thanks for writing in hcm
in your case , heart palpitations does not seem related to problem in mouth.
bad smell and rotten taste can be due to infection in gums , calculus , plaque
, any decayed tooth or teeth
do revisit your dentist
for the same.
for heart palpitations i advised you to consult a physician.
meanwhile maintain oral hygiene
do warm saline rinses , flossing regularly.