Why would a doctor ask me to go for an echocardiogram prior to a surgery when just 3 weeks earlier a gastro md's nurse attached, as would be typical, about 10 electrodes to my chest and i had no problem with the colonoscopy procedure going forward?

It depends on what the procedure is that you are now having done. It sounds like an electrocardiogram was done prior to your colonoscopy. An echocardiogram is a very different test. Is it possible you have a heart murmur? An echocardiogram shows what is happening with blood flow through the heart as well as valves. If it is being recommended, it is for the safety of your procedure. Good luck!

If you were deeply sedated it's likely your heart was monitored during colonoscopy, but if no electrodes were placed on your arms & legs, I doubt you had a 12 lead,standard EKG at that time. Unless you had a rather recent EKG it's most unusual to request a preop echocardiogram without having a preop EKG first. Your PCP can clarify this issue for you.