What Causes Decrease In Heart Function?

I am 49 overweight female High BP under control mild mitral valve prolapse My heart function was 70% 18 months ago Now it has decreased to 40% with no known Reason. Heart Cath revealed no blockages Doc put me on carvedilol 3.125mg 2 times a day Will check heart function in 3 months Does this sound like a good treatment plan Or should I go to a heart speciality hospital in a large city