Atrial flutter (AFL) and atrial fibrillation (AF) are quite different tachycardias. I've been advised that flutter ablation is generally the easier procedure but, especially if you began with fibrillation, and perhaps if you've had both flutter and fibrillation at the same time, then the destruction of the flutter circuit may be succeeded at some point by the appearance of AF. Hopefully your cardiologist has explained to you carefully that a further procedure may be necessary in the future, either because the ablation itself is unsuccessful or because, while successful, it is nevertheless followed by the emergence of AF. I've appreciated being well informed in advance.