Bedside to Bench
Arrhythmia Grand Rounds, June 2015, Volume 1, Issue 2: 79-86
Basic Foundations of Clinical Electrophysiology. Electrophysiological Mechanism of Phase 4 Conduction Block in The His Purkinje System: A Comparison With Phase 3 Block
1 Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York, USA
2 Harvard-Thorndike Electrophysiology Institute, Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA
We describe the mechanism underlying paroxysmal AV block that follows a sudden long cycle length. The phases and characteristics of the Purkinje fiber action potential are reviewed. Phase 4 block occurs when an impulse conducts into regions of Purkinje cells that have undergone spontaneous (phase 4) depolarization causing a reduction in the level of the membrane potential during diastole. This results in a decrease in inward sodium current during the depolarization phase (0) of the action potential, slow conduction and conduction block. The mechanisms involved are discussed in detail and compared to phase 3 block.
You must be registered and logged in to leave comments.
There have been no comments posted yet
- Start a new comment or
Ask a question (publicly)
- Send a Question to the Author (privately)
- Query the Editorial Board
All comments will be screened and reviewed before posting. Statements, opinions, and results of studies published in AGR are those of the authors and do not reflect the policy or position of The Journal and Science International and the Editorial Board and provides no warranty as to their accuracy or reliability. Material is copyrighted and owned by Science International and cannot be used without expressed permission.