The use of myoglobin/carbonic anhydrase III ratio as a marker for myocardial damage in patients with renal failure.

To evaluate the clinical significance of myoglobin and myoglobin/CA III ratio as a biochemical marker for acute myocardial infarction (AMI) in patients with renal failure; we studied 300 patients admitted to the hospital with a history of symptoms characteristic of AMI, and 33 renal failure patients who were undergoing chronic maintenance dialysis treatment and who did not have clinical or electrocardiographic evidence of AMI. Fifteen of 300 patients admitted to the hospital had AMI based on the WHO criteria, and a concomitant value of serum creatinine concentration (S-Crea) over 140 mumol/l indicating renal failure. Fourteen of these 15 patients (93%) had serum myoglobin concentration over 70 micrograms/l and myoglobin/CA III ratio over 2.20 as measured by time-resolved fluoroimmunoassay (TR-FIA); these values were cutoff values for AMI diagnosis. Twenty-two of 300 patients admitted to the hospital had S-Crea over 140 mumol/l in the absence of myocardial injury. Sixteen of these 22 (73%) patients had increased serum myoglobin concentration, but only four of 22 (18%) had myoglobin/CA III ratio over 2.20. A positive correlation between serum myoglobin and CA III concentrations (rs = 0.933, P < 0.001) was observed in hemodialyzed patients with chronic renal failure. The values for serum myoglobin/CA III ratio observed in this group were similar to those measured in the 22 non-AMI patients with S-Crea over 140 mumol/l admitted to the hospital and differed statistically from that for patients with AMI (P < 0.001). We conclude that serum myoglobin, as well as CA III values, are elevated in patients with renal failure, and therefore S-myoglobin can not be used as a marker for AMI in these patients. Our results suggest that the serum myoglobin/CA III ratio is a reliable AMI marker even in renal failure patients, and therefore provides a tool for AMI diagnosis in this patient group.