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
Most cases of sudden cardiac death are attributed to sustained ventricular tachyarrhythmias(VTs), triggered by acute coronary occlusion. Autonomic dysfunction, an important arrhythmogenic mechanism in this setting, is...Most cases of sudden cardiac death are attributed to sustained ventricular tachyarrhythmias(VTs), triggered by acute coronary occlusion. Autonomic dysfunction, an important arrhythmogenic mechanism in this setting, is being actively investigated, aiming at the advent of preventive strategies. Recent experimental studies have shown vagal withdrawal after anterior myocardial infarction, coinciding with high incidence of VTs, followed by more gradual sympathetic activation coinciding with a second arrhythmia peak. This article summarizes recent knowledge on this intriguing topic, generating hypotheses that can be investigated in future experimental and clinical studies.展开更多
Sickle cell disease (SCD) has been regarded as an inflammatory and pro-?coagulatory disease with profound cardiovascular abnormalities including propensity for ventricular arrhythmogenesis. Tp-e and Tpe/QTc ratio howe...Sickle cell disease (SCD) has been regarded as an inflammatory and pro-?coagulatory disease with profound cardiovascular abnormalities including propensity for ventricular arrhythmogenesis. Tp-e and Tpe/QTc ratio however has?been proposed as better indicators of arrythmogenesis and has?been shown to be prolonged in many inflammatory conditions and correlate with levels of inflammatory markers. However, correlation between Tpe/QTc ratio and the level of highly sensitive C-reactive protein (hs-CRP) and plasminogen activator inhibitor (PAI) have not been reported in SCD. This study aims at evaluating Tp-e Interval and Tp-e/QTc ratio among steady state Sickle cell disease patients in relationship to the degree of anaemia, inflammatory and profibrotic markers.?Methodology:?A cross-sectional hospital-based study comprises?30 sickle cell anaemia patients in steady state with an?equal number of controls having genotype HbAA and HbAS respectively.Clinical, laboratory and ECG parameters were obtained.?Results:?A total of 90 participants?are?with mean age 24.2?±?5.6. The study showed that sickle cell disease patient had significantly lower level of PCV and higher level of PAI, platelet and total white cell count (p value??0.05). C-reactive protein was also higher in them. 76.7% of HbSS patients had abnormal ECG. QTc and Tp-e were also prolonged in sickle cell disease patients compared with controls. An association was found between the level of PCV, PAI and prolonged Tp-e and QTc.?Conclusion:?Sickle cell disease patients have higher levels of inflammatory markers and abnormal ECG patterns are common in them. Moreover, the levels of these inflammatory markers correlate with Tp-e parameters.展开更多
The mechanism of idiopathic ventricular tachycardia originating from the right ventricular outflow tract （RVOT） is not clear. Many clinical reports have suggested a mechanism of triggered activity. However, there ar...The mechanism of idiopathic ventricular tachycardia originating from the right ventricular outflow tract （RVOT） is not clear. Many clinical reports have suggested a mechanism of triggered activity. However, there are few studies investigating this be- cause of the technical difficulties associated with examining this theory. The L-type calcium current （/Ca-L）, an important in- ward current of the action potential （AP）, plays an important role in arrhythmogenesis. The aim of this study was to explore differences in the APs of right ventricular （RV） and RVOT cardiomyocytes, and differences in electrophysiological character- istics of the ICa-L in these myocytes. Rabbit RVOT and RV myocytes were isolated and their AP and Ic,-L were investigated us- ing the patch-clamp technique. RVOT cardiomyocytes had a wider range of AP duration （APD） than RV cardiomyocytes, with some markedly prolonged APDs and markedly shortened APDs. The markedly shortened APDs in RVOT myocytes were abolished by treatment with 4-AP, an inhibitor of the transient outward potassium current, but the markedly prolonged APDs remained, with some myocytes with a long AP plateau not repolarizing to resting potential. In addition, early afterdepolariza- tion （EAD） and second plateau responses were seen in RVOT myocytes but not in RV myocytes. RVOT myocytes had a high- er current density for/Ca-L than RV myocytes （RVOT （13.16±0.87） pA pF-1, RV （8.59±1.97） pA pF-1; P〈0.05）. The ICa-L and the prolonged APD were reduced, and the EAD and second plateau response disappeared, after treatment with nifedipine （10 μmol L^-1）, which blocks the Ica-L. In conclusion, there was a wider range of APDs in RVOT myocytes than in RV myocytes, which is one of the basic factors involved in arrhythmogenesis. The higher current density for ICa-L is one of the factors causing prolongation of the APD in RVOT myocytes. The combination of EAD with prolonged APD may be one of the mechanisms of RVOT-VT generation.展开更多
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.
文摘Most cases of sudden cardiac death are attributed to sustained ventricular tachyarrhythmias(VTs), triggered by acute coronary occlusion. Autonomic dysfunction, an important arrhythmogenic mechanism in this setting, is being actively investigated, aiming at the advent of preventive strategies. Recent experimental studies have shown vagal withdrawal after anterior myocardial infarction, coinciding with high incidence of VTs, followed by more gradual sympathetic activation coinciding with a second arrhythmia peak. This article summarizes recent knowledge on this intriguing topic, generating hypotheses that can be investigated in future experimental and clinical studies.
文摘Sickle cell disease (SCD) has been regarded as an inflammatory and pro-?coagulatory disease with profound cardiovascular abnormalities including propensity for ventricular arrhythmogenesis. Tp-e and Tpe/QTc ratio however has?been proposed as better indicators of arrythmogenesis and has?been shown to be prolonged in many inflammatory conditions and correlate with levels of inflammatory markers. However, correlation between Tpe/QTc ratio and the level of highly sensitive C-reactive protein (hs-CRP) and plasminogen activator inhibitor (PAI) have not been reported in SCD. This study aims at evaluating Tp-e Interval and Tp-e/QTc ratio among steady state Sickle cell disease patients in relationship to the degree of anaemia, inflammatory and profibrotic markers.?Methodology:?A cross-sectional hospital-based study comprises?30 sickle cell anaemia patients in steady state with an?equal number of controls having genotype HbAA and HbAS respectively.Clinical, laboratory and ECG parameters were obtained.?Results:?A total of 90 participants?are?with mean age 24.2?±?5.6. The study showed that sickle cell disease patient had significantly lower level of PCV and higher level of PAI, platelet and total white cell count (p value??0.05). C-reactive protein was also higher in them. 76.7% of HbSS patients had abnormal ECG. QTc and Tp-e were also prolonged in sickle cell disease patients compared with controls. An association was found between the level of PCV, PAI and prolonged Tp-e and QTc.?Conclusion:?Sickle cell disease patients have higher levels of inflammatory markers and abnormal ECG patterns are common in them. Moreover, the levels of these inflammatory markers correlate with Tp-e parameters.
文摘The mechanism of idiopathic ventricular tachycardia originating from the right ventricular outflow tract （RVOT） is not clear. Many clinical reports have suggested a mechanism of triggered activity. However, there are few studies investigating this be- cause of the technical difficulties associated with examining this theory. The L-type calcium current （/Ca-L）, an important in- ward current of the action potential （AP）, plays an important role in arrhythmogenesis. The aim of this study was to explore differences in the APs of right ventricular （RV） and RVOT cardiomyocytes, and differences in electrophysiological character- istics of the ICa-L in these myocytes. Rabbit RVOT and RV myocytes were isolated and their AP and Ic,-L were investigated us- ing the patch-clamp technique. RVOT cardiomyocytes had a wider range of AP duration （APD） than RV cardiomyocytes, with some markedly prolonged APDs and markedly shortened APDs. The markedly shortened APDs in RVOT myocytes were abolished by treatment with 4-AP, an inhibitor of the transient outward potassium current, but the markedly prolonged APDs remained, with some myocytes with a long AP plateau not repolarizing to resting potential. In addition, early afterdepolariza- tion （EAD） and second plateau responses were seen in RVOT myocytes but not in RV myocytes. RVOT myocytes had a high- er current density for/Ca-L than RV myocytes （RVOT （13.16±0.87） pA pF-1, RV （8.59±1.97） pA pF-1; P〈0.05）. The ICa-L and the prolonged APD were reduced, and the EAD and second plateau response disappeared, after treatment with nifedipine （10 μmol L^-1）, which blocks the Ica-L. In conclusion, there was a wider range of APDs in RVOT myocytes than in RV myocytes, which is one of the basic factors involved in arrhythmogenesis. The higher current density for ICa-L is one of the factors causing prolongation of the APD in RVOT myocytes. The combination of EAD with prolonged APD may be one of the mechanisms of RVOT-VT generation.
