Estrogens and the heart

Cardiac Pharmacology

“…It has also been observed in the Purkinje cells of dogs (13) and in other cells of dogs' atria and ventricles. The coincidence of these results is in sharp contrast with the differences in their interpretation (13,(21)(22)(23). The action of quinidine on arrhythmias resulting from an ectopic focus may be attrib uted to a depression of excitability (13,24) or to a decrease of the rate of diastolic depolarization (10,21), or both, which are probably conditioned by changes in ionic permeability (decrease of permeability to sodium) (25).…”

Antiarrhythmic Drugs: Electrophysiological Actions

“…The decrease in membrane responsiveness induced by these drugs explains why the increase in the effective refractory period that they cause is greater than one would expect to result from the drug-induced lengthening-of action potential (20). Weidmann's observations were confirmed by other investigators who found that quinidine and procaine amide reduced V MAX and increased effective refractoriness in several isolated preparations of cardiac tissue (62)(63)(64)(65) and in one study on in situ dog heart (66).…”

Estrogen and Progestin Use and the QT Interval in Postmenopausal Women

“…The gender difference appears at puberty and decreases but does not disappear later in life 4 . In vitro studies have reached discrepant conclusions, but the weight of evidence does not support an acute electrophysiologic effect of estrogen, or androgens, on action potential duration 8,9 . Studies also suggest that corrected QT interval (QT C ) in the absence of antiarrhythmic drugs does not vary significantly throughout the menstrual cycle.…”