Does the measurement of left ventricular isovolumic relaxation time allow early prediction of cardiac allograft rejection?

In order to evaluate the value of isovolumic relaxation time measurement for the diagnosis of moderate acute rejection episodes in cardiac allograft recipients a comparison was made with the histological results from the endomyocardial biopsy. A total of 202 isovolumic relaxation time measurements from 26 patients were compared to the biopsy results. The technique used to record isovolumic relaxation time was dual M-mode echocardiography. In addition a combined phonoechocardiography was used for 54 isovolumic relaxation time measurements from 17 patients. A good correlation was found between these two methods. When the biopsy results were normal the isovolumic relaxation time was 71.4 +/- 15.1 ms. When moderate acute rejection episodes were present isovolumic relaxation time decreased to 50.2 +/- 21.2 ms (p < 0.001). In spite of the close correlation detected at group level, there was a large variability of the measurements without accompanying changes in the biopsy specimen. At the same time a significant overlap was found between the measurements taken during rejection and non-rejection periods making it impossible to use these methods for clinical decision making. We conclude that isovolumic relaxation time measured with these methods is not a sufficiently sensitive parameter for the diagnosis of moderate acute rejection episodes in the individual patient, and in our experience, it is not a substitute for endomyocardial biopsy and can not be applied for clinical decision making.