The external vest would not change the blood flow to the heart nor make it work harder. When the skin is cool the blood is redirected to the internal organs. the body has safeguards in place that protect the blood supply to vital organs, especially the heart and brain.
My guess, is that being cooler allowed you to do more than usual and you are sore. Or you have some inflammation in your chest wall that the coolness uncovered. Mary had a good idea to take the vest off at intervals.
One way to see if the pain is from the bones/and or muscle of the chest wall is to see if you can press on the areas of soreness and elicit more pain. If that happens then you might treat it with an anti-inflammatory. You also might wear alnother layer under the vest so that the chest wall doesn't get so cold.
Sorry a solution appears to have caused another problem.
As Rosanne Rosanna Danna says, "It's always sumpthin'!"
Quix
Cold will cause construction of the blood vessels, at least the ones closest to the skin surface. I doubt it's cutting down the blood supply to your heart but it may be making it work a little harder. Cold can also stimulate muscle tightness in some people. You might try taking the vest off at invertals.
Mary
Interesting question. As a heart patient, we are told to not over heat OR get too cold. But that has more to do with not overtaxing our respiratory system - the change in temps can affect our lungs and when the lungs are working harder, the heart has to work harder.
So glad the cooling vest helped - my instinct tells me the chest tightness and the vest use are not connected. Anyone else have a hunch?
-L