Subacute and chronic post-covid myoendocarditis: clinical presentation, role of coronavirus persistence and autoimmune mechanisms.

Aim    To study clinical features of myoendocarditis and its possible mechanisms, including persistence of SARS-Cov-2 in the myocardium, in the long-term period following COVID-19.Material and methods    This cohort, prospective study included 15 patients aged 47.8±13.4 years (8 men) with post-COVID myocarditis. The COVID-19 diagnosis was confirmed for all patients. Median time to seeking medical care after COVID-19 was 4 [3; 7] months. The diagnosis of myocarditis was confirmed by magnetic resonance imaging (MRI) of the heart (n=10) and by endomyocardial biopsy of the right ventricle (n=6). The virus was detected in the myocardium with PCR; immunohistochemical (IHC) study with antibody to SARS-Cov-2 was performed; anticardiac antibody level was measured; and echocardiography and Holter monitoring were performed. Hemodynamically significant coronary atherosclerosis was excluded for all patients older than 40 years.Results    All patients showed a clear connection between the emergence or exacerbation of cardiac symptoms and COVID-19. 11 patients did not have any signs of heart disease before COVID-19; 4 patients had previously had moderate arrhythmia or heart failure (HF) without myocarditis. Symptoms of myocarditis emerged at 1-5 months following COVID-19. MRI revealed typical late gadolinium accumulation, signs of hyperemia, and one case of edema. The level of anticardiac antibodies was increased 3-4 times in 73 % больных. Two major clinical variants of post-COVID myocarditis were observed. 1. Arrhythmic (n=6), with newly developed extrasystole or atrial fibrillation without systolic dysfunction. 2. Decompensated variant with systolic dysfunction and biventricular HF (n=9). Mean left ventricular ejection fraction was 34.1±7.8 %, and left ventricular end-diastolic dimension was 5.8±0.7 cm. In one case, myocarditis was associated with signs of IgG4­negative aortitis. SARS-Cov-2 RNA was found in 5 of 6 biopsy samples of the myocardium. The longest duration of SARS-Cov-2 persistence in the myocardium was 9 months following COVID-19. By using antibody to the Spike antigen and nucleocapsid, SARS-Cov-2 was detected in cardiomyocytes, endothelium, and macrophages. Five patients were diagnosed with lymphocytic myocarditis; one with giant-cell myocarditis; three patients had signs of endocarditis (infectious, lymphocytic with mural thrombosis).Conclusion    Subacute/chronic post-COVID myocarditis with isolated arrhythmias or systolic dysfunction is characterized by long-term (up to 9 months) persistence of SARS-Cov-2 in the myocardium in combination with a high immune activity. Endocarditis can manifest either as infectious or as nonbacterial thromboendocarditis. A possibility of using corticosteroids and anticoagulants in the treatment of post-COVID myoendocarditis should be studied.

[Multislice spiral computed tomography of the heart in dilated cardiomyopathy: possibilities in the verification of myocarditis (in comparison with myocardial biopsy) and in the evaluation of prognosis]. / Mul'tispiral'naia komp'iuternaia tomografiia serdtsa pri sindrome dilatatsionnoi kardiomiopatii: vozmozhnosti v verifikatsii miokardita (po sravneniiu s biopsiei miokarda) i otsenke prognoza.

AIM: To investigate whether intravenous contrast-enhanced multislice spiral computed tomography (computed tomography) (MSCT) versus myocardial morphological examination can diagnose myocarditis and the non-inflammatory causes of dilated cardiomyopathy (DCM) and evaluate prognosis in patients with the latter. SUBJECTS AND METHODS: A study group consisted of 130 patients, including 95 men (46.8±11.9 years), with DCM (mean left ventricular (LV) end-diastolic dimension (EDD), 6.6±0.8 cm; mean LV ejection fraction (EF), 29.8±9.3%; NYHA functional class (FC) III (II; III)). All the patients underwent intravenous contrast-enhanced 320-slice CT of the heart; myocardial morphological examination was made in 48 patients (endomyocardial biopsy in 29 patients, intraoperative biopsy in 7, and autopsy in 9, and study of the explanted heart in 3). In addition, cardiotropic viral DNA in the blood and myocardium and the level of anticardiolipin antibodies were determined; echocardiography (in all the patients), scintigraphy (n = 45), magnetic resonance imaging (MRI) (n = 21), and coronary angiography (CG) (n = 46), and a genetic consultation were performed. A comparison group comprised 20 patients, including 14 men (69.3±9.2 years), with coronary atherosclerosis (40% or more stenoses) according to MSCT findings in the absence of criteria for DCM (mean LV EDD, 4.8±0.5 cm; mean LV EF, 59.4±4.6%). RESULTS: Morphological/comprehensive examination showed that myocarditis as a cause of DCM was diagnosed in 76 (65%) patients; its concurrence with genetic cardiomyopathies was in 17 more patients (17%). MSCT of the heart revealed lower accumulation areas in 2 (1.5%) patients (type 1 based on the proposed rating scale), delayed myocardial contrast agent accumulation (DMCAA) in 81 (62.3%): subendocardial accumulation (type 2) in 8, intramyocardial accumulation in 4 (type 3), subepicardial accumulation in 52 (type 4), and transmural accumulation in 15 (type 5); DMCAA was not noted in 49 patients. DMCAA was not found in the comparison group. As compared with biopsy, the sensitivity, specificity, predictive value of positive and negative results of the tests in detecting active myocarditis for all the types of DMCAA were 77.4, 47.1, 72.7, and 53.3%, respectively; those for types 3-5 of DMCAA were 77.4, 52.9, 75.0, and 56.3%; those in detecting all the morphological types of myocarditis were 68.3, 28.6, 84.8, and 13.3%, and those for types 3-5 were 65.9, 28.6, 84.4, and 12.5%, respectively. Comparison of the data of MSCT and those of comprehensive examination in all the patients with DCM, the diagnostic significance in detecting myocarditis for all the types of DMCAA was 70.6, 67.9, 88.9 and 38.8%, respectively; that for DMCAA types 3-5 was 60.8, 67.9, 87.3, and 32.3%. In the study group, MSCT also identified the non-compacted myocardium (n = 31 (23.8%)), coronary atherosclerosis (n = 31 (23%)), which is confirmed by CG findings in 15 patients. The patients with DMCAA significantly more frequently showed a relationship with previous infection, acute onset, significantly higher NYHA FCs, end-diastolic and end-systolic LV volumes, and insignificantly lower LV EF. During a mean follow-up periods of 12 (6; 37.25) months, the overall mortality rate was 17.7% (23 deaths); the death + transplantation index was 20% (n = 26). All the types of DMCAA were found to be significantly related to prognosis: in the DMCAA group, the mortality rate was 21.5% versus 7.8% in the non-DMCAA group (odds ratio 3.22; 95% confidence interval, 1.02 to 10.21; p < 0.05). CONCLUSION: MSCT with the assessment of delayed contrast enhancement (and simultaneous CT coronary angiography) can be used for the non-invasive diagnosis of myocarditis in patients with DCM, including that in the presence of contraindications to MRI. DMCAA correlates with the presence of myocarditis, its activity, the degree of functional disorders, and prognosis.

[Idiopathic arrhythmias: possibilities of complex nosological diagnosis, and differentiated treatment].

AIM: of the study was to elucidate nosological nature of "idiopathic" arrhythmias by means of complex clinical-morphological examination and to assess efficacy of differentiated (including etiotropic and pathogenetic) treatment. MATERIAL AND METHODS: We examined 190 patients (117 women, mean age 45.33 ± 14.84 years) with "idiopathic" arrhythmias: atrial fibrillation (38.9%) (AF,) and flutter (11.1%), supraventricular (44.7%) and ventricular (55.3%) extrasystoles (SVE and VE), bouts of ventricular tachycardia (15.8%), atrioventricular block (22,6%) et al. Mean number of antiarrhythmic drugs per patient was 3 (from 1 to 8). Examination included Holter ECG monitoring, echocardiography, determination of anticardiac antibodies (97.4%) and markers of cardiotropic viruses (87.4%), treadmill test (26.3%), transesophageal cardiac pacing (12.1%), electrophysiological investigation (10%), multispiral computed tomography (22.1%), magnetic resonance tomography (21.6%), scintigraphy (27.4%), coronary angiography (10.0%), endomyocardial biopsy (EMB) (10.0%), DNA diagnostics (8.9%). RESULTS: EMB revealed immune-inflammatory (myo/endocarditis, systemic/myocardial vasculitis) or genetic pathology in 78.9 and 21.1% of cases, respectively. Level of anticardiac antibodies (including specific antinuclear factor) most closely correlated with EMB findings. On the basis of comparison of EMB data with data of complex examination we created algorithm of nosological diagnostics in "idiopathic" arrhythmias. According to nosology all patients were distributed in the following way: 1) chronic infectious-immune myocarditis (n=144, 75.7%), morphologically verified in 14, viral in 27 patients; 2) genetic cardiomyopathy (n=15, 7.9%), morphologically verified in 4, virus positive in 1 (arrhythmogenic right ventricular dysplasia, non-compaction myocardium, Fabri disease, Brugada syndrome, undetermined); in 4 patients mutations in plakophilin 2, desmoglein, desmin, -galactosidase A genes were found; 3) combination of genetic diseases with myocarditis (n=18; 9.5%) including viral (n=3); 4) isolated myocardiodystrophy (tonsillogenic< dyshormonal, n=3, 1.6%); 5) proper idiopathic arrhythmias (n=10, 5.3%). Therapy of myocarditis included antiviral (43.2%) and immunosuppressive (76.3%) drugs. Cardiotropic and antiarrhythmic therapy was also administered. Only in patients with myocarditis it was possible to withdraw effective antiarrhythmic (16.7%) and to improve effect of previously ineffective drugs. Surgical treatment (implantation of pacemaker or cardioverter-defibrillator, radiofrequency ablation) was more frequently used in patients with genetic (39.4%) and idiopathic arrhythmias (53.8%) than in patients with myocarditis (16.0%). CONCLUSION: Etiology of idiopathic arrhythmias can be established in most cases. Their main causes are immune-inflammatory diseases, genetic cardiomyopathies and their combination. Therapy of myocarditis improves antiarrhythmic activity of treatment, in some patients allows to withdraw antiarrhythmic drugs, decrease requirements in surgical treatment and to optimally prepare patients to radiofrequency ablation.

[Possibilities myocardial biopsy in the diagnosis of myocarditis verification in patients with idiopathic arrhythmias].

UNLABELLED: Aim of the study was to elucidate nosological nature of "idiopathic" arrhythmias by means of right ventricular endomyocardial biopsy (EMB) and to assess effect of etiotropic and pathogenetic treatment. MATERIAL AND METHODS: We included into this study 19 patients (mean age 42.6 +/-11.3 years, 9 women) with atrial fibrillation (AF, n = 16), supraventricular (n = 10) and ventricular (n = 4) extrasystoles (SVE and VE), supraventricular (n = 2) and ventricular (n = 1) tachycardia (SVT and VT), left bundle branch block (LBBB, n = 2), atrioventricular block (n = 2) without structural changes of the heart. In addition to standard examination we performed the following tests: determination of IgG to herpes and Coxsackie B virus, polymerase chain reaction (PCR) for DNA detection of human herpesviruses 1, 2, and 6, Epstein-Barr virus, Varicellae-zoster virus (human herpesvirus 3) and cytomegalovirus in blood; determination of anticardiac antibodies; EMB with subsequent PCR-diagnostics including that of parvovirus B19 and pathomorphological study. DNA diagnostics (n = 4), coronary angiography (n = 6), skin biopsy (n = 1) and some other studies were also performed when indicated. RESULTS AND CONCLUSIONS: Histological picture was abnormal in all cases. Nosological diagnosis was established in all patients: infectious-immune myocarditis (n = 11), parvovirus positive endomyocarditis (n = 1); systemic vasculitis (n = 2); myocardial vasculitis (n = 1), Fabri disease (n = 1), arrhythmogenic right ventricular dysplasia (ARVD, n = 1), undetermined genetic cardiomyopathy (n = 2). Level of various anticardiac antibodies including antinuclear factor with bovine heart antigen was most valuable for diagnosis of myocarditis (sensitivity 78.6%, prognostic value of positive result 91.7%). The following therapy was used in patients with myocarditis/vasculitis: intravenous or oral acyclovir (n = 10), gabreglobine (n = 2), meloxicam (n = 12), hydroxychloroquine (n = 15 for 15 [7.0; 24.] months), glucocorticosteroids (n = 14 for 18 [4.0; 25.5] months), azathioprine (n = 2). Mean duration of follow up was 4 years (48 [31; 62] months). At baseline 62.5% of patients with AF were resistant to all antiarrhythmic drugs. Treatment of myocarditis resulted in significant reduction of mean frequency of attacks of AF from 8 to 3 points, more than in 40% of patients AF emerged less than once a month and 1 patient had no attacks at all. Disappearance of tachycardia dependent LBBB was also noted. Cardioverter defibrillator and cardiac pacemaker were implanted to patients with ARVD and Fabri disease, respectively. EMB helped to establish immunoinflammatory and genetic diseases as causes of idiopathic arrhythmias (in 78.9 and 21.1% of patients, respectively). Antiviral immunosuppressive therapy of myocarditis allowed to increase efficacy of antiarrhythmic therapy in resistant patients and when necessary to optimize their preparedness to interventional treatment.

[Noncoronary dilated cardiomyopathy after reverse remodeling heart surgery].

We present here analysis of surgical treatment of 24 patients (5 women, 19 men, age 20-75, mean age 50.7 +/- 2.5 years) with dilated cardiomyopathy (DCM) operated during the period from 2008 to 2013. Duration of the disease ranged from 4 months to 12 years (mean 49.4 +/- 7.5 months). According to symptoms and results of 6-minute walk test 3 patients (13%) had heart failure NYHA class III and 21 patients (87%)--NYHA class IV. Average end-diastolic left ventricular size was 7.4 +/- 0.18 cm (6.0-9.2 cm), ejection fraction--26.7 +/- 2.1% (13-47%), mean pulmonary artery pressure 54.9 +/- 2.9 mm Hg (35-80 mmHg). All patients underwent organ-conserving surgery aimed at reverse remodeling of the heart. Surgery was accompanied with implantation of implantable cardioverter defibrillator in 3 patients and/or cardiac resynchronization therapy device in 6 patients. Two patients (8.3%) died during hospitalization of hemodynamically significant ventricular arrhythmias; seven patients (29.2%) died in the late postoperative period. The results of the analysis indicate that reverse-remodeling surgery may be effective in patients with DCM of any age group with preserved reserves of the liver, kidney, and lung function in the absence of active myocarditis. Further observations are needed to determine the place of this operation in the protocol of treatment of patients with DCM.

[Noncompaction myocardium as a primary phenomenon or consequence of myocardial dysfunction: clinical masks of the syndrome].

Noncompaction myocardium (NCM) is a genetic heterogeneous primary cardiomyopathy which affects both children and adults and can be either isolated or combined with other congenital heart disorders. It has common pathogenesis of symptoms but is distinguished by pronounced clinical polymorphism. We have observed 25 adult patients (15 men, 10 women aged from 20 to 62 years, mean age 42.9+/-13.3 years) with NCM syndrome. Heart failure have been found in 96% of patients (functional class [FC] I in 7, II - in 6, III in 7, and IV - in 4 patients). Ninety two percent of patients have ventricular extrasystoles, 32% - atrial fibrillation, 28% - FC I-III angina. Mean end diastolic left ventricular dimension is 6.5+/-0.8cm, ejection fraction 29.7+/-13.0%, mean pulmonary artery pressure - 42.6+/-13.5 mm Hg. Intracardiac thrombosis have been found in 24% of patients. In 7 patients morphological study of myocardium has been performed. NCM syndrome was diagnosed at initial investigation just in 1 case. We distinguished the following clinical masks (variants of diagnosis) of NCM: 1) clinically not manifest, is revealed at accidental examination (4%); 2) exists under mask of "idiopathic" rhythm disturbances (8%); 3) has a mask of ischemic heart disease; 4) is revealed in patients with acute or subacute myocarditis (12%); 5) has a mask of dilated cardiomyopathy (52%); 6) NCM in patients with other primary cardiomyopathies (hypertrophic, restrictive, genetic myopathy, arrhythmogenic right ventricular dysplasia). Combination of NCM with congenital heart defects has been found in 20% of patients. In 56% of cases myocarditis was diagnosed (it was viral in no less than 44%). Only in 32% of patients it is possible to consider presence of isolated NCM syndrome. This paper contains discussion of problems of diagnostics (including morphological) and treatment in the presented group of patients, significance of myocarditis for development of decompensation, role of NCM in patients with other primary cardiomyopathies, possibility of compensatory (secondary) character of NCM in severe systolic dysfunction.

[Dilated cardiomyopathy as clinical syndrome: experience with nosological diagnostics with biopsy and treatment approaches].

AIM: To study possibility of nosological diagnosis in patients with dilated cardiomyopathy (DCMP) with use of myocardial biopsy. MATERIAL AND METHODS: The trial enrolled 62 patients (23 females) with DCMP syndrome (end diastolic left ventricular size > 5.5 cm, ejection fraction < 55%). Mean age of the patients was 46.0 +/- 12.8 years. The examination included diagnosis of viral infections (Herpes virus, parvovirus B19), measurement of anticardial antibodies titer, 99Tc-MIBI single photon emission computed tomography of the myocardium, multislice computed tomography, MRT of the heart, coronarography, morphological study of the myocardium (n=20) with application of polymerase chain reaction (PCR) for H.simplex viruses of types 1, 2 and 6, herpes zoster, Epstein-Barr, cytomegalovirus, parvovirus B-19, adenoviruses. The control group (20 operated patients with valvular heart disease and coronary heart disease) was examined for viral genome in the blood and myocardium. RESULTS: Complex examination of DCMP patients showed the following distribution by nosological entuities: myocarditis (n=41, 66.1%) including virus-positive (n=14), primary DCMP (n=16, 25.9%) including with non-compact myocarditis (NCM) in 3, with debute at delivery of the child--in 3. Arrhythmogenic right ventricular dysplasia combined with viral myocarditis (n=2), genetic myopathy (n=1) and Takayasu disease (n=1) combined with NCM, isolated NCM (n=1) were diagnosed in the rest cases. Morphological investigation of the myocardium was made in 20 patients: diagnosis of myocarditis and primary DCMP were made in 70% (including in 2 patients with CHD) and 20%. Detection of viral genome was 20 and 15% in the study and control group, respectively, in the myocardium--in 57.9 (test for parvovirus B19 was not made in 26%) and 65.0% (complete diagnosis). All the virus-positive patients with DCMP were diagnosed to have signs of active/borderline myocarditis. Diagnostic criteria and poor prognosis factors were defined. CONCLUSION: The nosological diagnosis of DCMP was made in all the examinees basing on the complex of clinical, case history and device evidence. The diagnosis was morphologically verified in 33.9% patients. Treatment approaches are developed.

[A comparative study of the dynamics of deep burns healing in using medullary allogenic fibroblast-like mesenchymal stem cells from bone marrow immobilized on biodegrading membranes or taken from cultural plastic].

Transplantation of suspention of allogenic fibroblast-like mesenchymal stem cells (AFMSC) of the bone marrow and AFMSC immobilized on the biodegradable membrane (BM) stimulates healing of deep burn wounds compared to control (without cell transplantation) because these cells produce biologically active substances into the wound. AFMSC immobilized on BM activate repair processes in the wounds earlier. This may be due to their higher functional activity created in the monolayer by adequate intercellular interactions. To avoid complications caused by low diffuse properties of BM (protein precipitation), BM should be removed from the surface of the burn wound maximum 3 days after its application.

[Cardiomyocyte cytoskeleton in dilated cardiomyopathy and ischemic heart disease]. / Ul'trastruktura mezhmitokhondrial'nykh kontaktov kardiomiotsitov cheloveka pri alkogol'noi kardiomiopatii i ischemicheskoi bolezni serdtsa.

Summary. Vinculin, the protein of cardiomyocyte cytoskeleton in the myocardium of patients with a dilated cardiomyopathy and ischemic heart disease, was revealed by means of monoclonal antibodies and by a method of indirect immunofluorescence. Cytoskeleton of patients with dilated cardiomyopathy is disorganized, hypertrophic and contains greater amounts of vinculin than cytoskeleton of normal cardiomyocytes. This most likely negatively influences cell contractile capacity. The vinculin content was also higher in cardiomyocyte cytoskeleton of patients with ischemic heart disease but at a less degree than in patients with dilated cardiomyopathy.

[The use of pre-differentiated mesenchymal bone marrow stem cells for treatment of deep burn wounds]. / Ispol'zovanie preddifferentsirovannykh mezenkhimal'nykh stvolovykh kletok kostnogo mozga dlia lecheniia glubokikh ozhogovykh ran.

The opportunity of faster closing deep burn wounds by using fibroblast-like mesenchymal bone marrow stem cells (FMSC) and embryonic fibroblasts (EF) was investigated in rats. It was shown that FMSC as well as EF transplanted onto burn surfaces reduced the expression of cell infiltration but accelerated the formation of vessels de novo and granulation tissue in the wounds. These changes form the conditions for faster closing the burn wounds as compared to the control wounds (without cell transplantation). High rate of wound closing induced by FMSC and EF is thought to be caused by a long period (up to 30 days) of vital activity of the cells grafted on the burn surface. It was also found out that the rate of wound regeneration induced by FMSC was higher that that induced by EF.

Cell transplantation inhibits inflammatory reaction and stimulates repair processes in burn wound.

We compared the effects of transplantation of fetal fibroblasts and fibroblast-like mesenchymal stem cells of the bone marrow on healing of deep burn wound in rats. It was found that transplantation of fetal fibroblasts and fibroblast-like mesenchymal stem cells on the burn surface reduces cell infiltration, promotes the formation of vessels and granulation tissue, which creates conditions for more rapid healing of the burn wounds.

Use of recombinant AdSV40-BetaGal adenoviral construction for monitoring of transplanted cells.

Original recombinant adenoviral construction carrying E. coli beta-galactosidase LacZ gene designed by the authors is convenient for labeling and monitoring of bone marrow mesenchymal (stromal) progenitor cells and myocardial and skin fetal cells transplanted in damaged rat tissues (in the perinecrotic zone of the myocardium and onto burnt skin surface) for their reparation. This genetic construction after pre-inactivation of endogenous beta-galactosidase allows to detect transplanted cells in the foci of injury; positive effects of transplantation on tissue reparation processes can be attributed to the presence of transplanted cells.

ElastoPHB membrane systems with immobilized bone marrow stromal cells optimize conditions for regeneration of damaged tissue.

The effects of autologous bone marrow stromal cells immobilized on ElastoPHB membranes on reparative processes were studied on a model of rat skeletal muscle injury. Bone marrow stromal cells inhibited substitute (sclerosing) regeneration and activated reparative (reconstructive) regeneration of tissues.

Mesenchymal bone marrow stem cells more effectively stimulate regeneration of deep burn wounds than embryonic fibroblasts.

Regeneration of deep burn wounds after transplantation of allogenic and autogenic fibroblast-like bone marrow mesenchymal stem cells and embryonic fibroblasts on burn surface was studied in 40 Wistar rats. Transplantation of allogenic and autogenic fibroblast-like bone marrow mesenchymal stem cells and transplantation of embryonic fibroblasts decreased cell infiltration of the wound and accelerated the formation of new vessels and granulation tissue in the wound in comparison with the control (burn wounds without cell transplantation). Regeneration processes were most active after transplantation of fibroblast-like bone marrow mesenchymal stem cells, in particular, autogenic cells, which was confirmed by more rapid decrease in burn surface area. Wound healing after transplantation of fibroblast-like bone marrow mesenchymal cells and embryonic fibroblasts was associated with long functioning of transplanted cells (as was shown by staining for beta-galactosidase, the cells were transfected with an adenovirus vector carrying the marker gene). It is hypothesized that more rapid regeneration of burn wounds after transplantation of fibroblast-like bone marrow mesenchymal stem cells was due to low differentiation of these cells in comparison with embryonic fibroblasts.

Recovery of contractile function of cryodamaged rat myocardium after transplantation of fetal cardiomyocytes and predifferentiated bone marrow stromal stem cells.

The effect of cell transplantation into cryodamaged rat myocardium was studied on isolated hearts by increasing functional load to the left ventricle. Transplantation of allogeneic fetal cardiomyocytes improved the function of the left ventricle under conditions of considerably increased preload. Transplantation of autologous mesenchymal stem cells repaired left-ventricular function under conditions of increased pre- and afterload.

Differentiation of bone marrow stromal stem cells into cardiomyocyte-like cells in different mammalian species.

We describe the possibility of obtaining cardiomyocyte-like cell cultures from rat, guinea pig, and human bone marrow stromal stem cells. The content of troponin I-positive cells attains 35-45% of the total number of cells in the cultures and persists at this level for up to 4 months under differentiation conditions. Spontaneous contractions of cardiomyocyte-like cells were observed after the formation of cell monolayer under differentiation conditions.