question: A week ago i had acl replacement surgery. I had been exhausted since which is to be expected from recovering, however, when i am lying down and doing nothing like icing my knee, i notice that my heart rate is around 75-95bpm and my heart is beating hard. like i can feel it beating without trying. Its more annoying than anything but sometimes it can keep me up at night thus making me more exhausted. Im not sure if its the exhaustion, the hydrocodone im taking (because it still beats hard after the medicine has worn off), the body working to heal the knee, or even maybe some anxiety i am having about it. Im not really looking for a definite fix I just want to know whats going on just to give me some assurance. I am a 16 year old male, 6'2 and about 180 lbs im in great shape and exercise all the time ans have low blood pressure so i dont think its anything serious. I just hate not knowing whats going on with me. Thanks