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

摘要: Abstract Previous studies have provided evidence for an important contribution of the transient outward current to electrical activity canine ventricular epicardium, but not endocardium. The present study examines characteristics action potential duration and refractoriness in these two tissue types. time rate dependence changes observed epicardium were significantly more accentuated than restitution paralleled phase 1 amplitude this tissue. correlation between I recorded from a large number epicardial endocardial preparations was significant under both steady state conditions. 4-Aminopyridine, blocker, decreased concomitantly epicardium. 4-Aminopyridine abbreviated at slow stimulation rates had little effect or prolonged it fast after premature stimulation. (The availability is relatively small stimulation.) data support hypothesis that prominent presence endocardium, contributes differences results also demonstrate prolongthe blocker abbreviatethe potential. These observations may aid our understanding basis rate-dependent T wave electrocardiogram, cardiac arrhythmias, greater sensitivity ischemia differential effects drugs on muscle tissues spanning wall.