Hello.Your diagnose,very probably,is congestive
heart failure.You have
symptoms(
fatigue)signs(swollen feet and lower legs)and additional
test(
enlarged heart in ecg,increased levels bnp)all the usual diagnose.Cardiologist,surely,will request too thorax
radiography and heart ultrasound( is a very important test because you know the pathology that causes your heart failure and measure the capacity of your left ventricle pumping blood)to confirme the diagnose.After test,Cardiologyst,surely,will prescribe other additional drugs to improve your heart function and prevent fluid retention.
Lower bnp level indicates that these best,result of treatment with diuretics
but you must know that congestive heart failure is a cronic pathology
and you will need treatment and periodic medical reviews forever.
I wish you good health
(In case the answer would have been useful please indicate this)