The goal of this study is to detect AR and CR in the transplanted heart by quantitative assessment of myocardial blood flow and its constituents by myocardial contrast echocardiography (MCE). Further we investigate the collateral circulation in these patients.

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).

Inclusion Criteria:

• Patients with heart transplantation, age 18-82 years
• EMB or EMB and coronary angiography
• Written informed consent to participate in the study

Exclusion Criteria:

• Known adverse reaction to adenosine or echo contrast (SonoVueâ)
• Second or third degree AV block, unprotected sick sinus syndrome, atrial fibrillation with uncontrolled ventricular rate
• Asthma, severe pulmonary arterial hypertension (systolic pulmonary artery pressure >50mmHg assessed by echocardiography)
• Severe obstructive pulmonary disease

Prospective study with consecutive inclusion of transplanted patients undergoing follow-up exams. Examinations comprise endomyocardial biopsy (EMB) and, partly, coronary angiography on the subsequent day. Group A patients (i.e. those without coronary angiography) undergo MCE and pharmacologic stress with adenosine, the results of which are compared with the EMB done at the same day. If they have an acute rejection, they are reexamined during a histologically proven rejection free period, and the results are compared with those obtained during acute rejection. Group B patients (i.e. with EMB and coronary angiography) undergo the same procedure as in group A. Additionally, coronary collateral flow index (CFI) is obtained and an IVUS exam is performed during coronary angiography.