I went to ER about 36 hrs after pellet inserted because my heart was racing and beating irratically. I had been using vivelle dot patch for last 6 months and most of the last 16 years but was not my first time using the pellet. The heart racing lasted full 12 weeks and has just started to get back to normal. My hormone levels measured three times what they did the last time I had the insertion 1 yr ago and over the target ranges But my dr said the were good. My GYN dr does not know why nor does she think that hormones are the issue. I went to two cardiologists, wore a halter monitor and the cardiologist said it could be the issue but no confirmation. I have no history of heart problems. I have normal cholesterol, normal BMI and am normally healthy. I am wondering if the compounding pharmacy could have made a mistake as to what they put in the pellet. Needless to say I will not use the pellet again because of the issues but for controlling headaches and hot flashes the pellet was more effective than the patch.