So to clarify for those who don't want to read the article and a few supporting pieces, this is talking about the presence of plastic micro particles in plaques removed from patients.
Removing the plaque can reduce the risk of stroke so it is done fairly frequently. When they took out the plaque they checked for polyethylene, common plastic for bottles, plastic containers, and similar uses, and for PVC, famous for pipes and incredibly sweaty pants.
In both cases microplastics were found in the plaque. Both of these plastics have been shown to cause inflammation in other experiments where the plastic is introduced into the body.
What they seem to be suggesting is that some amount of the inflammation around a plaque could be caused or enhanced by these microplastics.
This study shows that in some plaques, about half of those examined, these two plastics were present. Previous studies have shown plastics can cause or enhance inflammation.
This study does not show that plastics are the primary cause of heart disease. It also does not show how much of an impact microplastics have on the formation of plaques, how dangerous they are, or whether they grow.
Because of the lack of information on how impactful microplastics are and the difficulty of reducing exposure the best evidence currently suggests focussing on removing the big known risks for heart disease. Those are smoking, alcohol, excessive sugar, burned or oxidised fats and oils, and a lack of physical activity. It would be wise to focus on those factors which we know cause heart disease rather than worrying about this small to nonexistent factor.