What as been know in practice for many many years has now been explained by medical scientists - that a rise in 'stress' causes the immune system to make pre-existing arterial plaques 'unstable' and more likely to develop into dangerous clots.
This can all happen rather quickly. We would ideally have smooth, plaque free arteries - but if not, at least be aware that high levels of stress can potentially trigger an unpleasant cardio-vascular event!
With stress, the first and most important thing is to be aware of the stress, and of what you are feeling. You can then build on that. 'Unaware' stress is particularly dangerous.