I have had a couple of stress tests - one done on a treadmill, where I proved that cyclists are indeed the most awkward runners known to man, and last year I had a chemical stress test because my heart was deemed to be too damaged to perform one on a treadmill. One thing I've learned is to not trust all medical tests, as the echocardiogram that prompted last year's chemical stress test showed an ejection fraction of 28%, and a catheterization done right afterwards estimated it at 20%. I thought my days were numbered, but the final test, taken a couple of weeks later, was an MRI, which then showed about a 45% ejection fraction, and they basically said "oops" about the other tests being invalid! They apparently either used the wrong contrast or not enough contrast in those other tests. Anyway, the good news is that, while there is left atrial enlargement, I believe the valves themselves are OK. About a month or two ago I was having pretty bad breathing issues, so I got checked out to see if it was another pulmonary embolism. Luckily, this time around no clots were found. Since nothing abnormal showed up on the CT scan of my chest, and none of the blood tests came back with anything conclusive (troponin included), and the EKG came back without anything "new", I asked my doctor for a prescription for an inhaler. That really seems to have helped! I don't have a big enough sample size yet to say conclusively that it was asthma causing the "pins and needles", but even on today's ride, I did a couple of pretty solid efforts that would have previously caused me to almost pass out, but now I only have a "slight" pins and needles sensation, or none at all, when above 160 BPM. Goes to show that you should always start with the simple things!
All of that being said, what I'm trying to determine is if my heart is capable of doing 5-minute VO2Max efforts that are about 15% higher than my FTP, does that mean that the heart is not solely what is holding me back from improving my FTP? If we just push aside that whole "risk of dying" thing and pretend that no additional heart damage would occur, would I be still be able to improve my FTP / VO2Max? What gets "trained" in order to improve a healthy person's VO2 / FTP? Normally that would be a stronger heart, increased lung capacity, lactate buffering, more efficient muscles, etc. Assuming that I can't improve the damaged heart or slightly scarred lungs, what other things CAN still be improved to lift my FTP a bit higher?