Hello and thank you for your question,
I am glad to hear that the tests which you had all came back normal and that there is nothing wrong with your heart.
The redness from the patches can take a couple of weeks to go away. Some people may have a skin reaction to the glue that is used on the patch which is why skin turns slightly red and may itch. You can use Hydrocortisone 1% cream (available over-the-counter) to speed-up how quickly the redness disappears. But it is of no concern and it will go away on its own even if you don't apply anything on it.
In terms of the pain in your rib cage...yes, it is very common after an echocardiogram to have rib cage pain. Because of the pressure applied during echocardiogram to visualize the heart, there might be some inflammation in the muscles of the rib cage. Your pain is typical for a muscle inflammation and will go away on its own within a week or two as well. You can take an anti-inflammatory medication such as Aleve or Advil and apply an ice pack to the area of pain to speed up the healing process.
I hope you find this information helpful. Please feel free to follow-up with any other questions you might have.
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Best wishes and good luck,