Hi thanks for your question.
Your 50 year old and complain of fast heart beat along with other symptoms and you think this is due to stress
because of death of your baby dog.
Yes it could be due to stress, but your 50 year old and overweight
and you have chest discomfort
besides increased heart rate
It would be better for you to get consultation from a physician, who will investigate you for any underlying pathological cause for your symptoms, besides the stress.
You may need ECG,your lipid profile(blood test
),to rule out any pathological cause of your symptoms
Hope this answers your question.