The potential role of ultrasonic strain imaging and immunophenotyping in diagnosing acute rejection after heart transplantation

Background: There has been a continued search for an accurate noninvasive technique for detecting subclinical acute rejection in heart transplant recipients. Ultrasonic deformation imaging - strain/strain rate (SR) - is sensitive in detecting sub-clinical abnormalities in regional myocardial function and could potentially be sensitive tool to detect changes in deformation induced by graft rejection. There is an evidence of the importance of immunophenotyping in determining transplant rejection as well.

Aim: to assess the potential role of cardiac ultrasound velocity/strain imaging and immunological testing (alterations in peripheral blood T-cells subsets activation) in the detection of acute allograft rejection proven by endomyocardial biopsy.

Patients and methods: A retrospective observational study was carried out involving 28 patients (22 men and 6 women) who underwent a total of 167 routine follow up endomyocardial biopsies with correlative cardiac ultrasound and immunophenotyping data. Myocardial velocity derived from pulsed wave tissue Doppler imaging (PW-TDI) was calculated in the longitudinal direction in basal lateral segment of left ventricle (LV) in 4-chamber view and in the radial direction in basal posterior LV segment in long parasternal axis view. Global systolic strain by speckle tracking was calculated in the longitudinal, radial and circumferential directions.

Results: According to the International Society of Heart and Lung Transplantation criteria, 90 biopsies (Group 1) had grade 0, 1R or 2R rejection, and 30 biopsies (Group 2) had grade 3R rejection. The results of the forward selection revealed that the best indicator to predict the rejection was the amount of CD4+/HLA-DR+ cells. Univariate logistic regression analysis showed that global radial systolic strain performs better in terms of receiver-operator-characteristic curves (ROC) than the rest of the measurements (area-under-curve 0.83, where a cut-off value of 32.4% had 91.7% sensitivity and 77.8% specificity).

Conclusions: One of the best non-invasive parameters in the detection of acute sub-clinical rejection appears to be the expression of CD4+/HLA-DR+ cells. Among ultrasound markers the best predictor of acute rejection is global radial systolic strain.