Participants will undergo tests and diagnostics investigations to identify signs of chronic rejection after heart transplantation.

Coronary angiography gives information about the degree of stenosis in the coronary arteries. In connection with the angiography Optical Coherence Tomography (OCT) will be performed. A precise measurement and characterization of the intima can be performed by OCT.

Right heart catheterization will be performed using a Swan-Ganz pulmonary artery thermodilution catheter. Right atrial pressure (RAP), mean pulmonary artery pressure (MPAP), pulmonary capillary wedge pressure (PCWP) and mean arterial pressure (MAP). Cardiac output (CO) and cardiac index (CI) will be recorded by thermodilution. The transpulmonary gradient (TPG) is obtained by subtracting PCWP from MPAP and PVR (in Wood units (WU) by dividing TPG by CO. Measurement will be performed both at rest and after supine bicycle exercise. A restrictive allograft filling pattern will be defined as PCW at rest exceeding 15 mmHg and/or exceeding 25 mmHg during exercise.

Coronary flow reserve (CRF) measurements may provide functional assessment of the microvasculature. Coronary blood flow velocity (CBFV) is measured in the left anterior descending coronary artery (LAD) before, and during constant adenosine infusion using conventional color Doppler ultrasound equipped with coronary imaging protocol. Mid-distal LAD segment is visualized using high frequency color Doppler (>3 MHz) in the anterior interventricular sulcus. A CINE-loop is then stored to document the 2-D image of LAD. Thereafter spectral Doppler is used to record CBFV. Mean diastolic flow velocity is calculated by manually tracing the diastolic flow velocity signal. Baseline CBFV values are calculated using the mean value of three representative heart beats during resting condition. The mean hyperemic CBFV is calculated as the mean of the three highest CBFV values recorded during the whole infusion period. The ratio between hyperemic and baseline CBFV is defined as CFR.