Post-Infarction Inflammation and Left Ventricular Remodeling

After myocardial infarction (MI), inflammatory cells such as neutrophils, followed by monocytes and macrophages, infiltrate and phagocytose the necrotic tissues, as well as secreting a variety of inflammatory cytokines. The vulnerable myocardium, which consists of necrotic tissue and inflammatory cells, is susceptible to wall stress, resulting in infarct expansion. Subacute cardiac rupture is an extreme form of infarct expansion, whereas ventricular aneurysm is its chronic form and a trigger for subsequent left ventricular (LV) remodeling. Although post-infarction inflammation is essential for the healing process, excessive inflammation could play an important role in the development of LV remodeling. Increase in the C-reactive protein level, which reflects myocardial inflammation, is reported to be a useful predictive marker for cardiac rupture, ventricular aneurysm and LV remodeling. In addition, an increase in peripheral monocyte count is associated with a poor outcome after MI, and an animal study has demonstrated that granulocyte/macrophage-colony stimulating factor induction causes excessive macrophage infiltration in the infarcted area and worsening of LV remodeling. Recently, it was also found that dendritic cells play an important role in controlling excessive inflammation caused by monocytes/macrophages. Thus, inflammation that develops after MI is a double-edged sword, and how to control inflammation to suppress pathological remodeling is an important issue to be considered in developing new treatment for heart failure.