Flutter usually takes place in the right atrium, but it can also happen in the left where the atrial fibrillation problems lie. If AF is the culprit, and if an ablation is undertaken, in something like 30% of all 'successful' ablations flutter will crop up in short order, often inside of days. The EPs know this, and they'll usually let their patients know ahead of time if they suspect this particular person might need a touchup or might still get PACs (premature atrial contractions), or might develop flutter. Remember, only about 65% of all index (first) ablations are still holding after one full year. So, the honest EP knows that he/she will see about 35% of their patients at least a second time.

Flutter is simply the musculature of whichever atrium has it contracting dutifully, as it is designed to do, to signals that come one after the other with no pausing interval. If you look at an EKG, and I strongly encourage every heart patient to learn how to read one (it takes some doing, but if doctors can do it, how hard can it be?!), there is a timing and a sequence to a normal heartbeat. There are pauses to let the various chamber fill so that their contents of blood can be propelled, or expelled, on the next contractions. It's a pump after all. With flutter, the affected atrium pretty much quivers...constantly. It never has a chance to fill with blood properly and then to expel a full volume into the receiving ventricle, which are the big pump parts of the heart. In AF, the atrium doesn't quiver...it beats. But, it's chaotic in its timing, meaning it, too, doesn't fully engorge itself with blood as it is supposed to do before it contracts and forces its contents past the mitral valve between it and the left ventricle to fill that vessel. Worse, maybe the atrium contracts at the same time as the ventricle below it, meaning it can't expel ANY of its contents, and that ventricular contraction was completely wasted energy because it sent next to no blood out through the aorta. Flutter is just a rapid 1, 2, 3, 4,,1200 half-beats that are ineffective. This leaves, just as it does with fibrillation, the other three vessels to do all the pumping...except they're not doing a good job because the one atrium is not doing its part to move a full volume of blood along.
Do you still have to take medications, maybe for life, even if an ablation is successful or if I don't seem to get any more AF or flutter? Generally...yes. Sometimes....no. The person to help you to decide is the person who has your care in her hands and who understands what your RISKS are for stroke. Generally, to help to situate you, as you get older, more goes wrong and the risk for calamity, which a stroke almost always is, is higher. If you have fibrosis inside of your heart due to an arrhythmia, or due to the scarring that ablation produces as a necessity for the signals to be blocked, or if you have some lingering arrhythmia that might let blood congeal inside your left atrial appendage (LAA), your risk for stroke is higher. This is just not-so-cheap and not-so-unintrusive insurance against a severe calamity...IF..it should happen.
I urge you to google 'CHAD2s-Vasc or use this link to calculate your risk:

My posts tend to be wordy and lengthy, big blocks of text....sorry. I hope this has been of some use to you and that you have persisted in reading it.