Molecular Mechanisms of Increased Heart Rate in Shenxianshengmai-treated Bradycardia Rabbits.

BACKGROUND: The molecular mechanisms of Shenxianshengmai (SXSM), a traditional Chinese medicine, on bradycardia have been incompletely understood. The study tried to investigate the gene expression profile and proteomics of bradycardia rabbits' hearts after SXSM treatment. METHODS: Twenty-four adult rabbits were randomly assigned in four groups: sham, model, model plus SXSM treatment, and sham plus SXSM treatment groups. Heart rate was recorded in all rabbits. Then, total RNA of atria and proteins of ventricle were isolated and quantified, respectively. Gene expression profiling was conducted by gene expression chip, and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed to confirm the results of gene expression chip. We used isobaric tags for elative and absolute quantitation and Western blotting to identify altered proteins after SXSM treatment. RESULTS: There was a constant decrease in the mean heart rate (32%, from 238 ± 6 beats/min to 149 ± 12 beats/min) after six weeks in model compared with that in sham group. This effect was partially reversed by 4-week SXSM treatment. Complementary DNA microarray demonstrated that the increased acetylcholinesterase and reduced nicotinic receptor were take responsibility for the increased heart rate. In addition, proteins involved in calcium handling and signaling were affected by SXSM treatment. Real-time RT-PCR verified the results from gene chip. Results from proteomics demonstrated that SXSM enhanced oxidative phosphorylation and tricarboxylic acid (TCA) cycle in ventricular myocardium to improve ATP generation. CONCLUSIONS: Long-term SXSM stimulates sympathetic transmission by increasing the expression of acetylcholinesterase and reduces the expression of nicotinic receptor to increase heart rate. SXSM also restored the calcium handling genes and altered genes involved in signaling. In addition, SXSM improves the ATP supply of ventricular myocardium by increasing proteins involved in TCA cycle and oxidation-respiratory chain.

Variations of electroanatomic substrates and markers of successful ablation in idiopathic left ventricular tachycardia: role of electroanatomic substrates and potential mechanism of tachycardia.

OBJECTIVES: The variation of the substrates of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) was not understood. The purpose of this study was to investigate the variation of electroanatomic substrate [slow conduction zone (SCZ) and left ventricular conduction system (LVCS)] in ILVT and control individuals and markers of successful ablation. METHODS: Electroanatomical mapping was performed during sinus rhythm in 20 ILVT patients and 26 control individuals with paroxysmal supraventricular tachycardia. LVCS and SCZ were tagged in geometry and the anatomic aspects were investigated. RESULTS: According to the distribution of Purkinje potential, LVCS was distinguished into three types: left bundle branch (LBB) was divided into two discrete fascicles without interconnections; divided into three separate fascicles; and fanlike structure distribution over septum broadly. The length of LBB and its fascicles in patients with ILVT were slightly longer than those of controls (P > 0.05). In the ILVT group, the SCZ was located at the inferoposterior septum in 17, inferior apical septum in one and two SCZs were located at the posterior and mid-septal in the other two patients, which were greater in size and longer in length than those of six controls (P < 0.05). At the crossover junction area with diastolic potential and Purkinje potential, with the size of 1.5 ± 0.4 cm(2), concealed entertainment and ablation were obtained successfully in all patients with ILVT. CONCLUSION: The anatomy of the LVCS and SCZ is highly variable in patients with ILVT, and the crossover junction area with diastolic potential and Purkinje potential might be a marker of ablation.

The electrophysiological characteristics of isolated diastolic potentials in idiopathic ventricular arrhythmias arising from the right ventricular outflow tract.

OBJECTIVE: The significance of isolated diastolic potentials (IDPs) in patients with idiopathic ventricular arrhythmias (IVAs) arising from right ventricular outflow tract (RVOT) is currently unknown. The objective of this study was to clarify the characteristics of IDPs and its role in guiding ablation in RVOT-IVAs. METHODS AND RESULTS: Twenty-five consecutive patients with RVOT-IVAs and ten control subjects were studied. Electro-anatomical mapping was performed in RVOT during sinus rhythm. The electrophysiological characteristics of IDPs and its relation to successful ablation site were evaluated. Successful ablation was achieved during IVAs in 22 patients and during sinus rhythm in the remaining three. IDPs were recorded in all patients in the vicinity of successful ablation sites during sinus rhythm before ablation, with the area of 1.44 /- 0.28 cm2, maximal amplitude of 0.32 +/- 0.06 mV and the distance to pulmonary valve of 1.39 +/- 0.25 cm. IDPs could still be recorded after ablation except one. Moreover, IDPs were characterized by decremental and/or automatic property by studying intervals between ventricular activation and IDPs (V-IDPs) during sinus rhythm. And V-IDPs intervals during sinus rhythm were longerthan those during IVAs (P = 0.012). However, IDPs were only recorded in one patient in the control group and the incidence of IDPs was remarkably lower than that in the RVOT-IVAs group (1/10 vs. 25/25, P < 0.001). CONCLUSIONS: IDPs were present in patients with RVOT-IVAs. IDPs area and/or border region might be the successful ablation site and their precise mechanism remains to be clarified.

The effects of paeoniflorin monomer of a Chinese herb on cardiac ion channels.

BACKGROUND: Because of the potential proarrhythmic effect of current antiarrhythmic drugs, it is still desirable to find safer antiarrhythmic drugs worldwide. Paeoniflorin is one of the Chinese herb monomers that have different effects on many ion channels. The present study aimed to determine the effects of paeoniflorin on cardiac ion channels. METHODS: Whole-cell patch-clamp technique was used to record ion channel currents. L-type calcium current (I(Ca-L)), inward rectifier potassium current (I(K1)), and transient outward potassium current (I(to1)) were studied in rat ventricular myocytes and sodium current (I(Na)), slow delayed rectifier current (I(Ks)), and HERG current (I(Kr)) were investigated in transfected human embryonic kidney 293 cells. RESULTS: One hundred µmol/L paeoniflorin reduced the peak I(Ca-L) by 40.29% at the test potential of +10 mV (from (-9.78 ± 0.52) pA/pF to (-5.84 ± 0.89) pA/pF, n = 5, P = 0.028). The steady-state activation curve was shifted to more positive potential in the presence of the drug. The half activation potentials were (-11.22 ± 0.27) mV vs. (-5.95 ± 0.84) mV (n = 5, P = 0.007), respectively. However, the steady-state inactivation and the time course of recovery from inactivation were not changed. One hundred µmol/L paeoniflorin completely inhibited the peak I(Na) and the effect was reversible. Moreover, paeoniflorin inhibited the I(K1) by 30.13% at the test potential of -100 mV (from -25.26 ± 8.21) pA/pF to (-17.65 ± 6.52) pA/pF, n = 6, P = 0.015) without effects on the reversal potential and the rectification property. By contrast, 100 µmol/L paeoniflorin had no effects on I(to1), I(Ks) or I(Kr) channels. CONCLUSIONS: The study demonstrated that paeoniflorin blocked I(Ca-L), I(Na), and I(K1) without affecting I(to1), I(Ks), or I(Kr). The multi-channel block effect may account for its antiarrhythmic effects with less proarrhythmic potential.

[Evaluation of shensongyangxin capsules in the treatment of paroxysmal atrial fibrillation: a randomized, double-blind and controlled multicenter trial].

OBJECTIVE: To evaluate the efficacy and safety of Chinese medicinal shensongyangxin capsules in the treatment of paroxysmal atrial fibrillation. METHODS: From August 2007 to July 2008, Beijing Chaoyang Hospital conducted a multicenter study, select the eleven hospital's outpatient subjects, aged 18 to 75 years old, male or female, paroxysmal atrial fibrillation (at least one electrocardiogram diagnosis) seizure frequency ≥ 2 times/month, according to the ratio 1:1:1, subjects were randomly divided into three groups: a. shensongyangxin group, taking shensongyangxin capsule 4 + propafenone analogues 150 mg, 3 times a day; b. propafenone group, taking propafenone tablets 150 mg + 4 shensongyangxin analogues, 3 times a day; shensongyangxin capsule + propafenone group, taking shensongyangxin capsule 4 + propafenone 150 mg, 3 times a day. The treatment course is 8 weeks, with 3 times of follow-up. RESULTS: Total of 349 cases of paroxysmal atrial fibrillation, which 117 cases in shensongyangxin group, 115 cases in propafenone group; 117 cases in shensongyangxin + propafenone group. The baseline data analysis showed that there were no significantly difference (P > 0.05) among the three groups of atrial fibrillation seizure frequency, vital signs, general condition, medical history, 24-hour ambulatory ECG, 12-lead normal electrocardiogram, cardiac ultrasound and symptoms. The comparison before and after (8 weeks) treatment showed that the frequency (from 6 times/m to 2 times/m in each group, P < 0.01), number of cases [from 46 (43.3%) to 22 (20.8%), 43 (43.4%) to 25 (25.3%), and 40 (40.6%) to 31 (29.2%), respectively P < 0.01] and duration time of attack of atrial fibrillation (from 4 h to 0.5 h, 4 h to 0.5 h, and 4.25 h to 0.5 h, respectively P < 0.01) all decreased in three groups. No significant difference among the three groups comparing the overall effect (62.3%, 58.6%, and 58.5%, respectively, P > 0.05), while the efficacy of TCM symptoms in shensongyangxin group (80.2%) was better than that of propafenone group (67.7%) (P < 0.05). Safety evaluation showed that adverse reaction rate was 1.8% in shensongyangxin group, and 8.2% and 5.4% in propafenone group and shensongyangxin + propafenone group. CONCLUSION: Shensongyangxin capsules and propafenone have comparable efficacies in the treatment of PAF. The efficacy of TCM symptoms is better than propafenone. Shensongyangxin capsules have an excellent profile of safety.

[Clinical characteristics and outcome of 32 patients with long-QT syndrome accompanied with torsade de pointes].

OBJECTIVE: To summarize the clinical characteristics and outcome of patients with long-QT syndrome (LQTs) accompanied with torsade de pointes. METHODS: Thirty-two eligible patients were included in this study. Clinical and electrocardiographic data were analyzed and telephone or out-patient follow-up were made in all patients. RESULTS: There were 15 patients with inherited LQTs (h-LQTs) and 17 patients with acquired LQTs (a-LQTs). There are more women (n = 24) than men (n = 8). ß blockers, potassium and magnesium supplement were the basic therapy for h-LQTs patients, bivent pacemaker was implanted in 2 patients and implantable cardioverter defibrillator was implanted in 5 patients. Ventricular tachyarrhythmias and syncope occurred in 4 patients during (39.4 ± 25.1) months follow-up. In 17 a-LQTs patients, one patient with dilated cardiomyopathy died suddenly and another patient with implanted cardioverter defibrillator experienced one ventricular tachycardia during (30.9 ± 13.3) months follow-up. CONCLUSIONS: The prognosis in h-LQTs and a-LQTs patients with structure heart disease is poor. ICD or CRT-D therapy is suggestive for a-LQTs patients with structure heart disease.

Effects of Xinjining extract on inward rectifier potassium current in ventricular myocytes of guinea pig.

OBJECTIVE: To study the effect of Xinjining extract (, XJN) on inward rectifier potassium current (I(K1)) in ventricular myocyte (VMC) of guinea pigs and its anti-arrhythmic mechanism on ion channel level. METHODS: Single VMC was enzymatically isolated by zymolisis, and whole-cell patch clamp recording technique was used to record the I(k1) in VMC irrigated with XJN of different concentrations (1.25, 2.50, 5.00 g/L; six samples for each). The stable current and conductance of the inward component of I(K1) as well as the outward component of peak I(K1) and conductance of it accordingly was recorded when the test voltage was set on -110 mV. RESULTS: The suppressive rate of XJN on the inward component of I(K1) was 9.54% + or - 5.81%, 34.82% + or - 15.03%, and 59.52% + or - 25.58% with a concentration of 1.25, 2.50, and 5.00 g/L, respectively, and that for the outward component of peak I(K1) was 23.94% + or - 7.45%, 52.98% + or - 19.62%, and 71.42% + or - 23.01%, respectively (all P<0.05). Moreover, different concentrations of XJN also showed effects for reducing I(K1) conductance. CONCLUSION: XJN has inhibitory effect on I(K1) in guinea pig's VMC, and that of the same concentration shows stronger inhibition on outward component than on inward component, which may be one of the mechanisms of its anti-arrhythmic effect.

Electrophysiological effects of Chinese medicine Shen song Yang xin (SSYX) on Chinese miniature swine heart and isolated guinea pig ventricular myocytes.

BACKGROUND: Shen song Yang xin (SSYX) is a compound of Chinese medicine with the effect of increasing heart rate (HR). This study aimed to evaluate its electrophysiological properties at heart and cellular levels. METHODS: The Chinese miniature swines were randomly assigned to two groups, administered with SSYX or placebo for 4 weeks (n = 8 per group). Cardiac electrophysiological study (EPS) was performed before and after drug administration. The guinea pig ventricular myocytes were enzymatically isolated and whole cell voltage-clamp technique was used to evaluate the effect of SSYX on cardiac action potential (AP). RESULTS: SSYX treatment accelerated the HR from (141.8 +/- 36.0) beats per minute to (163.0 +/- 38.0) beats per minute (P = 0.013) without changing the other parameters in surface electrocardiogram. After blockage of the autonomic nervous system with metoprolol and atropin, SSYX had no effect on intrinsic HR (IHR), but decreased corrected sinus node recovery time (CSNRT) and sinus atrium conducting time (SACT). Intra cardiac EPS showed that SSYX significantly decreased the A-H and A-V intervals as well as shortened the atrial (A), atrioventricular node (AVN) and ventricular (V) effective refractory period (ERP). In isolated guinea pig ventricular myocytes, the most obvious effect of SSYX on action potential was a shortening of the action potential duration (APD) without change in shape of action potential. The shortening rates of APD(30), APD(50) and APD(90) were 19.5%, 17.8% and 15.3%, respectively. The resting potential (Em) and the interval between the end of APD(30) and APD(90) did not significantly change. CONCLUSIONS: The present study demonstrates that SSYX increases the HR and enhances the conducting capacity of the heart in the condition of the intact autonomic nervous system. SSYX homogenously decreases the ERP of the heart and shortens the APD of the myocytes, suggesting its antiarrhythmic effect without proarrhythmia.

Effects of Chinese herbs on multiple ion channels in isolated ventricular myocytes.

BACKGROUND: Shensong Yangxin (SSYX) is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current (I(Na)), L-type calcium current (I(Ca, L)), transient outward potassium current (I(to)), delayed rectifier current (I(K)), and inward rectifier potassium currents (I(K1)) in isolated ventricular myocytes. METHODS: Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes. RESULTS: SSYX decreased peak I(Na) by (44.84 +/- 7.65)% from 27.21 +/- 5.35 to 14.88 +/- 2.75 pA/pF (n = 5, P < 0.05). The medicine significantly inhibited the I(Ca, L). At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak I(Ca, L) was reduced by (19.22 +/- 1.10)%, (44.82 +/- 6.50)% and (50.69 +/- 5.64)%, respectively (n = 5, all P < 0.05). SSYX lifted the I - V curve of both I(Na) and I(Ca, L) without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of I(to) by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of I(K) was decreased by (30.77 +/- 1.11)% (n = 5, P < 0.05) at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of I(K) was also inhibited. Similar to the effect on I(K), the SSYX inhibited I(K1) by 33.10% at the test potential of -100 mV with little effect on reversal potential and the rectification property. CONCLUSIONS: The experiments revealed that SSYX could block multiple ion channels such as I(Na) I(Ca, L), I(k), I(to) and I(K1), which may change the action potential duration and contribute to some of its antiarrhythmic effects.

[Effects of solution of dry powder of ShenSongYangXin capsule on sodium current and L-type calcium current in ventricular myocytes: experiment with guinea pig].

OBJECTIVE: To investigate the effects of dry powder of ShenSongYangXin capsule on sodium current (I(Na)) and L-type calcium current (I(Ca, L)) in ventricular myocytes. METHODS: Ventricular myocytes were isolated from guinea pig. Solution of the dry powder of ShenSongYangXin capsule of the concentrations of 1%, 0.5%, and 0.25% was added into the suspension of the myocytes. Whole cell patch-clamp technique was used to detect the I(Na) and I(Ca, L) in the ventricular myocytes. RESULT: ShenSongYangXin decreased the peak I(Na) from 27.2 +/- 5.4 (pA/pF) to 14.9 +/- 2.8 (pA/pF), with a decrease rate of 44.8% +/- 7.7% (n = 5, P < 0.05). The solution of dry powder of ShenSongYangXin of the concentrations of 1%, 0.5%, and 0.25% decreased the peak L-type calcium channel current (I(ca, L)) significantly in a concentration dependent manner with the reduction rates of 50.7% +/- 5.6%, 44.8% +/- 6.5%, and 19.2% +/- 1.1% respectively (n = 5, all P < 0.05). ShenSongYangXin shifted up both the I approximately 1V curve of I(Na) and that of I(Ca, L), while their active, peak and reverse potentials didn't change. CONCLUSION: ShenSongYangXin blocks both I(Na) and I(Ca, L), which may contributes to some of its antiarrhythmic effect.

[Electrophysiological characterization of long QT syndrome associated mutations V630A and N633S].

OBJECTIVE: To identify the electrophysiological properties of long-QT syndrome (LQTS) associated missense mutations in the outer mouth of the HERG potassium channel in vitro. METHODS: Mutations V630A and N633S were constructed by Megaprimer PCR method and cRNA were produced by T7 RNA polymerase. The electrophysiological properties of the mutation were investigated in the Xenopus oocyte heterologous expression system. RESULTS: Coexpression of mutant and wild-type HERG subunits caused a dominant-negative effect, and the currents were significantly decreased. Compared with wild-type HERG channels, V630A and N633S mutations were related to decreased time constants for inactivation for V630A/WT and N633S/WT at all potentials, reduced slope conductance and the voltage dependence of steady-state inactivation was shifted to negative potentials for V630A/WT and N633S/WT. CONCLUSION: Present study shows that LQTS associated missense mutations located in the outer mouth of HERG cause a dominant-negative effect and alterations in steady-state voltage dependence of channel gating of heteromultimeric channels suggesting a reduction in expressional current might be one of the pathophysiologic mechanisms of LQTS.