Troponin T Research Articles

Complete heart block is a significant predictor of mortality in immune checkpoint inhibitor myocarditis

BackgroundImmune checkpoint inhibitor (ICI) myocarditis is associated with significant mortality risk. Electrocardiogram (ECG) changes in ICI myocarditis have strong prognostic value. However the impact of complete heart block (CHB) is not well defined. This study sought to evaluate the impact of CHB on mortality in ICI myocarditis, and to identify clinical predictors of mortality and CHB incidence.MethodsWe conducted a retrospective cohort study of patients with ICI myocarditis at three Mayo Clinic sites from 1st January 2010 to 31st September 2022 to evaluate mortality rates at 180 days. Clinical, laboratory, ECG, echocardiographic, and cardiac magnetic resonance imaging (CMR) characteristics were assessed. Cox and logistic regression were performed for associations with mortality and CHB respectively.ResultsOf 34 identified cases of ICI myocarditis, 7 (20.6%) had CHB. CHB was associated with higher mortality (HR 7.41, p = 0.03, attributable fraction 86.5%). Among those with CHB, troponin T (TnT) < 1000 ng/dL, low white blood cell count and high ventricular rate at admission were protective. There was trend towards increased survival among patients who underwent permanent pacemaker insertion (p = 0.051), although most experienced device lead complications. Factors associated with development of CHB included prolonged PR and QRS intervals and low Sokolow Lyon Index. Where these were normal and TnT was < 1000 ng/dL, no deaths occurred. Impaired myocardial longitudinal strain was sensitive for ICI myocarditis but was not prognostically significant.ConclusionThere is a strong temporal association between CHB and early mortality in people with ICI myocarditis. Focusing on arrhythmogenic complications can be helpful in predicting outcomes for this group of critically ill individuals.

Genome-Wide Association Study on the Content of Nucleotide-Related Compounds in Korean Native Chicken Breast Meat.

Meat flavor is an important factor that influences the palatability of chicken meat. Inosine 5'-monophosphate (IMP), inosine, and hypoxanthine are nucleic acids that serve as taste-active compounds, mainly enhancing flavor in muscle tissue. For this study, we performed a genome-wide association study (GWAS) using a mixed linear model to identify single-nucleotide polymorphisms (SNPs) that are significantly associated with changes in the contents of the nucleotide-related compounds of breast meat in the Korean native chicken (KNC) population. The genomic region on chicken chromosome 5 containing an SNP (rs316338889) was significantly (p < 0.05) associated with all three traits. The trait-related candidate genes located in this significant genomic region were investigated through performing a functional enrichment analysis and protein-protein interaction (PPI) database search. We found six candidate genes related to the function that possibly affected the content of nucleotide-related compounds in the muscle, namely, the TNNT3 and TNNT2 genes that regulate muscle contractions; the INS, IGF2, and DUSP8 genes associated with insulin sensitivity; and the C5NT1AL gene that is presumably related to the nucleotide metabolism process. This study is the first of its kind to find candidate genes associated with the content of all three types of nucleotide-related compounds in chicken meat using GWAS. The candidate genes identified in this study can be used for genomic selection to breed better-quality chickens in the future.

COVID-19-Associated Acute Myocarditis: Risk Factors, Clinical Outcomes, and Implications for Early Detection and Management.

Background The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus causing acute respiratory distress with multisystem complications, including cardiac complications. Acute myocarditis is onepossible complicationof coronavirus disease 2019 (COVID-19). Previous studies revealed that mortality from COVID-19 was higher in patients with cardiac complications. Objectives We aim to identify if patients with COVID-19 developmyocarditisand if this condition is associated with an increased incidence of ventilatory support and mortality. We also aim to identify if preexisting cardiac conditions are associated with an increased incidence of ventilatory support and mortality in those who developed COVID-19. Methods This is a multicenter, retrospective study including patients aged 18 years and older. Statistical analysis was performed to compare the incidence of in-hospital mortality and ventilatory support in COVID-19-positive patients with and without myocarditis. In this study, we defined myocarditis using elevated troponin-T (TnT) and brain natriuretic peptide (BNP) levels as proxy. Results A total of 8,162 patients with a positive COVID-19 polymerase chain reaction (PCR) testwere identified. Of those, 1,643 (20.1%) were found to have new-onset acute myocarditis. The risk of ventilation and mortality in these patients was significantly elevated (p<0.001) compared to patients without acute myocarditis. Underlying heart failure was associated with increased odds of in-hospital mortality, which was 1.6 times greater when compared to patients without heart failure. The odds of in-hospital mortality were 2.33 times as likely for those who had non-ischemic cardiomyopathy as opposed to those who did not. Conclusion Myocarditis is a serious and potentially fatal complication of COVID-19. The results of this study highlightthe importance of routine testing of troponin-T and BNP levels to identify those at risk. Furthermore, underlying heart conditions are associated with a worse outcome, and those patients should be watched closely.

Gene-echocardiography: refining genotype-phenotype correlations in hypertrophic cardiomyopathy.

This study aims to clarify the association between hypertrophic patterns and genetic variants in hypertrophic cardiomyopathy (HCM) patients, contributing to the advancement of personalized management strategies for HCM. A comprehensive evaluation of genetic mutations was conducted in 392 HCM-affected families using Whole Exome Sequencing. Concurrently, relevant echocardiographic data from these individuals were collected. Our study revealed an increased susceptibility to enhanced septal and interventricular septal thickness in HCM patients harbouring gene mutations compared with those without. Mid-septal hypertrophy was found to be associated predominantly with myosin binding protein C3 (MYBPC3) variants, while a higher septum-to-posterior wall ratio correlated with myosin heavy chain 7 (MYH7) variants. Mutations in MYH7, MYBPC3, and other sarcomeric or myofilament genes (troponin I3 [TNNI3], tropomyosin 1 [TPM1], and troponin T2 [TNNT2]) showed a relationship with increased hypertrophy in the anterior wall, interventricular septum, and lateral wall of the left ventricle. In contrast, alpha kinase 3 (ALPK3)-associated hypertrophy chiefly presented in the apical region, while hypertrophy related to titin (TTN) and obscurin (OBSCN) mutations exhibited a uniform distribution across the myocardium. Hypertrophic patterns varied with the type and category of gene mutations, offering valuable diagnostic insights. Our findings underscore a strong link between hypertrophic patterns and genetic variants in HCM, providing a foundation for more accurate genetic testing and personalized management of HCM patients. The novel concept of 'gene-echocardiography' may enhance the precision and efficiency of genetic counselling and testing in HCM.

Influence and mechanism of sodium-glucose cotransporter-2 inhibitors on the cardiac function: study protocol for a prospective cohort study.

Acute myocardial infarction (AMI) poses a significant threat to cardiovascular diseases (CVDs), leading to a high risk of heart failure (HF) and cardiovascular death. Growing evidence has unveiled the potential of sodium-glucose cotransporter-2 (SGLT2) inhibitors to improve cardiovascular outcomes in patients with CVD regardless of diabetes, but there is limited evidence in AMI patients. Furthermore, it is controversial whether the effects can be ascribed to the amelioration of left ventricular (LV) function, which further complicates the understanding of their underlying mechanism. This study is a prospective, phase IV, open-label, parallel group, single-center trial conducted in a large tertiary teaching hospital in China. A total of 120 patients with AMI and type 2 diabetes mellitus (T2DM) will be included. Those who received SGLT2 inhibitors are considered as the experimental group, and those taking other antidiabetic agents are considered as the control group. The primary outcome is change in LV end-systolic volume index (LVESVi) measured by cardiac magnetic resonance (CMR) imaging from baseline during 1-year follow-up period. Secondary outcomes include other LV parameters such as LV mass, LV volume, and LV ejection fraction (EF); quality of life and functional capacity such as Kansas City Cardiomyopathy Questionnaire overall summary score (KCCQ-OS) and EuroQol-5 dimension (EQ-5D); biomarkers associated with diagnostic parameters of AMI and possible mechanisms on cardiovascular protection, such as creatine kinase, troponin T (TnT) level, troponin I (TnI) level, soluble suppression of tumorigenicity-2 (sST2), galectin-3 (Gal-3), fibroblast growth factor 21 (FGF21), and microRNA (miRNA) level. This study aims to investigate whether SGLT2 inhibitors could improve LV function by measuring CMR, quality of life, and functional capacity in patients with AMI in real-world settings, providing evidence on the underlying mechanism of SGLT2 inhibitors on cardioprotection. https://www.chictr.org.cn/showproj.html?proj=173672, identifier ChiCTR2200065792.

The Definition of Sarcomeric and Non-Sarcomeric Gene Mutations in Hypertrophic Cardiomyopathy Patients: A Multicenter Diagnostic Study Across Türkiye.

Hypertrophic cardiomyopathy is a common genetic heart disease and up to 40%-60% of patients have mutations in cardiac sarcomere protein genes. This genetic diagnosis study aimed to detect pathogenic or likely pathogenic sarcomeric and non-sarcomeric gene mutations and to confirm a final molecular diagnosis in patients diagnosed with hypertrophic cardiomyopathy. A total of 392 patients with hypertrophic cardiomyopathy were included in this nationwide multicenter study conducted at 23 centers across Türkiye. All samples were analyzed with a 17-gene hypertrophic cardiomyopathy panel using next-generation sequencing technology. The gene panel includes ACTC1, DES, FLNC, GLA, LAMP2, MYBPC3, MYH7, MYL2, MYL3, PLN, PRKAG2, PTPN11, TNNC1, TNNI3, TNNT2, TPM1, and TTR genes. The next-generation sequencing panel identified positive genetic variants (variants of unknown significance, likely pathogenic or pathogenic) in 12 genes for 121 of 392 samples, including sarcomeric gene mutations in 30.4% (119/392) of samples tested, galactosidase alpha variants in 0.5% (2/392) of samples and TTR variant in 0.025% (1/392). The likely pathogenic or pathogenic variants identified in 69 (57.0%) of 121 positive samples yielded a confirmed molecular diagnosis. The diagnostic yield was 17.1% (15.8% for hypertrophic cardiomyopathy variants) for hypertrophic cardiomyopathy and hypertrophic cardiomyopathy phenocopies and 0.5% for Fabry disease. Our study showed that the distribution of genetic mutations, the prevalence of Fabry disease, and TTR amyloidosis in the Turkish population diagnosed with hypertrophic cardiomyopathy were similar to the other populations, but the percentage of sarcomeric gene mutations was slightly lower.

Boesenbergia rotunda displayed anti-inflammatory, antioxidant and anti-apoptotic efficacy in doxorubicin‐induced cardiotoxicity in rats

This study evaluated the cardioprotective properties of Boesenbergia rotunda extract (BrE) against doxorubicin (DOX) induced cardiotoxicity. Rats received oral gavage of BrE for 28 days and DOX (5 mg/kg/week for 3 weeks). Thereafter the animals were sacrificed, blood and cardiac samples were collected for biochemical, histological and immunohistochemical analyses. The results indicated that BrE attenuated DOX triggered body and cardiac weight loss and prevented against cardiac injury by mitigating histopathological alterations in cardiac tissues as well as serum cardiac function enzymes. BrE significantly reduced serum levels of aspartate transaminase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), troponin T (TnT) and creatine kinase-MB (CK-MB) in DOX-treated rats. Furthermore, BrE alleviated cardiotoxicity by reducing DOX instigated oxidative stress and potentiating the level of glutathione, as well as the activities superoxide dismutase and catalase in cardiac tissues. In addition, BrE significantly decreased the characteristic indices of DOX-induced cardiac inflammation and apoptosis. Immuno-histochemical analysis revealed that BrE decreased the stain intensity of p53 and myeloperoxidase (MPO) proteins compared to the DXB alone group. In conclusion, our results indicated that BrE modulated oxidative stress, inflammation and apoptosis to attenuate DOX-induced cardiac damage.

Determination of the Dissociation Constant for Polyvalent Receptors Using ELISA: A Case of M13 Phages Displaying Troponin T-Specific Peptides.

Phage-derived affinity peptides have become widespread thanks to their easy selection via phage display. Interactions between a target protein and its specific peptide are similar to those between antibodies and antigens. The strength of these non-covalent complexes may be described by the dissociation constant (Kd). In this paper, protein-specific peptides are exposed on the pIII protein present in the M13 bacteriophage virion with up to five copies. Therefore, one phage particle can bind from one to five ligands. Here, we discuss the dependences between phage-displayed peptides and their ligands in solution using a model system based on troponin T (TnT) binding phages. Moreover, a method of calculating Kd values from ELISA experiments was developed and is presented. The determined Kd values are in the picomolar range.

Ghrelin promotes cardiomyocyte differentiation of adipose tissue‑derived mesenchymal stem cells by DDX17‑mediated regulation of the SFRP4/Wnt/β‑catenin axis.

Adipose tissue‑derived mesenchymal stem cells (ADMSCs) differentiate into cardiomyocytes and may be an ideal cell source for myocardial regenerative medicine. Ghrelin is a gastric‑secreted peptide hormone involved in the multilineage differentiation of MSCs. To the best of our knowledge, however, the role and potential downstream regulatory mechanism of ghrelin in cardiomyocyte differentiation of ADMSCs is still unknown. The mRNA and protein levels were measured by reverse transcription‑quantitative PCR and western blotting. Immunofluorescence staining was used to show the expression and cellular localization of cardiomyocyte markers and β‑catenin. RNA sequencing was used to explore the differentially expressed genes (DEGs) that regulated by ghrelin. The present study found that ghrelin promoted cardiomyocyte differentiation of ADMSCs in a concentration‑dependent manner, as shown by increased levels of cardiomyocyte markers GATA binding protein 4, α‑myosin heavy chain (α‑MHC), ISL LIM homeobox 1, NK2 homeobox 5 and troponin T2, cardiac type. Ghrelin increased β‑catenin accumulation in nucleus and decreased the protein expression of secreted frizzled‑related protein 4 (SFRP4), an inhibitor of Wnt signaling. RNA sequencing was used to determine the DEGs regulated by ghrelin. Functional enrichment showed that DEGs were more enriched in cardiomyocyte differentiation‑associated terms and Wnt pathways. Dead‑box helicase 17 (DDX17), an upregulated DEG, showed enhanced mRNA and protein expression levels following ghrelin addition. Overexpression of DDX17 promoted protein expression of cardiac‑specific markers and β‑catenin and enhanced the fluorescence intensity of α‑MHC and β‑catenin. DDX17 upregulation inhibited protein expression of SFRP4. Rescue assay confirmed that the addition of SFRP4 partially reversed ghrelin‑enhanced protein levels of cardiac‑specific markers and the fluorescence intensity of α‑MHC. In conclusion, ghrelin promoted cardiomyocyte differentiation of ADMSCs by DDX17‑mediated regulation of the SFRP4/Wnt/β‑catenin axis.

Evaluation of the effect of boron derivatives on cardiac differentiation of mouse pluripotent stem cells

BackgroundThe heart is one of the first organs to form during embryonic development and has a very important place. So much that the formation of a functional heart is completed on the 55th day of human development and the 15th day of mouse development. Myocardial, endocardial and epicardial cells, which are derived from the mesoderm layer, are the cells that form the basis of the heart. Cardiac development, like other embryonic developments, is tightly controlled and regulated by various signaling pathways. The WNT signaling pathway is the most studied of these signaling pathways and the one with the clearest relationship with heart development. It is known that boron compounds and the Wnt/β-catenin pathway are highly correlated. Therefore, this study aimed to investigate the role of boron compounds in heart development as well as its effect on pluripotency of mouse embryonic stem cells for the first time in the literature. MethodsToxicity of boron compounds was evaluated by using MTS analysis and obtained results were supported by morphological pictures, Trypan Blue staining and Annexin V staining. Additionally, the possible boron-related change in pluripotency of embryonic stem cells were analyzed with alkaline phosphatase activity and immunocytochemical staining of Oct4 protein as well as gene expression levels of pluripotency related OCT4, SOX2 and KLF4 genes. The alterations in the embryonic body formation capacity of mouse embryonic stem cells due to the application boron derivatives were also evaluated. Three linage differentiation was conducted to clarify the real impact of boron compounds on embryonic development. Lastly, cardiac differentiation of mESCs was investigated by using morphological pictures, cytosolic calcium measurement, gene expression and immunocytochemical analysis of cardiac differentiation related genes and in the presence of boron compounds. ResultsObtained results show that boron treatment maintains the pluripotency of embryonic stem cells at non-toxic concentrations. Additionally, endodermal, and mesodermal fate was found to be triggered after boron treatment. Also, initiation of cardiomyocyte differentiation by boron derivative treatments caused an increased gene expression levels of cardiac differentiation related TNNT2, Nkx2.5 and ISL-1 gene expression levels. ConclusionThis study indicates that boron application, which is responsible for maintaining pluripotency of mESCs, can be used for increased cardiomyocyte differentiation of mESCs.

Different expression and prognostic value of troponin in ischemic cardiomyopathy and non-ischemic dilated cardiomyopathy

BackgroundEarly risk stratification of patients with ischemic cardiomyopathy (ICM) and non-ischemic dilated cardiomyopathy (NIDCM) may be beneficial for therapies.MethodsWe retrospectively enrolled all patients admitted for acute heart failure (HF) between January 2019 and December 2021 in Zhongshan Hospital Fudan University, dividing them according to etiology (ICM or NIDCM). Cardiac troponin T (TNT) concentration was compared between two groups. Risk factors for positive TNT and in-hospital all-cause mortality were investigated with regression analysis.ResultsA total of 1525 HF patients were enrolled, including 571 ICM and 954 NIDCM. The TNT positive patients were not different between the two groups (41.3% in ICM group vs. 37.8% in NIDCM group, P = 0.215). However, the TNT value in ICM group were significantly higher than that in NIDCM group (0.025 (0.015–0.053) vs. 0.020 (0.014–0.041), P = 0.001). NT-proBNP was independently associated with TNT in both ICM and NIDCM group. Although the in-hospital all-cause mortality did not show much difference between the two groups (1.1% vs. 1.9%, P = 0.204), the NIDCM diagnosis was associated with reduced risk of mortality after multiple adjustments (OR 0.169, 95% CI 0.040–0.718, P = 0.016). Other independent risk factors included the level of NT-proBNP (OR 8.260, 95% CI 3.168–21.533, P < 0.001), TNT (OR 8.118, 95% CI 3.205–20.562, P < 0.001), and anemia (OR 0.954, 95% CI 0.931–0.978, P < 0.001). The predictive value of TNT and NT-proBNP for all-cause mortality was similar. However, the best cutoff values of TNT for mortality were different between ICM and NIDCM groups, which were 0.113 ng/mL and 0.048 ng/mL, respectively.ConclusionThe TNT level was higher in ICM patient than that in NIDCM patients. TNT was an independent risk factor for in-hospital all-cause mortality for both ICM and NIDCM patients, although the best cutoff value was higher in ICM patients.

Muscle fiber characteristics and expression level of Troponin T3, Toll-like receptor 2, and Toll-like receptor 4 genes in chicken meat with white striping.

The poultry industry faces an emerging muscular defect in chicken meat called white striping (WS). The biological processes associated with WS myopathy are immune system activation, angiogenesis, hypoxia, cell death, and striated muscle contraction. We examined the Troponin T3 (TNNT3), Toll-like receptor 2 (TLR2), and Toll-like receptor 4 (TLR4) genes based on their functions related to muscle contraction and the innate immune system. This study aimed to determine the muscle fiber characteristics (MFCs) and expression level of TNNT3, TLR2, and TLR4 genes in white striping chicken meat (WSCM). A total of 428 breast samples were randomly collected from a commercial poultry processing plant. The samples were classified into four levels: 0 (normal), 1 (moderate WS), 2 (severe WS), and 3 (extreme WS). Five samples per group were selected to evaluate MFCs, including total number of muscle fibers, muscle fiber diameter, cross-sectional area, endomysium thickness, and perimysium thickness. Five samples per group were selected for ribonucleic acid (RNA) isolation to evaluate the messenger RNA (mRNA) expression levels of TNNT3, TLR2, and TLR4 genes related to WS. Statistical analysis revealed that the total number of fibers, endomysium thickness, and perimysium thickness significantly differed between groups (p < 0.05). Muscle fiber diameter and cross-sectional area did not significantly differ (p > 0.05). The expression of the TNNT3 gene did not significantly differ among groups (p > 0.05). Toll-like receptor 2 and TLR4 mRNA expression significantly differed among groups (p < 0.05). These detailed MFCs will provide baseline information to observe WS in chicken meat. Toll-like receptor 2 and TLR4 genes may play a role in the occurrence of WS in chicken meat through non-specific immune reactions.

Evaluation of the diagnostic value and differentiation efficacy of high sensitivity cardiac troponin T2 (hscTnT2) for STEMI and NSTEMI Iraqi patients with acute coronary syndrome

Evaluation of the diagnostic value and differentiation efficacy of high sensitivity cardiac troponin T2 (hscTnT2) for STEMI and NSTEMI Iraqi patients with acute coronary syndrome

Negative Charges Introduced Near the IT Helix of Cardiac Troponin T Stabilize the Active State of Actin Filaments.

The disordered and basic C-terminal 14 residues of human troponin T (TnT) are essential for full inhibition of actomyosin ATPase activity at low Ca2+ levels and for limiting activation at saturating Ca2+. In previous studies, stepwise truncation of the C-terminal region of TnT increased activity in proportion to the number of positive charges eliminated. To define key basic residues more closely, we generated phosphomimetic-like mutants of TnT. Phosphomimetic mutants were chosen because of reports that phosphorylation of TnT, including sites within the C terminal region, depressed activity, contrary to our expectations. Four constructs were made where one or more Ser and Thr residues were replaced with Asp residues. The S275D and T277D mutants, near the IT helix and adjacent to basic residues, produced the greatest activation of ATPase rates in solution; the effects of the S275D mutant were recapitulated in muscle fiber preparations with enhanced myofilament Ca2+ sensitivity. Actin filaments containing S275D TnT were also shown to be incapable of populating the inactive state at low Ca2+ levels. Actin filaments containing both S275D/T284D were not statistically different from those containing only S275D in both solution and cardiac muscle preparation studies. Finally, actin filaments containing T284D TnT, closer to the C-terminus and not adjacent to a basic residue, had the smallest effect on activity. Thus, the effects of negative charge placement in the C-terminal region of TnT were greatest near the IT helix and adjacent to a basic residue.

Risk Factors and Prognosis of Cardiovascular Damage in Hypereosinophilia

To investigate the risk factors and prognosis of cardiovascular damage in hypereosinophilia (HE). The clinical data of 62 patients with HE in Gansu Provincial Hospital from January 2015 to December 2020 were retrospectively analyzed, including clinical characteristics and laboratory indicators, and the influencing factors of survival and prognosis were also analyzed. In this study, there were 34 males and 28 females, with a median age of 53.5 (20-79) years, 35 patients without cardiovascular damage, 27 patients with cardiovascular damage, including 22 patients with abnormal electrocardiogram (ECG) (81.5%), 18 patients with abnormal echocardiography (ECHO) (66.7%), 9 patients with single ECG abnormality, 5 patients with single ECHO abnormality, and other 13 patients with multiple abnormalities. In cardiovascular damage group, peripheral white blood cell count, absolute value of eosinophils, troponin T (TNT), N-terminal pro-B-type natriuretic peptide (NT-proBNP), interleukin (IL)-4 and IL-5 levels at initial diagnosis were significantly higher than those in the non-cardiovascular damage group (P <0.01), while hemoglobin, IL-2 and interferon-γ levels were significantly lower (P <0.01). There were no significant differences in age, sex, course of disease, etiological classification, platelet count, serum creatine kinase, serum creatine kinase isoenzyme and lactate dehydrogenase between the two groups (P >0.05). The 5-year overal survival rate of patients with cardiovascular damage was 88.9%, and that of patients without cardiovascular damage was 100%, the difference was statistically significant (P =0.012). The 5-year event-free survival (EFS) rate of patients with cardiovascular damage was 59.3%, and the median time was 37 (21-52) months, while that of patients without cardiovascular damage was 80%, and the median time was 63 (51-74) months (P =0.002). Age (>60 years old), course of disease (>24 months), NT-proBNP (>3 000 pg/ml), TNT (>100 ng/L), elevated IL-4 and IL-5 were associated with EFS shortening in patients with cardiovascular damage, which were independent risk factors for EFS. The EFS rate in HE patients without cardiovascular damage is significantly higher than patients with cardiovascular damage. Age, course of disease, NT-proBNP, TNT, IL-4 and IL-5 are independent risk factors affecting EFS of patients with cardiovascular damage.

A changing heart in tako-tsubo syndrome.

A 63-year-old female presented with acute chest pain and ECG showing T wave inversion in the anterior and inferior leads. Troponin T (TnT) was significantly elevated (peak 1378 ng/L; normal <14 ng/L), as was NT-proBNP (3091 ng/L; normal <400 ng/L). Invasive angiography showed unobstructed coronary arteries with mid-ventricular ballooning and hypokinesia on ventriculography (see Supplementary data online, Video S1) and echocardiography (see Supplementary data online, Video S2), suggesting a mid-ventricular tako-tsubo syndrome (TTS). Cardiac magnetic resonance (CMR) was booked but the patient was unable to attend. Focussed history using the InterTAK diagnostic score assessment revealed no emotional or physical triggers. The patient re-presented six months later with similar symptoms and elevated TnT. Inpatient echocardiography showed a reverse TTS pattern (see Supplementary data online, Video S3) and CMR at 1.5T showed basal hypokinesia with matching elevated native T1 (1220 ms; normal 950–1100 ms) and T2 (69 ms; normal <48 ms) (Panels A–B). Quantitative perfusion maps following adenosine stress perfusion to investigate microvascular disease showed basal to mid circumferential hypoperfusion with normal apical myocardial blood flow, not suggestive of specific coronary artery territory ischaemia (Panel D) and no late gadolinium enhancement (LGE) (Panel C), confirming a reverse TTS. The patient further presented two months later with chest pain and TnT elevation. Repeat inpatient CMR on this occasion showed a classic TTS pattern with apical hypokinesia and elevated T1 and T2 (1261 ms and 81 ms, respectively) at the mid to apical segments with no LGE (Panels E–G). The case was further explored but no triggers, including neurological or psychiatric abnormalities were found. Recurrent TTS with different phenotypes has previously been described but is rare, especially without a trigger. Our case illustrates the utility of multimodality imaging in the investigation of TTS; in particular, multiparametric tissue mapping by CMR. Furthermore, the novel quantitative perfusion maps characterising myocardial blood flow added diagnostic utility.

Structural and Functional Properties of Kappa Tropomyosin.

In the myocardium, the TPM1 gene expresses two isoforms of tropomyosin (Tpm), alpha (αTpm; Tpm 1.1) and kappa (κTpm; Tpm 1.2). κTpm is the result of alternative splicing of the TPM1 gene. We studied the structural features of κTpm and its regulatory function in the atrial and ventricular myocardium using an in vitro motility assay. We tested the possibility of Tpm heterodimer formation from α- and κ-chains. Our result shows that the formation of ακTpm heterodimer is thermodynamically favorable, and in the myocardium, κTpm most likely exists as ακTpm heterodimer. Using circular dichroism, we compared the thermal unfolding of ααTpm, ακTpm, and κκTpm. κκTpm had the lowest stability, while the ακTpm was more stable than ααTpm. The differential scanning calorimetry results indicated that the thermal stability of the N-terminal part of κκTpm is much lower than that of ααTpm. The affinity of ααTpm and κκTpm to F-actin did not differ, and ακTpm interacted with F-actin significantly worse. The troponin T1 fragment enhanced the κκTpm and ακTpm affinity to F-actin. κκTpm differently affected the calcium regulation of the interaction of pig and rat ventricular myosin with the thin filament. With rat myosin, calcium sensitivity of thin filaments containing κκTpm was significantly lower than that with ααTpm and with pig myosin, and the sensitivity did not differ. Thin filaments containing κκTpm and ακTpm were better activated by pig atrial myosin than those containing ααTpm.

Blood-pressure targets in comatose survivors of cardiac arrest with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention - a BOX sub-study

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Novo Nordisk Foundation. Background After successful resuscitation from out-of-hospital cardiac arrest (OHCA), patients who remain comatose often need hemodynamic support with vasoactive drugs in order to secure an adequate perfusion pressure to vital organs. However, evidence regarding specific blood-pressure targets is sparse, and patients with concomitant heart disease such as acute ST-elevation myocardial infarction (STEMI) might benefit from a lower afterload and lower doses of vasoactive drugs. Purpose To assess the impact of blood-pressure on biochemical infarct size in comatose survivors of OHCA with STEMI and, further, to investigate whether a high or low mean arterial blood-pressure target is superior in preventing death or severe brain injury. Methods The BOX study (n=789) is a randomized trial with a 2-by-2 factorial design which evaluated a double-blind intervention of a high (77 mmHg) versus a low (63 mmHg) mean arterial blood-pressure target in comatose survivors of OHCA of presumed cardiac cause. In this pre-specified sub-study we included patients who had an initial electrocardiogram with STEMI recorded after return of spontaneous circulation (ROSC). The primary outcome was creatine kinase (CK), creatine kinase MB (CKMB), and troponin T (TnT) levels measured at 48 hours as surrogate markers of infarct size. A secondary outcome was a composite of all-cause death within one year from admission or discharge from the hospital with a Cerebral Performance Category (CPC) of 3 to 4, indicating severe neurological disability or a comatose or vegetative state. Results A total of 350 patients were included. Mean time to ROSC was 21±13 minutes. The mean age was 63±12 years and approximately 4 out of 5 were male. The prevalence of relevant prior medical history was as follows; hypertension 42%, diabetes 12%, chronic ischemic heart disease 20%, percutaneous coronary intervention 11%, coronary artery bypass grafting 4%, and congestive heart failure 10%. Mean CK, CKMB and TnT measured at 48 hours did not differ between the two blood-pressure target groups (p=0.42, p=0.14 and p=0.65, respectively). Within one year, 138 patients (39%) had died or been discharged with a CPC of 3 to 4 with no difference found between high or low blood pressure targets (hazard ratio, 1.02; 95% CI, 0.73-1.43; p=0.9). Conclusion Targeting a high versus a low mean arterial blood-pressure in comatose survivors of OHCA with STEMI did not affect infarct size estimated by coronary biomarkers at 48 hours nor did it result in a significant difference in death or severe neurologic disability. Although not evaluating side effects, this study thus suggests that the use of pharmacologic circulatory support in post-resuscitation care can be limited.

Anthracyclines and Biomarkers of Myocardial Injury: The Effect of Remote Ischemic Conditioning

BackgroundRemote ischemic conditioning (RIC) has been beneficial in laboratory studies of anthracycline cardiotoxicity, but its effects in patients is not established. ObjectivesThe authors studied the effect of RIC on cardiac biomarkers and function during and after anthracycline chemotherapy. MethodsThe ERIC-Onc study (Effect of Remote Ischaemic Conditioning in Oncology Patients; NCT02471885) was a randomized, single-blind, sham-controlled study of RIC at each chemotherapy cycle. The primary endpoint was troponin T (TnT) during chemotherapy and up to 1 year. Secondary outcomes included cardiac function, major adverse cardiovascular events (MACE), and MACE or cancer death. Cardiac myosin-binding-protein C (cMyC) was investigated in parallel with TnT. ResultsThe study was prematurely halted after the evaluation of 55 patients (RIC n = 28, sham n = 27). Biomarkers increased from baseline to cycle 6 of chemotherapy for all patients (median TnT 6 [IQR: 4-9] ng/L to 33 [IQR: 16-36)] ng/L; P ≤ 0.001; cMyC 3 (IQR: 2-5) ng/L to 47 (IQR: 18-49) ng/L; P ≤ 0.001). Mixed-effects regression analysis for repeated measures showed no difference in TnT between the 2 groups (RIC vs sham, mean difference 3.15 ng/L; 95% CI: −0.04 to 6.33; P = 0.053), or cMyC (RIC vs sham, mean difference 4.17 ng/L; 95% CI: −0.12 to 8.45; P = 0.056). There were more MACE and cancer deaths in the RIC group (11 vs 3; HR: 0.25; 95% CI: 0.07-0.90; P = 0.034), with more cancer deaths (8 vs 1; HR: 0.21; 95% CI: 0.04-0.95; P = 0.043) at 1 year. ConclusionsTnT and cMyC significantly increased during anthracycline chemotherapy with 81% having a TnT ≥14 ng/L at cycle 6. RIC did not affect the rise in biomarkers, but there was a small increase in early cancer deaths, possibly related to the greater proportion of patients with metastatic disease randomized to the RIC group (54%vs 37%). (Effect of Remote Ischaemic Conditioning in Oncology Patients [ERIC-ONC]; NCT02471885)

BS-452758-1 SUPPRESSION-REPLACEMENT GENE THERAPY REVERSE REMODELS THE INTRACELLULAR CALCIUM HANDLING DISEASE PHENOTYPE OF TNNT2-MEDIATED HYPERTROPHIC CARDIOMYOPATHY

Hypertrophic cardiomyopathy (HCM), characterized by otherwise unexplained left ventricular hypertrophy, has a prevalence of 1:500. Pathogenic variants in TNNT2-encoded cardiac troponin T causes a thin filament subtype of sarcomeric HCM. A key cellular feature of the pathological remodeling in TNNT2-mediated HCM involves dysregulation of intracellular calcium handling in ventricular cardiomyocytes (CMs). To develop a TNNT2 “suppression-replacement (SupRep)” gene therapy to reverse the intracellular calcium perturbations associated with thin filament, sarcomeric HCM using induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) derived from a patient with TNNT2-R288P-mediated HCM. Custom-designed TNNT2 targeting shRNAs were tested for knockdown (KD) efficiency using TSA201 cells and RT-qPCR. A dual-component SupRep TNNT2 gene therapy was created by cloning into a single construct a custom-designed TNNT2 shRNA that produced greatest KD (suppression) and a “shRNA-immune” (shIMM) TNNT2 cDNA (replacement). Patient-specific TNNT2-R288P and CRISPR/Cas9 variant-corrected isogenic control (IC) iPSC-CMs were generated from a patient with HCM. The intracellular calcium indicator, Fluo-4, was used to detect intracellular free calcium. Our lead TNNT2-shRNA had an 80% KD efficiency of TNNT2. TNNT2-R288P iPSC-CMs treated with TNNT2-SupRep showed a similar KD efficiency. Compared to the IC iPSC-CMs, the TNNT2-R288P iPSC-CMs showed increased irregular events (30.4% vs. 10.9%, p<0.0001), prolonged calcium transient duration 90 (CTD90, 1.01 ± 0.03 s vs. 0.89 ± 0.02 s, p<0.0001) and prolonged peak to 90% decay time (0.57 ± 0.02 s vs. 0.49 ± 0.01 s, p=0.0012). Compared to untreated cells, transfection with TNNT2-SupRep gene therapy, the TNNT2-R288P iPSC-CMs showed a decrease in irregular events (30.4% vs. 14%, p<0.0001), shortened CTD90 (1.01 ± 0.03 s vs. 0.91 ± 0.01 s, p=0.003), and shortened peak to 90% decay time (0.57 ± 0.02 s vs. 0.50 ± 0.02 s, p=0.02). There was no significant difference in irregular events, CTD90, or peak to 90% decay time between TNNT2-R288P iPSC-CMs treated with TNNT2-SupRep and IC iPSC-CMs. Here, we provide the first proof-of-principle SupRep gene therapy for TNNT2-mediated HCM. TNNT2-SupRep gene therapy almost fully restored the impaired intracellular calcium handling properties of TNNT2-R288P patient-derived iPSC-CMs back to the normal state achieved by the CRISPR/Cas9 gene-edited cure.