Biomedical subjects

S F Schaal

Publications and source records attributed to S F Schaal.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Effects of tricyclic antidepressant drugs on the electrophysiological properties of drug Purkinje fibers.

Microelectrode techniques were used to study the electrophysiologic effects of the tricyclic antidepressant (TCA) drugs imipramine , amitriptyline, doxepin, desipramine, protriptyline, and nortriptyline on isolated Tyrode's ([K +]o= 4.0 mM) superfused dog Purkinje fibers. Drug concentrations ranged from 10(-7) to 10(-5) M. TCA drug concentrations greater than 10(-6) M resulted in decreases in action potential amplitude, duration, and maximum slope of phase O (Vmax). Simultaneously with decreases in action potential duration, the effective refractory period decreased. In addition, the voltage time course of repolarization between proximally and distally recorded action potentials became less obvious. Imipramine, doxepin, protriptyline, and nortriptyline (10(-6), 10(-5) M) depressed membrane responsiveness. Superfusion of dog Purkinje fibers with 10(-5) M concentrations of TCA drugs resulted in conduction delay, postrepolarization refractoriness and, occasionally, total inexcitability. TCA drugs caused an increase in escape time and a decrease in spontaneous rate of spontaneously automatic Purkinje fibers equilibrated with epinephrine (10(-7) M) in 5 X 10(-5) M EDTA. Imipramine, doxepin, protriptyline, and nortriptyline abolished extra nondriven action potentials, and diminished oscillatory afterpotentials in dog Purkinje fibers exposed to toxic concentrations of ouabain (2 X 10(-7) M).

Action Potentials↗

PubMedDate not supplied

Antiarrhythmic effects of flecainide against canine ventricular arrhythmias induced by two-stage coronary ligation and halothane-epinephrine.

We studied the electrophysiologic effects of flecainide on noninfarcted and infarcted dog hearts and in dogs anesthetized with halothane and administered intravenous epinephrine. Flecainide demonstrated no effect on atrial conduction times, but significantly (p less than 0.05) increased ventricular conduction times in noninfarcted, infarcted, and halothane-epinephrine-exposed dog hearts. Atrial and ventricular effective refractory periods (ERPs) were significantly (p less than 0.05) increased by flecainide. The increase in ERP was more pronounced in infarcted than in noninfarcted dog hearts. Flecainide significantly (p less than 0.05) decreased the echo zone for two or more repetitive ventricular responses in infarcted dog hearts and eliminated all ventricular arrhythmias observed at 48 h after coronary artery ligation. The dose of epinephrine required to induce ventricular arrhythmias in dogs anesthetized with halothane was significantly increased (p less than 0.05) by flecainide. Acute intravenous administration of flecainide to dogs with infarcted hearts produced sinus arrest, transient third-degree heart block, inability to pace, right bundle branch block, and torsade des pointes. Our results provide evidence that flecainide produces its antiarrhythmic effects by increased ventricular ERP and ventricular conduction time. Caution is advised when administering flecainide to patients with previous history of myocardial infarction.

Animals↗

PubMedDate not supplied

Evaluation of an open-loop, computer-based infusion system designed to achieve a series of constant, targeted plasma procainamide concentrations in patients undergoing electrophysiologic testing.

STUDY OBJECTIVE: To evaluate the performance of a computer-based procainamide infusion system in patients undergoing electrophysiologic testing. DESIGN: Prospective case series. SETTING: Electrophysiology laboratory in a university hospital. PATIENTS: Thirty-four patients with inducible sustained ventricular tachycardia. INTERVENTIONS: Intravenous infusion of procainamide to achieve and maintain targeted plasma concentrations. MEASUREMENTS AND MAIN RESULTS: System performance was assessed by comparing targeted and observed plasma concentrations. The population median absolute performance error (size of typical miss) was 12.6% (95% CI 11.2-14.1%). The population median performance error (system bias) was not significantly different from zero. A small but statistically significant improvement in performance over time was observed (population absolute performance error divergence -0.125%/min). Population wobble (overall system stability) was 7.6% (95% CI 6.8-8.3%). Population-based estimates of central compartment volume and volume of distribution at steady state were significantly higher and lower, respectively, than estimates used by the infusion system. CONCLUSION: The computer-based infusion system is capable of achieving and maintaining a series of targeted procainamide concentrations in patients undergoing electrophysiologic testing.

Adult↗