Biomaterial Database

Rate dependence of action potential duration and refractoriness in canine ventricular endocardium differs from that of epicardium: role of the transient outward current. 1989

S H Litovsky, and C Antzelevitch

Masonic Medical Research Laboratory, Utica, New York.

Previous studies have provided evidence for an important contribution of the transient outward current to the electrical activity of canine ventricular epicardium, but not endocardium. The present study examines the characteristics of action potential duration and refractoriness in these two tissue types. The time and rate dependence of changes in action potential duration and refractoriness observed in epicardium were significantly more accentuated than in endocardium. The restitution of action potential duration in epicardium paralleled the restitution of phase 1 amplitude of the action potential in this tissue. The correlation between phase 1 amplitude and action potential duration recorded from a large number of epicardial and endocardial preparations was significant under both steady state and restitution conditions. 4-Aminopyridine, a transient outward current blocker, decreased the time dependence of phase 1 amplitude and concomitantly decreased the time dependence of action potential duration in epicardium. 4-Aminopyridine abbreviated the action potential duration of epicardium at slow stimulation rates but had little effect or prolonged it at fast rates or after premature stimulation. (The availability of a transient outward current is relatively small after premature stimulation.) The data support the hypothesis that the prominent presence of a transient outward current in epicardium, but not endocardium, contributes to the differences in the time and rate dependence of action potential duration and refractoriness in the two tissue types. The results also demonstrate the effect of an outward current to prolong the action potential and the effect of an outward current blocker to abbreviate the action potential.(ABSTRACT TRUNCATED AT 250 WORDS)

UI	MeSH Term	Description	Entries
D008297	Male		Males
D010210	Papillary Muscles	Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.	Muscle, Papillary,Muscles, Papillary,Papillary Muscle
D010496	Pericardium	A conical fibro-serous sac surrounding the HEART and the roots of the great vessels (AORTA; VENAE CAVAE; PULMONARY ARTERY). Pericardium consists of two sacs: the outer fibrous pericardium and the inner serous pericardium. The latter consists of an outer parietal layer facing the fibrous pericardium, and an inner visceral layer (epicardium) resting next to the heart, and a pericardial cavity between these two layers.	Epicardium,Fibrous Pericardium,Parietal Pericardium,Pericardial Cavity,Pericardial Space,Serous Pericardium,Visceral Pericardium,Cavities, Pericardial,Cavity, Pericardial,Pericardial Cavities,Pericardial Spaces,Pericardium, Fibrous,Pericardium, Parietal,Pericardium, Serous,Pericardium, Visceral,Pericardiums, Fibrous,Pericardiums, Serous,Serous Pericardiums,Space, Pericardial,Spaces, Pericardial
D004285	Dogs	The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)	Canis familiaris,Dog
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004562	Electrocardiography	Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY.	12-Lead ECG,12-Lead EKG,12-Lead Electrocardiography,Cardiography,ECG,EKG,Electrocardiogram,Electrocardiograph,12 Lead ECG,12 Lead EKG,12 Lead Electrocardiography,12-Lead ECGs,12-Lead EKGs,12-Lead Electrocardiographies,Cardiographies,ECG, 12-Lead,EKG, 12-Lead,Electrocardiograms,Electrocardiographies, 12-Lead,Electrocardiographs,Electrocardiography, 12-Lead
D004699	Endocardium	The innermost layer of the heart, comprised of endothelial cells.	Endocardiums
D006329	Heart Conduction System	An impulse-conducting system composed of modified cardiac muscle, having the power of spontaneous rhythmicity and conduction more highly developed than the rest of the heart.	Conduction System, Heart,Conduction Systems, Heart,Heart Conduction Systems,System, Heart Conduction,Systems, Heart Conduction
D006339	Heart Rate	The number of times the HEART VENTRICLES contract per unit of time, usually per minute.	Cardiac Rate,Chronotropism, Cardiac,Heart Rate Control,Heartbeat,Pulse Rate,Cardiac Chronotropy,Cardiac Chronotropism,Cardiac Rates,Chronotropy, Cardiac,Control, Heart Rate,Heart Rates,Heartbeats,Pulse Rates,Rate Control, Heart,Rate, Cardiac,Rate, Heart,Rate, Pulse
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential