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FAQs Understanding A-Fib: Pulmonary Veins
“Why does so much Atrial Fibrillation come from the Pulmonary Veins (PVs)?”
Revised January 14, 2020
In A-Fib, PVs Can Beat Out of Sync with the Sinus and AV Node
Perhaps A-Fib signals come from the PV openings (Ostia) because the embryonic origin of the Pulmonary Veins is the same as that of the Sinus and AV Nodes. They are similar in structure and have similar smooth muscle tissue. Any of the heart’s muscular cells (cardiomyocytes) can initiate and transmit electrical impulses.
The Pulmonary Veins are electrically active in the heart like the Sinus and AV Nodes but usually beat in sync with them. Disease, viral infections, stretching, fibrosis, aging or other factors may cause the Pulmonary Veins to start beating out of sync with the Sinus and AV Nodes thereby producing A-Fib signals.
Ion Channel Receptors
Electrical signals in the heart are caused by the movement of positively and negatively charged ions through proteins called ion channel receptors. When there is a relative difference in concentration inside and outside the cells of these different ions, this produces an electrical gradient/stimulus. For example, when an individual heartbeat starts, the sodium channel ion receptor opens because there is more sodium outside the cell than inside. This floods the cell. When the number of ions hits a certain threshold, the ion receptor closes and another receptor opens like a domino effect which produces an electrical impulse. (For an excellent explanation of this, see Dr. Aseem Desai’s soon to be published book “Restart Your Heart”.)
But in some cases of A-Fib, heart cells build up with calcium ions which can generate or trigger an abnormal heartbeat. These cells start beating on their own (automaticity) and are no longer in sync with the Sinus and AV Node. The antiarrhythmic drugs used to treat A-Fib often work by attempting to selectively modify or block these ion channels.
Please be advised that the above statement is an observation, an attempt to explain, rather than a medical fact. Further research is necessary to confirm this observation.
Go back to FAQ Understanding A-Fib
Last updated: January 13, 2020
