Geographic variation in the incidence of myocardial calcification associated with acute myocardial infarction.

There is reason to believe that calcium influx into heart muscle during acute myocardial infarction (AMI) can aggravate myocyte injury. Furthermore, the degree of such influx might correlate with the occurrence of microscopic myocyte calcification observed at autopsy. We have searched for evidence of myocyte calcification in hearts of patients found to have AMI at autopsy at the Veterans Administration Medical Center in Salt Lake City (SLCVA), a region with a low myocardial infection death rate, and at the George Washington University Medical Center in Washington, DC (GWUMC), a region with a high myocardial infection death rate. Of 23 consecutive cases examined under "blind" conditions at the GWUMC in which AMI was found, there were 15 instances of cardiac myocyte calcification observed in von Kossa-stained sections. Not a single example of myocyte calcification was found in 23 comparable cases at the SLCVA. The basis of this difference in myocyte calcification is unknown, but may be related to the fact that the Salt Lake City drinking water contains a higher level of magnesium, which is known to protect against soft tissue calcification, than does that of Washington, DC. This may be the basis for the apparent protection that dietary magnesium exerts against myocardial infarction death.