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Cardiac involvement in secondary haemochromatosis: a catheter biopsy study and analysis of myocardium
Insights
Endomyocardial biopsy is unreliable for detecting early myocardial iron in Thalassemia Major due to iron distribution and sampling variability. This method may not accurately assess iron overload in the heart.
Area of Science:
- Cardiology
- Hematology
- Pathology
Background:
- Thalassemia Major patients experience improved longevity with transfusions, but cardiac complications like failure and arrhythmias persist.
- Myocardial iron deposition is a significant concern, and its preventability by chelation therapy remains uncertain.
- Assessing myocardial iron is crucial for managing cardiac risks in Thalassemia Major.
Purpose of the Study:
- To evaluate the efficacy of endomyocardial biopsy in assessing myocardial iron deposition in Thalassemia Major patients.
- To investigate the distribution and nature of iron in the myocardium.
- To correlate myocardial iron levels with cardiac function.
Main Methods:
- Analysis of endomyocardial biopsies from four patients with severe hemochromatosis.
- Assessment of myocardial iron content and distribution.
- Characterization of myocardial iron proteins using CM32 cation exchange resin chromatography.
Main Results:
- Only one of four patients showed myocardial iron comparable to severe hemochromatosis.
- The patient with cardiac failure had normal endomyocardial iron levels.
- Subendocardial iron content was half that of the subepicardial layer, indicating significant sampling variation.
- The haemosiderin: ferritin ratio increased significantly in iron-overloaded myocardium (5:1) compared to normal hearts (2:1).
Conclusions:
- Catheter endomyocardial biopsy is an insensitive method for detecting early myocardial iron deposition due to iron location and sampling variability.
- Increased haemosiderin suggests potential myocardial cell damage via lysosomal rupture, similar to observations in liver iron overload.
- Further research is needed to develop accurate methods for assessing cardiac iron burden in Thalassemia Major.
Abstract:
Although high blood transfusion regimens have improved the life expectancy of the patient with Thalassemia Major, cardiac failure and arrhythmias remain a cause of early death. It is not certain whether the massive myocardial iron deposition found in such patients is preventable by intensive chelation therapy. This study evaluates endomyocardial biopsy as a method of assessing myocardial iron deposition. Of four patients with clinical and biochemical evidence of severe haemochromatosis, only one had a myocardial iron content comparable to that found in severe haemochromatotic myocardium. The one patient with cardiac failure had an endomyocardial iron content within the normal range. Studies of the iron distribution in haemochromatotic myocardium demonstrate that the subendocardial myocardium contains only half the iron content of the subepicardial layer, and there is a large sampling variation. It is concluded that catheter endomyocardial biopsy is an insensitive method of determining early myocardial deposition because of the location of iron and the variability of the sampling. Studies of the nature of the myocardial iron protein with CM32 cation exchange resin chromatography show that there is a large increase in the haemosiderin: ferritin ratio (5:1) in iron overload myocardium as compared with the normal heart (2:1). Similar results have been observed in the liver with iron overload, where the increase in hepatic haemosiderin was associated with greater lysosomal fragility. It is possible that myocardial cell damage may also occur by the rupture of iron engorged lysosomes.