I understand that the objection to blood transfusions by Jehovah's Witnesses is purely a scriptural one. Whether or not there are medical benefits to avoiding blood transfusions is, or should be, irrelevant. However, for those who are not convinced by JW understanding of the scriptures in this regard, and those who don't believe either in the Bible and/or in God, the fact that blood transfusion is associated with increased mortality in heart attacks may be of interest.
A systematic search of studies published between January 1, 1966, and March 31, 2012, was conducted using MEDLINE, EMBASE, CINAHL, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials databases. English-language studies comparing blood transfusion with no blood transfusion or a liberal vs restricted blood transfusion strategy were identified.
Analyses of blood transfusion in myocardial infarction revealed increased all-cause mortality associated with a strategy of blood transfusion vs no blood transfusion during myocardial infarction (18.2% vs 10.2%)...Blood transfusion was also significantly associated with a higher risk for subsequent myocardial infarction.