Left atrial physiology and pathophysiology:Role of deformation imaging

The left atrium(LA) acts as a modulator of left ventricular(LV) filling. Although there is considerable evidence to support the use of LA maximum and minimum volumes for disease prediction,theoretical considerations and a growing body of literature suggest to focus on the quantification of the three basic LA functions:(1) Reservoir function:collection of pulmonary venous return during LV systole;(2) Conduit function:passage of blood to the left ventricle during early LV diastole; and(3) Contractile booster pump function(augmentation of ventricular filling during late LV diastole. Tremendous advances in our ability to non-invasively characterize all three elements of atrial function include speckle tracking echocardiography(STE),and more recently cardiovascular magnetic resonance myocardial feature tracking(CMR-FT). Corresponding imaging biomarkers are increasingly recognized to have incremental roles in determining prognosis and risk stratification in cardiac dysfunction of different origins. The current editorial introduces the role of STE and CMR-FT for the functional assessment of LA deformation as determined by strain and strain rate imaging and provides an outlook of how this exciting field may develop in the future.

Prognostic utility of global longitudinal strain in myocardial infarction

Cardiovascular magnetic resonance(CMR) represents the reference standard for cardiac morphology and function assessment. Since introduction in 2009, CMR feature tracking(CMR-FT) has become a frequently used tool in the assessment of myocardial deformation and wall motion on the basis of routinely acquired b-SSFP cine images. Extensive validation has led to excellent intra-and inter-observer as well as inter-study reproducibility. CMR-FT derived myocardial deformation indices such as left ventricular(LV) strain have been shown to be impaired in cardiac diseases such as cardiomyopathies as well as myocardial infarction. Although LV ejection fraction(LVEF) is the routinely and frequently utilized parameter for systolic myocardial function assessment and major adverse clinical event(MACE) prediction, it fails to assess regional differences. Recently, LV strain has emerged as a superior measure for risk assessment and MACE prediction as compared to the established markers e.g., LVEF. This editorial aims to elucidate current discussions in the field of strain assessment in myocardial infarction in the light of recent data from a large prospective multicentre CMR study.

Low immunogenicity of endothelial derivatives from rat embryonic stem cell-like cells

Embryonic stem cells （ESC） are suggested to be immune-privileged, but they carry the risk of uncontrolled expansion and malignancy. Upon differentiation they lose their tumor-forming capacity, but they become immunogenic by the expression of a normal set of MHC molecules. This immunogenicity might trigger rejection after application in regenerative therapies. In this study MHC expression of and immune responses to endothelial derivatives of rat embryonic stem cell-like cells （RESC） under inflammatory conditions were determined in comparison to primary rat aortic endothelial cells （ECs）. Cellular as well as humoral allo-recognition was analyzed in vitro. In addition, im- mune reactions in vivo were assessed by allo-antibody production and determination of interferon-y （IFNy）-secreting alio-reactive T cells. RESC derivatives expressed low but significant levels of MHC class I, and no MHC class II. In response to IFNy MHC class I expression was enhanced, while class II transactivator induction failed completely in these cells; MHC class II expression remained consistently absent. Functionally, the RESC derivatives showed a reduced allo-stimulatory capacity, protection against humoral allo-recognition in vitro and a slightly diminished sus- ceptibility to cytotoxic T cell lysis. Furthermore, in vivo experiments demonstrated that these ceils do not trigger host immune reactions, characterized by no allo-antibody production and no induction of allo-reactive memory T cells. Our results show that endothelial derivatives of RESC have a distinctive reduced immunogenic potency even under inflammatory conditions.

Role of cardiac magnetic resonance imaging in troponinemia syndromes

Cardiac magnetic resonance imaging(MRI)is an evolving technology,proving to be a highly accurate tool for quantitative assessment.Most recently,it has been increasingly used in the diagnostic and prognostic evaluation of conditions involving an elevation in troponin or troponinemia.Although an elevation in troponin is a nonspecific marker of myocardial tissue damage,it is a frequently ordered investigation leaving many patients without a specific diagnosis.Fortunately,the advent of newer cardiac MRI protocols can provide additional information.In this review,we discuss several conditions associated with an elevation in troponin such as myocardial infarction,myocarditis,Takotsubo cardiomyopathy,coronavirus disease 2019 related cardiac dysfunction and athlete’s heart syndrome.

MDCT in the diagnostic algorithm in patients with symptomatic atrial fibrillation

Atrial fibrillation(AF) is the most common supraventricular arrhythmia and a major cause of morbidity.Arrhythmogenic foci originating within the pulmonary veins(PVs) are an important cause of both paroxysmal and persistent AF.A variety of endovascular and surgical techniques have been used to electrically isolate the PV from the left atrium.Pulmonary venography for localization of the PV ostium can be difficult to perform during the ablation procedure.While the anatomy of the PV is patientspecific,non-invasive imaging techniques may provide useful diagnostic information prior to the intended intervention.In this context,multidetector computed tomography(MDCT) visualization of the left atrial and PV anatomy prior to left atrial ablation and PV isolation is becoming increasingly important.MDCT imaging provides pre-procedural information on the left atrial anatomy,including atrial size and venous attachments,and it may identify potential post-procedural complications,such as pulmonary vein stenosis or cardiac perforations.Here,we review the relevant literature and present the current"state-of-the-art"of left atrial anatomy,PV ostia as well as the clinical aspects of refractory AF with MDCT imaging protocols and procedural aspects of PV ablation.

Long noncoding RNA MALAT1-derived mascRNA is involved in cardiovascular innate immunity

Dear Editor,Next-generation sequencing revealed that the majority of the human genome is transcribed but has no coding function.It is estimated that.30000 long noncoding RNAs(lncRNAs)are expressed in humans,but their functions are largely unknown(Suckau et al.,2009;Rinn and Chang,2012;Poller et al.,2013).Consideration of noncoding genomic elements in pathogenetic studies is warranted and enabled by technological advances allowing comprehensive transcriptome mapping of protein-coding genes as well as small and long ncRNAs.

SLM2 Is A Novel Cardiac Splicing Factor Involved in Heart Failure due to Dilated Cardiomyopathy

Alternative mRNA splicing is a fundamental process to increase the versatility of the genome.In humans,cardiac mRNA splicing is involved in the pathophysiology of heart failure.Mutations in the splicing factor RNA binding motif protein 20(RBM20) cause severe forms of cardiomyopathy.To identify novel cardiomyopathy-associated splicing factors,RNA-seq and tissue-enrichment analyses were performed,which identified up-regulated expression of Sam68-Like mammalian protein 2(SLM2) in the left ventricle of dilated cardiomyopathy(DCM) patients.In the human heart,SLM2 binds to important transcripts of sarcomere constituents,such as those encoding myosin light chain2(MYL2),troponin 13(TNNI3),troponin T2(TNNT2),tropomyosin 1/2(TPM1/2),and titin(TTN).Mechanistically,SLM2 mediates intron retention,prevents exon exclusion,and thereby mediates alternative splicing of the mRNA regions encoding the variable proline-,glutamate-,valine-,and lysine-rich(PEVK) domain and another part of the I-band region of titin.In summary,SLM2 is a novel cardiac splicing regulator with essential functions for maintaining cardiomyocyte integrity by binding to and processing the mRNAs of essential cardiac constituents such as titin.