In the larger diameter blood vessels, it’s also due to relieving back pressure and finding a path of least resistance. This causes existing pathways to dilate and eventually join together to form a new channel / anastomosis (aortic coarctation is quite an extreme example - because of severe narrowing at the aorta existing blood vessels widen so much they cause notching of the ribs, which is visible on chest x-ray). Things like liver cirrhosis can cause back pressure and dilatation in a similar way.
Indeed. One family member with a rare desease discovered new blood vessels last week after an internal bleeding. These vessels had developed in the wrong places in the stomach and will be closed again and the normal vessels, which had been blocked by blood clothing, will be unblocked.
> another possible adaptive mechanism of coronary circulation to chronic intermittent ischemia of OSA patients is the development of coronary collaterals
Is this how some people have managed to grow secondary aortic passages naturally and usually without knowing until some cardiac event shows it?