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L Mary-Rabine

Publications and source records attributed to L Mary-Rabine.

27 records · Page 2Linked to original sources
PubMed1980

The efficacy of intravenous moxaprindine on ventricular ectopic activity.

Moxaprindine, a new derivative of aprindine, has been showed to possess strong antiarrhythmic properties in the dog. It is significantly less toxic than aprindine on hematopoietic cells in culture. This drug was given intravenously (2 mg/kg given over a 30 min period), to 10 patients with severe, refractory and symptomatic ventricular arrhythmias. In 8 of them, all ventricular ectopic activity was suppressed for at least 90 min following the end of perfusion. In 7, no ventricular ectopic beats recurred before the end of the experimentation (150 min). There were two non-responders: one of them developed a torsade de pointes phenomenon under the influence of the drug. The mean drug concentration which was reached at the end of perfusion was 4.83 +/- 2.46 gamma/ml. It progressively fell to a value of 1.11 +/- 0.35 gamma/ml, 150 min later. The drug prolongs the PR interval, QRS duration and QT interval. Moxaprindine is a powerful antiarrhythmic agent which deserves further assessment in long term studies.

Adult↗
PubMed1979

Participation of slow inward current in the Purkinje fiber action potential overshoot.

We used microelectrode techniques to study the relationship of canine Purkinje fiber membrane potential and the action potential (AP) overshoot. At the maximum diastolic potential, -93.0 +/- 0.5 (SE) mV, AP overshoot was +37.7 +/- 0.4 mV. There was a range of membrane potentials (MP) less negative than the maximum diastolic potential from which action potentials were elicited with an overshoot greater than the control. Starting at an MP of less than -78.7 +/- 0.4 mV, AP overshoot was less than control. A maximum overshoot of +40.2 +/- 0.4 mV occurred at an MP of -85.4 +/- 0.4 mV. The relationship of the maximum upstroke velocity (Vmax) of phase 0 depolarization to MP was sigmoidal. Peak Vmax, 497 +/- 13 V/s, occurred at MP greater than or equal to -89.3 +/- 0.5 mV. The increase in overshoot was enhanced as perfusate [Ca2+] increased and decreased as [Ca2+] decreased. Slow-channel blocking agents and tetrodotoxin (TTX) depressed the peak of the curve relating overshoot to MP. TTX also decreased Vmax. The effect of TTX on overshoot but not on Vmax was reversed with Ca2+, 8.1 mM. The increase in overshoot for action potentials initiated during the terminal part of phase 3 was due to a slow, delayed component of the upstroke and appears to result from the slow inward current.

Action Potentials↗
PubMed1978

Alpha and beta adrenergic effects on human atrial specialized conducting fibers.

We determined the effects of epinephrine on automaticity and action potential characteristics of right atrial specialized fibers (RAF) from human atria obtained during cardiac surgery. RAF were studied with standard microelectrode techniques during superfusion with Tyrode's solution at 37 degrees C. A biphasic response to epinephrine was seen, rate slowing at low agonist concentrations and increasing at high concentrations. The epinephrine-induced slowing of spontaneous rate was due to a decrease in the slope of phase 4 depolarization. At the high epinephrine concentrations RAF hyperpolarized. The alpha-adrenergic blocker, phentolamine, shifted the dose-response curve upward and to the left and enhanced the hyperpolarization of RAF. The beta blocker, propranolol, shifted the curve to the right and decreased the degree of hyperpolarization. Our study suggests the presence of alpha and beta receptors in RAF. The alpha response consists of a slowing of rate, the beta response of an acceleration of rate and hyperpolarization of RAF.

Action Potentials↗
PubMed1978

The cellular electrophysiologic effects of digitalis on human atrial fibers.

We used microelectrode techniques to study the indirect and direct actions of ouabain on human atrial fibers (HAF) obtained from patients with congenital heart disease undergoing open heart surgery. At 15 min of superfusion ouabain, 2 X 10(-7) M, induced an increase in maximum diastolic potential (MDP), action potential (AP) amplitude and upstroke velocity of phase 0 depolarization (Vmax) and a decrease in AP duration. Spontaneously beating HAF showed a decrease in automaticity. Acetylcholine (3 X 10(-6) M) induced identical effects on AP characteristics and automaticity. Prior treatment with atropine (1 X 10 (-6) M) blocked these effects of ouabain and acetylcholine. Superfusion with ouabain (2 X 10 (-7) M) for 30 to 90 min resulted in decreased MDP, AP amplitude and Vmax, and a further decrease in AP duration. Phase 4 depolarization and spontaneous rate increased and delayed afterdepolarization and tachyarrythmia occurred. The ACh-like effects of digitalis decrease automaticity and increase MDP of HAF; the direct effects decrease MDP, increase automaticity, and induce tachyarrythmias.

Acetylcholine↗
PubMed1978

Lidocaine effects on action potentials of Purkinje fibers from neonatal and adult dogs.

We studied the effects of lidocaine (L), 2 to 40 mg/l, on the cellular electrophysiologic properties of Purkinje fibers (PF) from neonatal (0-10 days) and adult dogs. Microelectrode impalements of neonatal and adult PF were selected so that there were no differences between the two groups in control maximum diastolic potential, action potential amplitude and maximum upstroke velocity of phase 0 depolarization (Vmax). However, control action potential duration was significantly shorter in neonates than in adults (P less than .05). At a superfusate [K+] = 4 mmol/1, the threshold concentration for L effects on action potential amplitude in neonates was 40 mg/1 and in adults, 20 mg/1; on Vmax in neonates threshold was 5 mg/1 and in adults was 2 mg/1; on action potential duration in neonates and adults threshold was 2 mg/1. For all variables studied the effect of L on adult PF action potentials was greater than on neonatal PF. The effects of L on action potential duration also suggest that potassium conductance may be greater in neonatal fibers. When superfusate [K+] was increased to 6 mM the effects of L on adult PF were potentiated more than on neonates. These results provide further experimental evidence of the age-related changes in sensitivity of the specialized conducting system to cardioactive drugs.

Action Potentials↗
PubMedDate not supplied

The treatment of amiodarone-induced hyperthyroidism. Is there a place for surgery?

In many instances amiodarone-induced hyperthyroidism has been reported as mild, thyroid functions returning to normal after discontinuation of the drug. Nevertheless, life-threatening amiodarone-induced thyrotoxicosis has also been described. Conventional treatments such as with antithyroid drugs (Thionamide) and corticosteroids are essentially ineffective or fail to stop the dramatic course of the thyroid crisis. This limited efficacy of medical therapy, particularly in patients with previously--neglected or unknown--thyroid disease, prompted us to intervene surgically. We report a series of six patients who underwent total or nearly total thyroidectomy as first line therapy for four of them. Surgery resulted in rapid resolution of thyrotoxicosis with an uneventful postoperative course. This approach has the advantage of immediate and safe efficacy, low risk of relapse and finally, appears to be the only antithyroid treatment that permits continued therapy with amiodarone.

Amiodarone↗