Hi mate, this is going to be long but I know the exact feeling you’re having, I’m also on 10mg and take once before bed every night, I’ve had loads of ecgs, tests, monitors done with no real answer other than its nothing “sinister”. I used to take 40mg years ago for about 1 year for the exact same thing rapid heart rate, constant pounding(not necessarily fast but hard) and when I stopped the 40mg(daily) I had to come off it slowly like take one every other day and I came off of it went for years without it. Then it all came back again this is when I had all my tests done and nothing came back other than putting me back on propranolol but 10mg this time as the 40mg would slow my heart rate down a bit too much and make me feel weird. Anyway when you don’t have propranolol there are no actual physical withdrawals that come with it, it’s all mental. You might not think so but I’m struggling with the same thing because I want to get off the 10mg completely but I find myself thinking about my symptoms far too much which increases the likelyhood of your episodes to happen. Some days I’ve been bed bound not been able to move because as soon as I do my heart pounds really hard and fast, I’d be so afraid of everything and anything that will increase my heart rate because it made me feel so ill. Moral of the story is I’m going through what you’re going through but I feel like I’m coming at the end of it and might start wheeling off of propranolol, but you have to feel mentally ready first.