Effects of angiotensin-converting enzyme inhibition on the development of the atrial fibrillation substrate in dogs with ventricular tachypacing-induced congestive heart failure

Antihypertensive strategy based on angiotensin II receptor blockers: a new gateway to reduce risk in hypertension

Effective treatment of high blood pressure levels represents a key strategy for reducing global cardiovascular risk. Other factors, beyond blood pressure control, however, appear to be of potential relevance in reducing the risk related to hypertension. Recent clinical trials have demonstrated that those pharmacological agents that counteract the renin-angiotensin system may confer additional clinical benefits across the spectrum of cardiovascular disease, beyond their blood pressure-lowering properties. These studies are largely based on the use of an antihypertensive strategy, based on the association between angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers (ARBs) and low-dose thiazide diuretics or calcium channel blockers. Over the last few decades, clinical trials have also tested the potential effects of combination therapy based on the association between angiotensin-converting enzyme inhibitors or ARBs and other renin-angiotensin system-blocking agents, including mineralocorticoid receptor antagonists and, more recently, renin inhibitors. This review highlights the evidence derived from recent clinical trials, supporting a role for pharmacological strategies based on ARBs in primary and secondary prevention of cardiovascular and renal disease.

Structural and Functional Remodeling of the Left Atrium: Clinical and Therapeutic Implications for Atrial Fibrillation

Atrial fibrillation (AF) is the most commonly encountered arrhythmia in clinical practice. Despite advances in our understanding of the pathophysiology of this complex arrhythmia, current therapeutic options remain suboptimal. This review aimed to delineate the atrial structural and functional remodeling leading to the perpetuation of AF. We explored the complex changes seen in the atria in various substrates for AF and the therapeutic options available to prevent these changes or for reverse remodeling. Here we also highlighted the emerging role of aggressive risk factor management aimed at the arrhythmogenic atrial substrate to prevent or retard AF progression.

Mechanisms with clinical implications for atrial fibrillation-associated remodeling: cathepsin K expression, regulation, and therapeutic target and biomarker

BACKGROUND

The cysteine protease cathepsin K (CatK) has been implicated in the pathogenesis of cardiovascular disease. We sought to determine the link between atrial fibrillation (AF) and plasma CatK levels and to investigate the expression of and therapeutic target for CatK in vivo and in vitro.

METHODS AND RESULTS

Plasma CatK and extracellular matrix protein peptides (intact procollagen type I of N-terminal propeptide; carboxyl-terminal telopeptide of type I collagen [ICTP]) were measured in 209 consecutive patients with AF (paroxysmal AF, 146; persistent AF, 63) and 112 control subjects. In addition, the regulation of CatK expression was investigated in vivo and vitro. Patients with AF had higher plasma CatK and ICTP levels than did control subjects. Patients with persistent AF had higher levels of plasma CatK and ICTP than did patients with paroxysmal AF. CatK was correlated with ICTP concentration and left atrial diameter in all subjects. In rabbits, superoxide production, CatK activity, fibrosis, and the levels of atrial tissue angiotensin II, angiotensin type 1 receptor, gp91phox, phospho-p38 mitogen-activated protein kinase, and CatK were greater in those with tachypacing-induced AF than in controls, and these changes were reversed with angiotensin type 1 receptor antagonist. Olmesartan and mitogen-activated protein kinase inhibitor decreased the CatK expression induced by angiotensin II in rat neonatal myocytes.

CONCLUSIONS

These data indicated that increased plasma CatK levels are linked with the presence of AF. Angiotensin type 1 receptor antagonist appears to be effective in alleviating atrial fibrosis in a rabbit AF model, partly reducing angiotensin type 1 receptor-p38mitogen-activated protein kinase-dependent and -independent CatK activation, thus preventing AF.

Atrial fibrillation from the pathologist's perspective

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia encountered in clinical practice, is associated with increased morbidity and mortality. Electrophysiologically, it is characterized by a high rate of asynchronous atrial cell depolarization causing a loss of atrial contractile function and irregular ventricular rates. For a long time, AF was considered as a pure functional disorder without any structural background. Only in recent years, have new mapping and imaging techniques identified atrial locations, which are very often involved in the initiation and maintenance of this supraventricular arrhythmia (i.e. the distal portion of the pulmonary veins and the surrounding atrial myocardium). Morphological analysis of these myocardial sites has demonstrated significant structural remodeling as well as paved the way for further knowledge of AF natural history, pathogenesis, and treatment. This architectural myocardial disarrangement is induced by the arrhythmia itself and the very frequently associated cardiovascular disorders. At the same time, the structural remodeling is also capable of sustaining AF, thereby creating a sort of pathogenetic vicious circle. This review focuses on current understanding about the structural and genetic bases of AF with reference to their classification, pathogenesis, and clinical implications.

TheTGFB1 functional polymorphism rs1800469 and susceptibility to atrial fibrillation in two Chinese Han populations

Transforming growth factor-β1 (TGF-β1) is related to the degree of atrial fibrosis and plays critical roles in the induction and perpetuation of atrial fibrillation (AF). To investigate the association of the common promoter polymorphism rs1800469 in the TGF-β1 gene (TGFB1) with the risk of AF in Chinese Han population, we carried out a case-control study of two hospital-based independent populations: Southeast Chinese population (581 patients with AF and 723 controls), and Northeast Chinese population (308 AF patients and 292 controls). Two hundred and seventy-eight cases of AF were lone AF and 334 cases of AF were diagnosed as paroxysmal AF. In both populations, AF patients had larger left atrial diameters than the controls did. The rs1800469 genotypes in the TGFB1 gene were determined by polymerase chain reaction-restriction fragment length polymorphism. The genotype and allele frequencies of rs1800469 were not different between AF patients and controls of the Southeast Chinese population, Northeast Chinese population, and total Study Population. After adjustment for age, sex, hypertension and LAD, there was no association between the rs1800469 polymorphism and the risk of AF under the dominant, recessive and additive genetic models. Similar results were obtained from subanalysis of the lone and paroxymal AF subgroups. Our results do not support the role of the TGFB1 rs1800469 functional gene variant in the development of AF in the Chinese Han population.

Cross-talk between mineralocorticoid receptor/angiotensin II type 1 receptor and mitogen-activated protein kinase pathways underlies aldosterone-induced atrial fibrotic responses in HL-1 cardiomyocytes

BACKGROUND

Aldosterone is increasingly recognized for its involvement in atrial structural remodeling. However, the precise molecular mechanisms and signal pathways underlying aldosterone-induced atrial fibrosis are unknown.

METHODS

Western blotting was used to investigate the effects of aldosterone on the expression of mineralocorticoid receptor (MR), angiotensin II type I receptor (AT1), mitogen-activated protein kinases (MAPKs), and fibrotic marker proteins in cultured HL-1 cardiomyocytes.

RESULTS

Aldosterone upregulated MR and AT1 expressions in a concentration-dependent and time-dependent manner. Aldosterone (10(-6)M) significantly and time-dependently increased activation of the extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38MAPK pathways, and the protein expression of collagen 1A and 3A (COL1A and COL3A), transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA). Pre-treatment with eplerenone (10(-10)M) prevented the increased expression of MR, MAPK signals and the above profibrotic molecules, but amplified the increase in AT1 level stimulated by aldosterone (10(-6)M). Pre-treatment with losartan (10(-10)M) or MAPK pathway inhibitors (U0126 or SP600125) abolished aldosterone-induced MR upregulation and significantly inhibited the expression of the above fibrotic marker proteins, indicating the critical role of MR and the requirement for active AT1 in the development of aldosterone-induced atrial fibrosis.

CONCLUSIONS

Elevated MR activity plays a central role in aldosterone-mediated activation of the MAPK signaling pathway and subsequent profibrotic effects in HL-1 atrial cells. MR/AT1 and the MAPK signaling pathway interact to trigger the molecular mechanism underlying the aldosterone-induced atrial fibrotic response. Our results support the view that MR blockade in conjunction with AT1 blockade can prevent the occurrence of atrial fibrillation.

Ventricular rate control of atrial fibrillation in heart failure

In the last few years, there has been a major shift in the treatment of atrial fibrillation (AF) in the setting of hear failure (HF), from rhythm to ventricular rate control in most patients with both conditions. In this article, the authors focus on ventricular rate control and discuss the indications; the optimal ventricular rate-control target, including detailed results of the Rate Control Efficacy in Permanent Atrial Fibrillation: a Comparison Between Lenient versus Strict Rate Control II (RACE II) study; and the pharmacologic and nonpharmacologic options to control the ventricular rate during AF in the setting of HF.

Impact of aldosterone antagonists on the substrate for atrial fibrillation: aldosterone promotes oxidative stress and atrial structural/electrical remodeling

Atrial fibrillation (AF), the most common cardiac arrhythmia, is an electrocardiographic description of a condition with multiple and complex underlying mechanisms. Oxidative stress is an important driver of structural remodeling that creates a substrate for AF. Oxidant radicals may promote increase of atrial oxidative damage, electrical and structural remodeling, and atrial inflammation. AF and other cardiovascular morbidities activate angiotensin (Ang-II)-dependent and independent cascades. A key component of the renin-angiotensin-aldosterone system (RAAS) is the mineralocorticoid aldosterone. Recent studies provide evidence of myocardial aldosterone synthesis. Aldosterone promotes cardiac oxidative stress, inflammation and structural/electrical remodeling via multiple mechanisms. In HF patients, aldosterone production is enhanced. In patients and in experimental HF and AF models, aldosterone receptor antagonists have favorable influences on cardiac remodeling and oxidative stress. Therapeutic approaches that seek to reduce AF burden by modulating the aldosterone system are likely beneficial but underutilized.

Atrial fibrillation and heart failure in the elderly

Atrial fibrillation (AF) is a common clinical problem in elderly patients and especially in those with heart failure (HF). It is a major risk factor for serious cardiovascular events, such as stroke, HF and premature death. Both the prevalence and incidence of AF increase with age and its prevalence in the United States are estimated at more than 2.2 million, with nearly 75% of patients aged >65 years. Aging-related atrial remodeling with fibrosis, dilation and mitochondrial DNA mutations predispose elderly patients to AF. Current management options for AF, including rate control and anticoagulation therapy, can be successfully applied to the elderly population. New antiarrhythmic and anticoagulation medications such as dronedarone and dabigatran, respectively, can impact the approach to therapy in the elderly. Non-pharmacological options such as catheter-based ablation have also gained prominence and have been incorporated into the guidelines for management of AF. However, more trials in the elderly and very elderly segments are needed to clarify the safety and long-term efficacy of the new treatment options.

An Angiotensin receptor blocker prevents arrhythmogenic left atrial remodeling in a rat post myocardial infarction induced heart failure model

This study investigated the role of angiotensin II receptor blocker in atrial remodeling in rats with atrial fibrillation (AF) induced by a myocardial infarction (MI). MIs were induced by a ligation of the left anterior descending coronary artery. Two days after, the rats in the losartan group were given losartan (10 mg/kg/day for 10 weeks). Ten weeks later, echocardiography and AF induction studies were conducted. Ejection fraction was significantly lower in the MI rats. Fibrosis analysis revealed much increased left atrial fibrosis in the MI group than sham (2.22 ± 0.66% vs 0.25 ± 0.08%, P = 0.001) and suppression in the losartan group (0.90 ± 0.27%, P 0.001) compared with the MI group. AF inducibility was higher in the MI group than sham (39.4 ± 43.0% vs 2.0 ± 6.3%, P = 0.005) and significantly lower in losartan group (12.0 ± 31.6%, P = 0.029) compared with the MI. The left atrial endothelial nitric oxide synthase (NOS) and sarco/endoplasmic reticulum Ca(2+)-ATPase levels were lower in the MI group and higher in the losartan group significantly. The atrial inducible NOS and sodium-calcium exchanger levels were higher in the MI and lower in the losartan group significantly. Losartan disrupts collagen fiber formation and prevents the alteration of the tissue eNOS and iNOS levels, which prevent subsequent AF induction.

Molecular basis of selective atrial fibrosis due to overexpression of transforming growth factor-β1

AIMS

Animal studies show that transforming growth factor-β1 (TGF-β1) is an important mediator of atrial fibrosis and atrial fibrillation (AF). This study investigated the role of TGF-β1 in human AF and the mechanism of atrial-selective fibrosis.

METHODS AND RESULTS

Atrial specimens from 17 open heart surgery patients and left atrial and ventricular specimens from 17 explanted hearts were collected to assess the relationship between TGF-β1, AF, and differential atrial vs. ventricular TGF-β1 levels. A transgenic mouse model overexpressing active TGF-β1 was used to study the mechanisms underlying the resultant atrial-selective fibrosis. Higher right atrial total TGF-β1 levels (2.58 ± 0.16-fold, P < 0.0001) and active TGF-β1 (3.7 ± 0.7-fold, P = 0.013) were observed in those that developed post-operative AF. Although no ventricular differences were observed, 11 explanted heart failure hearts exhibited higher atrial TGF-β1 levels than 6 non-failing hearts (2.30 ± 0.87 fold higher, P < 0.001). In the transgenic mouse, TGF-β1 receptor-1 kinase blockade resulted in decreased atrial expression of fibrosis-related genes. By RNA microarray analyses in that model, 80 genes in the atria and only 2 genes in the ventricle were differentially expressed. Although these mice atria, but not the ventricles, exhibited increased expression of fibrosis-related genes and phosphorylation of Smad2, there were no differences in TGF-β1 receptor levels or Smads in the atria compared with the ventricles.

CONCLUSIONS

TGF-β1 mediates selective atrial fibrosis in AF that occurs via TGF-β Receptor 1/2 and the classical Smad pathway. The differential atrial vs. ventricular fibrotic response occurs at the level of TGF-β1 receptor binding or phosphorylation.

Human epicardial adipose tissue induces fibrosis of the atrial myocardium through the secretion of adipo-fibrokines

AIMS

Recent studies have reported a relationship between the abundance of epicardial adipose tissue (EAT) and the risk of cardiovascular diseases including atrial fibrillation (AF). However, the underlying mechanisms are unknown. The aim of this study was to examine the effects of the secretome of human EAT on the histological properties of the myocardium.

METHODS AND RESULTS

Samples of EAT and subcutaneous adipose (SAT), obtained from 39 patients undergoing coronary bypass surgery, were analysed and tested in an organo-culture model of rat atria to evaluate the fibrotic properties of human fat depots. The EAT secretome induced global fibrosis (interstitial and peripheral) of rat atria in organo-culture conditions. Activin A was highly expressed in EAT compared with SAT and promoted atrial fibrosis, an effect blocked using neutralizing antibody. In addition, Activin A levels were enhanced in patients with low left-ventricular function. In sections of human atrial and ventricular myocardium, adipose and myocardial tissues were in close contact, together with fibrosis.

CONCLUSION

This study provides the first evidence that the secretome from EAT promotes myocardial fibrosis through the secretion of adipo-fibrokines such as Activin A.

Associations between cardiac fibrosis and permanent atrial fibrillation in advanced heart failure

Atrial fibrosis is considered as the basis in the development of long-standing atrial fibrillation (AF). However, in advanced heart failure (HF), the independent role of fibrosis for AF development is less clear since HF itself leads to atrial scarring. Our study aimed to differentiate patients with AF from patients without AF in a population consisting of patients with advanced HF. Myocardial samples from the right atrial and the left ventricular wall were obtained during heart transplantation from the explanted hearts of 21 male patients with advanced HF. Long-standing AF was present in 10 of them and the remaining 11 patients served as sinus rhythm controls. Echocardiographic and hemodynamic measurements were recorded prior to heart transplantation. Collagen volume fraction (CVF), transforming growth factor-beta (TGF-beta), and connective tissue growth factor (CTGF) expression in myocardial specimens were assessed histologically and immunohistochemically. The groups were well matched according to age (51.9+/-8.8 vs. 51.3+/-9.3 y) and co-morbidities. The AF group had higher blood pressure in the right atrium (13.6+/-7.7 vs. 6.0+/-5.0 mmHg; p=0.02), larger left atrium diameter (56.1+/-7.7 vs. 50+/-5.1 mm; p=0.043), higher left atrium wall stress (18.1+/-2.1 vs. 16.1+/-1.7 kdynes/m(2); p=0.04), and longer duration of HF (5.0+/-2.9 vs. 2.0+/-1.6 y, p=0.008). There were no significant differences in CVF (p=0.12), in CTGF (p=0.60), and in TGF-beta expression (p=0.66) in the atrial myocardium between the two study groups. In conclusions, in advanced HF, atrial fibrosis expressed by CVF is invariably present regardless of occurrence of AF. In addition to atrial wall fibrosis, increased wall stress might contribute to AF development in long-standing AF.

The Impact of Suppressing the Renin-Angiotensin System on Atrial Fibrillation

Atrial fibrillation is very common in the United States. After a search of Medline, EMBASE, and CINAHL, 4 trials evaluating inhibitors of the renin-angiotensin system were identified for prevention of new-onset atrial fibrillation, facilitation of electrical cardioversion of atrial fibrillation, and prevention of atrial fibrillation recurrence after electrical cardioversion. A meta-analysis was performed using a random-effects model. Use of an angiotensin-converting enzyme (ACE) inhibitor or angiotensin-receptor blocker (ARB) was associated with a reduction in new-onset atrial fibrillation (OR [95% CI] = 0.51 [0.36-0.72]), a lower failure rate of electrical cardioversion of atrial fibrillation (0.47 [0.24-0.92]), and a lower rate of recurrence of atrial fibrillation after electrical cardioversion (0.39 [0.20-0.75]). With the exception of the new-onset atrial fibrillation analysis, these findings were not associated with statistical heterogeneity. These hypothesis-generating data suggest that inhibitors of the renin-angiotensin system may provide benefit across the spectrum of atrial fibrillation.

Oxidative stress, fibrosis, and early afterdepolarization-mediated cardiac arrhythmias

Animal and clinical studies have demonstrated that oxidative stress, a common pathophysiological factor in cardiac disease, reduces repolarization reserve by enhancing the L-type calcium current, the late Na, and the Na-Ca exchanger, promoting early afterdepolarizations (EADs) that can initiate ventricular tachycardia and ventricular fibrillation (VT/VF) in structurally remodeled hearts. Increased ventricular fibrosis plays a key facilitatory role in allowing oxidative-stress induced EADs to manifest as triggered activity and VT/VF, since normal non-fibrotic hearts are resistant to arrhythmias when challenged with similar or higher levels of oxidative stress. The findings imply that antifibrotic therapy, in addition to therapies designed to suppress EAD formation at the cellular level, may be synergistic in reducing the risk of sudden cardiac death.

Effects of irbesartan on gene expression revealed by transcriptome analysis of left atrial tissue in a porcine model of acute rapid pacing in vivo

BACKGROUND

Atrial fibrillation (AF) is characterized by electrical and structural remodeling of the atria with atrial fibrosis being one hallmark. Angiotensin II (AngII) is a major contributing factor and blockage of its type I receptor (AT1R) prevents remodeling to some extent. Here we explored the effects of the AT1R antagonist irbesartan on global gene expression and profibrotic signaling pathways after induction of rapid atrial pacing (RAP) in vivo in pigs.

METHODS AND RESULTS

Microarray-based RNA profiling was used to screen left atrial (LA) tissue specimens for differences in atrial gene expression in a model of acute RAP. RAP caused an overall expression profile that reflected AngII-induced ROS production, tissue remodeling, and energy depletion. Of special note, the mRNA levels of EDN1, SGK1, and CTGF encoding pro-endothelin, stress- and glucocorticoid activated kinase-1, and of connective tissue growth factor were identified to be significantly increased after 7h of rapid pacing. These specific expression changes were additionally validated by RT-qPCR or immunoblot analyses in LA, RA, and partly in LV samples. All RAP-induced differential gene expression patterns were partially attenuated in the presence of irbesartan. Similar results were obtained after RAP of HL-1 cardiomyocytes in vitro. Furthermore, exogenously added endothelin-1 (ET1) induced CTGF expression concomitant to the transcriptional activation of SGK1 in HL-1 cells.

CONCLUSIONS

RAP provokes substantial changes in atrial and ventricular myocardial gene expression that could be partly reversed by irbesartan. ET1 contributes to AF-dependent atrial fibrosis by synergistic activity with AngII to stimulate SGK1 expression and enhance phosphorylation of the SGK1 protein which, in turn, induces CTGF. The latter has been consistently associated with tissue fibrosis. These findings suggest ETR antagonists as being beneficial in AF treatment.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

Atrial fibrillation in heart failure

Heart failure (HF) and atrial fibrillation (AF) are highly prevalent debilitating conditions that often coexist and are frequently encountered in clinical practice. The presence of chronic AF is a marker of worse prognosis in patients with HF, and the onset of new AF in those with chronic HF is associated with increased morbidity and mortality. Advances in the development of novel drugs, nonpharmacologic modalities, and therapeutic strategies, as well the increased understanding of the pathobiology of HF and AF, are key to mitigating the tremendous public health burden that is associated with these conditions.

A functional variant in the promoter region regulates the C-reactive protein gene and is a potential candidate for increased risk of atrial fibrillation

OBJECTIVES

In a large population-based cohort, the level of C-reactive protein (CRP) in patients at baseline predicts an increased risk of future development of atrial fibrillation (AF). The mechanism of this increased risk is unknown. Furthermore, both the molecular effects of CRP on atrial myocytes and fibroblasts and whether genetic variants in the CRP gene predispose to AF are also unknown.

METHODS

A genetic association study between CRP gene polymorphisms and AF was performed in two independent populations (I: 100 AF patients and 101 controls; II: 348 AF patients and 356 controls), with functional studies to elucidate the mechanism of association.

RESULTS

Three polymorphisms (T-861C, A-821G and C-390A/C-390T) were found in the 1-kb promoter of CRP. A triallelic polymorphism (C-390A/C-390T) captured all haplotype information and determined the CRP gene promoter activity and the plasma CRP level, and was in nearly complete linkage disequilibrium with G1059C polymorphism in exon 2. The -390A variant was associated with a higher CRP gene promoter activity, a higher plasma CRP level and a higher risk of AF. Patients with AF also had a higher plasma CRP level than controls. CRP significantly increased the inward L-type calcium current in atrial myocytes with no changes in other ionic currents. CRP did not affect the expressions of type I alpha 1 (COL1A1), type III alpha 1 (COL3A1) and type 1 alpha 2 (COL1A2) procollagens in atrial fibroblasts.

CONCLUSION

A CRP gene promoter triallelic polymorphism was associated with CRP gene promoter activity, determined the plasma level of CRP, and predicted the risk of AF. The mechanism of this may be via augmention of calcium influx by CRP in atrial myocytes, but not because of atrial fibrosis.

The role of extracellular signal-related kinase during abdominal aortic aneurysm formation

BACKGROUND

It is hypothesized that activation of extracellular signal-related kinase (ERK) is critical in activating matrix metalloproteinases (MMPs) during abdominal aortic aneurysm (AAA) formation.

STUDY DESIGN

C57BL/6 male mice underwent either elastase or heat-inactivated elastase aortic perfusion (n = 9 per group). Mouse aortic smooth muscle cells were transfected with ERK-1 and 2 siRNA along with or without elastase treatment. Mouse and human aortic tissue were analyzed by Western blots, zymograms, and immunohistochemistry, and statistical analysis was done using Graphpad and Image J softwares.

RESULTS

Western blot and immunohistochemistry documented increased phospho-mitogen-activated protein kinase kinase-1/2 (pMEK-1/2; 153%, p = 0.270 by Western) and pERK (171%, p = 0.004 by Western blot) in the elastase perfused aortas. Male ERK-1(-/-) mice underwent elastase perfusion, and aortic diameter was determined at day 14. ERK-1(-/-) mice failed to develop AAA, and histologic analysis depicted intact collagen and elastin fibers in the aortas. Zymography of aortas of elastase-treated ERK-1(-/-) mice showed lower levels of proMMP2 (p < 0.005) and active MMP2 (p < 0.0001), as well as proMMP9 (p = 0.037) compared with C57BL/6 mice. siRNA transfection of ERK-1 and -2 significantly reduced formation of pro- and active MMP2 (p < 0.01 for both isoforms) in aortic smooth muscle cells treated with elastase in vitro. Human AAA tissue had significantly elevated levels of pMEK-1/2 (150%, p = 0.014) and pERK (159%, p = 0.013) compared with control tissues.

CONCLUSIONS

The MAPK (mitogen-activated protein kinase)/ERK pathway is an important modulator of MMPs during AAA formation. Targeting the ERK pathway by reagents that inhibit either the expression or phosphorylation of ERK isoforms could be a potential therapy to prevent AAA formation.

How Are n-3 LCPUFAs Antiarrhythmic? A Reassessment of n-3 LCPUFAs in Cardiac Disease

Long-chain n-3-polyunsaturated fatty acids (n-3 LCPUFAs), referring particularly to marine-derived eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to be effective in treating arrhythmias in some clinical trials and animal studies. The mechanism for this effect of n-3 LCPUFAs is not well understood. Experimental studies and clinical trials published in the 1980s and 1990s suggested that n-3 LCPUFAs may be antiarrhythmic drugs, but more recent trials have not confirmed this. In this paper, we examine evidence for, and against, the direct antiarrhythmic action of n-3 LCPUFAs and suggest that antistructural remodeling effects of n-3 LCPUFAs may be more relevant in accounting for their clinical effects.

Adjunctive Pharmacotherapy for Elective Direct Current Cardioversion in Patients With Atrial Fibrillation

BACKGROUND

Direct current cardioversion (DCCV) can restore sinus rhythm in patients with atrial fibrillation (AF), but the long term efficacy is poor. Pharmacological therapies may improve the initial success of the procedure, but whether long term maintenance of sinus rhythm can be improved is unclear. The aim of this study was to evaluate which pharmacotherapies, including antiarrhythmic and renin-angiotensin-aldosterone system (RAAS) inhibiting drugs, most successfully promotes sinus rhythm after elective DCCV in unselected patients with atrial fibrillation.

METHODS

A retrospective cohort was to study of AF patients attending or DCCV between Jan 2010 and Feb 2012. The data were analysed using multivariate logistical regression models. Initial success of DCCV was the dependent variable in the first analysis. Maintenance of sinus rhythm at follow up was the dependent variable in the second analysis.

RESULTS

One hundred and thirty patients were included in the first analysis, and 71 patients were included in the second analysis. The only association observed was a positive association between flecainide and an increased odds of maintaining sinus rhythm at follow up (OR 2.14, SE ± 0.93, P = 0.02) .Other antiarrhythmic drugs and RAAS inhibiting drugs had no association with an increased odds of successful DCCV or maintenance of sinus rhythm thereafter.

CONCLUSIONS

This is the first study to demonstrate an association between flecainide and a increased odds of maintaining sinus rhythm after DCCV in the long term. This warrants further research, and should be taken into account when choosing adjunctive antiarrhythmic therapy for elective DCCV for AF.

Role of miR-21 in the pathogenesis of atrial fibrosis

Atrial fibrosis is important for the pathogenesis of atrial fibrillation (AF) but the underlying signal transduction is incompletely understood. We therefore studied the role of microRNA-21 (miR-21) and its downstream target Sprouty 1 (Spry1) during atrial fibrillation. Left atria (LA) from patients with AF showed a 2.5-fold increased expression of miR-21 compared to matched LA of patients in sinus rhythm. Increased miR-21 expression correlated positively with atrial collagen content and was associated with a reduced protein expression of Spry1 and increased expression of connective tissue growth factor (CTGF), lysyl oxidase and Rac1-GTPase. Neonatal cardiac fibroblasts treated with angiotensin II (AngII) or CTGF showed an increased miR-21 and decreased Spry1 expression. Pretreatment with an inhibitor of Rac1 GTPase, NSC23766, reduced the AngII-induced upregulation of miR-21. A small molecule inhibitor of lysyl oxidase, BAPN, prevented the AngII as well as the CTGF-induced miR-21 expression. Transgenic mice with cardiac overexpression of Rac1, which develop spontaneous AF and atrial fibrosis with increasing age, showed upregulation of miR-21 expression associated with reduced Spry1 expression. miR-21 expression and signalling in vivo were prevented by long-term treatment of the mice with statins. Direct inhibition of miR-21 by antagomir-21 prevented fibrosis of the atrial myocardium post-myocardial infarction. Left atria of patients with atrial fibrillation are characterized by upregulation of miR-21 und reduced expression of Spry1. Activation of Rac1 by angiotensin II leads to a CTGF- and lysyl oxidase-mediated increase of miR-21 expression contributing to structural remodelling of the atrial myocardium.

Fibrosis in Atrial Fibrillation - Role of Reactive Species and MPO

Atrial fibrosis with enhanced turnover and deposition of matrix proteins leads to inhomogeneous atrial electrical conduction and gives rise to electrical reentry circuits resulting in atrial fibrillation. The multifactorial pathogenesis of atrial fibrosis involves resident cardiac cells as well as infiltrating leukocytes, both generating and sequestering matrix metalloproteinases (MMPs), a key enzyme family involved in fibrosis. A growing body of evidence points toward an important role of reactive oxygen species (ROS) in the release and activation of pro-MMPs and the stimulation of pro-fibrotic cascades. Myeloperoxidase (MPO), a bactericidal enzyme released from activated polymorphonuclear neutrophils (PMN) is not only associated with a variety of cardiovascular diseases, but has also been shown to be mechanistically linked to atrial fibrosis and fibrillation. MPO catalyzes the generation of reactive species like hypochlorous acid, which affect intracellular signaling cascades in various cells and advance activation of pro-MMPs and deposition of atrial collagen resulting in atrial arrhythmias. Thus, inflammatory mechanisms effectively promote atrial structural remodeling and importantly contribute to the initiation and perpetuation of atrial fibrillation.

Correlation between atrial fibrillation, serum amyloid protein A and other inflammatory cytokines

Atrial fibrillation (AF) may occur and persist due to atrial remodeling exacerbated by inflammation. However, whether inflammatory cytokines, such as serum amyloid protein A (SAA), are elevated in patients with atrial arrhythmias remains unclear. In a case-control study design, serum levels of inflammatory cytokines SAA, IL-1, IL-6, TNF-α and high-sensitivity C-reactive protein (hsCRP) were compared between 122 patients with AF and 63 non-AF controls. Of 122 AF patients, 48 had lone AF and 74 organic AF; 65 had paroxysmal AF, 36 persistent AF and 21 permanent AF. In unadjusted analyses, the levels of SAA, hsCRP, TNF-αP, IL-1 and IL-6 were significantly higher in AF patients compared to control patients (P<0.01). Patients with permanent and persistent AF had higher serum levels of inflammatory cytokines than those with paroxysmal AF; all AF patients had higher serum levels than controls (P<0.05). Using a multivariate logistic regression analysis, we found that SAA (OR 3.11; 95% CI, 1.12-6.05), hsCRP (OR 2.53; 95% CI, 1.17-4.38), TNF-α (OR 1.80; 95% CI, 1.03-3.20) and IL-6 (OR 1.21; 95% CI, 0.68-2.87) were correlated with AF (P<0.05). SAA and related inflammatory cytokines are elevated in AF patients. This study is the first to document elevated SAA in AF patients. Although the cause of elevated SAA levels in AF patients remains unknown, elevated SAA may reflect an inflammatory state that promotes the occurrence and persistence of AF.

Differential regulation of mitogen-activated protein kinase signaling pathways in human with different types of mitral valvular disease

BACKGROUND

Mitogen-activated protein kinases (MAPKs) are considered to play a prominent role in cardiac development, function, and pathogenesis. The different types of mitral valvular disease (MVD), including mitral regurgitation (MR) and mitral stenosis (MS), have different underlying pathophysiologic changes, but the precise intracellular signal transduction mechanisms are not clear. Thus, we investigated the differential regulation of MAPK signaling pathways in humans with different types of MVD.

METHODS

Left atrial appendage tissue samples from 32 patients with MVD who were undergoing mitral valve replacement surgery were studied. Serum angiotensin II concentrations were measured using enzyme-linked immunosorbent assay. The expression of MAPK pathway-related genes and proteins was assessed using quantitative polymerase chain reaction, Western blot, and immunohistochemistry.

RESULTS

Echocardiography showed that patients with MS had a greater left atrial pressure overload than those with MR. The relative amounts of angiotensin II, extracellular signal-regulated kinase 1, p38α, c-Jun N-terminal kinase 2, c-Fos, activating transcription factor 2, and c-Jun mRNA were significantly upregulated in those with MS compared with those with MR (P < 0.05). The serum angiotensin II concentrations were significantly increased in those with MS compared with those with MR (P = 0.017). Substantial changes in the phosphorylated forms of the MAPK proteins were detected. Phosphorylated extracellular signal-regulated kinase 1/2, and phosphorylated p38 were significantly increased in those with MS compared with those with MR (P < 0.001), and phosphorylated c-Jun N-terminal kinase in the MR group was significantly greater than that in the MS group (P < 0.001). Histologically, more serious myocardial cells losses, myolysis, and interstitial fibrosis were detected in the MS group.

CONCLUSIONS

The different types of MVD have different hemodynamic characteristics, and different MAPK pathways were activated in the MR and MS groups, which could lead to diverse left atrial histologic changes.

Xanthine oxidase inhibition prevents atrial fibrillation in a canine model of atrial pacing-induced left ventricular dysfunction

AIMS

Oxidative stress could be a possible mechanism and a therapeutic target of atrial fibrillation (AF). Xanthine oxidase (XO) inhibition reduces oxidative stress, but the effects of XO inhibitor on AF have not been evaluated. Hence, we assessed the effects of XO inhibitor, allopurinol, on progression of atrial vulnerability in dogs associated with tachycardia-induced cardiomyopathy.

METHODS AND RESULTS

The dogs were subjected to atrial tachypacing (ATP, 400 bpm) without atrioventricular block for 4 weeks. The dynamics of atrial-tachycardia remodeling were evaluated in allopurinol-treated dogs (ALO, n = 5), placebo-treated controls (CTL, n = 6), and sham-operated dogs (n = 6). In CTL dogs, 4 weeks of ATP significantly increased AF duration (DAF; from 0.2 ± 0.2 seconds to 173 ± 67 seconds, P < 0.05) and decreased atrial effective refractory period (ERP; from 152 ± 9 milliseconds to 80 ± 4 milliseconds at a cycle length of 350 milliseconds, P < 0.01). Allopurinol attenuated the ATP effects on ERP (118 ± 6 milliseconds, P < 0.01) or DAF (0.6 ± 0.3 seconds, P < 0.05). In CTL dogs, ATP-induced rapid ventricular responses decreased left ventricular ejection fraction (LVEF; from 58.6 ± 0.1 to 23.5 ± 2.4%, P < 0.01), and increased left atrial diameter (LAD; from 17 ± 1 mm to 24 ± 1 mm, P < 0.01). ATP increased atrial fibrosis when compared with sham-operated dogs (CTL 10.7 ± 0.8% vs Sham 1.1 ± 0.3%, P < 0.01). Allopurinol suppressed atrial fibrosis (2.3 ± 0.6%, P < 0.01 vs CTL) and eNOS reduction without affecting LVEF (20.6 ± 2.2%, ns) and LAD (23 ± 1 mm, ns).

CONCLUSION

Allopurinol suppresses AF promotion by preventing both electrical and structural remodeling. These results suggest that XO may play an important role in enhancement of atrial vulnerability, and might be a novel target of AF therapy.

The biological effects of ivabradine in cardiovascular disease

A large number of studies in healthy and asymptomatic subjects, as well as patients with already established cardiovascular disease (CAD) have demonstrated that heart rate (HR) is a very important and major independent cardiovascular risk factor for prognosis. Lowering heart rate reduces cardiac work, thereby diminishing myocardial oxygen demand. Several experimental studies in animals, including dogs and pigs, have clarified the beneficial effects of ivabradine associated with HR lowering. Ivabradine is a selective inhibitor of the hyperpolarisation activated cyclic-nucleotide-gated funny current (If) involved in pacemaker generation and responsiveness of the sino-atrial node (SAN), which result in HR reduction with no other apparent direct cardiovascular effects. Several studies show that ivabradine substantially and significantly reduces major risks associated with heart failure when added to guideline-based and evidence-based treatment. However the biological effect of ivabradine have yet to be studied. This effects can appear directly on myocardium or on a systemic level improving endothelial function and modulating immune cell migration. Indeed ivabradine is an 'open-channel' blocker of human hyperpolarization-activated cyclic nucleotide gated channels of type-4 (hHCN4), and a 'closed-channel' blocker of mouse HCN1 channels in a dose-dependent manner. At endothelial level ivabradine decreased monocyte chemotactin protein-1 mRNA expression and exerted a potent anti-oxidative effect through reduction of vascular NADPH oxidase activity. Finally, on an immune level, ivabradine inhibits the chemokine-induced migration of CD4-positive lymphocytes. In this review, we discuss the biological effects of ivabradine and highlight its effects on CAD.

Heart failure, diastolic dysfunction and atrial fibrillation; mechanistic insight of a complex inter-relationship

Atrial fibrillation (AF) and heart failure (HF) commonly coexist, and their co-presence is associated with adverse outcomes relating to thromboembolic events, HF progression, hospitalisation and death. Diastolic dysfunction (DD) is also frequently present in patients with HF and is an independent predictor of hospitalisation and mortality. The presence of DD is a strong predictor of incident AF in patients with HF. In this review, we provide mechanistic insight into pathophysiological processes that frequently promote the occurrence of AF, HF and DD and outline the yin-yang relationship between AF, DD and HF. More recently, invasive studies have also shown that asymptomatic paroxysmal atrial fibrillation (PAF) is a common phenomenon in HF patients. We examine complex inter-relationships between PAF, HF and DD and speculate upon the possible clinical influence of undiagnosed PAF in HF patients.

[Biology of the substrate of atrial fibrillation]

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia in clinical practice, is often associated with progressive dilatation and remodeling of the atria which constitute the substrate of the arrhythmia. This atrial remodeling is characterized by complex structural and functional alterations of the atrial myocardium: short action potentials, heterogeneous refractory periods, dystrophic myocytes and interstitial fibrosis which act together to favor local conduction bloc, activation of ectopies and the forma-tion of microreentries of the electrical excitation. However, the underlying mechanisms of the AF substrate are not yet fully understood. The possibility of studying human atrial myocytes has led to the identification of ionic currents that contribute to the shortening of the action potential and refractory periods during AF. The down-regulation of the L-type calcium current plays a central role in this electrical remodeling. It results mainly from the dephosphorylation of calcium channels as the consequence of an excessive stimulation of atrial myocytes by neurohormones such as the atrial natriuretic factor. Abnormal trafficking and targeting of ion channels at the plasma membrane has emerged as mechanisms that can contribute to the abnormal electrical properties of the atria during AF. Fibrosis is the other feature of the AF substrate and it is favored by the atrial hemodynamic overload. Local activation of the renin-angiotensin system is involved in the extracellular matrix remodeling of the atrial myocardium. Thrombin that accumulates in dilated and fibrillating atria could be another important mediator of the myocardial structural alterations during AF. This peptide, by binding on its receptor PAR1, can modulate several signaling pathways regulating growth and survival of myocardial cells. Better understanding of pathogenic factors involved in the formation of the AF substrate is crucial for the identification of novel biomarkers and therapeutic targets that could be used to improve the diagnostic and treatment of AF.

The role of the renin-angiotensin system blocking in the management of atrial fibrillation

OBJECTIVE

To review current available evidence for the role of renin-angiotensin system blockade in the management of atrial fibrillation.

METHOD

We conducted a PubMed and Medline literature search (January 1980 through July 2011) to identify all clinical trials published in English concerning the use of angiotensin converting enzyme inhibitors or angiotensin II receptor blockers for primary and secondary prevention of atrial fibrillation. We also discussed renin-angiotensin system and its effects on cellular electrophysiology.

CONCLUSION

The evidence from the current studies discussed does not provide a firm definitive indication for the use of angiotensin converting enzyme inhibitors or angiotensin II receptor blockers in the primary or secondary prevention of atrial fibrillation. Nevertheless, modest benefits were observed in patients with left ventricular dysfunction. In view of the possible benefits and the low incidence of side-effects with angiotensin converting enzyme inhibitors and angiotensin II receptor blockers, they can be given to patients with recurrent AF, specifically those with hypertension, heart failure and diabetes mellitus.

Loss of proteostatic control as a substrate for atrial fibrillation: a novel target for upstream therapy by heat shock proteins

Atrial fibrillation (AF) is the most common, sustained clinical tachyarrhythmia associated with significant morbidity and mortality. AF is a persistent condition with progressive structural remodeling of the atrial cardiomyocytes due to the AF itself, resulting in cellular changes commonly observed in aging and in other heart diseases. While rhythm control by electrocardioversion or drug treatment is the treatment of choice in symptomatic AF patients, its efficacy is still limited. Current research is directed at preventing first-onset AF by limiting the development of substrates underlying AF progression and resembles mechanism-based therapy. Upstream therapy refers to the use of non-ion channel anti-arrhythmic drugs that modify the atrial substrate- or target-specific mechanisms of AF, with the ultimate aim to prevent the occurrence (primary prevention) or recurrence of the arrhythmia following (spontaneous) conversion (secondary prevention). Heat shock proteins (HSPs) are molecular chaperones and comprise a large family of proteins involved in the protection against various forms of cellular stress. Their classical function is the conservation of proteostasis via prevention of toxic protein aggregation by binding to (partially) unfolded proteins. Our recent data reveal that HSPs prevent electrical, contractile, and structural remodeling of cardiomyocytes, thus attenuating the AF substrate in cellular, Drosophila melanogaster, and animal experimental models. Furthermore, studies in humans suggest a protective role for HSPs against the progression from paroxysmal AF to persistent AF and in recurrence of AF. In this review, we discuss upregulation of the heat shock response system as a novel target for upstream therapy to prevent derailment of proteostasis and consequently progression and recurrence of AF.

Left atrial function predicts heart failure hospitalization in subjects with preserved ejection fraction and coronary heart disease: longitudinal data from the Heart and Soul Study

OBJECTIVES

This study sought to determine whether left atrial (LA) dysfunction predicts heart failure (HF) hospitalization in subjects with preserved baseline ejection fraction (EF).

BACKGROUND

Among patients with preserved EF, factors leading to HF are not fully understood. Cross-sectional studies have demonstrated LA dysfunction at the time of HF, but longitudinal data on antecedent atrial function are lacking.

METHODS

We performed resting transthoracic echocardiography in 855 subjects with coronary heart disease and EF ≥50%. Left atrial functional index (LAFI) was calculated as ([LA emptying fraction × left ventricular outflow tract-velocity time integral] / [indexed LA end-systolic volume]), where LA emptying fraction was defined as (LA end-systolic volume--LA end-diastolic volume) / LA end-systolic volume. We used Cox models to evaluate the association between LAFI and HF hospitalization.

RESULTS

Over a median follow-up of 7.9 years, 106 participants (12.4%) were hospitalized for HF. Rates of HF hospitalization were inversely proportional to quartile (Q) of LAFI: Q1, 47 per 1,000 person-years; Q2, 18.3; Q3, 9.6; and Q4, 5.3 (p < 0.001). Each standard deviation decrease in LAFI was associated with a 2.6-fold increased hazard of adverse cardiovascular outcomes (unadjusted hazard ratio: 2.6, 95% confidence interval: 2.1 to 3.3, p < 0.001), and the association persisted even after adjustment for clinical risk factors, N-terminal pro-B-type natriuretic peptide, and a wide range of echocardiographic parameters (adjusted hazard ratio: 1.5, 95% confidence interval: 1.0 to 2.1, p = 0.05).

CONCLUSIONS

Left atrial dysfunction independently predicts HF hospitalization in subjects with coronary heart disease and preserved baseline EF. The LAFI may be useful for HF risk stratification, and LA dysfunction may be a potential therapeutic target.

Extracellular matrix alterations in the atria: insights into the mechanisms and perpetuation of atrial fibrillation

Atrial fibrillation is the most common arrhythmia in clinical practice and is associated with increased cardiovascular morbidity and mortality. Atrial fibrosis, a detrimental process that causes imbalance in extracellular matrix deposition and degradation, has been implicated as a substrate for atrial fibrillation, but the precise mechanisms of structural remodelling and the relationship between atrial fibrosis and atrial fibrillation are not completely understood. A large number of experimental and clinical studies have shed light on the mechanisms of atrial fibrosis at the molecular and cellular level, including interactions between matrix metalloproteinases and their endogenous tissue inhibitors, and profibrotic signals through specific molecules and mediators such as angiotensin II, transforming growth factor-β1, connective tissue growth factor, and platelet-derived growth factor. This review focuses on the mechanisms of atrial fibrosis and highlights the relationship between atrial fibrosis and atrial fibrillation.

Promoter polymorphism G-6A, which modulates angiotensinogen gene expression, is associated with non-familial sick sinus syndrome

BACKGROUND

It is well known that familial sick sinus syndrome (SSS) is caused by functional alterations of ion channels and gap junction. Limited information is available on the mechanism of age-related non-familial SSS. Although evidence shows a close link between arrhythmia and the renin-angiotensin system (RAS), it remains to be determined whether the RAS is involved in the pathogenesis of non-familial SSS.

METHODS

In this study, 113 patients with documented non-familial SSS and 125 controls were screened for angiotensinogen (AGT) and gap junction protein-connexin 40 (Cx40) promoter polymorphisms by gene sequencing, followed by an association study. A luciferase assay was used to determine the transcriptional activity of the promoter polymorphism. The interaction between nuclear factors and the promoter polymorphism was characterized by an electrophoretic mobility shift assay (EMSA).

RESULTS

Association study showed the Cx40 -44/+71 polymorphisms are not associated with non-familial SSS; however, it indicated that four polymorphic sites at positions -6, -20, -152, and -217 in the AGT promoter are linked to non-familial SSS. Compared to controls, SSS patients had a lower frequency of the G-6A AA genotype (OR 2.88, 95% CI 1.58-5.22, P = 0.001) and a higher frequency of the G allele at -6 position (OR 2.65, 95% CI 1.54-4.57, P = 0.0003). EMSA and luciferase assays confirmed that nucleotide G at position -6 modulates the binding affinity with nuclear factors and yields a lower transcriptional activity than nucleotide A (P<0.01).

CONCLUSION

G-6A polymorphism, which modulates the transcriptional activity of the AGT promoter, may contribute to non-familial SSS susceptibility.

Renin-Angiotensin System and AtrialFibrillation:Understanding the Connection

Atrial fibrillation (AF) arises as a result of a complex interaction of triggers, perpetuators and the substrate. The recurrence of AF may be partially related to a biologic phenomenon known as remodeling, in which the electrical, mechanical, and structural properties of the atrial tissue and cardiac cells are progressively altered,creating a more favorable substrate. Atrial remodeling is in part a consequence of arrhythmia itself. Therefore,to prevent and to treat AF, much attention has been directed to upstream therapies to alter the arrhythmia substrate and to reduce atrial remodeling. The renin-angiotensin-aldosterone system (RAAS) plays a keyrole in these strategies. In this review we analyze the experimental and clinical evidence regarding the efficacy of RAAS inhibitors in AF treatment. In the primary prevention of AF, meta-analyses have shown that risk of new-onset AF in patients with congestive heart failure and left ventricular dysfunction is reduced by RAAS inhibitors, whereas in hypertensive and post-myocardial infarction patients, the results are less evident. In the secondary prevention of AF, some large, prospective, randomized, placebo-controlled studieswith angiotensin II-receptor blockers returned negative results. Unfortunately, the approach of using RAASinhibitors as antiarrhythmic drugs to prevent both new-onset and recurrent AF is in decline because negativetrial results are accumulating, with the exception of the results in patients with congestive heart failure.

Preoperative treatment with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker has no beneficial effect on the development of new-onset atrial fibrillation after off-pump coronary artery bypass graft surgery

BACKGROUND

The present study investigated whether preoperative angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) use affected the incidence of postoperative atrial fibrillation (POAF) in patients undergoing off-pump coronary artery bypass graft (OPCAB).

HYPOTHESIS

Preoperative use of ACEI or ARB was related to POAF in patients undergoing OPCAB.

METHODS

This retrospective, observational, cohort study involved 1050 patients who underwent OPCAB from January 2006 to December 2009.

RESULTS

ACEI or ARB, ACEI alone, and ARB alone did not exert beneficial effect on the occurrence of POAF, and ACEI or ARB use was rather associated with an increased incidence of POAF (ACEI or ARB: odds ratio [OR]: 1.66, 95% confidence interval [CI]: 1.04-2.62, P = 0.03; ACEI alone: OR: 1.30, 95% CI: 0.57-2.97, P = 0.53; ARB alone: OR: 1.57, 95% CI: 0.93-2.64, P = 0.09).

CONCLUSIONS

ACEI or ARB, ACEI alone, and ARB alone did not favorably influence the occurrence of POAF in patients undergoing OPCAB.