The heart gets old. For some, the muscle gets deposits of fibrosis and collagen, which stiffen up the walls of the heart and the heart becomes less efficient at filling itself for each pumping stroke. Sometimes this leads to mitral valve prolapse and even more fibrosis. Often this ends up causing PACs (premature atrial complexes) or AF (atrial fibrillation).

That's one cause, and it's a growing concern for the medical establishment as the western industrialized world moves through the time of the Baby Boomer Bulge. The other cause, still part of the normal aging process, is ischemia...lack of supply of oxygen to the heart muscle. This is due to deposition of atherosclerotic plaque. If there's enough plaque, the amount of blood squeezed through the narrow hole that's left inside the major blood vessels feeding the heart itself, is too little....ischemia. If you say that you can't do much physically any more, it suggests to me that you might need diagnostic imaging to rule out ischemia. Your heart doesn't seem to like too much activity because it can't meet the demands you place on it when you move around or lift too much.

Again, this is my inexpert guess....it's only a guess. An expert cardiologist will KNOW in short order once you see such a person and submit to his/her requests for diagnostic methods such as echocardiogram and MRI or a nuclear stress test with CT scan.

Don't panic yet, because there's time, but don't go six week thinking about it either...call tomorrow!!