ABSTRACT
Background and Objective Increased transmural dispersion of repolarization (TDR) has been shown to contribute toinitiation and maintenance of ventricular arrhythmia in long QT syndromes(LQTS).Intercellular uncoupling through gap junctions isan important mechanism for maintaining TDR in both intact and diseased heart.The present study was to test the hypothesis thatimproving gap junction communication reduces TDR and prevents ventricular arrhythmia in rabbit LQT2 model.Methods Anarterially perfused rabbit left ventricular preparation and E-403 (0.5μmol/L)were used to establish a model of LQT2.Preparationswere randomly assigned to control(n=10),AAP-100nmol/L(n=10),AAP-500nM(n=10)groups.Transmural ECG as well as actionpotentials from both endocardium and epieardium was simultaneously recorded. Resuits In LQT2 model.presence of 500nmol/LAAP10 reduced endocardial action potential and TDR and prevented ventricular arrhythmia comparing with the control and AAP 100nmol/Lgroups(P＜0.05).Conclusions The presence of 500 nmol/LAAP10 reduces TDR and prevents ventricular arrhythmia in rabbitventricular model of LOT2.This study suggests a possible role of GJs in TDR in rabbit LQT2 model and indicates a new clinicalapproach to the management of LQTS.
ABSTRACT
The imaging appearances of 99Tc(m)-HL91, a new hypoxic imaging agent, in ischemic myocardium were studied and the value of 99Tc(m)-HL91 in the evaluation of regional ischemic viable myocardium was explored. Acute myocardial ischemia models were made by coronary artery legations in 18 rats and randomly divided into 2 groups: 99Tc(m)-HL91 group and 99Tc(m)-MIBI group. Evan blue infusion during ischemia and TTC staining after operation were used to delineate the area of ischemic and viable myocardium. The isolated heart was sliced in the short axis and then autoradiography was performed. The electron microscopic examination was also done for the myocardial samples. 99Tc(m)-HL91 and 99Tc(m)-MIBI uptake activities (counts/g) were measured in the area of ischemic myocardium (T) and normal myocardium (NT) separately. The uptake ratios of 99Tc(m)-HL91 and that of 99Tc(m)-MIBI in ischemic myocardium were calculated as T/NT. It was found that the normal myocardium was blue and ischemic or infarct myocardium was negative with Evans blue in all experiment rats. Both the normal and ischemic myocardium was in red color with TTC staining. In the 99Tc(m)-HL91 group the ischemic myocardium showed much higher uptake over normal myocardium, that was demonstrated both in the autoradiography and quantitative analysis. The ischemic/normal activity ratios were 1.634 +/- 0.354. It was suggested that 99Tc(m)-HL91 might accumulate in ischemic and viable myocardium, which is helpful in the evaluation of hypoxic but viable myocardium and potentially used as a imaging agent to assess myocardial viability.
ABSTRACT
The effects of amiodarone on transmural dispersion of ventricular effective refractory periods (ERPs) in the normal and hypertrophic canine heart were investigated in vivo. By using the programmed stimulation protocol, the ERPs of epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were measured by inserting specially-designed electrodes into the three myocardial layers before and after mainlining of amiodarone. No significant ERPs-dispersion was observed in the three layers before and after mainlining of amiodarone in the normal group. In contrast, ERPs of all the three layers were prolonged in the hypertrophic heart, while the ERPs-dispersion was reduced significantly after mainlining of amiodarone. The ERPs-dispersion was significantly increased in the hypertrophic heart but not in the normal heart using "long-short" and "short-long" interval stimulation technique. It was concluded that (1) the differences in ERPs-dispersion among the three layers were significant in hypertrophic heart, and differences were not significant in normal canine heart;(2) ERPs of each three-myocardial layers were significantly prolonged after using amiodarone, but the ERPs-dispersion decreased in hypertrophic heart and (3) the programmed extrastimulus technique of "long-short" and "short-long" intervals increased the transmural ERPs-dispersion in the hypertrophic heart.
ABSTRACT
The imaging appearances of 99Tcm-HL91, a new hypoxic imaging agent, in ischemic myocardium were studied and the value of 99 Tcm-HL91 in the evaluation of regional ischemic viable myocardium was explored. Acute myocardial ischemia models were made by coronary artery legations in 18 rats and randomly divided into 2 groups: 99Tcm-HL91 group and 99Tcm-MIBI group. Evan blue infusion during ischemia and TTC staining after operation were used to delineate the area of ischemic and viable myocardium. The isolated heart was sliced in the short axis and then autoradiography was performed. The electron microscopic examination was also done for the myocardial samples. 99Tcm-HL91 and 99Tcm-MIBI uptake activities (counts/g) were measured in the area of ischemic myocardium (T) and normal myocardium (NT) separately. The uptake ratios of 99Tcm-HL91 and that of 99Tcm-MIBI in ischemic myocardium were calculated as T/NT. It was found that the normal myocardium was blue and ischemic or infarct myocardium was negative with Evans blue in all experiment rats. Both the normal and ischemic myocardium was in red color with TTC staining.In the 99Tcm-HL91 group the ischemic myocardium showed much higher uptake over normal myocardium, that was demonstrated both in the autoradiography and quantitative analysis. The ischemic/normal activity ratios were 1.634±0.354. It was suggested that 99Tcm-HL91 might accumulate in ischemic and viable myocardium, which is helpful in the evaluation of hypoxic but viable myocardium and potentially used as a imaging agent to assess myocardial viability.
ABSTRACT
In order to assess the diagnostic value of invasive electrophysiologic study (EPS) in the patients with unexplained syncope, the electrophysiologic findings of 268 patients with unexplained syncope despite a complete clinical evaluation were analyzed. Results showed positive EPS finding was 38% in total patients and 50% in the patients aged > 70 years. With increasing age, the diagnostic yield of EPS also increased. No significant differences of complication rate were found among the different age groups. It was concluded that EPS have high diagnostic value in the patients with unexplained syncope. Its complications are few and mild. EPS may be recommended in elderly patients with unexplained syncope.
Subject(s)
Age Factors , Arrhythmias, Cardiac/complications , Arrhythmias, Cardiac/diagnosis , Diagnosis, Differential , Electrocardiography , Electrophysiology , Follow-Up Studies , Monitoring, Physiologic , Retrospective Studies , Syncope/diagnosis , Syncope/etiology , Tachycardia/complications , Tachycardia/diagnosisABSTRACT
In order to assess the diagnostic value of invasive electrophysiologic study (EPS) in the patients with unexplained syncope, the electrophysiologic findings of 268 patients with unexplained syncope despite a complete clinical evaluation were analyzed. Results showed positive EPS finding was 38% in total patients and 50% in the patients aged > 70 years. With increasing age, the diagnostic yield of EPS also increased. No significant differences of complication rate were found among the different age groups. It was concluded that EPS have high diagnostic value in the patients with unexplained syncope. Its complications are few and mild. EPS may be recommended in elderly patients with unexplained syncope.
Subject(s)
Adult , Aged , Humans , Middle Aged , Age Factors , Arrhythmias, Cardiac , Diagnosis , Diagnosis, Differential , Electrocardiography , Electrophysiology , Follow-Up Studies , Monitoring, Physiologic , Retrospective Studies , Syncope , Diagnosis , Tachycardia , DiagnosisABSTRACT
Viele Studien haben das Vorliegen von M-Zellen im Midmyokard des Hundes in vitro beobachtet und weiterhin gefunden, da das Vorliegen von M-Zellen zur Differenz der Repolarisation und zur Dispersion der Refrakt?rzeit zwischen Midmyokard und Epi- und Endomyokard fuhren kann.Diese Dispersion hat enge Beziehungen mit der Entstehung der Arrhythmie. Aber die Beobachtungen in vitro waren nicht konkordant mit den Ergebnissen in vivo. Mittels direkten Messungen der ERP in drei Myokardschichten wurde erstmals im gesunden Hundemyokard und im hypertrophierten Hundemyokard in vivo untersucht. Die Untersuchung hat gezeigt, da die ERP von Endomyokard, Epimyokard und Midmyokard im gesunden Hundeherzen homogen sind. Die relevante transmurale Refrakt?rgradient, die die Induktion einer kreisenden Erregung begünstigt, besteht unter physiologischen Bedingungen nicht. Im Gegensatz dazu konnte eine deutliche Verl?ngerung der ERP in allen Myokardschichten von hypertrophierten Hundeherzen nachgewiesen werden. Weiterhin wurde gezeigt, d?eine transmurale ERP-Dispersion zwischen verschiedenen Myokardschichten im hypertrophierten Hundemyokard besteht. Es ist zu postulieren, d? diese transmurale ERP-Dispersion als Substrat für die Arrhythmie angesehen werden kann,weil diese Dispersion die lokalen kreisende Erregung zwischen Epikard und Midkard, oder zwischen Midkard und Endokard begünstigen kann. Nach den Ergebnissen l?t sich postulieren, d?eine transmurale ERP-Dispersion durch eine pl?tzliche Zyklusl?ngever?nderung, n?mlich durch eine Kurz-Lang- und eine Lang-Kurz-Sequenz verst?rkt werden kann.
ABSTRACT
Viele Studien haben das Vorliegen von M-Zellen im Midmyokard des Hundes in vitro beobachtet und weiterhin gefunden, da das Vorliegen von M-Zellen zur Differenz der Repolarisation und zur Dispersion der Refrakt?rzeit zwischen Midmyokard und Epi- und Endomyokard fuhren kann.Diese Dispersion hat enge Beziehungen mit der Entstehung der Arrhythmie. Aber die Beobachtungen in vitro waren nicht konkordant mit den Ergebnissen in vivo. Mittels direkten Messungen der ERP in drei Myokardschichten wurde erstmals im gesunden Hundemyokard und im hypertrophierten Hundemyokard in vivo untersucht. Die Untersuchung hat gezeigt, da die ERP von Endomyokard, Epimyokard und Midmyokard im gesunden Hundeherzen homogen sind. Die relevante transmurale Refrakt?rgradient, die die Induktion einer kreisenden Erregung begünstigt, besteht unter physiologischen Bedingungen nicht. Im Gegensatz dazu konnte eine deutliche Verl?ngerung der ERP in allen Myokardschichten von hypertrophierten Hundeherzen nachgewiesen werden. Weiterhin wurde gezeigt, d?eine transmurale ERP-Dispersion zwischen verschiedenen Myokardschichten im hypertrophierten Hundemyokard besteht. Es ist zu postulieren, d? diese transmurale ERP-Dispersion als Substrat für die Arrhythmie angesehen werden kann,weil diese Dispersion die lokalen kreisende Erregung zwischen Epikard und Midkard, oder zwischen Midkard und Endokard begünstigen kann. Nach den Ergebnissen l?t sich postulieren, d?eine transmurale ERP-Dispersion durch eine pl?tzliche Zyklusl?ngever?nderung, n?mlich durch eine Kurz-Lang- und eine Lang-Kurz-Sequenz verst?rkt werden kann.