Effect of His Bundle Pacing on Abnormal Myocardial Fatty Acid and Glucose Metabolism Induced by Right Ventricular Pacing.

BACKGROUND: Metabolic disorder is noted for pacing-induced cardiomyopathy. The benefits of His bundle pacing over right ventricular (RV) pacing in preventing pacing-induced cardiomyopathy from a metabolic perspective are yet to be fully understood. METHOD AND RESULTS: Three pig groups were established for this study: sham control, RV pacing (RV pacing for 6 months), and His pacing (RV pacing for 6 months, followed by His bundle pacing for 3 months). Complete atrioventricular block was created in the last 2 groups. Left ventricular function and dyssynchrony were assessed via echocardiography, while proteins linked to metabolism, endoplasmic reticulum stress, and inflammation in left ventricular myocardium were examined. The RV pacing group had significantly more left ventricular mechanical dyssynchrony compared with the other groups. The RV pacing group exhibited triglyceride and diacylglycerol accumulation in cardiomyocytes and higher expression of binding immunoglobulin protein and tumor necrosis factor-α than the other groups. Additionally, the expression of CD36 was activated, while the expression of hormone-sensitive lipase was downregulated in the RV pacing group compared with the His pacing and sham control groups. Furthermore, the expressions of GLUT4 and pyruvate dehydrogenase were higher in the RV pacing group than the sham control and His pacing groups. Notably, the abnormal fatty acid and glucose metabolic pathways in the left ventricular myocardium during RV pacing could be corrected by His bundle pacing. CONCLUSIONS: His bundle pacing can mitigate the abnormal metabolism disorders, endoplasmic reticulum stress, and inflammation induced during RV pacing and may contribute to the superiority of conduction system pacing over RV pacing in reducing heart failure hospitalization.

Downregulation of SIRT1 and GADD45G genes and left atrial fibrosis induced by right ventricular dependent pacing in a complete atrioventricular block pig model.

The molecular and genetic mechanisms underlying left atrial (LA) enlargement and atrial fibrosis following right ventricular (RV) dependent pacing remain unclear. Our objective was to investigate genetic expressions in the LA of pigs subjected to RV pacing for atrioventricular block (AVB), as well as to identify the differential gene expressions affected by biventricular (BiV) pacing. We established an AVB pig model and divided the subjects into three groups: a sham control group, an RV pacing group, and a BiV pacing group. Differential expression genes (DEGs) analyses conducted through next-generation sequencing (NGS) and enrichment analyses were employed to identify genes with altered expression in the LA myocardium. The RV pacing group showed a significant increase in extracellular fibrosis in the LA myocardium compared to the control group. NGS analysis revealed suppressed expression of the sirtuin signaling pathway in the RV pacing group. Among the DEGs within this pathway, GADD45G was found to be downregulated in the RV pacing group and upregulated in the BiV pacing group. Remarkably, the BiV pacing group exhibited elevated levels of GADD45G protein. In our study, we observed significant downregulation of SIRT1 and GADD45G genes, which are associated with the sirtuin signaling pathway, in the LA myocardium of the RV pacing group when compared to the control group. Moreover, these genes, which were downregulated in the RV pacing group, displayed a noteworthy upregulation in the BiV pacing group when compared to the RV pacing group.

Statins to prevent pacing-induced cardiomyopathy: Evidence from the bench applied to clinical studies.

BACKGROUND: Pacing-induced cardiomyopathy is an undesired outcome in patients with atrioventricular block (AVB), and our animal model showed lipotoxic cardiomyopathy after pacing. OBJECTIVES: The purpose of this study was to explore the mechanisms and clinical outcomes of statins in AVB patients receiving pacing. METHODS: Rat ventricular cardiomyocytes were treated with atorvastatin, liver X receptor (LXR) agonist, and LXR antagonist during pacing. Pigs were divided into 3 groups: right ventricular pacing, pacing with concomitant atorvastatin treatment, and sham control. Clinically, we enrolled 1717 AVB patients who had received a permanent pacemaker from Chang Gung Memorial Hospital Medical database. The primary outcome (cardiovascular death or heart failure [HF] hospitalization) and individual outcome were compared between statin and nonstatin groups after inverse probability of treatment weighting. RESULTS: Lipid accumulation in rat cardiomyocytes by pacing was significantly reduced by treatment with LXR agonist and atorvastatin, whereas LXR antagonist counteracted the atorvastatin effect on lipid expression. Left ventricular ejection fraction (LVEF) was significantly lower in the AVB pig pacing group compared to the group concomitantly treated with atorvastatin. Moreover, lipid accumulation and fibronectin expression were significantly ameliorated by concomitant treatment with atorvastatin. In the clinical study, the statin group had a significantly lower risk of the primary outcome event (hazard ratio [HR] 0.69; 95% confidence interval [CI] 0.56-0.84), less HF hospitalization (HR 0.45; 95% CI 0.30-0.67), and higher LVEF than the nonstatin group. CONCLUSION: In experimental models, atorvastatin ameliorated lipid accumulation in cardiomyocytes and fibrosis in left ventricular myocardium induced by pacing. Clinically, treatment with statins was associated with less HF hospitalization and cardiovascular death in AVB patients receiving pacemaker therapy.

Sarcomeres Morphology and Z-Line Arrangement Disarray Induced by Ventricular Premature Contractions through the Rac2/Cofilin Pathway.

The most common ventricular premature contractions (VPCs) originate from the right ventricular outflow tract (RVOT), but the molecular mechanisms of altered cytoskeletons of VPC-induced cardiomyopathy remain unexplored. We created a RVOT bigeminy VPC pig model (n = 6 in each group). Echocardiography was performed. The histopathological alternations in the LV myocardium were analyzed, and next generation sequencing (NGS) and functional enrichment analyses were employed to identify the differentially expressed genes (DEGs) responsible for the histopathological alternations. Finally, a cell silencing model was used to confirm the key regulatory gene and pathway. VPC pigs had increased LV diameters in the 6-month follow-up period. A histological study showed more actin cytoskeleton disorganization and actin accumulation over intercalated disc, Z-line arrangement disarray, increased ß-catenin expression, and cardiomyocyte enlargement in the LV myocardium of the VPC pigs compared to the control pigs. The NGS study showed actin cytoskeleton signaling, RhoGDI signaling, and signaling by Rho Family GTPases and ILK Signaling presented z-scores with same activation states. The expressions of Rac family small GTPase 2 (Rac2), the p-cofilin/cofilin ratio, and the F-actin/G-actin ratio were downregulated in the VPC group compared to the control group. Moreover, the intensity and number of actin filaments per cardiomyocyte were significantly decreased by Rac2 siRNA in the cell silencing model. Therefore, the Rac2/cofilin pathway was found to play a crucial role in the sarcomere morphology and Z-line arrangement disarray induced by RVOT bigeminy VPCs.

Liver X Receptor/Retinoid X Receptor Pathway Plays a Regulatory Role in Pacing-Induced Cardiomyopathy.

Background The molecular mechanisms through which high-demand pacing induce myocardial dysfunction remain unclear. Methods and Results We created atrioventricular block in pigs using dependent right ventricular septal pacing for 6 months. Echocardiography was performed to evaluate dyssynchrony between pacing (n=6) and sham control (n=6) groups. Microarray and enrichment analyses were used to identify differentially expressed genes ( DEG s) in the left ventricular ( LV ) myocardium between pacing and sham control groups. Histopathological and protein changes were also analyzed and an A cell pacing model was also performed. Pacing significantly increased mechanical dyssynchrony. Enrichment analysis using Ingenuity Pathway Analysis and the activation z-score analysis method demonstrated that there were 5 DEG s ( ABCA 1, APOD , CLU , LY 96, and SERPINF 1) in the LV septum (z-score=-0.447) and 5 DEG s ( APOD , CLU , LY 96, MSR 1, and SERPINF 1) in the LV free wall (z-score=-1.000) inhibited the liver X receptor/retinoid X receptor ( LXR / RXR ) pathway, and 4 DEG s ( ACTA 2, MYL 1, PPP 2R3A, and SNAI 2) activated the integrin-linked kinase ( ILK ) pathway in the LV septum (z-score=1.000). The pacing group had a larger cell size, higher degree of myolysis and fibrosis, and increased expression of intracellular lipid, inflammatory cytokines, and apoptotic markers than the sham control group. The causal relationships between pacing and DEG s related to LXR / RXR and ILK pathways, apoptosis, fibrosis, and lipid expression after pacing were confirmed in the cell pacing model. Luciferase reporter assay in the cell pacing model also supported inhibition of the LXR pathway by pacing. Conclusions Right ventricular septal-dependent pacing was associated with persistent LV dyssynchrony-induced cardiomyopathy through inhibition of the LXR / RXR pathway.

Idi1 and Hmgcs2 Are Affected by Stretch in HL-1 Atrial Myocytes.

BACKGROUND: Lipid expression is increased in the atrial myocytes of mitral regurgitation (MR) patients. This study aimed to investigate key regulatory genes and mechanisms of atrial lipotoxic myopathy in MR. METHODS: The HL-1 atrial myocytes were subjected to uniaxial cyclic stretching for eight hours. Fatty acid metabolism, lipoprotein signaling, and cholesterol metabolism were analyzed by PCR assay (168 genes). RESULTS: The stretched myocytes had significantly larger cell size and higher lipid expression than non-stretched myocytes (all p < 0.001). Fatty acid metabolism, lipoprotein signaling, and cholesterol metabolism in the myocytes were analyzed by PCR assay (168 genes). In comparison with their counterparts in non-stretched myocytes, seven genes in stretched monocytes (Idi1, Olr1, Nr1h4, Fabp2, Prkag3, Slc27a5, Fabp6) revealed differential upregulation with an altered fold change >1.5. Nine genes in stretched monocytes (Apoa4, Hmgcs2, Apol8, Srebf1, Acsm4, Fabp1, Acox2, Acsl6, Gk) revealed differential downregulation with an altered fold change <0.67. Canonical pathway analysis, using Ingenuity Pathway Analysis software, revealed that the only genes in the "superpathway of cholesterol biosynthesis" were Idi1 (upregulated) and Hmgcs2 (downregulated). The fraction of stretched myocytes expressing Nile red was significantly decreased by RNA interference of Idi1 (p < 0.05) and was significantly decreased by plasmid transfection of Hmgcs2 (p = 0.004). CONCLUSIONS: The Idi1 and Hmgcs2 genes have regulatory roles in atrial lipotoxic myopathy associated with atrial enlargement.

Differential Gene Expression Profile of Renin-Angiotensin System in the Left Atrium in Mitral Regurgitation Patients.

BACKGROUND: Left atrial enlargement is a mortality and heart failure risk factor in primary mitral regurgitation (MR) patients. Pig models of MR have shown differential expression of genes linked to the renin-angiotensin system. Therefore, the aim of this study was to investigate the key genes of the renin-angiotensin that are expressed differentially in the left atrial myocardium in MR patients. METHODS: Quantitative RT-PCR was used to compare gene expression in the renin-angiotensin system in the left atrium in MR patients, aortic valve disease patients, and normal subjects. RESULTS: Plasma angiotensin II concentrations did not significantly differ between MR patients and aortic valve disease patients (P = 0.582). Compared to normal controls, however, MR patients had significantly downregulated expressions of angiotensin-converting enzyme, angiotensin I converting enzyme 2, type 1 angiotensin II receptor, glutamyl aminopeptidase, angiotensinogen, cathepsin A (CTSA), thimet oligopeptidase 1, neurolysin, alanyl aminopeptidase, cathepsin G, leucyl/cystinyl aminopeptidase (LNPEP), neprilysin, and carboxypeptidase A3 in the left atrium. The MR patients also had significantly upregulated expressions of MAS1 oncogene (MAS1) and mineralocorticoid receptor compared to normal controls. Additionally, in comparison with aortic valve disease patients, MR patients had significantly downregulated CTSA and LNPEP expression and significantly upregulated MAS1 expression in the left atrium. CONCLUSIONS: Expressions of genes in the renin-angiotensin system, especially CTSA, LNPEP, and MAS1, in the left atrium in MR patients significantly differed from expressions of these genes in aortic valve disease patients and normal controls. Notably, differences in expression were independent of circulating angiotensin II levels. The results of this study provide a rationale for pharmacological therapies or posttranslational regulation therapies targeting genes expressed differentially in the renin-angiotensin system to remedy structural remodeling associated with atrial enlargement and heart failure progression in patients with MR.

Exploring Regulatory Mechanisms of Atrial Myocyte Hypertrophy of Mitral Regurgitation through Gene Expression Profiling Analysis: Role of NFAT in Cardiac Hypertrophy.

BACKGROUND: Left atrial enlargement in mitral regurgitation (MR) predicts a poor prognosis. The regulatory mechanisms of atrial myocyte hypertrophy of MR patients remain unknown. METHODS AND RESULTS: This study comprised 14 patients with MR, 7 patients with aortic valve disease (AVD), and 6 purchased samples from normal subjects (NC). We used microarrays, enrichment analysis and quantitative RT-PCR to study the gene expression profiles in the left atria. Microarray results showed that 112 genes were differentially up-regulated and 132 genes were differentially down-regulated in the left atria between MR patients and NC. Enrichment analysis of differentially expressed genes demonstrated that "NFAT in cardiac hypertrophy" pathway was not only one of the significant associated canonical pathways, but also the only one predicted with a non-zero score of 1.34 (i.e. activated) through Ingenuity Pathway Analysis molecule activity predictor. Ingenuity Pathway Analysis Global Molecular Network analysis exhibited that the highest score network also showed high association with cardiac related pathways and functions. Therefore, 5 NFAT associated genes (PPP3R1, PPP3CB, CAMK1, MEF2C, PLCE1) were studies for validation. The mRNA expressions of PPP3CB and MEF2C were significantly up-regulated, and CAMK1 and PPP3R1 were significantly down-regulated in MR patients compared to NC. Moreover, MR patients had significantly increased mRNA levels of PPP3CB, MEF2C and PLCE1 compared to AVD patients. The atrial myocyte size of MR patients significantly exceeded that of the AVD patients and NC. CONCLUSIONS: Differentially expressed genes in the "NFAT in cardiac hypertrophy" pathway may play a critical role in the atrial myocyte hypertrophy of MR patients.

Circulating miR-148b-3p and miR-409-3p as biomarkers for heart failure in patients with mitral regurgitation.

BACKGROUND: MicroRNAs (miRs) regulate gene expression in heart failure. Circulating miRs as biomarkers for heart failure in mitral regurgitation patients (MR) remain unexplored. METHODS: This case-control study enrolled 32 MR patients with heart failure, 16 asymptomatic MR patients, and 12 control subjects without heart failure. We used next generation sequencing to study the gene expression profiles in the sera, and quantitative RT-PCR to study serum and tissue miRs in the left atria. RESULTS: Next generation sequencing analysis and enrichment analysis showed that 25 miRs were differentially expressed in the sera of MR patients with heart failure compared to control subjects. The circulating miR-148b-3p (p=0.002) and miR-409-3p (p=0.010) were significantly down-regulated in the MR patients with heart failure compared to control subjects. However, only circulation miR-148b-3p was significantly down-regulated in the MR patients without heart failure compared to control subjects (p=0.009). The tissue miR-409-3p was significantly down-regulated in the MR patients with heart failure compared to 3 purchased normal controls (p=0.041). Notably, the tissue RASGRP3 mRNA, target gene of miR-409-3p, was significantly up-regulated in the MR patients with heart failure compared to normal controls (p=0.010). The tissue FRY (p=0.010) and GADD45A (p=0.010) mRNAs, target genes of miR-148b-3p, were significantly up-regulated in the MR patients with heart failure compared to normal controls. CONCLUSIONS: Circulating miR-148b-3p might serve as biomarker for future development of heart failure and miR-409-3p might serve as biomarker for incident heart failure in MR patients.

Deciphering the gene expression profile of peroxisome proliferator-activated receptor signaling pathway in the left atria of patients with mitral regurgitation.

BACKGROUND: Differentially expressed genes in the left atria of mitral regurgitation (MR) pigs have been linked to peroxisome proliferator-activated receptor (PPAR) signaling pathway in the KEGG pathway. However, specific genes of the PPAR signaling pathway in the left atria of MR patients have never been explored. METHODS: This study enrolled 15 MR patients with heart failure, 7 patients with aortic valve disease and heart failure, and 6 normal controls. We used PCR assay (84 genes) for PPAR pathway and quantitative RT-PCR to study specific genes of the PPAR pathway in the left atria. RESULTS: Gene expression profiling analysis through PCR assay identified 23 genes to be differentially expressed in the left atria of MR patients compared to normal controls. The expressions of APOA1, ACADM, FABP3, ETFDH, ECH1, CPT1B, CPT2, SLC27A6, ACAA2, SMARCD3, SORBS1, EHHADH, SLC27A1, PPARGC1B, PPARA and CPT1A were significantly up-regulated, whereas the expression of PLTP was significantly down-regulated in the MR patients compared to normal controls. The expressions of HMGCS2, ACADM, FABP3, MLYCD, ECH1, ACAA2, EHHADH, CPT1A and PLTP were significantly up-regulated in the MR patients compared to patients with aortic valve disease. Notably, only ACADM, FABP3, ECH1, ACAA2, EHHADH, CPT1A and PLTP of the PPAR pathway were significantly differentially expressed in the MR patients compared to patients with aortic valve disease and normal controls. CONCLUSIONS: Differentially expressed genes of the PPAR pathway have been identified in the left atria of MR patients compared with patients with aortic valve disease and normal controls.

Mitochondrial apoptotic pathway activation in the atria of heart failure patients due to mitral and tricuspid regurgitation.

Apoptosis occurs in atrial cardiomyocytes in mitral and tricuspid valve disease. The purpose of this study was to examine the respective roles of the mitochondrial and tumor necrosis factor-α receptor associated death domain (TRADD)-mediated death receptor pathways for apoptosis in the atrial cardiomyocytes of heart failure patients due to severe mitral and moderate-to-severe tricuspid regurgitation. This study comprised eighteen patients (7 patients with persistent atrial fibrillation and 11 in sinus rhythm). Atrial appendage tissues were obtained during surgery. Three purchased normal human left atrial tissues served as normal controls. Moderately-to-severely myolytic cardiomyocytes comprised 59.7±22.1% of the cardiomyocytes in the right atria and 52.4±12.9% of the cardiomyocytes in the left atria of mitral and tricuspid regurgitation patients with atrial fibrillation group and comprised 58.4±24.8% of the cardiomyocytes in the right atria of mitral and tricuspid regurgitation patients with sinus rhythm. In contrast, no myolysis was observed in the normal human adult left atrial tissue samples. Immunohistochemical analysis showed expression of cleaved caspase-9, an effector of the mitochondrial pathways, in the majority of right atrial cardiomyocytes (87.3±10.0%) of mitral and tricuspid regurgitation patients with sinus rhythm, and right atrial cardiomyocytes (90.6±31.4%) and left atrial cardiomyocytes (70.7±22.0%) of mitral and tricuspid regurgitation patients with atrial fibrillation. In contrast, only 5.7% of cardiomyocytes of the normal left atrial tissues showed strongly positive expression of cleaved caspase-9. Of note, none of the atrial cardiomyocytes in right atrial tissue in sinus rhythm and in the fibrillating right and left atria of mitral and tricuspid regurgitation patients, and in the normal human adult left atrial tissue samples showed cleaved caspase-8 expression, which is a downstream effector of TRADD of the death receptor pathway. Immunoblotting of atrial extracts showed that there was enhanced expression of cytosolic cytochrome c, an effector of the mitochondrial pathways, but no expression of membrane TRADD and cytosolic caspase-8 in the right atrial tissue of mitral and tricuspid regurgitation patients with sinus rhythm, and right atrial and left atrial tissues of mitral and tricuspid regurgitation patients with atrial fibrillation. Taken together, this study showed that mitochondrial pathway for apoptosis was activated in the right atria in sinus rhythm and in the left and right atria in atrial fibrillation of heart failure patients due to mitral and tricuspid regurgitation, and this mitochondrial pathway activation may contribute to atrial contractile dysfunction and enlargement in this clinical setting.

Enhanced expression of ROCK in left atrial myocytes of mitral regurgitation: a potential mechanism of myolysis.

BACKGROUND: Severe mitral regurgitation (MR) may cause myolysis in the left atrial myocytes. Myolysis may contribute to atrial enlargement. However, the relationship between Rho-associated kinase (ROCK) and myolysis in the left atrial myocytes of MR patients remain unclear. METHODS: This study comprised 22 patients with severe MR [12 with atrial fibrillation (AF) and ten in sinus rhythm]. Left atrial appendage tissues were obtained during surgery. Normal left atrial tissues were purchased. Immunofluorescence histochemical and immunoblotting studies were performed. RESULTS: The expression of ROCK2 in the myolytic left atrial myocytes of MR AF patients (p = 0.009) and MR sinus patients (p = 0.011) were significantly higher than that of the normal subjects. Similarly, the expression of ROCK1 in the myolytic left atrial myocytes of MR AF patients was significantly higher than that of the normal subjects (p = 0.010), and the expression of ROCK1 in the myolytic left atrial myocytes of MR sinus patients was higher than that of the normal subjects (p = 0.091). Immunofluorescence study revealed significant co-localization and juxtaposition of ROCK2 and cleaved caspase-3 in the left atrial myocytes both in the MR AF group (Pearson's coefficient = 0.74 ± 0.03) and the MR sinus group (Pearson's coefficient = 0.73 ± 0.02). Similarly, immunofluorescence study revealed significant co-localization and juxtaposition of ROCK1 and cleaved caspase-3 in the left atrial myocytes both in the MR AF group (Pearson's coefficient = 0.65 ± 0.03) and the MR sinus group (Pearson's coefficient = 0.65 ± 0.03). Correlation analysis demonstrated that there was a significant direct relationship between the expression of ROCK2 in the myolytic left atrial myocytes and left atrial diameter in the MR patients (p = 0.041; r = 0.440). Moreover, the ratio of phosphorylated myosin-binding subunit of myosin light chain phosphatase (pMBS)/total MBS of left atrial tissues was significantly higher in the MR AF group (p < 0.04) and the MR sinus group (p < 0.04) compared with the normal control group. CONCLUSIONS: The enhanced expression of ROCKs might be involved in the myolysis of the left atrial myocytes of MR patients.

Unraveling regulatory mechanisms of atrial remodeling of mitral regurgitation pigs by gene expression profiling analysis: role of type I angiotensin II receptor antagonist.

Left atrial enlargement associated with mitral regurgitation (MR) predicts a poor prognosis. However, the underlying regulatory mechanisms of atrial remodeling remain unclear. We used high-density oligonucleotide microarrays and enrichment analysis to identify the alteration of RNA expression pattern and biological processes involved in the atrial remodeling of pigs with and without MR. Gene arrays from left atria tissues were compared in 13 pigs (iatrogenic MR pigs [n = 6], iatrogenic MR pigs treated with valsartan [n = 4], and pigs without MR [n = 3]). A total of 22 genes were differentially upregulated by altered fold change >2.0 (Log2FC > 1), and 49 genes were differentially downregulated by altered fold change <0.5 (Log2FC < -1) in the left atria of the MR pigs compared with the pigs without MR. Enrichment analysis showed that renin-angiotensin system was identified in the Kyoto Encyclopedia of Genes and Genomes pathway. Notably, 12 of the 22 upregulated genes were identified to be downregulated by valsartan and 10 of the 49 downregulated genes were identified to be upregulated by valsartan. The tissue concentrations of angiotensin II and gene expression of hypertrophic gene, myosin regulatory light chain 2, ventricular isoforms, and fibrosis-related genes were significantly increased in the MR pigs compared with pigs without MR. In conclusion, differentially expressed transcriptome and related biological pathways have been identified in the left atria of the MR pigs compared with pigs without MR. Additionally, some of the differentially expressed genes could be regulated by type I angiotensin II receptor blocker.

Plasma C-reactive protein is not related to sinus non-conversion by maze procedure adjunct to mitral valve surgery.

In Framingham cohort study, C-reactive protein was not associated with incident atrial fibrillation (AF) after adjustment for left atrial size. This study examined whether levels of plasma inflammatory markers would be significant risk factors for failed maze procedure for AF. This study enrolled 88 patients with mitral valve disease undergoing valve surgery (n=32, sinus control group) or concomitant maze procedure for persistent atrial fibrillation (AF) (n=56, AF group). The mean follow-up in the AF group was 55.0 ± 17.5 months. The AF and sinus control groups did not differ in preoperative levels of C-reactive protein (p=0.636). In the AF group receiving maze procedure, the sinus conversion (n=37) and non-conversion (n=19) groups did not significantly differ in preoperative levels of interleukin-6 (p=0.607) and tumor necrosis factor-α (p=0.379). In multivariate analysis after adjustment for preoperative plasma inflammatory markers, independent factors associated with sinus conversion were AF duration (p=0.003), and left atrial area (p=0.014). In conclusion, plasma inflammatory markers are not associated with sinus non-conversion by radiofrequency maze procedure.

Autophagy as a mechanism for myolysis of cardiomyocytes in mitral regurgitation.

BACKGROUND: Myolysis of atrial cardiomyocytes occurs in patients with severe mitral and tricuspid regurgitation. This morphological remodelling may involve autophagy. METHODS: This study comprised 20 patients (10 with long-standing persistent atrial fibrillation and 10 with sinus rhythm) with severe mitral and tricuspid regurgitation. Atrial appendageal tissues were obtained during surgery. The appearance of autophagosomes (LC3B) in myocytes can reflect autophagy induction. Complement 9 is used as a reliable marker of oncosis. RESULTS: In the fibrillating right atria, 68·4 ± 18·9% of total myocytes showed moderate-to-severe myolysis, while 64·2 ± 15·8% of total myocytes comprised these cells in right atrial myocardium with sinus rhythm. Immunohistochemical study revealed LC3B-positive myocytes in 8·0% of myocytes without myolysis, 11·9% of myocytes with mild myolysis and 49·4% of myocytes with moderate-to-severe myolysis in right atrial myocardium with sinus rhythm (P < 0·0001). Similarly, in the fibrillating right atria, LC3B-positive myocytes were observed in 5·9% of myocytes without myolysis, 12·2% of myocytes with mild myolysis and 50·7% of myocytes with moderate-to-severe myolysis (P < 0·0001). Moreover, in the fibrillating left atria, LC3B-positive myocytes were observed in 4·9% of myocytes without myolysis, 12·6% of myocytes with mild myolysis and 52·0% of myocytes with moderate-to-severe myolysis (P < 0·0001). None of the atrial myocytes displayed intracellular deposition of complement 9. CONCLUSIONS: Induction of autophagy, but not oncosis, occurs in most cases of atrial cardiomyocytes with severe mitral and tricuspid regurgitation, even those without atrial fibrillation, and is closely associated with the development of myolysis in this disease.

Expression of spliceosome assembly factor SC-35 in TUNEL-positive atrial cardiomyocytes in mitral and tricuspid regurgitation: viability of atrial cardiomyocytes.

BACKGROUND: Most of the atrial cardiomyocytes with positive terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end-labelling (TUNEL) reaction are not apoptotic in patients with mitral and tricuspid valve diseases. The TUNEL-positive myocytes with expression of spliceosome assembly factor SC-35, an indicator of increased RNA synthesis, should be living cardiomyocytes. METHODS: This study analyzed twenty-three patients with significant mitral and tricuspid regurgitation. Fifteen patients had persistent atrial fibrillation, and eight had sinus rhythm. Atrial appendageal tissues were obtained during surgery. Immunohistochemical study was performed. RESULTS: Immunohistochemical study of fibrillating right atrial myocardium demonstrated that 44.8 ± 24.6% of myocytes had TUNEL-positive nuclei whereas 39.4 ± 21.4% of myocytes had TUNEL-positive nuclei in sinus right atrial myocardium (p=0.682). However, most (81.6%) nuclei of TUNEL-positive myocytes in the fibrillating right atria also expressed proliferating cell nuclear antigen (PCNA), an indicator of DNA replication and repair, and most nuclei (91.8%) of TUNEL-positive myocytes also expressed SC-35. In fibrillating left atria, most (88.1%) nuclei of TUNEL-positive myocytes also expressed SC-35. Similarly, in sinus right atrial myocardium, most (78.0%) nuclei of TUNEL-positive myocytes expressed PCNA, and most (91.4%) nuclei of TUNEL-positive myocytes also expressed SC-35, but none expressed Ki-67, a replication-associated antigen. Additionally, the percentage of TUNEL-positive myocytes in the right atria significantly and positively correlated with the percentage of PCNA-positive myocytes (r=0.826, p<0.001) and SC-35 positive myocytes (r=0.713, p<0.001). CONCLUSIONS: Most TUNEL-positive atrial cardiomyocytes in patients with mitral and tricuspid regurgitation are living cardiomyocytes.