Dad's 4x cabg was a success 17 months ago, and has been fine since. now, he gets winded when walking (but didn't use to in 1yr following cabg). ideas?

Yes: He needs a stress test and echo to look for residual or new ischemia (new blockage or failed graft) and to determine his systolic and diastolic lv function and pulmonary artery pressure. If he's gained weight or been sedentary during the winter, it may be simple deconditioning that will improve with exercise. But, again, a stress test is indicated before starting an exercise program.