Blood pressure meds, as well as statins, can and do cause weight gain in some patients. It IS very common, especially when taking both.
If you are taking Coreg, which is a BP medication, there is a very good chance it is causing you to gain weight, it is a side effect that is common. It slows down the heart rate, the body isn't working as hard, the weight comes on. Other beta blockers do that as well. Like you, I had a healthy lifestyle with exercise, diet, etc but I put on a quick fifteen pounds when I started taking Coreg. However, I adjusted my exercise, diet, etc like mammo advised and the weight came off quickly. Also, be sure that you aren't gaining weight because of water retention, that's certainly a sign of heart trouble.
Some BP medications can cause weight gain, but it's very rare. The stent would not cause this in any way. I too, was active (walking 6 miles a day), good diet, all you are, but developed a weight problem. I had all my meds evaluated for a side effect of weight gain, and none had this. I drastically changed my eating habits, and eat every 3 hours, small amounts of good stuff. I started doing this in Jan. and have lost 42 lbs.