There are a couple of other possibilities other than what has been mentioned.
a) You could have a higher-than-average HRmax.
b) Your device could be giving you false readings.
How do you FEEL when your HR is 180 or 193? The 220-age formula would give you an HRmax of 195. If your max is REALLY 195, and your are REALLY pumping 193 bpm, you should be feeling pretty darn maxed! If that is not the case, then you might want to consider the possibilities I have mentioned.
Years ago, I began a program of training with a HRM. For several months, I stayed carefully within my target zone. My running became slower...and slower...and slower, until finally I had to walk to stay in my target zone. I was worried, so I made a doctor appointment. He found nothing wrong with my heart, except that I was out of shape. Through trial and error, I eventually found out that I have an abnormally high HRmax. The "target" rate that I was training at was so pitifully low (for me) that I actually lost condition while training at that pace. This may or may not be the case with you, Orangetang. But you would do well to investigate and figure out what's going on.
Best of luck to you!