hi Anthony,
Although it's quite understandable why you may be feeling this cardiac depression, but it's important to note that you are completely fine physically. You were 100% physically fit, if not 110%, after your first surgery. Then you hit a unique situation with the infection, and you needed the second surgery. This time, you are being restrained physically even though you are once again 100% physically fit. You situation is different from those that you indicated as having cardiac despressions. If you had no restrictions, you wouldn't have this depression. For someone like you, who is used to intense physical activity and someone you had an ambitious physical agenda after the first surgery, the lack of the physical element is playing around with your mind. So that's the first reason of your cardiac depression.
The second reason may be that of uncertainty (with infection). Once again, even though a normal mind would feel that given the circumstances, the probability of any such infection again is one in a light year. This factor will expire on its own, my prediction is. I think, after the 3-4 months (the same time elapsed between your first surgery and the infection) have passed away, this worry will expire worthless. And you will not look back.
In 6 months time if not earlier, with the second reason faded away, and the first one also (as you are allowed to have a reasonable physical activity), you will have an opposite effect of this so-called cardiac depression. It would be such a morale booster, as you would go back to your active life and goals. And that would provide all the rest of us our own set of booster
Hang on my friend, it's around the corner when this round of worry is gone for good. And in the mean-time remember, you are 100% physically (and gradually mending mentally as well).