Anesthesia Pharmacology:   Antiarrhythmic Agents

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Cardiac Electrophysiology

Cardiac Cell Phase 0 and Sodium Current

  • Note the rapid "upstroke" characteristic of Phase 0 depolarization.

  • This abrupt change in membrane potential is caused by rapid, synchronous opening of Na+ channels.

  • Note the relationships between the the ECG tracing and phase 0

 

Ca2+:  Channel Activation Sequence similar to sodium; but occurring at more positive membrane potentials (phases 1 and 2)

  • Following intense inward Na+ current (phase 0), Ca2+currents:

  • Phases 1 & 2, are slowly inactivated.   (Ca2+channel activation occurred later than for Na+)

 

 

Channel Inactivation, Re-establishing the Resting Membrane Potential

  • Final repolarization (phase 3):

    • Complete Na+ and Ca2+ channel inactivation

  • Increased potassium permeability

  • Membrane potential approaches K+ equilibrium potential -- which approximates the normal resting membrane potential

Hondeghem, L.M. and Roden, D.M., "Agents Used in Cardiac Arrhythmias", in Basic and Clinical Pharmacology, Katzung, B.G., editor, Appleton & Lange, 1998, pp 216-241.

 

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