Myocardial iron grading by endomyocardial biopsy. A clinico-pathologic study on iron overloaded patients.

Endomyocardial biopsy was performed in 13 patients with primary or secondary iron overload. Prussian blue staining showed visible iron in the biopsy fragments of 8 out of 13 patients. Because of the inhomogeneity of iron deposition in the biopsy fragments, a semi-quantitative myocardial iron grading system was used in which the percentage of Perls' positive cells on 4 to 6 biopsy fragments was averaged from each case. The presence of stainable iron in the myofibrils was not predictable from serum iron, transferrin saturation, serum ferritin or liver iron grading, nor from evidence of endocrine dysfunction. In patients with Perls' positive material in the myocardium, there was a significant correlation between the endomyocardial iron grade and serum iron and transferrin saturation. These results suggest that other factors besides the body iron load determine cardiac iron deposition. The fact that myocardial siderosis was documented only in patients with hepatic cirrhosis, irrespective of the hepatic iron load, suggests that severe liver damage may be a prerequisite for the accumulation of iron in the heart.