Serum myoglobin does not predict cardiac allograft rejection.

Noninvasive studies are useful, but limited, in detecting rejection among cardiac allograft recipients. Because an elevated serum myoglobin level is a sensitive indicator of necrosis in acute myocardial infarction, we postulated that myoglobin levels might correlate with the presence, absence, or degree of rejection. Therefore we prospectively measured serum myoglobin levels at the time of endomyocardial biopsy in 45 heart transplant recipients and correlated these levels with biopsy scores (grade 0 through grade 4). There was no significant difference in mean myoglobin levels among patients with grade 0 biopsy scores and those with grade 1 through grade 4 scores. Serial myoglobin levels and endomyocardial biopsy specimens were obtained in five patients during a 4- to 9-week period; no significant directional change in myoglobin levels appeared to correlate with changes in endomyocardial biopsy score. In addition, a normal myoglobin level did not exclude, nor did an elevated level confirm, any grade of rejection. We conclude that neither the absolute level nor a directional change in serum myoglobin is useful in identifying rejection among heart transplant recipients.