Enzhao Liu

Enalapril, irbesartan, and angiotensin-(1–7) prevent atrial tachycardia-induced ionic remodeling

BACKGROUND Atrial fibrillation (AF) is associated with activation of the renin-angiotensin system (RAS) in the atria. Angiotensin-(1-7) [Ang-(1-7)] is a biologically active component of the RAS, it not only counterbalances the actions of angiotensin II (Ang II) but also is a potential inhibitor of angiotensin-converting enzyme (ACE). The purpose of this study was to investigate the effects of the ACE inhibitor enalapril, the angiotensin-receptor blocker (ARB) irbesartan, and Ang-(1-7) on the chronic atrial ionic remodeling. METHODS Thirty dogs were assigned to sham, paced, paced + enalapril, paced + irbesartan or paced + Ang-(1-7) group, 6 dogs in each group. Rapid atrial pacing at 500 beats per minute was maintained for 14 days, but dogs in sham group were instrumented without pacing. During the pacing, enalapril (2 mg · Kg(-1) · d(-1)) and irbesartan (60 mg · Kg(-1) · d(-1)) were given orally and Ang-(1-7) (6 μg · Kg(-1) · h(-1)) was given intravenously. Whole-cell patch-clamp technique was used to record atrial ionic currents and action potential duration (APD). And RT-PCR was applied to assess atrial mRNA expression of I(TO) Kv4.3 and I(CaL)α1C subunits. RESULTS Compared with sham, rapid pacing shortened APD90 (P < 0.05) of atrial myocytes, and decreased APD90 rate adaptation (P<0.05). APD90 changes were prevented by irbesartan and Ang-(1-7), but not enalapril. In atria from paced group, the densities and gene expression of I(TO) and I(CaL) were reduced (P < 0.01 vs. sham). Enalapril increased the density and gene expression of I(TO) compared with sham (P < 0.01), Ang-(1-7) prevented the decrease of I(TO) and I(CaL) (P < 0.05 vs. control) and Kv4.3 mRNA expression (P < 0.01 vs. control). Irbesartan had no effect on I(TO) and I(CaL) densities or mRNA expression. CONCLUSIONS These results suggest that enalapril, irbesartan, and Ang-(1-7) have differing influences on atrial tachycardia-induced atrial ionic remodeling.

Elevated red cell distribution width level is associated with oxidative stress and inflammation in a canine model of rapid atrial pacing

Atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia. The prevalence of AF has been increasing for the past few decades with the aging population [1]. The pathogenesis underlying AF is multi-factorial. Accumulating evidences suggest that oxidative stress and inflammation may play an important role in the pathogenesis and perpetuation of AF [2–6]. The red blood cell distributionwidth (RDW) reflects variability in the size of circulating red blood cells (RBCs) and is mostly used in the differential diagnosis of anemia. Recently, several studies showed the potential association of increased RDW levels with adverse cardiovascular events. Elevated RDW levels may also have been correlated with nonvalvular AF [7]. However, the potential mechanisms between elevated RDW and the development of AF are still unclear. In the present study, we aimed to assess whether elevated levels of RDW are associated with oxidative stress and inflammation markers in a canine model of rapid atrial pacing (RAP). In the present study, all animals were cared for and used in compliance with the Experimental Animal Administration Committee of Tianjin Medical University and the Tianjin Municipal Commission for ‘Experimental Animal Control’. For this study, 20 mongrel dogs of either gender were randomly divided into two groups: sham group and paced group, 10 dogs in each group. We used a previously described approach to induce and maintain sustained AF in our experimental animals [8]. The dogs were anesthetized with intravenous 3% sodium pentobarbital (30 mg · kg−1). After mechanical ventilation, under aseptic condition, a modified unipolar J pacing lead (St. Jude Medical, USA) was inserted via the right jugular vein and the distal end of the lead was positioned in the right atrium or right auricular appendage under fluoroscopy. The proximal end of the pacing lead was connected to a programmable pacemaker (Fudan University, China), which was implanted into a subcutaneous pocket in the neck. The dogs in the paced group were paced at 500 bpm (120-ms cycle length) with the 0.2-ms square-wave pulses at twice the threshold current for 2 weeks. The dogs in the sham group were also instrumented but without pacing. Electrocardiogram (ECG) was verified after 24 h in awake dogs to ensure continuous 1:1 atrial capture. Hemodynamics parameters were monitored by a multi-channel electrophysiological recorder (Hongtong TOP2001, China) at baseline and after 2 weeks of rapid atrial pacing (RAP). After the above treatment for 2 weeks, venous blood samples were obtained from the two groups of dogs, and RDW levels were analyzed using an automated hematology analyzer (Mindray BC6800, China). The serum levels of superoxide dismutase (SOD), malondialdehyde (MDA), Toll-like receptor 4 (TRL4) and interleukin-18 (IL-18) were measured by ELISA kit (Nanjing Jiancheng Bioengineering Institute, China). All animals were survived to the end of the experiment. There was no difference in gender, body weight, ventricular rate and blood pressure between the two groups whether at baseline and after 2 weeks of RAP (P N 0.05) (Table 1). Our study showed that the RDW level was increased apparently by RAP from 12.37% ± 1.48% to 14.83% ± 2.24% (P b 0.05). We investigated the circulating serum levels of SOD, MDA, TLR4 and IL-18 in the two groups and found that the levels of SOD, MDA, TLR4 and IL-18 were higher in the paced group compared to the sham group (P b 0.01) (Table 1). The serum levels of SOD, MDA, TLR4 and IL-18 had no correlation to RDW in the sham group (r = 0.014, P = 0.976; r = 0.479, P =0.276; r = 0.101, P = 0.830; r = 0.032, P = 0.946, respectively), whereas they were correlated to RDW levels (P b 0.05 or P b 0.01) in the paced group (Fig. 1). Several studies have shown that RDW, a laboratory measure of the variability of red blood cell sizes, is a strong independent predictor of increased morbidity and mortality in patients with cardiovascular disease [9–14]. Our recent study [15] indicated that RDWmay serve as a promising and useful marker for paroxysmal AF. Adamsson et al. [16] also showed that RDW was associated with incidence of AF independently of several cardiovascular, nutritional and hematological factors in a recent study of middle-aged subjects from the general population. However, there are limited data regarding the potential mechanisms between RDW and AF in animal models. The potential mechanism behind their relationship may result from a direct effect of changes in erythrocyte volume and function on the heart, or may reflect other pathophysiological processes acting

Probucol for the prevention of cystatin C-based contrast-induced acute kidney injury following primary or urgent angioplasty: a randomized, controlled trial.

BACKGROUND Probucol, a lipid-lowering drug with potent antioxidant properties, may reduce the risk of cystatin C (CyC)-based contrast-induced acute kidney injury (CIAKI). The aim of this study was to observe the incidence of CyC-based CIAKI and assess the efficacy of probucol on prevention of CIAKI following primary or urgent coronary angioplasty. METHODS A total of 204 patients with acute coronary syndrome (ACS) were prospectively randomized to a control group (108 patients, 74 male, 65.4 ± 12.5 years) or probucol group (96 patients, 67 male, 65.1 ± 10.5 years) 1000 mg orally before primary or urgent angioplasty and 500 mg twice daily for 3 days following intervention. Serum CyC and serum creatinine (Scr) concentrations were measured before, and on day 1, day 2 and day 3 after coronary intervention. RESULTS The clinical characteristics of the patients from the two groups were similar. Scr-based CIAKI was developed in 23 patients of the control group (21.3%) and in 4 patients of the probucol group (4.2%) (P<0.001). Furthermore, CyC-based CIAKI occurred in 56 patients of the control group (51.9%) and 28 patients of the probucol group (29.2%) (P<0.001). The CyC increase ≥ 10% after exposure to contrast medium was the best increment cutoff value for the early identification of patients at risk of CIAKI. CONCLUSIONS Our study suggests that CyC is a reliable marker for early identification and ruling out the patients at the risk of CIAKI. Among the patients with ACS who are undergoing primary or urgent angioplasty, prophylactic treatment with probucol reduces the risk of both Scr and CyC-based CIAKI.

Atrial electrical remodeling in a canine model of sinus node dysfunction.

AIMS To study atrial tachycardia-induced electrical remodeling in a canine model of sinus node dysfunction (SND). MATERIALS AND METHODS A canine model of SND was established by contacting a cotton patch with 20% formaldehyde on the sinus node. Atrial effective refractory period (ERP), ERP dispersion, and inducibility of atrial fibrillation (AF) were recorded at multiple sites in the atrium, before and after SND induction as well as after rapid atrial pacing. The recovery of atrial ERP in the left and right atrium (LA and RA) after cessation of atrial pacing was also recorded. RESULTS Compared with baseline, the atrial ERPs were shortened after SND (P<0.05). After rapid atrial stimulation, the atrial ERPs were further decreased significantly (P<0.05), and the dispersion of atrial ERPs measured at different pacing cycle lengths (PCLs) showed significant variation. Seven sites were used to induce AF in each dog (56 sites in 8 dogs). The average duration and inducibility of AF after SND was increased compared with baseline (16.5±4.7 vs 2.3±1.2 s and 12/56 vs 4/56 sites, P<0.05). After rapid atrial stimulation, the average duration and inducibility of AF were further increased (16.5±4.7 vs 33.6±16.1 s and 12/56 vs 25/56 sites, P<0.05). The recovery of atrial ERP in LA was significantly delayed compared to the RA. CONCLUSION SND induces atrial electrical remodeling which is further aggravated by atrial tachycardia. Therefore, SND creates an electrophysiological substrate that facilitates AF initiation and perpetuation.

Effects of the angiotensin-(1-7)/Mas/PI3K/Akt/nitric oxide axis and the possible role of atrial natriuretic peptide in an acute atrial tachycardia canine model

Objective: To investigate the effects of the angiotensin-(1-7) signaling pathway and the possible role of atrial natriuretic peptide (ANP) on atrial electrical remodeling in canines with acute atrial tachycardia. Methods: Forty dogs were randomly assigned to eight groups (five dogs/group): sham, paced control, paced + angiotensin-(1-7), paced + angiotensin-(1-7) + Mas inhibitor, paced + angiotensin-(1-7) + Akt inhibitor, paced + angiotensin-(1-7) + PI3K inhibitor, paced + angiotensin-(1-7) + nitric oxide (NO) inhibitor, and paced + angiotensin-(1-7) + A-71915 (ANP receptor antagonist). Rapid atrial pacing was maintained at 600 bpm for 2 h for all groups, except the sham group, and angiotensin-(1-7) (6 μg kg−1 h−1), Mas inhibitor (5.83 μg kg−1 h−1), Akt inhibitor (2.14 μg kg−1 h−1), PI3K inhibitor (2.86 μg kg−1 h−1), NO synthase inhibitor (180 μg kg−1h−1), or A-71915 (0.30 μg kg−1 h−1) were administered intravenously. Atrial effective refractory periods, inducibility, and duration of atrial fibrillation (pacing cycle lengths: 300, 250, and 200 ms), and left atrial ANP concentrations were measured. Results: After pacing, the atrial effective refractory periods at the six sites shortened with increased inducibility and duration of atrial fibrillation, which was attenuated by angiotensin-(1-7), and increased ANP concentrations, which was promoted by angiotensin-(1-7) (paced control vs. sham; P < 0.05). All inhibitors and A-71915 blocked the electrophysiological effects of angiotensin-(1-7). ANP secretion induced by angiotensin-(1-7) was also blocked by all inhibitors. Conclusion: Angiotensin-(1-7) prevented acute electrical remodeling in canines with acute atrial tachycardia via the angiotensin-(1-7)/Mas/PI3K/Akt/NO signaling pathway. ANP was related to the anti-arrhythmic effects of angiotensin-(1-7).

Circulating serum levels of growth differentiation factor-15 and neuregulin-1 in patients with paroxysmal non-valvular atrial fibrillation

Growth differentiation factor-15 (GDF-15) is a stress-responsivememberofthetransforminggrowthfactor- βsuperfamilythatwasorig-inally cloned as a macrophage-inhibitory cytokine [1]. It rapidly in-creases following myocardial stretch, volume overload, oxidativestress and inflammatory state [2,3]. In recent years, it is emerging as anovel biomarker to predict mortality and adverse events in patientswith heart failure (HF) [4–7], acute coronary syndrome (ACS) [8–10]and acute pulmonary embolism [11]. Neuregulin-1 (NRG-1) is a mem-beroftheepidermalgrowthfactor(EGF)family[12]andplaysacriticalrole in cardiovascular development, cell survival, growth, and metabo-lism [13,14]. Recently, NRG-1 was shown to be a stress-related cardiacgrowth and angiogenic biomarker [15,16].Atrialfibrillation(AF)isthemostcommoncardiacarrhythmiaandisassociated with an increased risk of morbidity and mortality [17]. Therole of GDF-15 and NRG-1 in the setting of AF has not been studied.We soughttoinvestigate thepotentialrelationshipbetweencirculatingserum levels of GDF-15, NRG-1 and non-valvular AF.We enrolled 67 consecutive patients with paroxysmal AF and 67patientswithoutAFmatchedforsex,ageandatheroscleroticriskfactorspresenting to our institution between August 2012 and June 2013.Exclusioncriteriawerehistoryofmyocardialinfarction,ACS,congestiveHF, history of cardiac surgery, valvular heart disease, congenital heartdisease, cardiomyopathy, liver and kidney dysfunction, recent strokeor transient ischemic attack, inflammatory or neoplastic diseases, thy-roid disorder and anemia. The ethics committee of Second Hospital ofTianjin Medical University approved this study and written informedconsent was obtained from all patients enrolled.Baseline demographic and clinical characteristics were collected.Serumcreatinine(Cr),fastingblood-glucose(FBG),alanineaminotrans-ferase (ALT), and aspartate aminotransferase (AST) were measuredafter overnight fasting of 12 h with an automatic analyzer (TBA-120FR, Toshiba, Shenzhen, China). Blood samples were collected after supinerest for at least 10 min and overnight fasting of 12 h. The blood sampleswere then centrifuged for 15 min at 3500 r/min to obtain superna-tants which were stored at −80 °C until use. Serum levels of SOD andCAT were measured by colorimetry (Nanjing Jiancheng BioengineeringInstitute, China). Serum high-sensitivity C-reactive protein (hs-CRP)was measured using a high-sensitivity immmunonephelometric assay.Serum levels of NRG-1 and GDF-15 were assayed using commerciallyavailable ELISA kit (Cusabio Biotech Corporation, China). The kit has adetection range of 31.25 to 2000 pg/ml for GDF-15 with intra-assayand inter-assay variability of b8% and b10% respectively. The detectionrange for NRG-1 was 7.8 to 500 ng/ml with intra-assay and inter-assayvariability of b8% and b10% respectively. Transthoracic echocardio-graphicexaminationwasperformedusingtheVivid-7systemequippedwitha2.4 MHztransducer (GE Medical Systems, Milwaukee, WI,USA).Leftatrialdiameter(LAD), interventricularseptalwallthickness(IVST),left ventricular posterior wall thickness (LVPWT) and left ventricularend-diastolic diameter (LVEDD) were measured. Left ventricular ejec-tion fraction (LVEF) was determined from apical four-chamber andtwo-chamber views using Simpsons biplane formula.Categorical variables were reported as percentage and continuousvariables as means ± SD or median (interquartile range). Statisticalanalysis was performed using t-test or Kolmogorov–Smirnov test forcontinuousvariableswhiletheChisquaretestwasusedtocomparecat-egorical variables. Multivariable regressionanalyses were performed toinvestigate the relationship between GDF-15, NRG-1 and AF. A P valueof b0.05 was regarded as statistically significant. All tests were two-tailed and analyses were performed using SPSS 17.0 Statistical PackageProgram (SPSS Inc., Chicago, IL, USA).Clinical characteristics of study population are shown in Table 1.Patients with paroxysmal AF and controls had a similar distribution incardiovascular risk factors and medications. Baseline laboratory andechocardiographic characteristics of study population are shown inTable2.PatientswithAFhadhigherLAD, NRG-1andGDF-15comparedto non-AF patients. No significant difference in hs-CRP, SOD and CAT

Radiofrequency catheter ablation at the non-coronary cusp for the treatment of para-hisian accessory pathways

AIMS Radiofrequency catheter ablation (RFCA) is well established as a definitive therapy of accessory pathways (APs). Successful RFCA of anteroseptal APs at the non-coronary cusp (NCC) have been reported in several case reports. We aimed to evaluate the prevalence, safety, efficacy, and long-term outcome of RFCA at the NCC for the treatment of para-hisian APs. METHODS AND RESULTS Our study included 17 patients (58.8% female, mean age 46.9 ± 15.9 years) with para-hisian APs. We performed two different ablation approaches which targeted at either the right anterior septum (RAS) (n = 10) or the NCC (n = 7) as the initial target. We compared safety, efficacy, and long-term outcome between these two approaches. The para-hisian APs were successfully ablated in 15 patients and damaged in 1 patient, for the remaining patients, the ablation was abandoned for the suspicion of no atrioventricular conduction. Considering all ablation sites of the para-hisian APs, radiofrequency (RF) delivered at the NCC had a higher success rate (11/12 vs. 5/12, P < 0.05) and a lower complication rate (0/12 vs. 4/12, P < 0.05) compared with the RAS. During a mean follow-up period of 22.4 ± 15.0 months, all the patients were free of arrhythmias without any anti-arrhythmic drugs. CONCLUSION Para-hisian APs can be safely and effectively ablated at the NCC. Compared with the ablation at the RAS, RF delivered at the NCC has a higher immediate success, lower complication rate, and good long-term outcome.

The potential role of atrial natriuretic peptide in the effects of Angiotensin-(1-7) in a chronic atrial tachycardia canine model.

Objective: The objective of this article is to investigate the possible role of atrial natriuretic peptide (ANP) in Angiotensin-(1–7) (Ang-(1–7)) signaling pathway on atrial electrical and structural remodeling in a chronic rapid atrial pacing canine model. Methods: Twenty-four dogs were randomly assigned to four groups: a sham group, paced control group, a paced + Ang-(1–7) group and a paced + Ang-(1–7) + A-71915 group. Atrial rapid pacing (ARP) at 600 bpm was maintained for 14 days except in the animals from the sham group. During the pacing, Ang-(1–7) (6 μg•kg-1•h-1) or Ang-(1–7) (6 μg•kg-1•h-1) + A-71915 (ANP receptor antagonist, 0.30 μg•kg-1•h-1) were given intravenously, respectively. After pacing, it was measured that electrophysiological parameters including atrial effective refractory periods (ERPs), inducibility and duration of atrial fibrillation (AF), ICaL and INa changed, where ICaL refers to voltage-dependent L-type Ca2+ current and INa refers to cardiac sodium current. Then, the fibrosis and the expression of Cav1.2, INav1.5α subunit, TGF-β1 and ANP in atria were assessed. Results: After ARP, compared with the sham group, the atrial ERPs at six sites in each dog were shortened with the increasing in inducibility and duration of AF in the paced control group. The density of ICaL, INa and the expression of Cav1.2, INav1.5α subunit mRNA were decreased. Atrial tissue from the paced dogs showed significant interstitial fibrosis. The expression of TGF-β1 and ANP in mRNA and protein levels were increased. Compared with the paced control group, the shortening of atrial ERPs, and the increasing of inducibility and duration of AF induced by ARP were alleviated by Ang-(1–7) treatment (p < 0.05). The density of ICaL and INa and the expression of Cav1.2 and INav1.5α subunit mRNA were slightly decreased. Atrial tissue showed less interstitial fibrosis after Ang-(1–7) treatment. The increasing of ANP expression was improved by Ang-(1–7), while the increasing of TGF-β1 expression was alleviated by Ang-(1–7) (p < 0.05). A-71915 treatment blocked the beneficial effects of Ang-(1–7) on the aforementioned electrophysiological parameters and atrial fibrosis. And A-71915 treatment blocked Ang-(1–7), improving the expression of TGF-β1. Conclusion: Ang-(1–7) prevented atrial structural and electrical remodeling induced by ARP. Furthermore, Ang-(1–7) promoted ANP secretion, and ANP played a crucial role in the cardiac protection of the former.

Discrete potentials guided radiofrequency ablation for idiopathic outflow tract ventricular arrhythmias

AIMS Discrete potentials (DPs) have been recorded and targeted as the site of ablation of the outflow tract arrhythmias. The aim of the present study was to investigate the significance of DPs with respect to mapping and ablation for idiopathic outflow tract premature ventricular contractions (PVCs) or ventricular tachycardias (VTs). METHODS AND RESULTS Seventeen consecutive patients with idiopathic right or left ventricular outflow tract PVCs/VTs who underwent radiofrequency catheter ablation were included. Intracardiac electrograms during the mapping and ablation were analysed. During sinus rhythm, sharp high-frequency DPs that displayed double or multiple components were recorded following or buried in the local ventricular electrograms in all of the 17 patients, peak amplitude 0.51 ± 0.21 mV. The same potential was recorded prior to the local ventricular potential of the PVCs/VTs. Spontaneous reversal of the relationship of the DPs to the local ventricular electrogram during the arrhythmias was noted. The DPs were related to a region of low voltage showed by intracardiac high-density contact mapping. At the sites with DPs, lower unipolar and bipolar ventricular voltage of sinus beats were noted compared with the adjacent regions without DPs (unipolar: 6.1 ± 1.8 vs. 8.3 ± 2.3 mV, P < 0.05; bipolar: 0.62 ± 0.45 vs. 1.03 ± 0.60 mV, P < 0.05). The targeted DPs were still present in 12 patients after successful elimination of the ectopies. Discrete potentials were not present in seven controls. CONCLUSION Discrete potentials and related low-voltage regions were common in idiopathic outflow tract ventricular arrhythmias. Discrete potential- and substrate-guided ablation strategy will help to reduce the recurrence of idiopathic outflow tract arrhythmias.

Cilostazol ameliorates atrial ionic remodeling in long-term rapid atrial pacing dogs

Objective: Ionic remodeling has a close correlation with the occurrence of atrial fibrillation (AF). Atrial tachypacing remodeling is associated with characteristic ionic remodeling. The purpose of this study was to assess the efficacy of cilostazol, an oral phosphodiesterase 3 inhibitor, for preventing atrial ionic remodeling in long-term rapid atrial pacing (RAP) dogs. Methods: We use the methods of patch-clamp and molecular biology to investigate the effect of cilostazol on ion channel and channel gene expression in long-term RAP dogs. Twenty-one dogs were randomly assigned to sham, control paced, and paced+cilostazol (5 mg/kg/d, cilo) groups, with 7 dogs in each group. The sham group was instrumented with a pacemaker but without pacing. RAP at 500 beats/min was maintained for 2 weeks in the paced and cilo groups. During the pacing, cilostazol was given orally in the cilo group. Whole-cell patch-clamp technique was used to record atrial L-type Ca2+ (ICaL) and fast sodium channel (INa) ionic currents. Western blot and RT-PCR were applied to estimate the gene expression of the ICaLa) 1C (Cav1.2) and INav1.5a) Nav1.5a) subunits. Statistical analysis was performed using SPSS 13.0. Results: The density of ICaL and INa currents (pA/pF) was significantly reduced in the paced group (ICaL: -6.55±1.42 vs. -4.46±0.59 pA/pF; INa: -48.24±10.54 vs. -30.48±5.20 pA/pF, p<0.01). The paced+cilo group could not increase the density of ICaL currents (ICaL: -4.37±1.25 pA/pF, p>0.05], while the INa currents were recovered (-44.54±12.65 pA/pF, p<0.01) compared with the paced group. The mRNA and protein expression levels of Cav1.2 and Nav1.5a were apparently down-regulated in the paced group (p<0.01), but after cilostazol treatment, both of these subunits were up-regulated significantly (p<0.01). Conclusion: Cilostazol may have protective effects on RAP-induced atrial ionic remodeling.