I have been a runner for 40 years. About two years ago I found it difficult to run even a 1/4 mile as my breathing shut me down. Since then, I have had every test done except heart cath. to check for blockages. All my test have come back normal. Lung function has me at a 20 year old, I am 53. My weight is up a bit but when it's where it should be, I still have the same breathing issues. Should I have a heart cath. done to rule out blockages even though my ECG, EKG, Echo stress test all came back normal?