Hello and Welcome to Justanswer
Thank you very much for your question
My sincere apologies for delay in reply as no Cardiology expert was on line in the meantime
Crestor has been reported to cause palpitation but only rarely it causes any clinically significant problem and not heard of when coming off it
With the background of leaky valve (which I suspect would be mitral valve)what seems more likely that you are having arrythmia episode most likely atrial fibrillation/flutter
Leaky valve has a natural course of progression with time which can cause heart chamber dilatation and predisposes to atrial fibrillation
You are so far on right track
Holter monitor is the next best logical step as it will clearly show the nature of rythm problem and also its frequency
I would also suggest an Echocardiogram (heart ultrasound scan) to re-assess leaky valve (how far it has progressed)
If there are any symptoms of chest pain/heaviness, dizziness or shortness of breath associated with these fluttering then these are alarming symptoms warranting an urgent evaluation and likely a stress test to check for any blockage in heart vessels
Palpitations are quite common with such fluttering sensations
You need to be watchful for any of above mentioned symptoms and if they occur do not hesitate to seek medical help without delay
Once again I am sorry for any delay
You are welcome for any further queries/clarifications
Best Regards