No abstract available.
Doxorubicin* ; Membrane Potentials* ; Membranes* ; Purkinje Fibers* ; Sodium*

Arrhythmias, Cardiac ; pathology ; physiopathology ; Humans ; Purkinje Fibers

BACKGROUND: Bupivacaine is a potent, and commonly used, long acting local anesthetic. If accidentally injected into the systemic circulation, bupivacaine can cause lethal dysrhythmias and circulatory collapse. Attempts to treat bupivacaine induced cardiac toxicity have been varied and controversial, and they have not been very successful. The aim of this study was to investigate the electrophysiologic effects of bupivacaine in Purkinje fibers. METHODS: Effects of bupivacaine on the membrane potential were studied in 12 isolated canine Purkinje fibers. Purkinje fibers from ventricle were dissected and mounted in a tissue chamber perfused with Tyrode's solution. Transmembrane potentials recorded through glass microelectrodes filled with 3M KCI in the beating or quiescent Purkinje fibers during infusions of bupivacaine at concentratons of 3*10/-7M,10/-6M, 3*10/-6M,10/-5M, and 3*10/-5M. RESULTS: Bupivacaine reduced action potential druation in a dose-dependent manner. Bupivacaine produced a decrease in intracelullar sodium ion activity in driven(1Hz) and quiescent canine Purkinje fibers. Bupivacaine-induced hyperpolarizaton of diastolic membrane potential in quiescent Purkinje fibers was dose dependent, and the hyperpolarization by bupivacaine was attenuated by depolarization induced by high potassium extracellular concentration in part. CONCLUSIONS: These results suggest that bupivacaine decreases the fast inward sodium current, and inhibits pacemaker current in canine Purkinje fibers.
Action Potentials ; Bupivacaine* ; Glass ; Membrane Potentials* ; Membranes* ; Microelectrodes ; Potassium ; Purkinje Fibers ; Shock ; Sodium ; Sodium Channels

Hyperkalemia induces wide spectrum of electrocardiographic abnormalities on its severity. In general, hyperkalemia produces a gradual depression of the excitability, conduction velocity of the specialized pacemaker cells and conducting tissues throughout the heart. High serum potassium levels are thought to impair the conduction in the Purkinje fibers and ventricles more than in the AV node, although complete AV block can occur. So, hyperkalemia-induced complete AV block without prolongation of the QRS complex is a rare condition. We report a case of complete AV block without QRS complex widening in patient with hyperkalemia. To our knowledge, this is the first reported case in Korea.
Atrioventricular Block* ; Atrioventricular Node ; Depression ; Electrocardiography ; Heart ; Humans ; Hyperkalemia ; Korea ; Potassium ; Purkinje Fibers

A contralateral bundle branch block (BBB) aberration during tachycardia with a preexisting BBB strongly suggests the presence of ventricular tachycardia. We report on a middle-aged, female patient presented with wide QRS tachycardia. The patient had orthodromic atrioventricular tachycardia with a left BBB aberration in the presence of a preexisting right BBB due to an abnormal His-Purkinje system. We learned that the contralateral BBB aberration with supraventricular tachycardia could be seen when the His-Purkinje system was abnormal.
Bundle of His ; Bundle-Branch Block* ; Female ; Humans ; Purkinje Fibers ; Tachycardia ; Tachycardia, Supraventricular* ; Tachycardia, Ventricular

Bundle of His ; Bundle-Branch Block ; Cardiac Pacing, Artificial ; Electrocardiography ; Humans ; Purkinje Fibers

We reviewed the anatomical characteristics of the conduction system in the ventricles of human and ungulate hearts and then raised some questions to be answered by clinical and anatomical studies in the future. The ventricular conduction system is a 3-dimensional structure as compared to the 2-dimensional character of the atrial conduction system. The proximal part consisting of the atrioventricular node, the bundle of His and fascicles are groups of conducting cells surrounded by fibrous connective tissue so as to insulate from the underlying myocardium. Their location and morphological characters are well established. The bundle of His is a cord like structure but the left and right fascicles are broad at the proximal and branching at the distal part. The more distal part of fascicles and Purkinje system are linear networks of conducting cells at the immediate subendocardium but the intra-mural network is detected at the inner half of the ventricular wall. The papillary muscle also harbors Purkinje system not in the deeper part. It is hard to recognize histologically in human hearts but conducting cells as well as Purkinje cells are easily recognized in ungulate hearts. Further observation on human and ungulate hearts with myocardial infarct, we could find preserved Purkinje system at the subendocardium in contrast to the damaged system at the deeper myocardium. Further studies are necessary on the anatomical characteristics of this peripheral conduction system so as to correlate the clinical data on hearts with ventricular arrhythmias.
Arrhythmias, Cardiac ; Atrioventricular Node ; Bundle of His ; Connective Tissue ; Heart ; Heart Conduction System ; Humans ; Myocardial Infarction ; Myocardium ; Papillary Muscles ; Purkinje Cells ; Purkinje Fibers ; Tachycardia, Ventricular

The membrane permeability to potassium at a resting state is greater than to any other ions and the maintenance of resting membrane potential is largely dependent on K+ concentration of outside medium (Hodgkin and Horowicz 1959), i.e. an increase of K+ concentration of medium induces a depolarization, vice versa. However, on the contrary to this prediction, in some mammalian heart muscle a reduction of external K+ concentration induces a depolarization of membrane potential rather than a hyperpolarization (Vassalle 1965). In this study it was aimed to elucidate the possible mechanism of spontaneous depolarization induced by low external K+ in canine Purkinje fibers. The membrane potential was constantly recorded while components of cations in the bathing medium were replaced one by one by equimolar sucrose until the low K+ induced depolarization was blocked. The results are summarized as follows; The membrane potential of canine Purkinje fibers was spontaneously depolarized by low external K+, and the magnitude of depolarization was not affected by verapamil TEA, and a partial replacement of external Na+ and Ca2+ with choline chloride. But the membrane potential was hyperpolarized only when the all external cations were substitued with sucrose; and this hyperpolarization was disappeared again by substitution of sucrose with choline chloride. From these results, it may be concluded that the depolarization induced by low external K+ in canine Purkinje fibers is due to the nonspecific increase of membrane permeability to external cations and/or combinations with decreased K+ conductance.
Animal ; Dogs ; Guinea Pigs ; Heart/physiology* ; Membrane Potentials/drug effects* ; Papillary Muscles/physiology ; Potassium/pharmacology* ; Purkinje Fibers/physiology ; Rest

Adolescent ; Adult ; Bundle of His ; pathology ; physiopathology ; Child ; Female ; Humans ; Male ; Purkinje Fibers ; pathology ; physiopathology ; Tachycardia, Ventricular ; pathology ; physiopathology

Sibutramine is an anorectic that has been banned since 2010 due to cardiovascular safety issues. However, counterfeit drugs or slimming products that include sibutramine are still available in the market. It has been reported that illegal sibutramine-contained pharmaceutical products induce cardiovascular crisis. However, the mechanism underlying sibutramine-induced cardiovascular adverse effect has not been fully evaluated yet. In this study, we performed cardiovascular safety pharmacology studies of sibutramine systemically using by hERG channel inhibition, action potential duration, and telemetry assays. Sibutramine inhibited hERG channel current of HEK293 cells with an IC50 of 3.92 muM in patch clamp assay and increased the heart rate and blood pressure (76 Deltabpm in heart rate and 51 DeltammHg in blood pressure) in beagle dogs at a dose of 30 mg/kg (per oral), while it shortened action potential duration (at 10 muM and 30 muM, resulted in 15% and 29% decreases in APD50, and 9% and 17% decreases in APD90, respectively) in the Purkinje fibers of rabbits and had no effects on the QTc interval in beagle dogs. These results suggest that sibutramine has a considerable adverse effect on the cardiovascular system and may contribute to accurate drug safety regulation.
Action Potentials ; Animals ; Blood Pressure ; Cardiovascular System ; Counterfeit Drugs ; Dogs ; Heart Rate ; HEK293 Cells ; Inhibitory Concentration 50 ; Pharmaceutical Preparations ; Pharmacology* ; Purkinje Fibers ; Rabbits ; Telemetry