Early repolarization syndrome(ERS), demonstrated as J-point elevation on an electrocardiograph, was formerly thought to be a benign entity, but the recent studies have demonstrated that it can be linked to a considera...Early repolarization syndrome(ERS), demonstrated as J-point elevation on an electrocardiograph, was formerly thought to be a benign entity, but the recent studies have demonstrated that it can be linked to a considerable risk of life- threatening arrhythmias and sudden cardiac death(SCD). Early repolarization characteristics associated with SCD include high-amplitude J-point elevation, horizontal and/or downslopping ST segments, and inferior and/or lateral leads location. The prevalence of ERS varies between 3% and 24%, depending on age, sex and J-point elevation(0.05 m V vs 0.1 m V) being the main determinants.ERS patients are sporadic and they are at a higher risk of having recurrent cardiac events. Implantable cardioverter-defibrillator implantation and isoproterenol are the suggested therapies in this set of patients. On the other hand, asymptomatic patients with ERS are common and have a better prognosis. The risk stratification in asymptomatic patients with ERS still remains a grey area. This review provides an outline of the up-to-date evidence associated with ERS and the risk of life- threatening arrhythmias. Further prospective studies are required to elucidate the mechanisms of ventricular arrhythmogenesis in patients with ERS.展开更多
Malignant cardiac arrhythmias which result in sudden cardiac death may be present in individuals apparently healthy or be associated with other medical conditions. The way to predict their appearance represents a chal...Malignant cardiac arrhythmias which result in sudden cardiac death may be present in individuals apparently healthy or be associated with other medical conditions. The way to predict their appearance represents a challenge for the medical community due to the tragic outcomes in most cases. In the last two decades some ventricular repolarization(VR) markers have been found to be useful to predict malignant cardiac arrhythmias in several clinical conditions. The corrected QT, QT dispersion, Tpeak-Tend, Tpeak-Tend dispersion and Tp-e/QT have been studied and implemented in clinical practice for this purpose. These markers are obtained from 12 lead surface electrocardiogram. In this review we discuss how these markers have demonstrated to be effective to predict malignant arrhythmias in medical conditions such as long and short QT syndromes, Brugada syndrome, early repolarization syndrome, acute myocardial ischemia, heart failure, hypertension, diabetes mellitus, obesity and highly trained athletes. Also the main pathophysiological mechanisms that explain the arrhythmogenic predisposition in these diseases and the basis for the VR markers are discussed. However, the same results have not been found in all conditions. Further studies are needed to reach a global consensus in order to incorporate these VR parameters in risk stratification of these patients.展开更多
Summary： To study the effect of of lidocaine and amiodarone on the transmural heterogeneity of ventricular repolarization in isolated rabbit hearts model of sustained global ischemia and to explore the mechanisms und...Summary： To study the effect of of lidocaine and amiodarone on the transmural heterogeneity of ventricular repolarization in isolated rabbit hearts model of sustained global ischemia and to explore the mechanisms underlying the antiarrhythmic activity of lidocaine and amiodarone, rabbits were randomly divided into 4 groups： control group, ischemia group, lidocaine group and amiodarone group. By the monophasic action potential （MAP） recording technique, MAPs of epicardium, midmyocardium and endocardium were simultaneously recorded across the left ventricular free wall in rabbit hearts perfused by low-flow ischemia （2. 5 mL/min） in Langendorff method to study the transmural dispcrsion of repolarization （TDR） and arrhythmic induced by ischemia.Our results showed that TDR of three myocardial layers in ischemia group were significantly lengthened after ischemia. TDR was increased from 17.5±3.9 ms to 31.2±4.6 ms at the time that concided with the onset of sustained ventricle arrhythmic. Amiodarone could decrease TDR, but lidocaine could increase TDR at initial ischemia, and no significant difference was found at other ischemia time points. 5 cases had ventriclar arrhythmia in ischemia group （62. 5%）, but no case in lidocaine group （P〈0.01） and only 1 case in amiodarone group had ventrilar arrhythmia （P〈 0.01）. No significant difference was found between amiodarone group and lidocaine group. It is concluded that TDR of of three myocardial layers increases significantly at ischemia and it is closely associated with development of ventricular arrhythmia, and amiodarone could decrease TDR, but lidocaine could increase TDR at initial ischemia and has no effects at other ischemia time points.展开更多
Objective:To observe effects of hypokalemia on transmural heterogeneity of ventricular repolarization in left ventricular myocardium of rabbit,and explore the role of hypokalemia in malignant ventricular arrhythmia（...Objective:To observe effects of hypokalemia on transmural heterogeneity of ventricular repolarization in left ventricular myocardium of rabbit,and explore the role of hypokalemia in malignant ventricular arrhythmia（MVA）.Methods:A total of 20 rabbits were randomly divided into control group and hypokalemic group.Isolated hearts in the control group were simply perfused with modified Tyrode’s solution,and were perfused with hypokalemic Tyrode’s solution in hypokalemic group.Ventricular fibrillation threshold（VFT）,90%monophasic action potential repolarization duration(APD<sub>90</sub>) of subepicardial,midmyocardial and subendocardial myocardium,transmural dispersion of repolarization（TDR） and Cx43 protein expression in three layers of myocardium were measured in both groups.Results:VFT in the control group and the hypokalemic group were（13.40±2.95） V,and（7.00±1.49） V,respectively.There was a significant difference between two groups（P【0.01）.APD<sub>90</sub> of three myocardial layers in the hypokalemic group were significantly prolonged than those in the control group（/’【0.01）.△APD<sub>90</sub>in the hypokalemic group and the control group were（38.10±10\29） ms and（23.7015.68） ms,and TDR were（52.90<sub>r</sub> 14.55） ms and（36.10±12.44） ms,respectively.△APD<sub>90</sub> and TDR in the hypokalemic group were significantly higher than those in the control group(P【0.05|,and the increase in△APD<sub>90</sub> of midmyocardium was more significant in the hypokalemic group.Cx43 protein expression of all three myocardial layers were decreased significantly in the hypokalemic group（P【0.01）, and△APD<sub>90</sub> was significantly increased {P【0.05).Reduction of Cx43 protein expression was more significant in the midmyocardium.Conclusions:Hypokalemic can increase transmural heterogeneity of Cx43 expression and repolarization in left ventricular myocardium of rabbit,and decrease VFT and can induce MVA more easily.展开更多
Objective To explore the effects of particulate matters less than 2.5 μm in aerodynamic diameter （PM2.5） on heart repolarization/depolarization and heart rate variability （HRV）. Methods We conducted a panel study...Objective To explore the effects of particulate matters less than 2.5 μm in aerodynamic diameter （PM2.5） on heart repolarization/depolarization and heart rate variability （HRV）. Methods We conducted a panel study for elderly subjects with heart disease in Beijing from 2007 to 2008. PM2.5 was measured at a fixed station for 20 h continuously each day while electrocardiogram （ECG） indexes of 42 subjects were also recorded repeatedly. Meteorological data was obtained from the China Meteorological Data Sharing Service System. A mixed linear regression model was used to estimate the associations between PMz.s and the ECG indexes. The model was adjusted for age, body mass index, sex, day of the week and meteorology. Results Significant adverse effects of PM2.5 on ECG indexes reflecting HRV were observed statistically and the strongest effect of PM2.s on HRV was on lag i day in our study. However, there were no associations between PM2.5 and ECG indexes reflecting heart repolarization/depolarization. Additionally, the effects of PM2.5 on subjects with hypertension were larger than on the subjects without hypertension. Conclusion This study showed ambient PM2.5could affect cardiac autonomic function of the elderly people with heart disease, and subjects with hypertension appeared to be more susceptive to the autonomic dysfunction induced by PM2.5.展开更多
Sudden cardiac death （SCD） affects approximately 800,000 individuals per annum globally. It is most frequently due to cardiac tachy-arrhythmias, which include mono-morphic or polymorphic ventricular tachycardia （VT...Sudden cardiac death （SCD） affects approximately 800,000 individuals per annum globally. It is most frequently due to cardiac tachy-arrhythmias, which include mono-morphic or polymorphic ventricular tachycardia （VT）, torsade de pointes and ventricular fibrillation （VF）. Risk stratification for SCD remains a challenging problem in clinical practice.展开更多
Malignant ventricular arrhythmias are a major adverse event and worsen the prognosis of patients affected by ischemic and non-ischemic dilated cardiomyopathy.The main parameter currently used to stratify arrhythmic ri...Malignant ventricular arrhythmias are a major adverse event and worsen the prognosis of patients affected by ischemic and non-ischemic dilated cardiomyopathy.The main parameter currently used to stratify arrhythmic risk and guide decision making towards the implantation of a cardioverter defibrillator is the evaluation of the left ventricular ejection fraction.However,this strategy is characterized by several limitations and consequently additional parameters have been suggested in order to improve arrhythmic risk stratification.The aim of this review is to critically revise the prognostic significance of non-invasive diagnostic tools in order to better stratify the arrhythmic risk prognosis of dilated cardiomyopathy patients.展开更多
Repolarization heterogeneity(RH)is an intrinsic property of ventricular myocardium and the reason for T-wave formation on electrocardiogram(ECG).Exceeding the physiologically based RH level is associated with appearan...Repolarization heterogeneity(RH)is an intrinsic property of ventricular myocardium and the reason for T-wave formation on electrocardiogram(ECG).Exceeding the physiologically based RH level is associated with appearance of life-threatening ventricular arrhythmias and sudden cardiac death.In this regard,an accurate and comprehensive evaluation of the degree of RH parameters is of importance for assessment of heart state and arrhythmic risk.This review is devoted to comprehensive consideration of RH phenomena in terms of electrophysiological processes underlying RH,cardiac electric field formation during ventricular repolarization,as well as clinical significance of RH and its reflection on ECG parameters.The formation of transmural,apicobasal,left-toright and anterior-posterior gradients of action potential durations and end of repolarization times resulting from the heterogenous distribution of repolarizing ion currents and action potential morphology throughout the heart ventricles,and the different sensitivity of myocardial cells in different ventricular regions to the action of pharmacological agents,temperature,frequency of stimulation,etc.,are being discussed.The review is focused on the fact that RH has different aspects–temporal and spatial,global and local;ECG reflection of various RH aspects and their clinical significance are being discussed.Strategies for comprehensive assessment of ventricular RH using different ECG indices reflecting various RH aspects are presented.展开更多
Objective:To observe the effects of angiotensin Ⅱ(Ang Ⅱ) pefusion on transmural heterogeneity of Cx43 expression in the rabbit model with acute myocardial ischemia reperfusion(MIR),and investigate the role of rennin...Objective:To observe the effects of angiotensin Ⅱ(Ang Ⅱ) pefusion on transmural heterogeneity of Cx43 expression in the rabbit model with acute myocardial ischemia reperfusion(MIR),and investigate the role of rennin-angiotensin system in malignant ventricular arrhythmia induced by MIR.Methods:Twenty rabbits were randomly divided into MIR group(n=10) and Ang Ⅱ group(n=10).MIR model was produced with traditional ligation and opening of the anterior descending coronary artery in all animal.The hearts in vitro in the MIR group and the Ang Ⅱ group were perfused with simply improved Tyrode's solution and containing Ang Ⅱ Tyrode's solution respectively.90%monophasic action potential repolarization duration,transmural dispersion of repolarization.Cx43 protein(Cx43-pro) and mRNA(Cx43-Cq) expression in subepicardial,midmyocardial and subendocardial myocardium were measured in both groups.The greatest differences of Cx43-pro and Cx43-Cq among three myocardial layers were calculated and shown with △Cx43-pro and △Cx43-Cq respectively.Results:After Ang Ⅱ perfusion,90%monophasic action potential repolarization duration among three myocardial layer were significantly prolonged(P < 0.05 and P < 0.01),and transmural dispersion of repolarization also significantly increased compared with the MIR group(P < 0.05).Compare with the MIR group,three myocardial Cx43-pro and Cx43-Cq expression in the Ang Ⅱ group were significantly decreased(P < 0.05 and P < 0.01).but△Cx43-pro and △Cx43-Cq were significant increased.Conclusions:Renin-angiotensin system increases transmural heterogeneity of Cx43 expression in the rabbit model with MIR by Ang Ⅱ,and enlarge transmural dispersion of repolarization among three myocardial layers of left ventricular which induces malignant ventricular arrhythmia.展开更多
AIM: To examine the effect of ibutilide on novel indexes of repolarization in patients with persistent atrial fibrillation (AF). METHODS: We studied consecutive patients scheduled for elective electrical cardioversion...AIM: To examine the effect of ibutilide on novel indexes of repolarization in patients with persistent atrial fibrillation (AF). METHODS: We studied consecutive patients scheduled for elective electrical cardioversion. Intravenous ibutilide (1+1mg) was administered before the electrical cardioversion while close electrocardiographic (ECG) monitoring was performed. ECG indexes such as corrected QT interval (QTc), the interval from the peak until the end of T wave (Tpe), and the Tpe/QT ratio were measured before ibutilide infusion and 10 min after the end of infusion. RESULTS: The final study population consisted of 20 patients (mean age: 67.1±9.9 years, 10 men). Six patients were cardioverted pharmacologically and did not proceed to electrical cardioversion. Two patientsdeveloped short non-sustained episodes of torsades de pointes ventricular tachycardia. All but one of the aforementioned ECG indexes increased significantly after ibutilide administration. In specific, the QTc interval increased from 442 ± 29 to 471 ± 37 ms (P=0.037), the Tpe interval in precordial leads from 96 ms (range 80-108 ms) to 101 ms (range 91-119 ms) (P=0.021), the Tpe interval in lead Ⅱ from 79 ms (range 70-88 ms) to 100 ms (range 87-104 ms) (P<0.001), the Tpe/QT ratio in precordial leads from 0.23 ms (range 0.18-0.26 ms) to 0.26 ms (range 0.23-0.28 ms) (P=0.028), and the Tpe interval dispersion from 25 ms (range 23-30 ms) to 35 ms (range 27-39 ms) (P=0.012). However, the Tpe/QT ratio in lead II did not change significantly. CONCLUSION: Ibutilide increases the duration and dispersion of ventricular repolarization. The prognostic value of Tpe and Tpe/QT in the setting of drug-induced proarrhythmia needs further study.展开更多
We read the original article by Nuis, et al. and the reply by Dogan, et al. with great interest. Nuis, et al. examined whether transcatheter aortic valve implantation （TAVI） in patients suffering from severe aortic ...We read the original article by Nuis, et al. and the reply by Dogan, et al. with great interest. Nuis, et al. examined whether transcatheter aortic valve implantation （TAVI） in patients suffering from severe aortic stenosis led to changes in corrected QT dispersion （cQTD）, previously used to predict arrhythmic risk. Dogan, et al. proposed that a different marker, transmural dispersion of repolariza- tion （TDR）, has better accuracy in risk prediction.展开更多
AIM To describe echocardiographically left ventricular false tendon characteristics and the correlation with ventricular repolarization abnormalities in young athletes.METHODS Three hundred and sixteen healthy young a...AIM To describe echocardiographically left ventricular false tendon characteristics and the correlation with ventricular repolarization abnormalities in young athletes.METHODS Three hundred and sixteen healthy young athletes from different sport disciplines were evaluated from 2009 to 2011 during routine screening for agonistic sports eligibility. All subjects, as part of standard preparticipation screening medical evaluation, underwent a basal and post step test 12-lead electrocardiogram(ECG). The athletes with abnormal T-wave flattening and/or inversion were considered for an echocardiogram evaluation and an incremental maximal exercise test on a cycle ergometer. Arterial blood pressure and heart rate, during and after exercise, were also measured.RESULTS Twenty-one of the 316 subjects(6.9%) showed false tendons in the left ventricle. The majority of false tendons(52.38%) were localized between the middle segments of the inferior septum and the lateral wall, 19.06% between the distal segments of the septum and the lateral wall, in 5 subjects between the middle segments of the anterior and inferior walls, and in one subject between the middle segments of the anterior septum and the posterior wall. ECG abnormalities, represented by alterations of ventricular repolarization, were found in 11 subjects(52.38%), 90% of these anomalies were T wave abnormalities from V1 to V3. These anomalies disappeared with an increasing heart rate following the three minute step test as well as during the execution of the maximal exercise.CONCLUSION Left ventricular false tendons are frequently localized between the middle segments of the inferior septum and the lateral wall and are statistically associated with ventricular repolarization abnormalities.展开更多
Brugada syndrome is a primary electrical disorder of theheart, predisposing affected individuals to potentially lethal,ventricular tachy-arrhythmias. A number of mechanismshave been identified as being important incre...Brugada syndrome is a primary electrical disorder of theheart, predisposing affected individuals to potentially lethal,ventricular tachy-arrhythmias. A number of mechanismshave been identified as being important increasing the riskof these rhythms. Wavelength （γ） restitution has beensuggested to predict the onset of action potential duration（APD） alternans in mouse Scn5a^＋/- hearts modelling Bru-gada syndrome.展开更多
Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the ...Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the QRS complex and the end of the T wave or U wave(QT). Several physiological, pathological and iatrogenic factors can influence ventricular repolarization. It has been demonstrated that small perturbations in this process can be a potential trigger of malignant arrhythmias, therefore the analysis of ventricular repolarization represents an interesting tool to implement risk stratification of arrhythmic events in different clinical settings. The aim of this review is to critically revise the traditional methods of static analysis of ventricular repolarization as well as those for dynamic evaluation, their prognostic significance and the possible application in daily clinical practice.展开更多
The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization in intact canine was investigated. By using the monophasic action potential (MAP) recording technique, monophasic action po...The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization in intact canine was investigated. By using the monophasic action potential (MAP) recording technique, monophasic action potentials (MAPs) of the epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were recorded simultaneously by specially designed plunge needle electrodes at the left ventricular free wall in 12 open chest dogs. MAPD 90 and transmural dispersion of repolarization among three myocardial layers as well as the incidence of the EAD before autonomic nervous stimulation and during autonomic nervous stimulation were compared. The results showed that the MAPD 90 of Epi, Mid and Endo before autonomic nervous stimulation were 278±11 ms, 316±16 ms and 270±12 ms respectively, the MAPD 90 of Mid was significantly longer than that of Epi or Endo ( P <0.01). MAPD 90 of Epi, Mid and Endo were shortened by 19±4 ms, 45±6 ms, 18±3 ms respectively during sympathetic stimulation. Compared with that of the control, the transmural dispersion of repolarization during sympathetic stimulation was shortened from 44±4 ms to 15±3 ms ( P <0.01), but early afterdepolarizations were elicited in the Mid of 5 dogs (41 %) during sympathetic stimulation. Parasympathetic stimulation did not significantly affect the MAPD 90 in the three layers. It is concluded that there is the transmural dispersion of ventricular repolarization in intact canine. Sympathetic stimulation can reduce transmural dispersion of repolarization, but it can produce early afterdepolarizations in the Mid. Parasympathetic stimulation does not significantly affect the transmural dispersion of ventricular repolarization.展开更多
The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization(TDR)under acute myocardial ischemia in intact canine was investigated.Using the monophasic action potential(MAP)recording t...The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization(TDR)under acute myocardial ischemia in intact canine was investigated.Using the monophasic action potential(MAP)recording technique,MAPs of the epicardium(Epi),midmyocardium(Mid)and endocardium(Endo)were recorded simultaneously by specially designed plunge-needle electrodes at the left ventricular free wall under acute myocardial ischemia in 12 open-chest dogs.MAPD 90 and TDR among three myocardial layers as well as the incidence of the early afterdepolarization(EAD)before autonomic nervous stimulation and during autonomic nervous stimulation were compared.It was found that 10 min after acute myocardial ischemia,TDR was increased from 55±8 ms to 86±15 ms during sympathetic stimulation(P<0.01).The TDR(53±9 ms)during parasympathetic stimulation was not significantly different from that of the control(55±8 ms)(P>0.05).The EAD was elicited in the Mid of 2 dogs(16%)10 min after acute myocardial ischemia,but the EAD were elicited in the Mid of 7 dogs(58%)during sympathetic stimulation(P<0.01).It was concluded that:(1)Sympathetic stimulation can increase the transmural dispersion of repolari-zation and induce early afterdepolarizations in the Mid under acute myocardial ischemia,which provide the opportunity for the ventricular arrhythmia developing;(2)Parasympathetic stimulation has no significant effect on the transmural dispersion of repolarization under myocardial ischemia.展开更多
Brugada syndrome is a primary arrhythmia syndrome characterized by loss-of-function mutations in the SCN5A gene, which encodes for the cardiac Na^＋ channel. In affected individuals, the risk of developing malignant v...Brugada syndrome is a primary arrhythmia syndrome characterized by loss-of-function mutations in the SCN5A gene, which encodes for the cardiac Na^＋ channel. In affected individuals, the risk of developing malignant ventricular arrhythmias and sudden cardiac death are increased.展开更多
BACKGROUND： Ventricular arrhythmia （VA） is one of the most common complications of myocardial infarction （MI）, and ventricular tachycardia and fibrillation are the main causes for sudden cardiac death. This study...BACKGROUND： Ventricular arrhythmia （VA） is one of the most common complications of myocardial infarction （MI）, and ventricular tachycardia and fibrillation are the main causes for sudden cardiac death. This study aimed to explore the effect of ramipril on the occurrence of VA and its mechanism after MI in rabbits. METHODS： Twenty-four New Zealand rabbits purchased from the Wuhan Laboratory Animal Research Center were divided into three groups： sham-operated （SHAM） group （n=8）, MI group （n=8） and MI with ramipril （RAM） group （n=8）. Rabbits in the SHAM group received a median sternotomy without ligation of the left ventricular coronary artery. Rabbits in the MI and RAM groups received a median sternotomy followed by ligation of the left coronary artery. The successful anterior MI was confirmed by elevation of the ST segment with more than 0.2 mV in lead II and II1. After MI, rabbits in the RAM group were fed with intragastric ramipril （1 mg/kg per day ） for 12 weeks. Before and 12 weeks after MI in the three groups, ventricular tachycardia or fibrillation （VT/VF） episodes and MAP in cadiocytes of the epicardium, mid-myocardium and endocardium were recorded by a multichannel physiograph. Student＇s t test and ANOVA were used for statistical analysis. RESULTS： VT/VF episodes were decreased more markedly in the RAM group than in the MI group after 12 weeks （2.6±0.8 vs. 12.±＋2.9, P〈0.05）. Twelve weeks after MI, the duration of repolarization for 90% （APD90） of three-tier ventricular myocytes in the MI group was longer than that before MI （258.2±21.1 vs. 230.1±23.2,278.0±23.8 vs. 245.8±25.4,242.6±22.7 vs. 227.0±21.7, P〈0.05）. However, the APD90 was not significantly different at 12 weeks before and after MI in the RAM group （P〉0.05）. Moreover, the transmural dispersion of repolarization （TDR） was increased more markedly 12 weeks after MI in the MI group than in the SHAM and RAM groups （36.2±10.2 vs. 18.7±6.2, 24.9±8.7, P〈0.05）. But the TDR was not significantly different between the RAM and SHAM groups （18.7±6.2 vs. 24.9±8.7, P〉0.05）. CONCLUSION： Ramipril may reduce the incidence of malignant ventricular arrhythmia via mprovement of transmembrance repolarization heterogeneity after MI.展开更多
We read the article written by Nuis, et al. The authors investigated the effects of transcatheter aortic valve implantation （TAVI） on corrected QT dispersion （cQTD） in severe aortic stenosis patients. They conclud...We read the article written by Nuis, et al. The authors investigated the effects of transcatheter aortic valve implantation （TAVI） on corrected QT dispersion （cQTD） in severe aortic stenosis patients. They concluded that, 40% of patients had defective cQTD recovery at six months after the procedure and this was associated with increased late mortality risk. We would like to contribute to the study from a different methodological perspective.展开更多
Objective： To investigate the effects of carvedilol （CVD） on transmural dispersion of repolarization（TDR） and arrhythmia in pressure over-load rabbits. Methods： Left ventricular hypertrophied（LVH） rabbit model...Objective： To investigate the effects of carvedilol （CVD） on transmural dispersion of repolarization（TDR） and arrhythmia in pressure over-load rabbits. Methods： Left ventricular hypertrophied（LVH） rabbit models were established by pressure over-load; All animal models were assigned into CVD group or LVH group randomly. The action potentials of endocardium, cpicardium and transmural ECG of arterially perfused left ventricular preparations were recorded concurrently. Action potential duration （APD）, TDR, ventricular arrhythmia and ultrasonic parameters, ratio of LVM to body weight （LVMI） were compared correspondingly. The stable plasma concentration of carvedilol in CVD group was detected by HPLC. APD, TDR and arrhythmia of LVH models were compared just preor post-perfusion with stable concentration of CVD. Results： In Contrast with values in LVH group, LVEFof CVD group were significantly elevated while the LVMI was remarkably reduced, TDRs were significantly shortened, and ratio of ventricular arrhythmia was lowered remarkably. No significant difference of APD, TDR and ratio of arrhythmia was found preor post-perfusion at stable plasma concentration of CVD. Conclusion： CVD can ameliorate the structure and function of pressure over-load ventricles; CVD contributes to the improvement of ventricular arrhythmia associated with its long-term effect on APD,TDR shortening ,whereas has nothing to do with its transient function on ionic channel blockade展开更多
文摘Early repolarization syndrome(ERS), demonstrated as J-point elevation on an electrocardiograph, was formerly thought to be a benign entity, but the recent studies have demonstrated that it can be linked to a considerable risk of life- threatening arrhythmias and sudden cardiac death(SCD). Early repolarization characteristics associated with SCD include high-amplitude J-point elevation, horizontal and/or downslopping ST segments, and inferior and/or lateral leads location. The prevalence of ERS varies between 3% and 24%, depending on age, sex and J-point elevation(0.05 m V vs 0.1 m V) being the main determinants.ERS patients are sporadic and they are at a higher risk of having recurrent cardiac events. Implantable cardioverter-defibrillator implantation and isoproterenol are the suggested therapies in this set of patients. On the other hand, asymptomatic patients with ERS are common and have a better prognosis. The risk stratification in asymptomatic patients with ERS still remains a grey area. This review provides an outline of the up-to-date evidence associated with ERS and the risk of life- threatening arrhythmias. Further prospective studies are required to elucidate the mechanisms of ventricular arrhythmogenesis in patients with ERS.
文摘Malignant cardiac arrhythmias which result in sudden cardiac death may be present in individuals apparently healthy or be associated with other medical conditions. The way to predict their appearance represents a challenge for the medical community due to the tragic outcomes in most cases. In the last two decades some ventricular repolarization(VR) markers have been found to be useful to predict malignant cardiac arrhythmias in several clinical conditions. The corrected QT, QT dispersion, Tpeak-Tend, Tpeak-Tend dispersion and Tp-e/QT have been studied and implemented in clinical practice for this purpose. These markers are obtained from 12 lead surface electrocardiogram. In this review we discuss how these markers have demonstrated to be effective to predict malignant arrhythmias in medical conditions such as long and short QT syndromes, Brugada syndrome, early repolarization syndrome, acute myocardial ischemia, heart failure, hypertension, diabetes mellitus, obesity and highly trained athletes. Also the main pathophysiological mechanisms that explain the arrhythmogenic predisposition in these diseases and the basis for the VR markers are discussed. However, the same results have not been found in all conditions. Further studies are needed to reach a global consensus in order to incorporate these VR parameters in risk stratification of these patients.
文摘Summary： To study the effect of of lidocaine and amiodarone on the transmural heterogeneity of ventricular repolarization in isolated rabbit hearts model of sustained global ischemia and to explore the mechanisms underlying the antiarrhythmic activity of lidocaine and amiodarone, rabbits were randomly divided into 4 groups： control group, ischemia group, lidocaine group and amiodarone group. By the monophasic action potential （MAP） recording technique, MAPs of epicardium, midmyocardium and endocardium were simultaneously recorded across the left ventricular free wall in rabbit hearts perfused by low-flow ischemia （2. 5 mL/min） in Langendorff method to study the transmural dispcrsion of repolarization （TDR） and arrhythmic induced by ischemia.Our results showed that TDR of three myocardial layers in ischemia group were significantly lengthened after ischemia. TDR was increased from 17.5±3.9 ms to 31.2±4.6 ms at the time that concided with the onset of sustained ventricle arrhythmic. Amiodarone could decrease TDR, but lidocaine could increase TDR at initial ischemia, and no significant difference was found at other ischemia time points. 5 cases had ventriclar arrhythmia in ischemia group （62. 5%）, but no case in lidocaine group （P〈0.01） and only 1 case in amiodarone group had ventrilar arrhythmia （P〈 0.01）. No significant difference was found between amiodarone group and lidocaine group. It is concluded that TDR of of three myocardial layers increases significantly at ischemia and it is closely associated with development of ventricular arrhythmia, and amiodarone could decrease TDR, but lidocaine could increase TDR at initial ischemia and has no effects at other ischemia time points.
文摘Objective:To observe effects of hypokalemia on transmural heterogeneity of ventricular repolarization in left ventricular myocardium of rabbit,and explore the role of hypokalemia in malignant ventricular arrhythmia（MVA）.Methods:A total of 20 rabbits were randomly divided into control group and hypokalemic group.Isolated hearts in the control group were simply perfused with modified Tyrode’s solution,and were perfused with hypokalemic Tyrode’s solution in hypokalemic group.Ventricular fibrillation threshold（VFT）,90%monophasic action potential repolarization duration(APD<sub>90</sub>) of subepicardial,midmyocardial and subendocardial myocardium,transmural dispersion of repolarization（TDR） and Cx43 protein expression in three layers of myocardium were measured in both groups.Results:VFT in the control group and the hypokalemic group were（13.40±2.95） V,and（7.00±1.49） V,respectively.There was a significant difference between two groups（P【0.01）.APD<sub>90</sub> of three myocardial layers in the hypokalemic group were significantly prolonged than those in the control group（/’【0.01）.△APD<sub>90</sub>in the hypokalemic group and the control group were（38.10±10\29） ms and（23.7015.68） ms,and TDR were（52.90<sub>r</sub> 14.55） ms and（36.10±12.44） ms,respectively.△APD<sub>90</sub> and TDR in the hypokalemic group were significantly higher than those in the control group(P【0.05|,and the increase in△APD<sub>90</sub> of midmyocardium was more significant in the hypokalemic group.Cx43 protein expression of all three myocardial layers were decreased significantly in the hypokalemic group（P【0.01）, and△APD<sub>90</sub> was significantly increased {P【0.05).Reduction of Cx43 protein expression was more significant in the midmyocardium.Conclusions:Hypokalemic can increase transmural heterogeneity of Cx43 expression and repolarization in left ventricular myocardium of rabbit,and decrease VFT and can induce MVA more easily.
基金supported by the National Natural Science Foundation of China (Grant No. 20637020)
文摘Objective To explore the effects of particulate matters less than 2.5 μm in aerodynamic diameter （PM2.5） on heart repolarization/depolarization and heart rate variability （HRV）. Methods We conducted a panel study for elderly subjects with heart disease in Beijing from 2007 to 2008. PM2.5 was measured at a fixed station for 20 h continuously each day while electrocardiogram （ECG） indexes of 42 subjects were also recorded repeatedly. Meteorological data was obtained from the China Meteorological Data Sharing Service System. A mixed linear regression model was used to estimate the associations between PMz.s and the ECG indexes. The model was adjusted for age, body mass index, sex, day of the week and meteorology. Results Significant adverse effects of PM2.5 on ECG indexes reflecting HRV were observed statistically and the strongest effect of PM2.s on HRV was on lag i day in our study. However, there were no associations between PM2.5 and ECG indexes reflecting heart repolarization/depolarization. Additionally, the effects of PM2.5 on subjects with hypertension were larger than on the subjects without hypertension. Conclusion This study showed ambient PM2.5could affect cardiac autonomic function of the elderly people with heart disease, and subjects with hypertension appeared to be more susceptive to the autonomic dysfunction induced by PM2.5.
文摘Sudden cardiac death （SCD） affects approximately 800,000 individuals per annum globally. It is most frequently due to cardiac tachy-arrhythmias, which include mono-morphic or polymorphic ventricular tachycardia （VT）, torsade de pointes and ventricular fibrillation （VF）. Risk stratification for SCD remains a challenging problem in clinical practice.
文摘Malignant ventricular arrhythmias are a major adverse event and worsen the prognosis of patients affected by ischemic and non-ischemic dilated cardiomyopathy.The main parameter currently used to stratify arrhythmic risk and guide decision making towards the implantation of a cardioverter defibrillator is the evaluation of the left ventricular ejection fraction.However,this strategy is characterized by several limitations and consequently additional parameters have been suggested in order to improve arrhythmic risk stratification.The aim of this review is to critically revise the prognostic significance of non-invasive diagnostic tools in order to better stratify the arrhythmic risk prognosis of dilated cardiomyopathy patients.
文摘Repolarization heterogeneity(RH)is an intrinsic property of ventricular myocardium and the reason for T-wave formation on electrocardiogram(ECG).Exceeding the physiologically based RH level is associated with appearance of life-threatening ventricular arrhythmias and sudden cardiac death.In this regard,an accurate and comprehensive evaluation of the degree of RH parameters is of importance for assessment of heart state and arrhythmic risk.This review is devoted to comprehensive consideration of RH phenomena in terms of electrophysiological processes underlying RH,cardiac electric field formation during ventricular repolarization,as well as clinical significance of RH and its reflection on ECG parameters.The formation of transmural,apicobasal,left-toright and anterior-posterior gradients of action potential durations and end of repolarization times resulting from the heterogenous distribution of repolarizing ion currents and action potential morphology throughout the heart ventricles,and the different sensitivity of myocardial cells in different ventricular regions to the action of pharmacological agents,temperature,frequency of stimulation,etc.,are being discussed.The review is focused on the fact that RH has different aspects–temporal and spatial,global and local;ECG reflection of various RH aspects and their clinical significance are being discussed.Strategies for comprehensive assessment of ventricular RH using different ECG indices reflecting various RH aspects are presented.
基金supported by National Natural Science Foundation of China(NO.81160024)Natural Science Foundation of Hainan Province(NO.814371)
文摘Objective:To observe the effects of angiotensin Ⅱ(Ang Ⅱ) pefusion on transmural heterogeneity of Cx43 expression in the rabbit model with acute myocardial ischemia reperfusion(MIR),and investigate the role of rennin-angiotensin system in malignant ventricular arrhythmia induced by MIR.Methods:Twenty rabbits were randomly divided into MIR group(n=10) and Ang Ⅱ group(n=10).MIR model was produced with traditional ligation and opening of the anterior descending coronary artery in all animal.The hearts in vitro in the MIR group and the Ang Ⅱ group were perfused with simply improved Tyrode's solution and containing Ang Ⅱ Tyrode's solution respectively.90%monophasic action potential repolarization duration,transmural dispersion of repolarization.Cx43 protein(Cx43-pro) and mRNA(Cx43-Cq) expression in subepicardial,midmyocardial and subendocardial myocardium were measured in both groups.The greatest differences of Cx43-pro and Cx43-Cq among three myocardial layers were calculated and shown with △Cx43-pro and △Cx43-Cq respectively.Results:After Ang Ⅱ perfusion,90%monophasic action potential repolarization duration among three myocardial layer were significantly prolonged(P < 0.05 and P < 0.01),and transmural dispersion of repolarization also significantly increased compared with the MIR group(P < 0.05).Compare with the MIR group,three myocardial Cx43-pro and Cx43-Cq expression in the Ang Ⅱ group were significantly decreased(P < 0.05 and P < 0.01).but△Cx43-pro and △Cx43-Cq were significant increased.Conclusions:Renin-angiotensin system increases transmural heterogeneity of Cx43 expression in the rabbit model with MIR by Ang Ⅱ,and enlarge transmural dispersion of repolarization among three myocardial layers of left ventricular which induces malignant ventricular arrhythmia.
文摘AIM: To examine the effect of ibutilide on novel indexes of repolarization in patients with persistent atrial fibrillation (AF). METHODS: We studied consecutive patients scheduled for elective electrical cardioversion. Intravenous ibutilide (1+1mg) was administered before the electrical cardioversion while close electrocardiographic (ECG) monitoring was performed. ECG indexes such as corrected QT interval (QTc), the interval from the peak until the end of T wave (Tpe), and the Tpe/QT ratio were measured before ibutilide infusion and 10 min after the end of infusion. RESULTS: The final study population consisted of 20 patients (mean age: 67.1±9.9 years, 10 men). Six patients were cardioverted pharmacologically and did not proceed to electrical cardioversion. Two patientsdeveloped short non-sustained episodes of torsades de pointes ventricular tachycardia. All but one of the aforementioned ECG indexes increased significantly after ibutilide administration. In specific, the QTc interval increased from 442 ± 29 to 471 ± 37 ms (P=0.037), the Tpe interval in precordial leads from 96 ms (range 80-108 ms) to 101 ms (range 91-119 ms) (P=0.021), the Tpe interval in lead Ⅱ from 79 ms (range 70-88 ms) to 100 ms (range 87-104 ms) (P<0.001), the Tpe/QT ratio in precordial leads from 0.23 ms (range 0.18-0.26 ms) to 0.26 ms (range 0.23-0.28 ms) (P=0.028), and the Tpe interval dispersion from 25 ms (range 23-30 ms) to 35 ms (range 27-39 ms) (P=0.012). However, the Tpe/QT ratio in lead II did not change significantly. CONCLUSION: Ibutilide increases the duration and dispersion of ventricular repolarization. The prognostic value of Tpe and Tpe/QT in the setting of drug-induced proarrhythmia needs further study.
文摘We read the original article by Nuis, et al. and the reply by Dogan, et al. with great interest. Nuis, et al. examined whether transcatheter aortic valve implantation （TAVI） in patients suffering from severe aortic stenosis led to changes in corrected QT dispersion （cQTD）, previously used to predict arrhythmic risk. Dogan, et al. proposed that a different marker, transmural dispersion of repolariza- tion （TDR）, has better accuracy in risk prediction.
文摘AIM To describe echocardiographically left ventricular false tendon characteristics and the correlation with ventricular repolarization abnormalities in young athletes.METHODS Three hundred and sixteen healthy young athletes from different sport disciplines were evaluated from 2009 to 2011 during routine screening for agonistic sports eligibility. All subjects, as part of standard preparticipation screening medical evaluation, underwent a basal and post step test 12-lead electrocardiogram(ECG). The athletes with abnormal T-wave flattening and/or inversion were considered for an echocardiogram evaluation and an incremental maximal exercise test on a cycle ergometer. Arterial blood pressure and heart rate, during and after exercise, were also measured.RESULTS Twenty-one of the 316 subjects(6.9%) showed false tendons in the left ventricle. The majority of false tendons(52.38%) were localized between the middle segments of the inferior septum and the lateral wall, 19.06% between the distal segments of the septum and the lateral wall, in 5 subjects between the middle segments of the anterior and inferior walls, and in one subject between the middle segments of the anterior septum and the posterior wall. ECG abnormalities, represented by alterations of ventricular repolarization, were found in 11 subjects(52.38%), 90% of these anomalies were T wave abnormalities from V1 to V3. These anomalies disappeared with an increasing heart rate following the three minute step test as well as during the execution of the maximal exercise.CONCLUSION Left ventricular false tendons are frequently localized between the middle segments of the inferior septum and the lateral wall and are statistically associated with ventricular repolarization abnormalities.
文摘Brugada syndrome is a primary electrical disorder of theheart, predisposing affected individuals to potentially lethal,ventricular tachy-arrhythmias. A number of mechanismshave been identified as being important increasing the riskof these rhythms. Wavelength （γ） restitution has beensuggested to predict the onset of action potential duration（APD） alternans in mouse Scn5a^＋/- hearts modelling Bru-gada syndrome.
文摘Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the QRS complex and the end of the T wave or U wave(QT). Several physiological, pathological and iatrogenic factors can influence ventricular repolarization. It has been demonstrated that small perturbations in this process can be a potential trigger of malignant arrhythmias, therefore the analysis of ventricular repolarization represents an interesting tool to implement risk stratification of arrhythmic events in different clinical settings. The aim of this review is to critically revise the traditional methods of static analysis of ventricular repolarization as well as those for dynamic evaluation, their prognostic significance and the possible application in daily clinical practice.
文摘The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization in intact canine was investigated. By using the monophasic action potential (MAP) recording technique, monophasic action potentials (MAPs) of the epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were recorded simultaneously by specially designed plunge needle electrodes at the left ventricular free wall in 12 open chest dogs. MAPD 90 and transmural dispersion of repolarization among three myocardial layers as well as the incidence of the EAD before autonomic nervous stimulation and during autonomic nervous stimulation were compared. The results showed that the MAPD 90 of Epi, Mid and Endo before autonomic nervous stimulation were 278±11 ms, 316±16 ms and 270±12 ms respectively, the MAPD 90 of Mid was significantly longer than that of Epi or Endo ( P <0.01). MAPD 90 of Epi, Mid and Endo were shortened by 19±4 ms, 45±6 ms, 18±3 ms respectively during sympathetic stimulation. Compared with that of the control, the transmural dispersion of repolarization during sympathetic stimulation was shortened from 44±4 ms to 15±3 ms ( P <0.01), but early afterdepolarizations were elicited in the Mid of 5 dogs (41 %) during sympathetic stimulation. Parasympathetic stimulation did not significantly affect the MAPD 90 in the three layers. It is concluded that there is the transmural dispersion of ventricular repolarization in intact canine. Sympathetic stimulation can reduce transmural dispersion of repolarization, but it can produce early afterdepolarizations in the Mid. Parasympathetic stimulation does not significantly affect the transmural dispersion of ventricular repolarization.
文摘The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization(TDR)under acute myocardial ischemia in intact canine was investigated.Using the monophasic action potential(MAP)recording technique,MAPs of the epicardium(Epi),midmyocardium(Mid)and endocardium(Endo)were recorded simultaneously by specially designed plunge-needle electrodes at the left ventricular free wall under acute myocardial ischemia in 12 open-chest dogs.MAPD 90 and TDR among three myocardial layers as well as the incidence of the early afterdepolarization(EAD)before autonomic nervous stimulation and during autonomic nervous stimulation were compared.It was found that 10 min after acute myocardial ischemia,TDR was increased from 55±8 ms to 86±15 ms during sympathetic stimulation(P<0.01).The TDR(53±9 ms)during parasympathetic stimulation was not significantly different from that of the control(55±8 ms)(P>0.05).The EAD was elicited in the Mid of 2 dogs(16%)10 min after acute myocardial ischemia,but the EAD were elicited in the Mid of 7 dogs(58%)during sympathetic stimulation(P<0.01).It was concluded that:(1)Sympathetic stimulation can increase the transmural dispersion of repolari-zation and induce early afterdepolarizations in the Mid under acute myocardial ischemia,which provide the opportunity for the ventricular arrhythmia developing;(2)Parasympathetic stimulation has no significant effect on the transmural dispersion of repolarization under myocardial ischemia.
文摘Brugada syndrome is a primary arrhythmia syndrome characterized by loss-of-function mutations in the SCN5A gene, which encodes for the cardiac Na^＋ channel. In affected individuals, the risk of developing malignant ventricular arrhythmias and sudden cardiac death are increased.
基金supported by a grant from the Natural Science Foundation of Hubei(2007ABA288)
文摘BACKGROUND： Ventricular arrhythmia （VA） is one of the most common complications of myocardial infarction （MI）, and ventricular tachycardia and fibrillation are the main causes for sudden cardiac death. This study aimed to explore the effect of ramipril on the occurrence of VA and its mechanism after MI in rabbits. METHODS： Twenty-four New Zealand rabbits purchased from the Wuhan Laboratory Animal Research Center were divided into three groups： sham-operated （SHAM） group （n=8）, MI group （n=8） and MI with ramipril （RAM） group （n=8）. Rabbits in the SHAM group received a median sternotomy without ligation of the left ventricular coronary artery. Rabbits in the MI and RAM groups received a median sternotomy followed by ligation of the left coronary artery. The successful anterior MI was confirmed by elevation of the ST segment with more than 0.2 mV in lead II and II1. After MI, rabbits in the RAM group were fed with intragastric ramipril （1 mg/kg per day ） for 12 weeks. Before and 12 weeks after MI in the three groups, ventricular tachycardia or fibrillation （VT/VF） episodes and MAP in cadiocytes of the epicardium, mid-myocardium and endocardium were recorded by a multichannel physiograph. Student＇s t test and ANOVA were used for statistical analysis. RESULTS： VT/VF episodes were decreased more markedly in the RAM group than in the MI group after 12 weeks （2.6±0.8 vs. 12.±＋2.9, P〈0.05）. Twelve weeks after MI, the duration of repolarization for 90% （APD90） of three-tier ventricular myocytes in the MI group was longer than that before MI （258.2±21.1 vs. 230.1±23.2,278.0±23.8 vs. 245.8±25.4,242.6±22.7 vs. 227.0±21.7, P〈0.05）. However, the APD90 was not significantly different at 12 weeks before and after MI in the RAM group （P〉0.05）. Moreover, the transmural dispersion of repolarization （TDR） was increased more markedly 12 weeks after MI in the MI group than in the SHAM and RAM groups （36.2±10.2 vs. 18.7±6.2, 24.9±8.7, P〈0.05）. But the TDR was not significantly different between the RAM and SHAM groups （18.7±6.2 vs. 24.9±8.7, P〉0.05）. CONCLUSION： Ramipril may reduce the incidence of malignant ventricular arrhythmia via mprovement of transmembrance repolarization heterogeneity after MI.
文摘We read the article written by Nuis, et al. The authors investigated the effects of transcatheter aortic valve implantation （TAVI） on corrected QT dispersion （cQTD） in severe aortic stenosis patients. They concluded that, 40% of patients had defective cQTD recovery at six months after the procedure and this was associated with increased late mortality risk. We would like to contribute to the study from a different methodological perspective.
文摘Objective： To investigate the effects of carvedilol （CVD） on transmural dispersion of repolarization（TDR） and arrhythmia in pressure over-load rabbits. Methods： Left ventricular hypertrophied（LVH） rabbit models were established by pressure over-load; All animal models were assigned into CVD group or LVH group randomly. The action potentials of endocardium, cpicardium and transmural ECG of arterially perfused left ventricular preparations were recorded concurrently. Action potential duration （APD）, TDR, ventricular arrhythmia and ultrasonic parameters, ratio of LVM to body weight （LVMI） were compared correspondingly. The stable plasma concentration of carvedilol in CVD group was detected by HPLC. APD, TDR and arrhythmia of LVH models were compared just preor post-perfusion with stable concentration of CVD. Results： In Contrast with values in LVH group, LVEFof CVD group were significantly elevated while the LVMI was remarkably reduced, TDRs were significantly shortened, and ratio of ventricular arrhythmia was lowered remarkably. No significant difference of APD, TDR and ratio of arrhythmia was found preor post-perfusion at stable plasma concentration of CVD. Conclusion： CVD can ameliorate the structure and function of pressure over-load ventricles; CVD contributes to the improvement of ventricular arrhythmia associated with its long-term effect on APD,TDR shortening ,whereas has nothing to do with its transient function on ionic channel blockade
