[Blood flow in the isovolumetric relaxation phase in heart transplant patients. Its use in the noninvasive diagnosis of acute rejection].

The aim of this study was to assess a Doppler-echocardiographic parameter which has not been previously reported for the diagnosis of acute cardiac rejection. The parameter was left ventricular isovolumic relaxation blood flow. Eighty patients who had undergone orthoptic cardiac transplantation were followed up regularly with echocardiography for a period of 2 years. In all, 495 echocardiographic studies were performed and the results compared with those of endomyocardial biopsy performed on the same day (11.4 echocardiographic studies per patient). In the absence of cardiac rejection, isovolumic relaxation Doppler signal was recorded in all patients (364/387 echo studies). This was a positive signal directed towards the apex detected by continuous mode Doppler in the apical position, arising along the interventricular septum in the mid part of the left ventricle (82% of cases) or from the basal region of the septum (18% of cases) and lasting throughout the phase of isovolumic relaxation. The maximal velocity was 0.53 +/- 0.08 m/s (range 0.32 to 0.73 m/s) : the velocity-time integral was 34 +/- 33 cm. This signal was associated with medioventricular endosystolic acceleration of blood flow in 75% of cases. The incidence of the isovolumic relaxation flow signal decreased in cardiac rejection with no significant changes in the other usual Doppler-echocardiographic parameters except for a significant decrease in the ejection fraction in the group with severe rejection. In the group with mild rejection (n = 89) an isovolumic relaxation flow signal was only observed in 52 cases (including 29 in whom immunosuppressive treatment was not increased). In patients with moderate rejection (n = 12) there were only 5 cases in which a isovolumic relaxation flow signal was recorded, and in the group with severe rejection (n = 7), the signal could only be recorded in 1 case. The authors conclude that the absence of an isovolumic relaxation blood flow signal in a cardiac transplant patient is a reliable sign of cardiac rejection with an excellent specificity (94%). The absence of this signal is a sensitive indicator of severe rejection (86%) but less so for moderate (58%) or mild rejection (42%).