Research study evaluating the individual and combined effects of inhaled nitric oxide (iNO) and inhaled prostacyclin (iPGI2), on the function of the right heart after surgery for either heart transplant or for left ventricular assist device (LVAD) placement. The investigators hope to learn if these two medications, when given together after surgery, improve right heart function by lowering blood vessel pressures in the lungs. The investigators hope to learn if the combined effects of these two medications are better than either medication used alone. Participants were selected as a possible participant in this study because right heart problems are common during and after surgery for heart transplant and for LVAD placement. In addition, iNO is always given during and after these two types of surgeries at Stanford to help improve how the right heart functions.