[Detection of acute graft rejection with Fourier transformation of the surface ECG in long-term follow-up of heart transplantation].

: Up to now, diagnosis of acute rejection after heart transplantation (HTx) has been based on endomyocardial biopsy (EMB), but there is the need for reliable noninvasive parameters. Spectral analysis of the surface ECG with fast Fourier transformation (FFT) has been shown to be useful for rejection monitoring in the immediate postoperative phase. We tested the method in the chronic phase after HTx: the QRS complex (2 bipolar leads, position tattooed with Indian ink) was repeatedly analyzed with FFT (segment size 120 ms, 512 points. Blackman-Harris window) in 38 patients for 4-36 months after HTx. In mean intervals of 3 months, 254 checkups with FFT and EMB were performed on the same day. EMB revealed 28 acute rejection episodes in 21 patients, and ongoing rejection was diagnosed in 17 EMB. During rejection the frequency content of the QRS complex between 70 and 110 Hz increased in 25/28 rejection episodes (89%) and in 15/17 ongoing rejection cases, whereas in the time domain no specific changes could be seen. The QRS-amplitudes did not reliably indicate rejection, but decreased slowly during follow-up. After therapy the spectral changes disappeared within weeks. No signs of acute rejection were evident in 209 EMB: in 156/209 frequency analyses (77%) the spectra were constant, in 45/209 cases the frequency content increased, and eight analyses could not be evaluated. As the number of rejection crises decreased in the first postoperative months, there was an increasing number of false positive FFT analyses (positive predictive value 35%). Thus, a change of frequency content requires control by biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)