Jen-Ping Chang

Atrial myocardial nox2 containing NADPH oxidase activity contribution to oxidative stress in mitral regurgitation: potential mechanism for atrial remodeling

BACKGROUNDnOxidative stress is linked with several cardiovascular diseases. However, the NADPH oxidase activity in severe mitral regurgitation patients with and without atrial fibrillation has not yet been explored.nnnMETHODSnThis study involved 16 adult patients (eight patients with persistent atrial fibrillation and eight with sinus rhythm) with severe mitral and moderate-to-severe tricuspid regurgitation and five control patients without mitral and tricuspid disease. Atrial tissues of the right and left atrial appendages were obtained during surgery. Superoxide anion production was measured by lucigenin-enhanced chemiluminescence, and the expression of nox2 containing NADPH oxidase mRNA was measured by quantitative real-time RT-PCR. Additionally, immunohistochemical study was performed.nnnRESULTSnNADPH-stimulated superoxide release was significantly higher than basal superoxide production from right [5671.9±3498.7 vs. 232.7±70.0 relative light units per second per milligram of protein (RLU s(-1) mg protein(-1)), P=.008) and left atrial homogenates (6475.1±1890.8 vs. 229.0±79.6 RLU s(-1) mg protein(-1), P=.008) in atrial fibrillation patients. The NADPH-stimulated superoxide release from right atrial homogenates was also significantly higher than basal superoxide production in sinus patients (6809.1±1327.1 vs. 244.2±65.5 RLU s(-1) mg protein(-1), P=.008). Additionally, there was a borderline significant correlation between NADPH-stimulated superoxide production from left atrial homogenates and left atrial sizes (r=0.683, P=.062) in atrial fibrillation patients. Membrane-bound nox2 containing NADPH oxidase mRNA expression was increased and was similar in both the atrial fibrillation patients and sinus patients. The NADPH-stimulated superoxide production in right atrial homogenates in control atrial samples was 1863.7±137.2 RLU s(-1) mg protein(-1). Immunohistochemical study demonstrated increased expression of nox2 in myocytes with moderate-to-severe myolysis and hypertrophy.nnnCONCLUSIONSnResults of this study demonstrate that membrane-bound nox2 containing NADPH oxidase activity and expression in the atrial myocardium is increased in patients with severe mitral regurgitation, possibly contributing to atrial remodeling in this clinical setting.

Autophagy as a mechanism for myolysis of cardiomyocytes in mitral regurgitation

Eur J Clin Invest 2011; 41 (3): 299–307

Dedifferentiation of atrial cardiomyocytes in cardiac valve disease: unrelated to atrial fibrillation.

BACKGROUNDnValvular heart disease has become an important public health concern. The increased wall stress and underlying disease entity associated with mitral valve disease provide unfavorable circumstances for atrial cardiomyocytes. The expression of the alpha-smooth muscle actin isoform is considered characteristic of cardiomyocyte dedifferentiation (embryonic cardiomyocyte), and cardiomyocyte dedifferentiation may indicate an adaptive state, enabling cardiomyocytes to survive despite unfavorable circumstances.nnnMETHODSnThis study comprised 20 adult patients with symptomatic severe mitral valve disease and moderate to severe tricuspid valve disease and without coronary artery disease undergoing valve operations for congestive heart failure. Ten patients had persistent atrial fibrillation and 10 patients had never been in atrial fibrillation by history and electrocardiograms before surgery. Atrial tissues of the right atrial appendage were obtained during surgery.nnnRESULTSnImmunohistochemical study demonstrated that alpha-smooth muscle actin protein expression was not altered by atrial fibrillation, and alpha-smooth muscle actin protein expression in atrial tissues was higher in patients with sinus rhythm than in those with atrial fibrillation (the percentage of cells that were alpha-smooth muscle actin-positive was 51.5+/-34.9% for right atria from patients in sinus rhythm vs. 16.2+/-15.0% for right atria from patients with atrial fibrillation) (P<.03). Semiquantitation of alpha-smooth muscle actin by immunoblotting of extracts from atrial tissues showed similar findings as in the immunohistochemical observations: that is, atrial fibrillation did not influence the expression of alpha-smooth muscle actin protein. Interstitial fibrosis represented 43.2+/-13.9% of the right atrial tissue in the sinus group, whereas interstitial fibrosis comprised 49.8+/-8.2% of the right atrial tissue in the atrial fibrillation group (P=.320).nnnCONCLUSIONSnDedifferentiation of atrial cardiomyocytes occurs in patients with cardiac valve disease, even without atrial fibrillation.

DNA repair in TUNEL-positive atrial cardiomyocytes of mitral and tricuspid valve diseases: Potential mechanism for preserving cardiomyocytes

BACKGROUNDnThe reported presence of DNA breaks, based on a positive reaction to the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end-labelling (TUNEL) assay, in fibrillating human right atria of cardiac valve disease may suggest apoptotic myocyte death. However, TUNEL positivity may reflect conditions other than cell death.nnnMETHODSnThis study comprised 27 adult patients (14 patients with persistent atrial fibrillation and 13 in sinus rhythm) with significant mitral and tricuspid valve diseases. Atrial tissues were obtained during surgery.nnnRESULTSnImmunohistochemical study demonstrated that 31.1±12.2% of the myocytes had TUNEL-positive nuclei in the fibrillating right atria whereas 37.4±23.2% of the myocytes had TUNEL-positive nuclei in the right atrial myocardium in sinus rhythm (p=0.505). However, most nuclei of TUNEL-positive myocytes in the right atria also expressed proliferating cell nuclear antigen (PCNA), an indicator of DNA replication and repair but never Ki-67, a replication-associated antigen (TUNEL(+)/PCNA(+) vs. TUNEL(+)/PCNA(-), 30.5±10.8% vs. 1.2±1.5%, p=0.005, in the atrial fibrillation group and 32.8±18.6% vs. 4.6±8.1%, p=0.003, in the sinus group), suggesting that most TUNEL-positive myocytes were undergoing DNA repair. In addition, the incidence of TUNEL-positive myocytes significantly and positively correlated with the incidence of PCNA-positive myocytes (r=0.5, p<0.03 in the right atria; r=0.661, p<0.04 in the left atria).nnnCONCLUSIONSnCell death by apoptosis occurs in a small percentage of atrial cardiomyocytes in mitral and tricuspid valve diseases and DNA repair is more important and preserves the cardiomyocytes.

Increased serum oxidative stress in patients with severe mitral regurgitation: A new finding and potential mechanism for atrial enlargement

OBJECTIVEnThe aim of this study was to examine the serum oxidative stress in patients with severe mitral regurgitation.nnnDESIGN AND METHODSnThis study analyzed serum oxidative stress index in patients with severe mitral regurgitation [persistent atrial fibrillation (AF) or sinus rhythm], paroxysmal lone AF patients and healthy subjects.nnnRESULTSnThe serum oxidative stress index was significantly higher in the mitral regurgitation AF group and sinus group than in the lone AF group and healthy subjects (p<0.0001). Left atrial size was significantly larger in the mitral regurgitation AF group and sinus group than in the lone AF group and healthy subjects (p<0.0001). The oxidative stress index significantly and positively correlated with left atrial size in the overall study population (r=0.439, p=0.0008).nnnCONCLUSIONSnThis study provides new evidence of increased oxidative stress in human severe mitral regurgitation, probably contributing to atrial enlargement.

Thrombocytopenia, Dual Antiplatelet Therapy, and Heparin Bridging Strategy Increase Pocket Hematoma Complications in Patients Undergoing Cardiac Rhythm Device Implantation

BACKGROUNDnPocket hematoma is a troublesome complication associated with the implantation of cardiac implantable electronic devices (CIEDs). This study aims to determinate the risk factors of pocket hematoma complications in relation to different antithrombotic strategies and severity of thrombocytopenia in Chinese patients.nnnMETHODSnWe conducted a retrospective study of 1093 consecutive patients undergoing implantation of CIEDs and divided them into 3 groups: no antithrombotic group (n = 512), continuing antiplatelet group (n = 477), and temporarily discontinuing warfarin with or without heparin bridging strategy (n = 104).nnnRESULTSnA pocket hematoma developed in 40 patients (3.7%). The temporarily discontinuing warfarin group (7.7%) had a higher incidence of pocket hematoma than no oral antithrombotic group (2.1%) and continuing antiplatelet group (4.4%) (P = 0.012). The dual antiplatelet group (16.2%) and the heparin bridging strategy group (14.0%) had significantly higher incidence of pocket hematoma compared with the no antithrombotic group (2.1%; P < 0.001, both). Patients having aspirin or clopidogrel alone had low incidence of pocket hematoma (3.9% and 1.2%, respectively), similar to the no antithrombotic group (P = not significant). Multivariate analysis revealed that dual antiplatelet agents (P = 0.004), heparin bridging strategy (P < 0.001), and moderate to severe thrombocytopenia (P = 0.007) were independent predictors for pocket hematoma complications.nnnCONCLUSIONSnThe use of dual antiplatelet agents, heparin bridging strategy, and the presence of moderate to severe thrombocytopenia significantly increased the risk of pocket hematoma complications in the periprocedural period of CIED implant. Aspirin or clopidogrel alone did not increase the risk of pocket hematoma complications.

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

BACKGROUNDnMost 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.nnnMETHODSnThis 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.nnnRESULTSnImmunohistochemical 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).nnnCONCLUSIONSnMost TUNEL-positive atrial cardiomyocytes in patients with mitral and tricuspid regurgitation are living cardiomyocytes.

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.

Role of the Simultaneous Sequential Strategy for Failed Acute Sinus Restoration after Modified Left Maze Procedure for Persistent Atrial Fibrillation with Concomitant Mitral Surgery

BackgroundWe assessed whether the simultaneous sequential strategy could (1) achieve additional sinus restoration for those patients who were not in sinus rhythm while coming off bypass after modified left maze procedure and (2) attain the same long-term success rates as the bi-atrial maze procedure in patients with persistent atrial fibrillation (AF) and mitral valve disease.Materials and MethodsTwenty-seven consecutive patients – ten men and 17 women with a mean age of 52 ± 13 years, all with persistent AF and mitral valve disease – underwent the modified maze procedure with the simultaneous sequential strategy. In the first phase, the modified left atrial maze operation was carried out with concomitant valvular surgery; the right side maze operation was subsequently carried out as a second phase of the sequential strategy only if AF re-appeared following the spontaneous restoration of heart beats during the operation.ResultsTwenty patients (74.1%) underwent the left atrial maze procedure only, and seven patients (25.9%) required the subsequent right atrial maze procedure as part of the sequential strategy. At a mean follow-up of 15.1 ± 7.7 months, six of the 27 patients (22.2%) who underwent additional right atrial maze procedure had restored sinus rhythm. At a mean follow-up of 17.8 ± 7.3 months, 24 of the 27 patients (88.9%) had restored sinus rhythm and 22 patients (81.5%) had restored bi-atrial transport function (right atrial filling fraction: 40.8 ± 11.7%; left atrial filling fraction: 22.9 ± 8.1%) after application of the sequential strategy.ConclusionsCompared with modified left atrial maze procedure, the application of the simultaneous sequential strategy successfully restored sinus rhythm in an additional 22.2% of patients with persistent AF. The overall sinus conversion rate of 88.9% was comparable with that of the standard bi-atrial maze procedure.

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.