DMT is stressful on the heart and blood vessels, but a healthy person should not significantly be at risk, nor would lasting issues be expected.
This is however something to take into account when considering drug combinations. Avoid stimulants mixed with DMT for this reason.
I think a more considerable concern is that it can be hard to integrate difficult experiences and it is important to try your best (regarding set and setting) not to get stuck in an agonizing experience. DMT is not recommended for those that are mentally unstable because it can have impact on your sense of reality.