Please Suggest A Remedy For Elevated Heart Rate

Hello. I am 32 years old healthy body type and active. I have been having a fast heart rate mostly when I stand up or go from sitting to standing. Sometimes nothing will bring it on just sitting reading a book. Walking up stairs puts rate up to 160bpm. Seen doctors and had tests. Found MVP and tricuspid regurgitation. Extensive family cardiac history heart attacks to afib and svt. I am currently on cardizem 120 twice a day, (was on betablockers dropped my blood pressure too low and did not control rate enough) controls rate better but still have average walking heart rate of 120. My cardiologist says it is sinus tachycardia and will not kill me but it is exhausting and makes me dizzy with horrible headaches. I did not know if there is anything else I can do. I am not an anxtious person but very active and would like my energy level back as has gone on well over a year now and cardiologist seems to write it off.