Finding and interpreting health data can be very challenging. There are many factors that go into gathering, analyzing, and reporting data. Some things to think about as you look for data:
Some basic starting points:
Additionally, you can search Goggle for additional information e.g. "myocardial infarction" prevalence.
Then when looking through the results, think about the credibility and possible biases of the sources and trade up to better sources where you can. For example, look at the hosting websites. In the above search, as I look through the results, I see one comes from Medscape, a source I recommend using for the Microbiology Poster Projects, the NIH website, the CDC, and the National Heart Association - all likely accurate primary sources (the groups that actually gather the data) of heart related health data. If you find health data in other sources, you can look at the references to see if you can get back to the primary source of the data.