What is the effect of low potassium blood levels on Atrial Fibrillation?
In response to your posting on the CCF website, I can provide you with some scientific information that is relevant to your question, but does not constitute medical advice. I am a basic scientist in the department of Cardiology here at CCF, and my work is focused on cellular studies of human atrial fibrillation, as well as in experimental models.
The excitability of cardiac cells is influenced by their resting electrical potential, and by the activity of specific protein molecules (ion channels) that are present in the surface membrane of the cardiac cells. There are ion channels with selectivity for different ions including potassium, sodium and calcium. Potassium channels are open at rest in cardiac myocytes, and control the electrical potential during periods of relaxation. During cardiac contraction (action potential), sodium and calcium channels both open and then close. A different set of potassium channel openings help to re-establish the quiet electrical period between heart beats.
At normal plasma (blood) potassium levels (4-5 mmol/liter), there is a healthy balance between potassium channels open at rest and channels that open to end a period of electrical activity (the action potential). When the potassium in the plasma is elevated (for example, 10 mmol/liter) the cardiac cell becomes depolarized and inexcitable. When the potassium concentration is low, the cells become unusually excitable, and the channels that normally open to terminate an action potential are less effective. The combined effect is that spontaneous activity tends to increase in areas of the heart that do not normally have spontaneous activity, and this can be noted as an increase in either premature atrial or ventricular contractions. These can potentially trigger more sustained arrhythmias, such as atrial fibrillation. Thus, it is very desirable to keep the blood potassium in the normal range.
Answer provided by: David R. Van Wagoner, Ph.D., Director, Basic Cardiac Electrophysiology Laboratories
For more information on atrial fibrillation and it's treatments, see the Center for Atrial Fibrillation website