Diagnostic Methods Cardiac Transplantation

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 (> 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. Our results offer promise that frequency analysis, but not QRS amplitude, of low-noise electrocardiographic recordings can be used for the noninvasive, early detection of acute rejection after cardiac transplantation. Circulation 76, No. 1, 101-108, 1987. THE TWO MAJOR complications after cardiac transplantation are acute rejection and infection. Until now the diagnosis of rejection has been based mainly on invasive endomyocardial biopsy, which cannot be done on a daily basis and is of potential risk for the immunocompromised patient. Reliable, noninvasive diagnostic tests to identify the beginning of rejection episodes are still necessary. Changes in the immune systems of recipients have proved to be sensitive for acute rejection but lack specificity.1 Hemodynamic alterations are absent in the initial stages of rejection, when therapy should be started. Electrophysiologic changes, such as reduction of QRS amplitude, have From Medical Hospital I and the Department of Cardiac Surgery, University of Munich, Federal Republic of Germany. Address for correspondence: Dr. Ralph Haberl, Med. Klinik I der Universitat, Klinikum Grosshadem, Marchioninistrasse 15, 8000 Munchen 70, Federal Republic of Germany. Received Dec. 10, 1986; revision accepted March 19, 1987. been shown not to correlate reliably with acute rejection2 and are too variable for therapeutic decisions. As a new approach for the noninvasive detection of acute rejection, we analyzed the frequency content of the QRS complex and ST segment of surface electrocardiograms (ECGs) by fast Fourier transform (FFI), a powerful analytic algorithm that reveals changes in the surface ECG that are invisible in the standard ECG.