The current difference between male and female rabbit ventricular myocytes was investigated for elucidating the mechanism of longer QT interval and higher incidence of drug-associated torsade de pointes in female rabbits than in male rabbits. Whole cell patch clamp technique was used to record APD, Ito, IK,tail, IK1 and ICa,L of myocytes from left ventricular apex. There was no difference in the membrane capacitance between male and female rabbit myocytes. APD90 was longer in female rabbits (560.4+/-26.5 ms, n=15) than in male ones (489.0+/-20.7 ms, n = 14), P<0. 05. In female rabbit myocytes, IKtail, Ito, IK1 and ICa,L were 0.71+/-0.05 pA/pF (n=17), 8.28+/-1.03 pA/pF (n=18), 24.5+/-3.6 pA/pF (n=12) and 9.0+/-2.3 pA/pF (n=15) respectively. In male rabbit myocytes, they were 0.84+/-0.07 pA/pF (n=18), 8.60+/-1.20 pA/pF (n=18), 25.9+/-4.5 pA/pF (n=14) and 9.3+2.6 pA/pF (n=16) respectively. IK,tail in female rabbits was significantly lower than that of male rabbits (P<0.05), but there was no difference in Ito,IK1 and ICa.L between male rabbits and female rabbits (P>0.05). The lower IK.tail of female rabbit myocytes may contribute to the longer repolarization and the higher incidence of drug-associated torsade de pointes.
Action Potentials/physiology ; Heart Ventricles/*physiology ; Myocytes, Cardiac/*physiology ; Patch-Clamp Techniques ; Potassium Channels/physiology ; Sex Characteristics ; Torsades de Pointes/chemically induced

In order to confirm the hypothesis that during acute hypoxia, the antiarrhythmic peptide (AAP10) could improve conductance by changing the phosphorylation state of connexin43 (Cx43), isolated perfused rat hearts were randomly divided into three groups: control, hypoxia and AAP10 (n=9 in each group). The change in Cx43 phosphorylation was tested by Western-blot; the distribution of Cx43 was observed by confocal immunofluorescence microscopy. Western-blot analysis revealed that the expression of total Cx43 protein was significantly decreased during acute hypoxia, while nonphosphorylated Cx43 (NP-Cx43) was unchanged. AAP10 could increase the expression of total Cx43 protein, but had no effects on the NP-Cx43 protein. Immunofluorescence study showed that during acute hypoxia, both total Cx43 and NP-Cx43 proteins were greatly decreased, while AAP10 only increased the expression of total Cx43 protein, but had no effect of the NP-Cx43 protein expression. These findings suggested that the decrease of intercellular communication may be associated with the reduction of phosphorylated Cx43 (p-Cx43) and translocation of NP-Cx43 from the surface of gap junction into intracellular pools during acute hypoxia. AAP10 can improve intercellular communication by enhancing phosphorylation of Cx43.

AIM: To elucidate the mechanism of arrhythmia in healed myocardial infarction (HMI), and to investigate the changes of action potential duration (APD),transient outward potassium current (I to ), delayed rectifier potassium current (I K) and inward rectifier potassium current (I K1 ) of left ventricular myocytes in noninfarcted zone of HMI. METHODS: 12 rabbits were randomly assigned in two groups: HMI group (thoracotomy and ligation of the circumflex coronary); sham-operated group (thoracotomy but no conorary ligation). 3 months after operation, whole cell patch clamp technique was used to record APD, I to , I K and I K1 of ventricular myocytes in non-infarcted zone. RESULTS: Membrane capacitance was larger in HMI group than that in sham-operated group. Action potential duration was lengthened significantly in HMI group and early after depolarization (EAD) appeared in HMI group. The densities of I to , I K,tail and I K1 were reduced significantly in HMI group (P

AIM: To investigate the mechanism of gend er difference in sotalol-induced torsade de pointes (TdP) in rabbits in vitro. METHODS: 40 rabbits of both sexes were divided into two groups: low concentration (1?10 -5 mol/L d-sotalol) group and high concentration (1?10 -4 mol/L d-sotalol) group. With the monophasic action potential (MAP ) recording technique, MAP of epicardium, midmyocardium and endocardium were sim ultaneously recorded by specially designed plunge-needle electrodes across the l eft ventricular free wall of rabbit hearts purfused by Langendorff method. TdP w as induced by bradycardia, d-sotalol and low-K+, Mg 2+ tyrode solution. RESULTS: d-sotalol prolonged the duration of 90% repolarizat ion (MAPD 90) of epicardium, midmyocardium and endocardium in a concentration-d ependent manner and the effect on midmyocardium was the most obvious. In low con centration group, MAPD 90 of midmyocardium of male rabbit heart increased f rom (222?11) ms to (230?10) ms and that of female rabbit heart increased from (263?12) ms to (281?12) ms. In high concentration group, MAPD 90 of midmy ocardium of male rabbit heart increased from (217?10) ms to (296?18) ms and th at of female rabbit heart increased from (258?10) ms to (368?19) ms. There was no difference in TDR between male and female rabbit hearts before perfusion wit h d-sotalol. D-sotalol prolonged TDR in a concentration-dependent manner. In low concentration group, TDR of male and female rabbit hearts was (20.0?5.1) ms and (28.0?5.6) ms. In high concentration group, TDR of male and female rabbit hearts was (38.0?4.8) ms and (55.0?7.7) ms, respectively. There was EAD i n 6 female hearts while no EAD develop ed in male heart and no TdP developed in low concentration group. In high concen tration group, 10 female, 9 male hearts developed EAD, 9 female and 3 male he arts developed TdP. CONCLUSION: The greater TDR induced by d-sotalol in female may b e responsible for the higher incidence of TdP of female rabbit heart.

Objective:To investigate the association between age and cardiac tamponade after radiofrequency ablation of atrial fibrillation(RAAF).Methods:Clinical data of patients undergone de novo AF ablation procedures at Beijing Anzhen Hospital from January 2013 to December 2016 were retrospectively collected.Patients were divided into an elderly group(age ≥60 years)and a non-elderly group(age <60 years). Logistic regression analyses were used to evaluate the association between old age and the risk of cardiac tamponade complicating RAAF.Results:A total of 5 313 patients were involved in this study, including 41 patients(0.77%)with cardiac tamponade.The proportion of cardiac tamponade was higher in the elderly group than in the non-elderly group(1.1% or 32/2 950 vs.0.4% or 9/2 363, χ2=8.489, P=0.004). One patient with cardiac tamponade in the elderly group required immediate surgical repair whereas none in the non-elderly group did.No patient died in hospital.Multivariate Logistic regression analysis showed that the risk of cardiac tamponade increased in the elderly group, compared with the non-elderly group( OR=2.570, 95% CI: 1.190-5.570, P=0.017). Stratified analysis revealed that among females and patients with oral anticoagulants, left atrium dimension < 40 mm or procedure duration≥ 120 min in the elderly group carried a higher risk of cardiac tamponade than those in the non-elderly group( OR=1.011, 2.914, 3.922 and 3.244, P<0.05). Conclusions:Old age(age ≥60 years)is an independent risk factor for cardiac tamponade complicating RAAF.

To elucidate the mechanism of arrhythmia in healed myocardial infarction (HMI), the changes of action potential duration (APD), transient outward potassium current (Ito), delayed rectifier potassium current (IK) and inward rectifier potassium current (IK1) of left ventricular myocytes in non-infarcted zone of HMI were investigated. Rabbits were randomly assigned into two groups: HMI group, in which animals were subjected to thoracotomy and ligation of the circumflex coronary and sham-operated group, in which rabbits underwent thoracotomy but no conorary ligation. 3 months after the operation, the whole myocyte patch clamp technique was used to record APD, Ito, IK, and IK1 of ventricular myocytes in non-infarcted zone. Our results showed that the membrane capacitance was larger in HMI group than in sham-operated group. Action potential duration was significantly lengthened in HMI group and early afterdepolarization (EAD) appeared in HMI group. The densities of Ito, I(K, tail), and IK1 were reduced significantly in HMI group, from 6.72 +/- 0.42 pA/pF, 1.54 +/- 0.13 pA/pF and 25.6 +/- 2.6 pA/pF in sham-operated group to 4.03 +/- 0.33 pA/pF, 1.14 +/- 0.11 pA/pF and 17.6 +/- 2.3 pA/pF, respectively. It is concluded that the reduced densities of Ito, I(K, tail) and IK1 in ventricular myocytes of non-infarcted zone in HMI were responsible for the prolongation of APD and the presentation of EAD which played important roles in the development of malignant arrhythmia in HMI.
Action Potentials ; Arrhythmia/*etiology ; Heart Ventricles/metabolism ; Myocardial Infarction/complications ; Myocardial Infarction/metabolism ; Myocardial Infarction/*pathology ; Myocytes, Cardiac/*cytology ; Patch-Clamp Techniques ; Potassium Channels/*metabolism

Objective: To explore the false-negative possibility in genetic test of congenital long QT syndrome (LQTS) by next-generation sequencing (NGS). Methods: A total of 28 genomic DNA samples were collected from 4 laboratories including 2 commercial medical laboratories using HiSeq2000 platform as Lab1,n=6 and Lab2,n=8; 1 commercial research service laboratory using Ion-torrent platform as Lab3,n=8 and 1 academic laboratory using HiSeq2000 platform as Lab 4,n=6. Sequencing coverage in the exons of protein-coding region in 3 main LQTS pathogenic genes as KCNQ1, KCNH2, SCN5A and possible pathogenic variants were quantitatively analyzed. Results: In Lab1, Lab 2 and Lab 4 with HiSeq2000 platform, above 98% protein coding regions in 3 pathogenic genes were covered with>10-fold reads and 90%-95% were covered with>30-fold reads. In 2 commercial medical laboratories, 3.63% and 9.84% protein coding regions of KCNQ1 gene in 14 samples were covered with<10-fold reads and with<30-fold reads; lower than 10-fold covering region was focused in the 1st exon including about 2% known or likely pathogenic variants. In 2 commercial medical laboratories, 2.64% and 15.76% protein coding regions of KCNH2 gene in 14 samples were covered with<10-fold reads and with<30-fold reads; low covering region was located in multiple exons. For the data from Lab 1, as high as 28.56% protein coding regions of KCNH2 gene were covered with<30-fold reads including 113 (19.79%) known or likely pathogenic variants. SCN5A gene had the best coverage of protein coding region, with no<10-fold reads in all 4 Labs and no<30-fold reads in 2 commercial medical laboratories. Conclusion: Currently, NGS has low coverage region in both KCNQ1 and KCNH2 genes, pathogenic variants could be missed and false-negative possibility should be highly alert.

Presented in this paper were 3 cases of a special kind of polymorphic ventricular tachycardia (VT). The clinical manifestation was recurrent syncope without organic heart disease. The electrocardiogram (ECG) was characterized by normal QT intervals with short-coupled variant of torsade de pointes. The efficacy of treatment with class Ⅰ,Ⅱ,Ⅲ antiarrhythmic drugs was not apparent but verapamil had an excellent therapeutic effect for it. This kind of VT had a high incidence of sudden death, so it was very important for physicians to identify and treat it promptly with long-term verapamil. The mechanism of short-coupled variant of torsade de pointes was unclear. It probably had some relationship with triggered activity or imbalance of autonomic nervous system.

Presented in this paper were 3 cases of a special kind of polymorphic ventricular tachycardia (VT). The clinical manifestation was recurrent syncope without organic heart disease. The electrocardiogram (ECG) was characterized by normal QT intervals with short-coupled variant of torsade de pointes. The efficacy of treatment with class Ⅰ,Ⅱ,Ⅲ antiarrhythmic drugs was not apparent but verapamil had an excellent therapeutic effect for it. This kind of VT had a high incidence of sudden death, so it was very important for physicians to identify and treat it promptly with long-term verapamil. The mechanism of short-coupled variant of torsade de pointes was unclear. It probably had some relationship with triggered activity or imbalance of autonomic nervous system.

Objective To investigate the mechanism of carbapenem-resistant in Enterobacteriaceae strains isolated from Fuyang First People′s Hospital and to analyze their epidemiological features. Methods The Enterobacteriaceae strains with reduced ertapenem susceptibility were isolated from the Fuy-ang First People′s Hospital during January 2013 to August 2014.K-B disk diffusion and E-test were per-formed to detect the antimicrobial susceptibilities of those strains.The modified Hodge test, ethylenediami-netetraacetic acid ( EDTA) disk synergy test and extended-spectrumβ-lactamases ( ESBLs) confirmation test were used to screen out the carbapenem-resistant phenotypes.PCR analysis and gene sequencing were used to analyze drug resistance genes, genetic structures surrounding the blaKPC-2 gene and seven house-keeping genes of Klebsiella pneumonia ( K.pneumoniae) strains.The sequences of the seven house-keeping genes were analyzed with multilocus sequence typing ( MLST) .Pulsed field gel electrophoresis ( PFGE) was per-formed for homology analysis within the same species.S1-PFGE in combination with Southern blot analysis was used to determine the location of carbapenem resistance genes.Results A total of 19 Enterobacteriace-ae isolates with reduced susceptibility to ertapenem were screened out.Each of them was resistant to multiple antibiotics and harbored several resistance genes.Seven genes including the blaKPC-2 , blaIMP-4 , blaSHV-1 , blaCTX-M-65 , blaCTX-M-15 , blaTEM-1 and rmtB genes were the prevalent drug resistance genes.Fourteen out of the nineteen strains were identified as K.pneumoniae strains, mainly belonged to the ST11 type according to the results of MLST.Among the nineteen strains, eleven K.pneumoniae isolates and one Escherichia coli isolate carried the blaKPC-2 gene, located on plasmids varying in size (95 kb, 140 kb, 200 kb and 240 kb) .The ge-netic structures of all isolates were ISKpn8, blaKPC-2 and ISKpn6-like from upstream to downstream.The blaIMP-4 gene was detected in one Klebsiella oxytoca isolate and one K.pneumoniae isolate, located on a plas-mid about 300 kb in size.Conclusion Carbapenemases KPC-2 and IMP-4 were closely related to the car-bapenem resistance in carbapenem-resistant Enterobacteriaceae strains isolated form the Fuyang First People′s Hospital.No predominant clone was found in those carbapenem-resistant K.pneumoniae isolates.