Lower abdominal bloating with gas and difficulty breathing and heart palpitations. Is this a digestive or heart issue?

Digestive. The heart is like a ship in the ocean, buffeted by hormones secreted when things go wrong. That is probably causing your palpitations. The bloating may be pressing on your diaphragm causing the difficulty breathing. This does not seem to be a heart problem, but it is always prudent to have your heart checked.