PERIPHERAL MONOCYTOSIS FOLLOWING ACUTE MYOCARDIAL-INFARCTION - INCIDENCE AND ITS POSSIBLE ROLE AS A BEDSIDE MARKER OF THE EXTENT OF CARDIACINJURY

Infiltration by mononuclear cells, mostly monocytes: into necrotic myo cardial tissue can be detected beyond the 3rd day after the onset of i nfarction. These monocytes, mobilized by an unknown mechanism, initiat e phagocytosis of necrotic tissue. We observed in patients having sust ained an acute myocardial infarction (AMI) a significant increase in m onocyte count 2-3 days following presentation, possibly representing p eripheral recruitment of monocytes to the injured myocardium. To estab lish this observation, we prospectively documented monocyte and neutro phil counts throughout hospitalization in 186 consecutive patients (11 8 patients having sustained an AMI, 34 patients with angina, and 34 pa tients admitted for nonischemic reasons). Average monocyte count, whic h rose on the 2nd day and reached a peak on day 3, was significantly e levated in these patients compared with control subjects (p < 0.001). Neutrophil count exhibited a similar phase-shifted response. Peak mono cyte count exceeded 800/mm(3) (upper limit of normal range) in 69 (58% ) of AMI patients but in only 3 of the 68 (4%) non-AMI patients, yield ing a sensitivity and specificity of 58 and 95%, respectively, for the diagnosis of AMI by this criterion. A significant correlation between maximal creatine kinase (CK) representing the extent of myocardial ne crosis and peak monocyte count was shown (r = 0.51, p < 0.0001). A cor relation between CK and monocyte count sum of days 1-3 (r = 0.51, p < 0.001) was found in a substudy of 25 patients with AMI. Similarly, a c orrelation was shown with cardiac function score as evaluated by 2-dim ensional echocardiography (p < 0.001 and p < 0.008 for difference betw een CK sum and monocyte count sum of high and low echo score groups, r espectively). Hence, the peak monocyte count recorded during the immed iate postinfarction period provides a bedside marker of the extent of myocardial damage that is the preponderant prognostic determinant, if validated in future studies this phenomenon may have diagnostic and pr ognostic implications.