This study is looking at people who have recently had a heart transplant to see if a simple blood test can help doctors better understand how the immune system is doing. By checking tiny molecules called microRNAs in the blood, researchers hope to find a way to tell if a patient might have problems like infection or rejection of their new heart. The goal is to help adjust medications so patients stay healthier after their transplant. The study involves taking blood samples during regular doctor visits over three years, but it doesn't change any of the usual care the patients would already get.

This research study aims to determine a less invasive way to assess heart function by taking measurements of the heart while subjects are performing an exercise cardiac MRI. Subjects will undergo two exercise phases and MRI measurements will be taken after each exercise phase. These measurements will be compared to available clinical data (including demographic, hemodynamic, radiologic, and functional) and future outcome data.

Elevated pressures in the heart can represent a severe medical condition known as pulmonary hypertension. This can result in chronic right heart failure. An abnormal increase in this pressure during exercise may be represent an early stage of vascular lung disease. This study will investigate the prognostic implications of the measured pressures obtained during exercise while undergoing a right heart catheterization procedure based on a large scale multi-center approach by using retrospective and prospective analysis of hemodynamic data.