atrial fibrillation progression and ectopy origin

[bill00]

I've read atrial fibrillation is progressive.
1) Can paritally controlled afib (average less than 1 episode per year) get worse or does the partial control hold off the progression of the disease ?

I've read that 95% of afib causing ectopy is from the pulmonary vein region. Another source say about 65% of such ectopy comes from there, that the 95% estimate came from a study involving too few patients.
2) Which of these numbers is more accurate ?

[is_something_wrong]

Sorry, forgot the conclusion on Q2. I would think if the atrias are healthy, A-fib is almost only caused by pulmonary vein PACs (which is why this is ablated in healthy hearts by isolating the pulmonary veins). In people with enlarged atrias or other heart disease I would think it could occur from the left atrium itself.

[is_something_wrong]

1) It may, or may not. I would say it depends on if the cause for A-fib continues to develop (like hypertension, dilated left atrium, etc). The A-fib itself, if it stands for long, may remodel the atrias in an undesirable way, mainly enlarging the left atrium).

2) The problem with pulmonary vein atrial tissue, is that it's partly electrically independent. Which means, PACs may fire off from there that disrupts the normal electrical conduction system, causing A-fib. As you maybe know, an electrical impulse that fires when other parts of the heart is in the relative refractory phase, may in some cases cause fibrillation. In the ventricles, this is known as the "R on T phenomenon" (I don't think there is a name for it when it occurs as an atrial phenomenon). Luckily, the ventricles in a healthy heart are usually stable enough to prevent V-fib due to R on T. Atrial tissue is much more irritable (which is the reason adrenaline and coffeine mainly causes PACs instad of PVCs) so unfortunately if this happens in the atria, it may cause A-fib.

Hope this somewhat clumsy explaination from a layman helped some.