Echocardiography improves detection of rejection after heterotopic mouse cardiac transplantation

Background: Current assessments of cardiac rejection in murine transplant models rely on subjective estimates of the force of the palpable heart beat that have limited sensitivity and precision. Methods: We used 2-dimensional echocardiography to evaluate changes in left ventricular posterior wall thickness (PWT) in a heterotopic cardiac mouse transplant model of rejection. Nine allografts and 6 isografts were imaged daily for 6 days and harvested. Thirteen allografts were imaged daily and harvested at day 3. Results: Intraobserver variability on PWT was 0.003 +/- 0.09 mm, interobserver variability 0.09 +/- 0.11 mm. Allograft PWT increased after transplantation (0.74 +/- 0.02 mm to 1.28 +/- 0.05 mm at day 5, P < .0001). For isografts, PWT remained constant (0.73 +/- 0.03 mm to 0.85 +/- 0.01 mm) after an initial increase at day 1. Palpation failed to identify rejection at day 3 whereas PWT was already increased (1.15 +/- 0.02 mm in the allografts at day 3 vs 0.85 +/- 0.02 mm in the isografts, P < .0001). There was a relation between histologic score and PWT (P < .0001). Conclusion: Two-dimensional echocardiography allows the noninvasive detection and follow-up of cardiac rejection after transplantation. It eliminates the subjectivity of palpation and provides quantitative and reliable indices of rejection.