Hello, This Last Sunday I Woke Up Feeling As I

Hello,
This last Sunday I woke up feeling as I normally do. I got a cup of coffee, took one sip and my heart started to beat iradically. I have had palpitations before and did the deep cough a few times hoping that would bring it back to normal. Nothing worked so off to the ER. They were really good, told me my options, medication or paddles. we tried the medication and were happy that it worked. They talked to a cardiologist that was on call. I am to see him soon, no appointment made yet. He prescribed Metoprolol 25mg for me to take. My question is how low is too low for heart rate? I've been really good at keeping my blood pressure at 127/80 heartrate 65. Now my BP is 119/73 heartrate 56. Is that still acceptable?
Thanks Ann McKague