Adipose tissue in myocardial infarction.

Introduction: The histologic evolution of myocardial infarction (MI) has been studied in some detail. However, there is little mention of the presence of adipose tissue in healed MI(HMI). Ninety-one hearts explanted during 1997-2001 were examined to determine the extent of adipose tissue within HMI.

Methods: The medical records, surgical pathology reports, and all histologic sections of the explanted heart, from patients undergoing heart transplantation for ischemic heart disease, were reviewed. Adipose tissue within the areas of HMI was quantified. The location of the HMI, the age and gender of the patient, age of HMI, and whether the patient was treated with coronary artery bypass surgery (CABG) were noted.

Results: Of the 91 hearts examined, 168 HMIs were identified; 141 (84%) contained some mature fat within the HMI. Adipose tissue increased with increasing age, in males, and in those patients who had CABG surgery. The amount of adipose tissue was not related to the location or age of the HMI.

Conclusion: Adipose tissue is a prevalent histological finding in HMIs. The pathogenesis of adipose tissue is unknown, but may be influenced by current medical therapy for ischemic heart disease, thus explaining why adipose tissue in HMIs was not reported until 1997. The presence of fat supports the speculation that a regenerative cell, or multipotent stem cell, exists within the heart, and under the influence of microenvironmental or therapeutic factors can differentiate into fat, other mesenchymal tissues, and potentially even myocardium.