Traditionally, when one considers exposure to methylmercury, adverse impacts upon the brain and kidneys are foremost in any risk assessment. See, for example, http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=113&tid=24. Given the state of the evidence, it would appear that this paradigm needs to be amended to include cardiovascular impacts.
Traditionally, EPA has estimated the neurological benefits of reductions in prenatal methylmercury exposure in cost-benefit assessments of rules whose purpose is to control mercury emissions and exposure (e.g., from combustion of coal-fired power plants, ingestion of fish & seafood). Because a growing body of evidence suggests that methylmercury exposure can also lead to increased risks of adverse cardiovascular impacts in exposed populations, EPA assembled a panel of experts to assess the data.
The experts found the body of evidence which addressed the potential link between methylmercury and acute myocardial infarction (aka "heart attack"; see http://en.wikipedia.org/wiki/Myocardial_infarction) to be sufficiently strong to support its inclusion in future benefits analyses, based both on direct epidemiological evidence of a methylmercury link and on methylmercury's association with intermediary impacts that contribute to acute myocardial infarction risk. The experts also noted that additional research in this area would be beneficial to further clarify key characteristics of this relationship and the biological mechanisms that underlie it. Even so, they considered the current epidemiological literature sufficiently "robust" to support a recommendation of the development of a disease-response function.
The assessment can be found at http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.1003012.