Good morning, Virginia. What you are describing is consistent with congestive heart failure. It is a frightening experience. Raising the head of your bed will reduce the frequency of this symptom if it is CHF related. A quick relief for the momentary terror is to purse your lips and blow out hard (like a hard, silent whistle). Doing this a couple of times usually works for me, then I sit up on the edge of the bed until my breathing settles.🌷

I am now aware that Brilinta (Thinner) has as one of its side effects, "shortness of breath. " I take Brilinta and HAVE experienced horizontal/wakeful shortness of breath, (Last M.I. was January 14th. New drug eluding stents[3] placed within old metal stent from 2011...) however, the more cardiac rehab I practice, 18 weeks thus far and counting, the less I experience the shortness of breath symptom. I have been told by Cardiac Surgeon in New York that one cause of this is fluid buildup within the heart and cardiologists checkups can and do help patients manage this. Good Luck to you!

I will repeat now that my Cardiac Rehab is continuing. I must say this again....the more minutes PER MONTH that I am achieving in stamina building exercise, including anaerobic level of either swimming or jogging/running,
the less I experience shortness of breath whether awake and horizontal or any other physical position. Lung health is a by-product of vigorous exercise. (With or without heart illness). The more I move, the less I experience ANY negative symptoms related to heart health or lack of it. (Also know that I am continuing to take the blood thinner Brilinta/ Ticagrelor.[..that has "shortness of breath" as a known side effect...] And, minutes per month is a more gainful statistic to measure than minutes (of exercise) per day. Lots of folks quit their exercise regimen after trying for only a week or so. If that's you, please ignore my advise above.
Take CARE!

Most definitely sounds like heart failure. You might be retaining water in your legs. Keep your head raised, and legs raised. You may need to take a lasix, talk to your doctor.

Your cardiologist has the best advice, but, If you have never utilized Cardiac Rehab, I would suggest that practice to enhance your heart's ability to handle small amounts of exercise followed by very slightly larger amounts over time. (With all your medications also helping at the same time.) I am 73, always active and have currently 4 stents placed in my Right Cor Artery.
Brilinta, Carvedilol, Lisinopril as well as aspirin, Statins and Jardiance working together to help me keep up my two moderate workouts per week in local health clubs. I use the Treadmill as well as 4 (static) strength stations in every workout I do. Almost Zero Alcohol and excellent sleep. Good luck Bhutton!