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Infarct expansion: pathologic analysis of 204 patients with a single myocardial infarct
Insights
Myocardial infarct expansion, a key factor in heart attack outcomes, varies significantly. Larger, transmural infarcts, especially those caused by left anterior descending artery blockages, show greater expansion, suggesting pre-infarction wall thickness influences this process.
Area of Science:
- Cardiovascular Pathology
- Myocardial Infarction Research
Background:
- The variability in myocardial infarct expansion remains poorly understood, impacting patient prognosis.
- Understanding factors influencing infarct expansion is crucial for developing targeted therapeutic strategies.
Purpose of the Study:
- To investigate the factors contributing to the marked variability in myocardial infarct expansion.
- To identify correlations between infarct characteristics, coronary artery lesions, and infarct expansion.
Main Methods:
- Retrospective review of 204 autopsied hearts with single myocardial infarcts.
- Analysis of infarct size, transmurality, presence of endocardial thrombus, fibroelastosis, heart weight, and left ventricular hypertrophy.
- Correlation of infarct expansion with coronary artery lesion distribution (left anterior descending, right coronary, left circumflex arteries).
Main Results:
- Infarct expansion was significantly greater in larger, more transmural infarcts (p < 0.001).
- Increased endocardial thrombus (p < 0.001) and fibroelastosis (p < 0.01) were associated with greater expansion.
- Infarcts in the left anterior descending coronary artery distribution showed markedly greater expansion (p < 0.001).
- Larger heart weight and left ventricular hypertrophy correlated negatively with infarct expansion (p < 0.05).
Conclusions:
- Infarct expansion is associated with larger infarcts and is less pronounced in hypertrophied hearts.
- Expansion predominantly occurs in infarcts within the left anterior descending coronary artery territory, suggesting regional myocardial characteristics influence the process.
- Pre-infarction ventricular wall thickness may play a role in modulating infarct expansion.
Abstract:
The reasons for the marked variability in expansion of myocardial infarcts are unknown. To examine this question, the hearts in 204 patients with a single myocardial infarct, autopsied at The Johns Hopkins Hospital and studied after coronary arteriography and fixation in distension, were reviewed. There were 58 (28%) hearts with marked infarct expansion, 34 (17%) with moderate expansion and 112 (55%) with no or minimal expansion. The degree of expansion was greater in larger, more transmural infarcts (p less than 0.001). Infarcts with greater expansion had significantly more endocardial thrombus (p less than 0.001) and endocardial fibroelastosis (p less than 0.01). Larger heart weight and degree of left ventricular hypertrophy had a significant negative correlation with infarct expansion (p less than 0.05). A markedly greater degree of expansion was noted in the 101 infarcts (50%) caused by lesions in the distribution of the left anterior descending coronary artery as compared with the 57 infarcts (28%) secondary to right coronary lesions and the 46 infarcts (23%) in the distribution of the left circumflex coronary artery (p less than 0.001). The results show that expansion is associated with large infarcts but is less marked in hearts with ventricular hypertrophy. Expansion occurs predominantly in infarcts in the left anterior descending coronary artery distribution, that is, regions of the left ventricular myocardium with the greatest curvature. These results suggest that the degree to which an infarct expands may be influenced by the preinfarction thickness of the ventricular wall.