OBJECTIVES: Mast cells (MCs) may play an important role in plaque 
destabilization and atherosclerotic coronary complications. Here, we have 
studied the presence of MCs in the intima and media of unstable and stable 
coronary lesions at different time points after myocardial infarction (MI).
METHODS: Coronary arteries were obtained at autopsy from patients with acute MI 
(up to 5 days old; n=27) and with chronic MI (5-14 days old; n=18), as well as 
sections from controls without cardiac disease (n=10). Herein, tryptase-positive 
MCs were quantified in the intima and media of both unstable and stable 
atherosclerotic plaques in infarct-related and non-infarct-related coronary 
arteries.
RESULTS: In the media of both acute and chronic MI patients, the number of MCs 
was significantly higher than in controls. This was also found when evaluating 
unstable and stable plaques separately. In patients with chronic MI, the number 
of MCs in unstable lesions was significantly higher than in stable lesions. This 
coincided with a significant increase in the relative number of unstable plaques 
in patients with chronic MI compared with control and acute MI. No differences 
in MC density were found between infarct-related and non-infarct-related 
coronary arteries in patients with MI.
CONCLUSION: The presence of MCs in the media of both stable and unstable 
atherosclerotic coronary lesions after MI suggests that MCs may be involved in 
the onset of MI and, on the other hand, that MI triggers intra-plaque 
infiltration of MCs especially in unstable plaques, possibly increasing the risk 
of re-infarction.