NONINVASIVE DIAGNOSIS OF CARDIAC ALLOGRAFT-REJECTION - THE EFFECT OF PROCAINAMIDE

The surface electrocardiogram (EGG) has been used as a noninvasive tec hnique for the diagnosis of cardiac allograft rejection. Alteration in conduction, R-wave amplitude, and rhythm have been associated with re jection. These ECG findings are modulated by the myocyte sodium channe l, but are inconsistent and occur only during severe rejection episode s. The purpose of this study was to (I) characterize changes in cardia c electrophysiology during allograft rejection using the highly sensit ive intramyocardial electrocardiogram and (2) determine whether pharma cological sodium channel blockade with procainamide enhances subtle EC G changes. Nine mongrel dogs underwent heterotopic heart transplantati on in which four intramyocardial leads (one anteriorly and posteriorly on each ventricle) were attached. Leads exited to a subcutaneously pl aced ECG block which was transcutaneously accessed posttransplant to r ecord direct intramyocardial electrocardiograms. Six animals were trea ted with procainamide, while three were not and served as controls. Da ily measurements included the QRS, QT, and QTc intervals and the R-wav e amplitude. Endomyocardial biopsies were performed weekly and also wh en significant decline in ECG amplitude occurred. Detailed ECG interva l analysis failed to establish any correlation between conduction and rejection, even in the procainamide-treated group. Intramyocardial amp litude analysis, however, had a sensitivity of 100% and a specificity of 86% for the diagnosis of rejection. The results indicate that intra myocardial ECG interval analysis is not predictive of rejection even w hen prolonging conduction with procainamide. Amplitude analysis, howev er, remains an accurate noninvasive means for the early detection of c ardiac allograft rejection and should allow more selective use of endo myocardial biopsy.