In Adam Higginbotham's article Chernobyl 20 years on, it's implied that nuclear radiation increases the risk of heart attacks:
Now, nearly 20 years after the disaster, the survivors of Chernobyl are scattered across the former Soviet Union, gradually succumbing to cancer and early heart attacks.
Fukushima Diary is also implying that the nuclear incidents associated with the March 2011 Tohoku earthquake and tsunami is making heart attacks more likely, and seemingly not because of a lack of exercise. From Death rate of heart disease in Fukushima became the highest in Japan
Though Fukushima prefecture conceals its health check result data, Akita prefecture publishes the data.
It revealed the death rate of heart disease, cerebrovascular disease, and renal failure increased since 2010, and the death rate of heart disease became the highest in Japan.
Cesium is known to damage your myocardial cell.[LINK] [Link is to YouTube video by RT]
Cesium-134/137 are known to accumulate in the heart muscle to cause heart disease.
Death cases increased for every cause except for “other”, but especially the death of heart disease went up to as double as 2010.
Does nuclear radiation make heart attacks more likely in and of itself? That is, not caused by the stress associated with a nuclear incident, or because of actions done to avoid radiation, such as not exercising outdoors.