Cardiac transplant rejection is associated with a decrease in the high-frequency components of the high-resolution, signal-averaged electrocardiogram.

To evaluate the utility of signal-averaged electrocardiograms (SA-ECGs) in assessing cardiac transplant rejection, SA-ECGs and endomyocardial biopsy specimens in 20 transplant recipients were prospectively obtained. Total root mean square amplitude of the QRS (RMSt) from 70 to 250 Hz was decreased in the 12 SA-ECGs accompanying rejection compared with the 65 SA-ECGs without rejection (26.0 +/- 13.2 mcV vs 37.7 +/- 13.6 mcV, p < 0.01), and the RMSt, terminal 40 msec root mean square voltage (RMS40), and the filtered QRS duration (QRSd) were all decreased for SA-ECGs with rejection compared with those without rejection when evaluated from 125 to 250 Hz (12.3 +/- 7.0 mcV vs 17.5 +/- 6.3 mcV, 10.4 +/- 5.1 mcV vs 14.9 +/- 7.4 mcV, and 78.8 +/- 6.0 msec vs 85.1 +/- 9.5 msec, respectively, p < 0.05 for all comparisons). These results demonstrate a relative loss of high-frequency SA-ECG components in patients undergoing cardiac transplant rejection and suggest that the SA-ECG may be useful in the noninvasive evaluation of cardiac transplant rejection.