Frequency analysis of the surface electrocardiogram for recognition of acute rejection after orthotopic cardiac transplantation in man.

Abstract

Recognition of acute rejection after heart transplantation has been based mainly on invasive methods until now. In this study we analyzed two well-defined surface electrocardiographic recordings by fast Fourier transform (FFT) (Blackman Harris window, 512 points) after low-noise, high-gain amplification (filter setting 0.5 to 300 Hz) each day for 4 weeks after cardiac transplantation in 27 patients. Twenty acute rejection crises requiring treatment were diagnosed by cytoimmunologic monitoring and endomyocardial biopsy. Single-beat analysis of the QRS complex by FFT revealed a progressive change of the spectral morphology (increase of the frequency content between 70 and 110 Hz) on the days of rejection in 19 of 20 patients. At that time there were no visible changes on the electrocardiogram in the time domain in most patients. At the same time, the frequency content of the ST segment decreased between 10 and 30 Hz in 16 of 20 patients. After successful treatment, the frequency spectra of the QRS complex and ST segment returned to control within 1 to 2 weeks in most patients. One false-positive result was seen in a patient with mediastinitis and large pericardial effusion. A drop in QRS amplitude (greater than 20%) occurred in 10 of 20 rejection crises and in 10 patients without rejection. Nine patients after cardiac transplantation without rejection and seven control patients after cardiac surgery (not transplantation) showed stable frequency plots from one day to the other after the first postoperative day, but with considerable changes in QRS amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)