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

Arrhythmias, Cardiac ; pathology ; physiopathology ; Humans ; 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

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

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

BACKGROUND: To investigate the role of alpha-adrenergic receptors in the development of delayed afterdepolarization, the effect of alpha-adrenoceptor stimulation and blockade on ouabain induced delayed afterdepolarization(DDAD) was examined in rabbit heart Purkinje fibers. METHODS: Purkinje fibers, taken from adult rabbit(1.8 - 2.0kg) heart anesthetized with penobarbital, were mounted in a Luicite chamber and superfused with Tyrode's solution. The transmembrane potentials were measured by the conventional microelectrode technique while the fibers were being stimulated with rectangular pulses of 50% above threshold voltage. The delayed afterdepolarizations were induced by overdrive excitation in the presence of ouabain. RESULTS: Delayed afterdepolarizations were not observed during superfusion of the control Tyrode's solution containing propranolol(5x10(-7)M). However, the addition of ouabain in the presence of propranolol elicited DADs which were dose-, time- and drive cycle length- dependent. Phenylephrine(PE ; 10(-7)M), and alpha-adrenoceptor agonist, potentiated the ouabain-induced DAD during the initial superfusion(for 10 or 20 min) of the test Tyrode's solution. However, it was followed by attenuating-effects after a superfusion time of 50 to 60 min. Both effects showed ouabain dose-dependence. Ouabain(2x10(-7)M), in the presence of propranolol, depolarized the maximum diastolic potential and shortened the action potential duration, and the addition of PE(10(-7)M) did not affect the characteristics of action potential except a decrease in velocity of phase 0 depolarization. Prazosin, an alpha1-adrenoceptor antagonist, inhibited the PE's enhancing effects of ouabaininduced DDAD at 20 min superfusion, but did not affect the attenuating-effects of PE at 60 min superfusion. On the other hand, yohimbine, an alpha2-adrenoceptor antagonist, did not affect the PE's DAD potentiating-effects at 20 min superfusion, but inhibited the attenunating-effects of PE at 60 min superfusion. CONCLUSION: It is inferred that alpha-adrenergic stimulation induce delayed afterdepolarization and triggered activity in the rabbits, being responsible for the arrhythmia development, and the effects are mainly due to the action of alpha1-subtpe adrenoceptor stimulation.
Action Potentials ; Adult ; Arrhythmias, Cardiac ; Hand ; Heart ; Humans ; Membrane Potentials ; Microelectrodes ; Ouabain ; Prazosin ; Propranolol ; Purkinje Fibers ; Rabbits ; Receptors, Adrenergic, alpha* ; Yohimbine