The distribution of cardiac macrophages in myocardial ischaemia and cardiomyopathy

Aims: Recent evidence has implicated the macrophage as an effector cell in the inflammatory processes in transplant rejection, as well as cardiac disease, including coronary atherosclerosis. Although the latter is a vascular disease, the entire myocardium is affected. We have previously demonstrated the presence and distribution of macrophages in the 'normal' human heart. In this paper the distribution of myocardial macrophages, in the various chambers of the failing human heart, from cases of coronary atheroma and cardiomyopathy undergoing heart transplantation is documented. Methods and results: Tissue blocks were removed at specific sites taken from six cases with ischaemic heart disease (IHD) (four males, two females, age range 54-62 years), and four cases with idiopathic dilated cardiomyopathy (IDCM) (three males, one female, age range 18-49 years). These were compared with hearts from five cases of sudden death, unrelated to heart disease. Sections were stained with a CD68 pan macrophage marker. Positive cells were enumerated in 20 random fields. Results were analysed using a generalized linear modelling method using a Poisson distribution. Macrophages were identified within the interstitium and often close to blood vessels in all hearts. Macrophages from IHD hearts demonstrated the most intense staining and were often larger and more elongated than those found in 'normal' control hearts. Macrophages were also often degranulated and staining was diffuse in the interstitium. Overall, there were significantly more macrophages in most areas from IHD hearts than from IDCM hearts or control hearts (P < 0.001). Conclusions: Significantly more macrophages were found in all four chambers in diseased hearts compared with controls. Macrophage numbers were higher in the atria than in ventricles in the diseased myocardium. This study suggests selective recruitment of macrophages into the atria in the disease states studied.