Microvascular Cardiac Allograft Vasculopathy Trial

Inclusion Criteria: * able to consent * Written consent of the participant after clarification and sufficient time to think about participation * heart transplant recipient * Indication for routine invasive diagnostics or due to symptoms * Exercise tolerant in everyday life - cycling, climbing stairs at least 2 floors at a moderate speed without symptoms of exertion or dyspnea Exclusion Criteria: * Addiction or other diseases that do not allow the patient to assess the nature and scope as well as possible consequences of the study * Patients or their legal guardians who do not sign the declaration of consent or who cannot fully understand it due to a lack of German language skills * Pregnant women, breastfeeding women * Severe comorbidities affecting the miRNA profile: diabetes mellitus, malignancy, end-stage renal disease with renal replacement therapy * Contraindication to the stress test: signs of cardiac decompensation, angina pectoris, dyspnea, hyperthyroidism, GFR \<30 ml/min, peripheral arterial disease, pheochromocytoma, angle-closure glaucoma, prostate adenoma, paroxysmal tachycardia, tachycardia atrial fibrillation * Evidence of an acute rejection or local wall motion disturbances in the resting echocardiography