The basement membrane of intramyocardial capillaries is thickened in patients with acute myocardial infarction.

Background: Atherosclerotic epicardial coronary arteries are a major cause of acute myocardial infarction (AMI). Recently, we found that intramyocardial capillaries may also play a role in AMI induction. We have now evaluated intramyocardial capillaries using ultrastructural analysis in AMI patients.

Methods: 43 AMI patients (with AMI in the left ventricle) and 27 controls. No patient included in either group had diabetes mellitus. Basement membrane (BM) thickness of intramyocardial capillaries was determined using electron microscopy. BM thickness was also studied in a rat AMI model.

Results: BM thickness in the left ventricle of AMI patients was significantly higher than in controls (102 +/- 9 vs. 77 +/- 4 nm; p = 0.016). This increase was not found in the right ventricle. In AMI patients, BM thickness was already increased in recent infarcts and did not increase further with infarct age. No correlation was found between BM thickness and the amount of stenosis or atherosclerotic plaque stability of epicardial coronary arteries. In addition, BM thickness did not differ between control rats and AMI rats.

Conclusions: These results suggest that BM thickening constitutes significant changes in the intramyocardial capillaries in patients that develop AMI. Also these changes are likely to occur prior to the induction of AMI.