Hello, 
Thanks for the query to H.C.M. Forum. 
Normal    E F ( 
ejection fraction ) 55- 78 %. 
As bypass is there. 
They started 
Chemotherapy  for intestinal tumor.
You stated that ejection fraction was 50 % after 4th cycle of Chemotherapy. 
Now after 5th chemotherapy  E F is 29 %. 
As there are medicines for Congestive 
heart failure and they stopped 
cardivas, but continued dytor ( 
diuretic) apart lanoxin,aspirin and cardace. 
Before any conclusion , we would like to know the heart condition as in March 2012 you operated for bypass. 
Still you are on Congestive Heart Failure treatment ,so even after bypass assessment of heart condition is very important. 
After tumor chemotherapy  reduction in Ejection Fraction is natural. 
It will reach up to normal level if condition of heart muscles are otherwise normal. 
Hope I have answered your query. 
If further any question I will gladly reply. 
Good wishes for recovery. 
Dr. HET