Heart transplantation has become an accepted therapy for end-stage heart failure. Acute allograft rejection (AR) remains a major cause of mortality in heart transplant recipients. Chronic rejection (CR) determines the long-term prognosis after cardiac transplantation and is responsible for more than one third of late deaths. Different non-invasive methods have been evaluated for the detection of AR, but the gold standard remains endomyocardial biopsy (EMB).

Very little is known about the impact of CR on the collateral circulation in transplant patients. Since the collateral circulation of the heart is mainly part of the microcirculation, it can be hypothesized that it is less developed than in “normal” coronary atherosclerosis without microvascular lesions.

The quantification of CR with non-invasive techniques has remained difficult. In this context, there is a need for a reliable non-invasive test to avoid regularly invasive evaluation.

Based on the above considerations we propose that both AR and CR can be accurately detected and differentiated using non-invasive quantitative myocardial contrast echocardiography (MCE).