

We performed a retrospective, multicenter study of heart transplant recipients with CASH between January 1984 and December 2020. In this study, 60 high-volume cardiac transplant centers were invited to participate.

Results

Data were available from 19 centers in North America (n = 7), South America (n = 1), and Europe (n = 11), with a total of 110 patients. A median of 3 (IQR 2–8.5) operations was reported by each center; five centers included ≥ 10 patients. Indications for CASH were valvular disease (n = 62), coronary artery disease (CAD) (n = 16), constrictive pericarditis (n = 17), aortic pathology (n = 13), and myxoma (n = 2). The median age at CASH was 57.7 (47.8–63.1) years, with a median time from transplant to CASH of 4.4 (1–9.6) years. Reoperation within the first year after transplantation was performed in 24.5%. In-hospital mortality was 9.1% (n = 10). 1-year survival was 86.2% and median follow-up was 8.2 (3.8–14.6) years. The most frequent perioperative complications were acute kidney injury and bleeding revision in 18 and 9.1%, respectively.

Conclusion

Cardiac surgery after heart transplantation has low in-hospital mortality and postoperative complications in carefully selected patients. The incidence and type of CASH vary between international centers. Risk factors for the worse outcome are higher European System for Cardiac Operative Risk Evaluation (EuroSCORE II) and postoperative renal failure.

Deciphering how naturally occurring sequence features impact the phase behaviours of disordered prion-like domains

Prion-like low-complexity domains (PLCDs) have distinctive sequence grammars that determine their driving forces for phase separation. Here we uncover the physicochemical underpinnings of how evolutionarily conserved compositional biases influence the phase behaviour of PLCDs. We interpret our results in the context of the stickers-and-spacers model for the phase separation of associative polymers. We find that tyrosine is a stronger sticker than phenylalanine, whereas arginine is a context-dependent auxiliary sticker. In contrast, lysine weakens sticker-sticker interactions. Increasing the net charge per residue destabilizes phase separation while also weakening the strong coupling between single-chain contraction in dilute phases and multichain interactions that give rise to phase separation. Finally, glycine and serine residues act as non-equivalent spacers, and thus make the glycine versus serine contents an important determinant of the driving forces for phase separation. The totality of our results leads to a set of rules that enable comparative estimates of composition-specific driving forces for PLCD phase separation.

Deciphering how naturally occurring sequence features impact the phase behaviours of disordered prion-like domains

Prion-like low-complexity domains (PLCDs) have distinctive sequence grammars that determine their driving forces for phase separation. Here we uncover the physicochemical underpinnings of how evolutionarily conserved compositional biases influence the phase behaviour of PLCDs. We interpret our results in the context of the stickers-and-spacers model for the phase separation of associative polymers. We find that tyrosine is a stronger sticker than phenylalanine, whereas arginine is a context-dependent auxiliary sticker. In contrast, lysine weakens sticker-sticker interactions. Increasing the net charge per residue destabilizes phase separation while also weakening the strong coupling between single-chain contraction in dilute phases and multichain interactions that give rise to phase separation. Finally, glycine and serine residues act as non-equivalent spacers, and thus make the glycine versus serine contents an important determinant of the driving forces for phase separation. The totality of our results leads to a set of rules that enable comparative estimates of composition-specific driving forces for PLCD phase separation.

Internal Bleeding Extending to the Retroperitoneum and Right Psoas With Severe Acute Respiratory Syndrome Coronavirus 2 Infection

Coronavirus disease 2019 (COVID-19 - severe acute respiratory syndrome coronavirus 2 {SARS-CoV-2}) infection has been associated with thromboembolic events and coagulopathy, leading to a surge in the use of anticoagulants. The dose and duration of therapy differ according to the followed protocol. Several case reports documented fatal bleeding as an adverse effect of anticoagulation. We report a case of nearly fatal retroperitoneal bleed in an otherwise healthy 60-year-old man who developed severe COVID-19 requiring ICU stay and mechanical ventilation. The development of retroperitoneal bleed led to a 50% drop in his hemoglobin. The patient happens to be a Jehovah's Witness, and the family refused blood transfusion, which added to the complexity of the situation. Anticoagulation is associated with a potential risk of fatal bleed in critically ill COVID-19 patients. There are different protocols of anticoagulation in the management of SARS-CoV-2. The risk of bleeding vs thrombosis should be weighed on a case-by-case basis. A high degree of suspicion, early intervention, and knowledge of alternatives to blood transfusion can improve outcomes.

In-hospital clinical outcomes of percutaneous coronary intervention for patients deemed ineligible for surgical revascularization

Background

Ineligibility for surgical revascularization remains subjective with limited data. Coronary artery bypass graft surgery (CABG)-ineligible patients usually have a high prevalence of risk factors and complex coronary disease, which lead to worse clinical outcomes.

Aim

We aimed to evaluate CABG surgical ineligibility reasons and in-hospital percutaneous coronary intervention (PCI) outcomes at a large tertiary centre.

Methods

Anonymized, prospectively collected data from the institutional electronic records between April 2013 and November 2020 were analysed retrospectively. All patients who were formally turned down for CABG and had PCI were included.

Results

There were 473 patients in total. Perceived frailty of the patient with associated comorbidities and/or the quality of distal coronary arteries were the main documented reasons for surgical ineligibility in 52.4% of patients. Mean age was 72±11 years, mean body mass index was 29±6 kg/m2 and 69.8% were male. Stable angina constituted 216 patients (45.7%) and 257 patients (54.3%) had acute coronary syndromes. Mean hospital stay was 4±5 days. Procedural success was documented in 457 out of 473 patients (96.6%). PCI adjunctive tools included coronary imaging in 97 patients (20.5%), rotational atherectomy in 96 patients (20.3%), laser atherectomy in 12 patients (2.5%), lithotripsy in 3 patients (0.6%) and physiological assessments in 34 patients (7.2%). In-hospital major adverse cardiac events were experienced in 32 patients (6.8%), death in 12 patients (2.5%), myocardial infarction in 21 patients (4.4%), ischaemic stroke in 1 patient (0.2%), coronary perforation in 7 patients (1.5%), repeat target vessel revascularization in 6 patients (1.3%), major access-site bleeding in 2 patients (0.4%), aortic dissection in 1 patient (0.2%) and new acute kidney injury requiring dialysis in 1 patient (0.2%).

Conclusions

PCI in surgically ineligible patients is generally safe and effective. The process of determining suitability for surgical revascularization remains complex in the real-world.

Funding Acknowledgement

Type of funding sources: None.

Positive predictive value of CT coronary angiography vs. CT fractional flow reserve in a real-world population

Background

Computerised tomography coronary angiography and fractional flow reserve (CTCA and CT-FFR) are non-invasive diagnostic tools for the detection of flow limiting coronary artery stenoses. Although their negative predictive values are well established, there is a concern that the high sensitivity of these tests may lead to overestimation of coronary artery disease (CAD) and unnecessary invasive coronary angiography (ICA). We compared the positive predictive value (PPV) of CT-FFR with computerised tomography coronary angiography (CTCA) against the gold standard of ICA in different real-world patient groups.

Methods

We conducted a retrospective study of 477 patients referred for CTCA or CT-FFR for investigation of possible coronary ischaemia. Patients were excluded if the image quality was poor or inconclusive. Patient-based PPV was calculated to detect or rule out significant CAD, defined as more than 70% stenosis on ICA. A sub-analysis of PPV by indication for scan was also performed. Patients that underwent invasive non-hyperaemic pressure wire measurements had their iFR or RFR compared with their CT-FFR values.

Results

In a patient-based analysis, the overall PPV was 59.3% for CTCA and 76.2% for CT-FFR. This increased to 81.0% and 86.7% respectively for patients with stable angina symptoms. In patients with atypical angina symptoms, CT-FFR considerably outperformed CTCA with a PPV of 61.3% vs. 37.5%. There was not a linear relationship between invasive pressure wire measurement and CT-FFR value (r=0.23, p=0.265).

Conclusion

The PPV of CTCA and CT-FFR is lower in the real-world than in previously published trials, partly due to the heterogeneity of indication for the scan. However, in patients with typical angina symptoms, both are reliable diagnostic tools to determine the presence of clinically significant coronary stenoses. CT-FFR significantly outperforms CTCA in patients with more atypical symptoms and the targeted use of CT-FFR in this group may help to avoid unnecessary invasive procedures.

Funding Acknowledgement

Type of funding sources: None.

Early outcomes of patients with Marfan syndrome and acute aortic type A dissection

BACKGROUND

Acute aortic Stanford type A dissection remains a frequent and life-limiting event for patients with Marfan syndrome. Outcome results in this high-risk group are limited.

METHODS

The German Registry for Acute Aortic Dissection Type A collected the data of 56 centers between July 2006 and June 2015. Of 3385 patients undergoing operations for acute aortic Stanford type A dissection, 117 (3.5%) were diagnosed with Marfan syndrome. We performed a propensity score match comparing patients with Marfan syndrome with patients without Marfan syndrome in a 1:2 fashion.

RESULTS

Patients with Marfan syndrome were significantly younger (42.9 vs 62.2 years; P < .001), predominantly male (76.9% vs 62.9%; P = .002), and less catecholamine dependent (9.4% vs 20.3%; P = .002) compared with the unmatched cohort. They presented with aortic regurgitation (41.6% vs 23.0%; P < .001) and involvement of the supra-aortic vessels (50.4% vs 39.5%; P = .017) more often. Propensity matching revealed 82 patients with Marfan syndrome (21 female) with no significant differences in baseline characteristics compared with patients without Marfan syndrome (n = 159, 36 female; P = .607). Although root preservation was more frequent in patients with Marfan syndrome, procedure types did not differ significantly (18.3% vs 10.7%; P = .256). Aortic arch surgery was performed more frequently in matched patients (87.5% vs 97.8%; P = .014). Thirty-day mortality did not differ between patients with and without Marfan syndrome (19.5% vs 20.1%; P = .910). Multivariate regression showed no influence of Marfan syndrome on 30-day mortality (odds ratio, 0.928; 95% confidence interval, 0.346-2.332; P = .876).

CONCLUSIONS

Marfan syndrome does not adversely affect 30-day outcomes after surgical repair for acute aortic Stanford type A dissection compared with a matched cohort. Long-term outcome analysis is needed to account for the influence of further downstream interventions.

Are Sutureless and Rapid-Deployment Aortic Valves a Serious Alternative to TA-TAVI? A Matched-Pairs Analysis

BACKGROUND

Transcatheter aortic valve implantation is a feasible alternative to conventional aortic valve replacement with expanding indication extending to low-risk patients. Sutureless and rapid-deployment aortic valves were developed to decrease procedural risks in conventional treatment. This paired-match analysis aims to compare patients undergoing surgical transcatheter aortic valve implantation to sutureless and rapid-deployment aortic valve implantation.

METHODS

Retrospective database analysis between 2010 and 2016 revealed 214 patients undergoing transcatheter aortic valve implantation procedures through surgical access (predominantly transapical) and 62 sutureless and rapid-deployment aortic valve procedures including 26 patients in need of concomitant coronary artery bypass surgery. After matching, 52 pairs of patients were included and analyzed.

RESULTS

In-hospital death (5.8% vs. 3.8%; p = 0.308) was comparable between transcatheter aortic valve implantation (mean age 77 ± 4.3 years) and sutureless and rapid-deployment aortic valve implantation groups (mean age 75 ± 4.0 years), including 32 females in each group. The logistic EuroSCORE was similar (19 ± 12 vs. 17 ± 10; p = 0.257). Postoperative renal failure (p = 0.087) and cerebrovascular accidents (p = 0.315) were without significant difference. The incidence of complete heart block requiring permanent pacemaker treatment was relatively low for both groups (1.9% vs. 7.7%; p = 0.169) for TAVI and sutureless and rapid-deployment valves respectively. Intraoperative use of blood transfusion was higher in the sutureless and rapid-deployment aortic valve implantation group (0.72 U vs. 1.46 U, p = 0.014). Estimated survival calculated no significant difference between both groups after 6 months (transcatheter aortic valve implantation: 74 ± 8% vs. sutureless and rapid-deployment aortic valve implantation: 92 ± 5%; log rank p = 0.097).

CONCLUSION

Since sutureless and rapid-deployment aortic valve implantation is as safe and effective as transapical transcatheter aortic valve implantation, combining the advantage of standard diseased-valve removal with shorter procedural times, sutureless and rapid-deployment aortic valve replacement may be considered as an alternative for patients with elevated operative risk considered to be in the "gray zone" between transcatheter aortic valve implantation and conventional surgery, especially if concomitant myocardial revascularization is required.

Multicentre experience with the frozen elephant trunk technique to treat penetrating aortic ulcers involving the aortic arch

OBJECTIVES

Our goal was to evaluate the use of the frozen elephant trunk (FET) technique for the treatment of penetrating aortic ulcers involving the aortic arch.

METHODS

Between January 2008 and January 2020, a total of 34 patients had the FET technique at 3 aortic centres. The indication for the FET technique was unsuitability for thoracic endovascular aortic repair due to the lack of a sufficient proximal landing zone even after supra-aortic rerouting (subclavian transposition, double transposition), ectasia of the ascending aorta/aortic arch (>40 mm) and/or a shaggy proximal thoracic aorta.

RESULTS

Additional cardiac procedures were performed in 14 patients (41%), and the beating heart technique was used in 7 patients (21%). Perioperative mortality was 18% (n = 6); 3 of these patients had a major stroke (9%). No case of spinal cord ischaemia was observed, and 2 patients (6%) developed a non-disabling stroke. After a median follow-up of 7 (first quartile: 1; third quartile 29) months, 2 patients (6%) died (1 of malignant disease and 1 of an unclear cause); 10 additional aortic interventions in all aortic segments (29%; endovascular: n = 8 [24%] and conventional surgical: n = 2 [6%]) were performed in 8 patients.

CONCLUSIONS

The FET technique is a good treatment option for patients with penetrating aortic ulcers involving the aortic arch unsuitable for thoracic endovascular aortic repair. However, the high obliterative atherosclerotic load in these patients is accompanied by an un-neglectable risk of perioperative neurological injury. Concomitant cardiac surgical procedures are frequently needed. Patients commonly require secondary aortic procedures in all aortic segments, emphasizing the need for thorough primary conceptual planning and stringent follow-up.

Correlation between plasma clot properties, thrombin generation and whole blood fibrinolytic assays in patients presenting with STEMI

Background

Impaired endogenous fibrinolysis is a novel risk factor for recurrent adverse cardiovascular events in acute coronary syndrome (ACS) patients. This is independent of conventional cardiovascular risk factors and unaffected by dual antiplatelet therapy (DAPT). The mechanism underlying impaired endogenous fibrinolysis in ACS patients is currently unclear.

Aim

To identify the relationship between whole blood fibrinolysis, plasma fibrinolysis and thrombin generation in samples from STEMI patients.

Methods

In a large, prospective, observational study of 500 patients presenting with ST-segment elevation myocardial infarction (STEMI), blood samples were taken on arrival, after DAPT loading, and before administration of heparin or PPCI. Non-anticoagulated venous whole blood was analysed using the point-of-care Global Thrombosis Test, which assesses the time taken for occlusive thrombus formation under high shear (occlusion time, OT) and time required for spontaneous restart of flow as a measure of endogenous fibrinolysis (lysis time, LT). Patients were divided into 4 groups based on quartiles (Q) of whole blood LT (Q1: LT&lt;1500s, Q2:1501–3000s, Q3:3001–4500s, Q4:&gt;4500s). Plasma samples (20 per quartile) were examined in a thrombin generation assay using 1pM tissue factor to initiate and using a turbidity assay to determine the plasma clot lysis time (CLT).

Results

Clinical characteristics of patients were similar in the four groups. The whole blood LT in the 4 groups were Q1: 1194 (1125–1329) s, Q2: 1859 (1634–2157) s, Q3: 3638 (3252–3962) s, Q4: 6000 (5523–6000) s. As LT increased, there was a trend towards longer plasma CLT (50% CLT Q2: 88.5 [73.5–102] vs. Q4: 100 [85–128.5] min, p=0.088). As a continuous variable, there was no significant relationship between whole blood LT and plasma CLT, or between endogenous thrombin potential (ETP) and either whole blood LT or plasma CLT. There was a significant negative correlation between OT and velocity index (r=−0.425, p=0.0138), ETP (r=−0.519, p=0.002), peak thrombin generation (r=−0.390, p=0.0247) and a positive correlation with lag-time (r=0.427, p=0.013). There was positive correlation between CLT and white cell count (WCC, r=0.388, p=0.026), C-reactive protein (CRP, r=0.477, p=0.005) and maximum absorbance (MA, r=0.530, p=0.002). MA correlated with WCC (r=0.436, p=0.011) and platelet count (r=0.357, p=0.042). There was a negative correlation between OT and WCC (r=−0.537, p=0.001) and CRP (r=−0.381, p=0.029).

Conclusion

In patients with STEMI, increased platelet reactivity (shorter OT) correlated with increased thrombin generation (higher ETP, peak thrombin generation, velocity index and reduced lag time), demonstrating the key role of thrombin in occlusive thrombus formation. Fibrinolysis in whole blood was poorly related to plasma CLT or thrombin generation, suggesting that cellular components such as platelets, erythrocytes and neutrophil extracellular traps may significantly influence endogenous fibrinolysis.

Funding Acknowledgement

Type of funding source: None

Temporary right ventricular circulatory support following right ventricular infarction: results of a groin-free approach

Aims

Acute right heart failure (RHF) is a severe complication of right ventricular infarction. The management of acute RHF poses a number of challenges, such as providing haemodynamic support. Temporary circulatory support (TCS) may be required upon failing medical therapy. The ProtekDuo® dual lumen cannula provides a minimally invasive option for (TCS) through a groin‐free internal jugular vein approach. We present the largest patient series to date using the ProtekDuo® cannula as temporary right ventricular assist device (t‐RVAD) in RHF after acute myocardial infarction (MI).

Methods and results

From July 2016 to November 2019, 10 patients underwent t‐RVAD implantation for RHF following acute MI. Transthoracic and transoesophageal echocardiography were performed in all patients to assess cardiac function, with a particular focus on RV function. Cumulative 30‐day survival was 60%. Mean TAPSE was 6.4 ± 3.1 mm, mean fractional area change was 12.1 ± 4.2%, and mean right ventricular end diastolic area was 19.8 ± 2.7 cm². Mean implantation time was 32.8 ± 8.3 min. Mean interval after first cardiac intervention was 4.6 ± 5.8 days. Mean t‐RVAD time was 10.0 ± 7.4 days with a significant reduction in central venous pressure 19.3 ± 2.7 vs. 8.2 ± 2.6 mmHg, P < 0.001 and a significant increase in central venous saturation 52.8 ± 15.6 vs. 80.0 ± 6.0%, P < 0.001. Mean intensive care unit stay was 18.6 ± 12.2 days. Four patients were weaned from TCS. Two patients were bridged to a long‐term paracorporeal RVAD. There were no t‐RVAD associated complications. Causes of death (n = 4) were multiorgan failure, electromechanical dissociation, and haemorrhagic stroke. Mean follow‐up time was 96.0 ± 107.6 days. No independent predictors of mortality were identified in univariate analysis.

Conclusions

We show that groin‐free, percutaneous implantation of the ProtekDuo® cannula is a feasible and safe tool for TCS in acute RHF post‐MI. This approach provides the advantages of percutaneous implantation including complete mobilization and non‐surgical bedside explantation, as well as the option for adding an oxygenator to the t‐RVAD circuit.

The Application of Digital Platforms in Supporting UK International Medical Graduates

Although international medical graduates (IMGs) constitute considerable percentage of doctors in the National Health Service (NHS), they face several challenges in acclimatizing to the NHS health system. Communication skills, language subtleties, and career progression difficulties are among the most important challenges that overseas doctors face.

Some resources are already available to support these doctors and several trusts across the UK have developed local interventions and educational programs to help their doctors bridge the gaps in their knowledge. However, there is no proof of the external validity of these programs and none are identified as effective on a national level.

Senior IMGs are leading very popular and inspiring projects using digital platforms, especially social media. We identified several social media pages, groups, and websites subscribed to by hundreds of thousands of doctors in the UK and around the world, including doctors who are planning a future career in the UK. These platforms provide information, resources, support, and answers to questions posed by junior IMGs.

Inspired by these projects and also by an Australian project that transformed a local IMG education program, we studied whether using digital platforms and transforming evidence-based local programs to national ones would be the best way forward to support IMGs.

The Pathophysiology of Type 2 Diabetes Mellitus in Non-obese Individuals: An Overview of the Current Understanding

The pandemic of type 2 diabetes mellitus (T2DM) has been largely attributed to the increasing prevalence of worldwide obesity at a geometric rate. However, the number of non-obese patients with T2DM is also on the rise, and it is as high as 60-80% in some Asian countries. These non-obese individuals have certain peculiarities and have a higher mortality rate compared with obese individuals. The pathophysiology of T2DM in non-obese individuals remains poorly understood, and this has an impact on defining its management. This review discusses the current understanding of the pathophysiology of T2DM in non-obese individuals. The definition of T2DM in non-obese individuals remains controversial because of the limited clinical measurements, and the current definition of obesity using body mass index (BMI) is not very helpful as these individuals have BMIs of <25K g/m3, which is considered normal. Many authors have argued that the so-called non-obese people are actually metabolically obese; however, in terms of the measurements clinically available, they are non-obese. The simplistic understanding of the mechanism of the pathophysiology sees it in terms of the balance between insulin secretion and insulin resistance. The pathogenesis of insulin resistance in a lean patient has been proven to be the same as what is seen in an obese individual, but most studies confirm more severe functional insulin secretory defects in lean individuals compared to the obese phenotype. The mechanism underlying this form of T2DM is still poorly defined, and more research is required to understand the mechanism of sarcopenic obesity, which some studies have revealed.

Valence and patterning of aromatic residues determine the phase behavior of prion-like domains

Prion-like domains (PLDs) can drive liquid-liquid phase separation (LLPS) in cells. Using an integrative biophysical approach that includes nuclear magnetic resonance spectroscopy, small-angle x-ray scattering, and multiscale simulations, we have uncovered sequence features that determine the overall phase behavior of PLDs. We show that the numbers (valence) of aromatic residues in PLDs determine the extent of temperature-dependent compaction of individual molecules in dilute solutions. The valence of aromatic residues also determines full binodals that quantify concentrations of PLDs within coexisting dilute and dense phases as a function of temperature. We also show that uniform patterning of aromatic residues is a sequence feature that promotes LLPS while inhibiting aggregation. Our findings lead to the development of a numerical stickers-and-spacers model that enables predictions of full binodals of PLDs from their sequences.

P327Predictive value of platelet reactivity, neutrophil to lymphocyte ratio, and hs-CRP at presentation in patients with ST-elevation myocardial infarction treated with percutaneous coronary intervention

Background

Patients with ST-elevation myocardial infarction (STEMI) exhibit enhanced platelet reactivity and a rise in inflammatory biomarkers such as neutrophil to lymphocyte ratio (NLR) and high-sensitivity C-reactive protein (hs-CRP). The extent of the prothrombotic and inflammatory state are predictive of adverse outcomes in patients with acute coronary syndromes. The relationship of these markers of inflammation and thrombosis in the hyperacute phase of STEMI and, whether together, they improve cardiovascular outcome prediction, is not known.

Purpose

The aim of this study was to assess the individual and combined predictive values of NLR, hs-CRP, and platelet reactivity for clinical outcomes in patients with STEMI.

Method

In a prospective study of 541 patients presenting with STEMI, acute admission bloods taken prior to emergency percutaneous coronary intervention, were analysed for NLR and hs-CRP. Platelet reactivity was measured using the point-of-care Global Thrombosis Test, which assesses platelet reactivity in native whole blood under high shear, and measures the occlusion time (OT, sec). Shorter occlusion time represents higher platelet reactivity. The study endpoint was occurrence of major adverse cardiovascular events (MACE, defined as composite of cardiovascular death [CVD], myocardial infarction [MI] or stroke [CVA]) at 30 days and 12 months.

Results

There was a weak, but significant, correlation between hs-CRP and NLR (r=0.25, p<0.001), and hs-CRP and platelet reactivity (r=0.14, p=0.003) on admission. There was no correlation between platelet reactivity and NLR. Amongst 541 patients, 42 patients experienced a MACE within the first 30 days, and 50 within 12 months. Cut-values associated with the highest specificity and sensitivity for 12-month MACE were NLR 5.6, hs-CRP 8 mg/L and OT 302 sec. Platelet reactivity and hs-CRP were each only weakly predictive of MACE at 30 days (platelet reactivity: hazard ratio [HR] 1.004 [95% confidence interval (CI) 1.002–1.006,] p<0.001; hs-CRP: HR 1.005 [95% CI 1.0009–1.009], p=0.016) and 12 months (platelet reactivity HR 1.004 (95% CI 1.002–1.006), p<0.001; hs-CRP HR 1.005 (95% CI 1.001–1.01), p=0.014). NLR was not predictive of MACE at either 30 days or 12 months (p=NS). When patients were divided into quartiles based on hs-CRP and platelet reactivity, patients in the highest quartile for both hs-CRP and platelet reactivity had an HR 3.46 (95% CI 1.81–6.63), p<0.001 compared to those in the lowest quartile for both (HR 0.04 (95% CI 0.005–0.27), p=0.001). The combination of enhanced platelet reactivity and raised hs-CRP was the strongest predictor of MACE at 30 days (HR 2.32 [95% CI 1.71–3.13], p<0.001) and 12 months (HR 2.31 [95% CI 1.71–3.11], p<0.001).

Conclusion

Both hs-CRP and platelet reactivity are very weakly predictive of MACE, but in combination provide a strong predictor of adverse outcome in STEMI.

Cardiac surgery in the heart transplant recipient: Outcome analysis and long-term results

BACKGROUND

Survival rates following cardiac transplantation continue to improve. Due to the scarcity of available organs, extended donor criteria have become more prevalent in clinical practice. In this context, the risk of developing cardiac pathology requiring surgical correction is increasing.

METHODS

Between January 1991 and October 2010, a total of 479 patients received cardiac transplantations at the University Hospital Heidelberg. Of those, 18 (3.8%) patients required subsequent cardiac surgery until 2018. Short- and long-term analyses were performed.

RESULTS

Indications for cardiac surgery included valvular disease (n = 16) with the majority of cases affecting the tricuspid valve (n = 10), while 6 patients received mitral valve surgery, of whom 3 patients underwent concomitant valve surgery. Other indications included CABG (n = 1) and re-transplantation (n = 1) for allograft dysfunction. Mean follow-up time was 6.5 years, while mean interval to surgery was 6.0 years. Early mortality was 11.1% (n = 2), while overall survival at 1, 5, and 10 years were, 88.1%, 81.4%, and 52.2%, respectively. Compared to an overall survival of that transplant cohort at 1, 5, and 10 years of 76.7%, 66.7%, and 52.4% percent, respectively (P = .271).

CONCLUSION

According to our data, redo cardiac surgery can be performed with acceptable mortality and morbidity. Atrioventricular valve pathology plays a chief role in these patients.