Based on one leg's angle swelling would not require the tests you have listed. It may be a good idea to have an EKG and BP measurements monitored. At the age of 78 there good be a heart problem without symptoms, but it would not be the ankle symptom. An echo can establish a basis for future health concerns. It will provide heart chamber and wall dimension, heart valve integrity, heart pumping strength, etc.
I was few years younger than you and had symptoms of heart failure, and I was shocked to hear I had had a silent heart attack. My first symptoms was a day or so with congested heart failure, and I had felt I was in pretty good health...felt good, etc.
Hope this helps. Take care.