ISSN:
1440-1681
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
1. The actions of lidocaine on cardiac pacemaker rhythms were studied in anaesthetized dogs and in Purkinje fibres from hearts of the same animals.2. In vivo, lidocaine (1 mg/ kg, intravenously) slowed the sino-atrial (SA) node rhythm (– 5.0%), and (during vagal stimulation) prolonged ventricular standstill by + 25.1% and slowed the idioventricular rhythm (– 16.7%). A higher dose (4 mg/kg) had more pronounced effects.3. Propranolol also slowed sinus (– 26.2%) and idioventricular (– 27.2%) rhythms, and prolonged ventricular standstill (+ 36.8%). In the presence of propranolol, the effects of lidocaine on idioventricular rhythm were exaggerated.4. In Purkinje fibres driven in vitro, lidocaine (10 μmol/L) decreased contractile force (– 47.9%) and (during the interruption of drive) prolonged the suppression of (+ 53.2%) and slowed the escape rhythm (– 67.0%).5. In the presence of lidocaine the threshold potential was shifted to less negative values and diastolic depolarization slope was decreased (– 23.6%).6. Lidocaine slowed spontaneously active Purkinje fibres, abolished early afterdepolarizations in low [K]0 and slow responses in high [K]0 (by shifting the threshold to less negative values), and antagonized strophanthidin arrhythmias.7. TTX reduced the hyperpolarization by lidocaine in low [K]0 and vice versa.8. We conclude that lidocaine enhances vagally-induced ventricular standstill by depressing the idioventricular rhythm far more than the sinus rhythm, an action enhanced by beta-blockade. Furthermore, lidocaine depresses normal and different types of abnormal automaticity through direct and indirect effects of the blockade of the fast sodium channel.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1440-1681.1991.tb01429.x
