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Cellular response of the evolving myocardial infarction after therapeutic coronary artery reperfusion
M J Cowan1, D Reichenbach, P Turner
1Department of Physiological Nursing, School of Nursing, University of Washington, Seattle 98195.
Insights
Early reperfusion therapy for myocardial infarction alters infarct healing. This study shows reperfusion changes histological signs, requiring updated criteria for assessing heart attack evolution.
Area of Science:
- Cardiovascular Pathology
- Myocardial Infarction Research
- Histopathology
Background:
- Acute myocardial infarction (AMI) cellular responses are typically assessed using established histological criteria.
- Early reperfusion therapies aim to restore blood flow to ischemic heart muscle, potentially altering the natural healing process.
Purpose of the Study:
- To compare the postmortem histological changes in human hearts with acute myocardial infarction (AMI) between patients treated with early reperfusion therapy and those receiving conventional therapy.
- To determine if early reperfusion alters the pattern of cellular response and histological age of myocardial infarcts.
Main Methods:
- A comparative postmortem histological analysis of 43 pairs of human hearts with AMI.
- Hearts were matched for clinical infarct age and infarct location.
- One group received early reperfusion therapy (streptokinase, angioplasty, tPA, or bypass graft surgery), while the control group received conventional therapy.
Main Results:
- Reperfusion therapy resulted in infarcts appearing histologically older than their clinical age (P < 0.002).
- The treatment group exhibited a higher Cellular Response Index (P < 0.017), increased hemorrhage (P < 0.001), more selective myocyte necrosis, less coagulation necrosis (P < 0.05), and a patchy distribution of necrosis (P < 0.04).
- Increased macrophages (P < 0.034) and reactive stromal cells (P < 0.05) indicated a more florid cellular response in the reperfusion group, with significant differences noted across various infarct age groups.
Conclusions:
- Early therapeutic coronary artery reperfusion significantly alters the pattern of injury and cellular response in evolving myocardial infarction.
- Established histological criteria for assessing infarct age and characteristics may need modification in patients treated with reperfusion therapies.
- Understanding these altered patterns is crucial for accurate pathological assessment of myocardial infarction in the context of modern treatments.
Abstract:
This study describes the cellular response of the evolving myocardial infarction in humans after early coronary artery reperfusion by one or more of the following therapies: streptokinase, percutaneous transluminal coronary angioplasty, tissue plasminogen activator, and/or coronary artery bypass graft surgery. Postmortem histologic changes were compared in two groups (n = 43 pairs) of human hearts with acute myocardial infarction matched for clinical age and left ventricular location of the infarct. The treatment group received one or more of the forms of reperfusion therapy. The control group received conventional therapy. The treatment group was judged to have an older histologic age infarct, P less than 0.002, compared with documented clinical age. For example, infarcts that were clinically 4 days old or less were judged histologically to be 1 day older. The treatment group had a higher Cellular Response Index, P less than 0.017; more hemorrhage within the infarct, P less than 0.001; a greater extent of selective myocardial cell necrosis, and a lesser extent of coagulation necrosis, P less than 0.05; more patchy, nontransmural distribution of necrosis, P less than 0.04; and a more florid cellular response, specifically more macrophages, P less than 0.034, and reactive stromal cells, P less than 0.05. In infarcts less than 3 days old clinically, the treatment group had hemorrhage and a cellular response which were wide-spread throughout the lesion, P less than 0.05, n = 18 pairs. In infarcts 3 to 4 days old clinically, the treatment group had a florid cellular response due to more macrophages, P less than 0.05, n = 9 pairs. In infarcts 5 to 10 days old, the treatment group had more macrophages, P less than 0.01; and more phagocytosis, P less than 0.003. In infarcts 10 to 40 days old clinically, the treatment group had scar formation that was patchy, P less than 0.05. In conclusion, this study demonstrates that early therapeutic coronary artery reperfusion after an acute myocardial infarction alters the pattern of injury and the cellular response to the evolving myocardial infarction so that the classical criteria for infarcts need to be modified.