I am a heavy Mephedrone user at times. Recently I have been having a heavy streak (500mgs Wednesday, 2g Thursday, 300 mgs today). I was feeling pretty good today so I decided to take a few doses to kill time. I'm a nursing student so I have a stethoscope and blood pressure cuff I use for classes. I was listening to my Apical pulse (the pulse taken on the chest over the heart and listened to with a stethescope. With this one you can hear irregularities). I lied flat on my bed and listened for a full minute. I noted a few times that my heart would speed up and slow down, and also double beat or skip a beat (I did the Apical a few times to double check). I did however retake it an hour later and the rhythm was back to normal with no abnormalities.