Expression of extracellular signal-regulated kinase and angiotensin-converting enzyme in human atria during atrial fibrillation

Acupuncture versus pharmacological conversation in treatment of atrial fibrillation in a randomized controlled trial: a systemic review and meta-analysis

Objective

This study aimed to investigate the effect of conventional drugs combined with acupuncture therapy on the conversion of sinus rhythm in patients with atrial fibrillation.

Methods

We searched databases, such as PubMed, Embase, WOS, Cochrane, CNKI (China National Knowledge Infrastructure), Wan fang Data, VIP, and CBM to collect data in randomized controlled trials of acupuncture included patients with atrial fibrillation. Publication time was limited from the beginning to May 15, 2021. The primary outcome is the number of participants who converted successfully.

Results

A total of 11 papers were included in this study. The combined effect indicated that acupuncture significantly effectively benefitted the patients with atrial fibrillation (RR = 1.208, 95% CI 1.123, 1.298, P < 0.001). Further subgroup analysis of persistent and paroxysmal atrial fibrillation and the timing of acupuncture suggested that the addition of acupuncture was not statistically significant in the treatment of persistent AF compared to the control group (RR = 1.147, 95% CI 0.811, 1.623 P = 0.147). The combination of acupuncture was more effective in paroxysmal AF RR = 1.148 (95% CI 1.064, 1.239) P < 0.001. In addition, when the acupuncture time was limited to 20 min, it had the best treatment effect (RR = 1.510, 95% CI 1.25, 1.82).

Conclusions

The combination of pharmacological resuscitation with acupuncture significantly improved the conversion of paroxysmal atrial fibrillation compared to pharmacological resuscitation only. The most significant benefit was achieved with an acupuncture duration of < 20 min. Thus, the combination of acupuncture could be considered in clinical practice for the resuscitation of patients with atrial fibrillation.

Risk factors for atrial fibrillation recurrence: a literature review

Atrial fibrillation is the most common arrhythmia managed in clinical practice and it is associated with an increased risk of mortality, stroke and peripheral embolism. Unfortunately, the incidence of atrial fibrillation recurrence ranges from 40 to 50%, despite the attempts of electrical cardioversion and the administration of antiarrhythmic drugs. In this review, the literature data about predictors of atrial fibrillation recurrence are highlighted, with special regard to clinical, therapeutic, biochemical, ECG and echocardiographic parameters after electrical cardioversion and ablation. Identifying predictors of success in maintaining sinus rhythm after cardioversion or ablation may allow a better selection of patients to undergo these procedures. The aim is to reduce healthcare costs and avoid exposing patients to unnecessary procedures and related complications. Recurrent atrial fibrillation depends on a combination of several parameters and each patient should be individually assessed for such a risk of recurrence.

Embryology and Anatomy of the Left Atrial Appendage: Why Does Thrombus Form?

The left atrial appendage (LAA) is a long tubular structure that opens into the left atrium. In patients with atrial fibrillation, the LAA develops mechanical dysfunction and fibroelastotic changes on the endocardial surface. The complex anatomy of the LAA makes it a good site for relative blood stasis. In addition, systemic factors exacerbate the hypercoagulable state, eventually resulting in endothelial dysfunction, release of tissue factor, and production of inflammatory cytokines and oxidative free radicals, and eventually initiating the coagulation cascade. Thus, the LAA is susceptible to thrombus formation and is the most common source of systemic thromboembolism.

Polymorphisms of the angiotensin-converting enzyme and angiotensinogen gene in patients with atrial fibrillation

Activation of the renin-angiotensin system (RAS) is associated with atrial fibrillation (AF). The aim of this study was to investigate the relation between AF and polymorphisms in RAS. One hundred and fifty patients with AF, 100 patients with no documented episode of AF and 100 healthy subjects were consecutively recruited into the study. The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism, and the M235T, A-20C, and G-6A polymorphisms of the angiotensinogen gene were genotyped. Patients with AF had significantly lower frequency of II genotype of ACE I/D and higher frequency of angiotensinogen M235T polymorphism T allele and TT genotype and G-6A polymorphism G allele and GG genotype compared with the controls. AF patients had significantly larger left atrium, higher left ventricular mass index (LVMI) and higher frequency of significant valvular pathology. ACE I/D polymorphism II genotype, angiotensinogen M235T polymorphism TT genotype and G allele and GG genotype of angiotensinogen G-6A polymorphism were still independently associated with AF when adjusted for left atrium, LVMI and presence of significant valvular pathology. Genetic predisposition might be underlying the prevalence of acquired AF. Patients with a specific genetic variation in the RAS genes may be more liable to develop AF.

The effects of cilazapril and valsartan on the mRNA and protein expressions of atrial calpains and atrial structural remodeling in atrial fibrillation dogs

Owing to relative inefficacy and side effects of currently available antiarrhythmic drugs, current interest has shifted to treatments that target atrial fibrillation (AF) substrate. It has been suggested that calpain-induced atrial structural remodelling is under the control of renin-angiotensin system during AF. The purpose of this study is to investigate the effects of cilazapril and valsartan on the mRNA and protein expression of atrial calpains and atrial structural remodelling in AF dogs induced by chronic rapid atrial pacing. Twenty-seven dogs were randomly divided into sham-operated group (n = 6), control group (n = 7), cilazapril group (n = 7) and valsartan group (n = 7). One thin silicon plaque containing 4 pairs of electrodes was sutured to each atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial appendage. The dogs in control group, cilazapril group and valsartan group were paced at 400 beats per minutes for 6 weeks. The dogs in cilazapril and valsartan groups received cilazapril (1mg x kg(-1)x d(-1)) or valsartan (30mg x kg(-1) x d(-1)) 1 week before rapid atrial pacing until pacing stop respectively. Transthoracic and transoesophageal echocardiographic examinations were performed in order to detect the changes of left atrium volume and contractile function. The inducibility and duration of AF were measured in all the groups. The expressions of atrial calpain I and calpain II mRNA were semi-quantified by reverse transcription-polymerase chain reaction. The protein levels of calpain I and calpain II in atrial myocardium were measured by Western-blot method. Pathohistological and ultrastructural changes in atrial tissue were tested by light and electron microscopy. Compared with the sham-operated control group, dramatic smaller left atrium and left atrial appendage volumes and significant higher atrial contractile function were observed in the cilazapril and valsartan groups. After 6-week atrial tachy-pacing, the mRNA and protein expressions of calpain I increased dramatically in the control group than that in the sham group, tissue calpain protein expression in all groups significantly correlated with the myolysis (r = 0.89, P < 0.01). Cilazapril and valsartan could significantly inhibit the gene and protein expressions of calpain I. No differences were found in the expression of calpain II mRNA and protein between the groups. Compared with atrial myocytes obtained from sham dogs, atrial myocytes from the control group dogs showed a reduced number of sarcomeres, a significant higher myolytic area of atria (24.3% vs. 3.1%, P < 0.01), increased vacuolization and dissolution. Cilazapril and valsartan could effectively prevent the pathohistological and ultrastructural changes induced by chronic rapid atrial pacing, dramatically decrease the area of myolysis (P < 0.05) and significantly reduce the inducibility and duration of AF. The expression of calpain I mRNA and protein increased remarkably in AF dogs. Cilazapril and valsartan can inhibit calpain I up-regulation, suppress atrial structural remodeling, and prevent the induction and promotion of AF in chronic rapid atrial pacing dogs.

Downregulation of angiotensin converting enzyme II is associated with pacing-induced sustained atrial fibrillation

Atrial fibrillation (AF), the most common cardiac arrhythmia, is frequently accompanied by atrial interstitial fibrosis. Angiotensin II (Ang II) dependent signaling pathways have been implicated in interstitial fibrosis during the development of AF. However, Ang II could be further degraded by angiotensin converting enzyme II (ACE2). We examined expression of ACE2 in the fibrillating atria of pigs and its involvement in fibrotic pathogenesis during AF. Nine adult pigs underwent continuous rapid atrial pacing to induce sustained AF and six pigs were sham controls (i.e., sinus rhythm; SR). In the histological examinations, extensive accumulation of extracellular matrix in the interstitial space of the atria, as evidenced by Masson's trichrome stain, were found in fibrillating atria. The relative amount of collagen type I in the atria with AF was significantly increased as compared with that in the SR. Local ACE activity in the fibrillating atria was also markedly higher than that in the SR subjects. ACE2 gene and protein expression in the AF subjects were significantly decreased compared with those in the SR subjects, whereas expression of mitogen-activated/ERK kinase 1/2 (MEK1/2), extracellular signal-regulated protein kinase 2 (ERK2), and activated ERK2 were significantly greater in the AF subjects. We propose that decreasing ACE2 expression during AF may affect the Ang II-dependent signaling pathway. In addition, our results suggest that atrial fibrosis in AF may be induced by antagonistic regulation between ACE and ACE2 expression.

Effects of Cilazapril on atrial electrical, structural and functional remodeling in atrial fibrillation dogs

BACKGROUND AND PURPOSE

The effects of angiotensin-converting enzyme inhibitor on long-term atrial electrophysiologic and structural remodeling are still unclear. The purpose of this study is to investigate the effects of Cilazapril on atrial electrical, structural, and functional remodeling in atrial fibrillation (AF) dogs induced by chronic rapid atrial pacing.

METHODS

Twenty dogs were randomly divided into sham-operated group (n = 6), control group (n = 7), and Cilazapril group (n = 7). One thin silicon plaque containing 4 pairs of electrodes was sutured to each atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial appendage. The dogs in control group and Cilazapril group were paced at 400 beats per minute for 6 weeks. The dogs in Cilazapril group received Cilazapril (0.5 mg x kg(-1) x d(-1)) 1 week before rapid atrial pacing until pacing stop. Before and after 6-week rapid atrial pacing, atrial effective refractory period (AERP) at 8 sites, AERP dispersion, intraatrium conduction time, inducibility, and duration of AF were measured. Transthoracic and transesophageal echocardiographic examinations included left atrium (LA) maximal volume, LA minimal volume, LA ejection fraction, left atrial appendage (LAA) maximal volume, LAA minimal volume, LAA ejection fraction, LAA maximal forward flow velocity, and LAA minimal backward flow velocity were performed. Atrial collagen volume fraction was analyzed by Masson staining.

RESULTS

After 6-week rapid atrial pacing, although there was no significant difference in AERP shortening and AERP rate adaptation reduction between the control group and the Cilazapril group, the inducibility and duration of AF were found to be dramatically lower in the Cilazapril group than those in the control group (AF inducibility, 65.7% vs 95.7%, P < .05; AF duration, 531.5 +/- 301.2 vs 1432.2 +/- 526.5 s, P < .01). The post-tachycardia intraatrium conduction times after 6 weeks with Cilazapril were significantly shorter than those in the control group. Cliazapril could partially prevent AERP dispersion increase induced by chronic rapid atrial pacing. Compared with the control group, the LA and LAA volumes were significantly smaller; LA ejection fraction, LAA ejection fraction, LAA maximal forward flow velocity, and LAA minimal backward flow velocity were dramatically higher in the Cilazapril group. The Cilazapril group had a significantly lower percentage of interstitial fibrosis than the control group.

CONCLUSIONS

Cilazapril can suppress structural and functional remodeling and prevent the induction and promotion of AF in chronic rapid atrial pacing dogs.

ACE-inhibitor treatment attenuates atrial structural remodeling in patients with lone chronic atrial fibrillation

OBJECTIVE

Chronic atrial fibrillation (AF) is characterized by a remodeling process which involves the development of fibrosis. Since angiotensin II has been suspected to be involved in this process, the aim of our study was to investigate a possible influence of an ACE-I therapy in patients with chronic AF regarding the occurrence of left atrial structural remodeling.

METHODS

Atrial tissue samples were obtained from patients with lone chronic AF or sinus rhythm (SR). Collagen I, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) protein expression were measured by quantitative Western Blotting techniques and calculated as mean +/- SEM. Histological tissue samples were used for calculating microvessel density (microvessel/mm(2) +/- SEM).

RESULTS

In AF, the collagen amount was higher (1.78 +/- 0.21; p = 0.01) vs. SR (0.37 +/- 0.07) accompanied by declining microcapillary density (AF: 145 +/- 13 vs. SR: 202 +/- 9; p = 0.01). Additionally, a negative correlation (p = 0.01) between collagen content and microcapillary density was observed. To investigate the influence of an ACE-I therapy on this remodeling process, patient groups were divided into AF and SR both with or without ACE-I. Interestingly, there was a significantly lower expression of collagen I in AF with ACE-I (1.04 +/- 0.26) vs. AF without ACE-I treatment (2.07 +/- 0.24, p = 0.02). The microcapillaries were not diminished in AF with ACE-I (180 +/- 15) vs. SR with ACE-I (196 +/- 9), but there was a significant rarification in AF without ACE-I (123 +/- 18; p = 0.03). The expression of VEGF and bFGF did not reveal any significant differences.

CONCLUSION

In patients undergoing ACE-I treatment: atrial structural remodeling was attenuated and the loss of atrial microcapillaries was prevented.