Between 14 and 10 days before your scheduled heart surgery, you will receive the first injection of the study medication. This will be either romiplostim (a medication that helps increase platelet counts) or placebo (an inactive substance). The medication will be given as an injection under the skin.

Neither you nor your medical team will know which treatment you are receiving during the study.

After receiving the first injection, you will continue with your preparations for the scheduled heart surgery. This period lasts from the day of the first injection until the day of your operation.

You will undergo the planned heart surgery. The surgery will be performed using extracorporeal circulation, which is a machine that temporarily takes over the function of your heart and lungs during the operation.

During the surgery, a blood recovery system will be used to collect and return your own blood.

The day of your surgery is considered day 0.

From the end of the surgery until the 7th day after the operation, your platelet count (the number of small blood cells that help with clotting) will be monitored through blood tests. Platelets are measured in number per cubic millimeter of blood.

The amount of bleeding from surgical drains will be measured at specific times: from closure of the breastbone until 12 hours after surgery, from hospital discharge until 24 hours after surgery, and from 24 hours after surgery until the drains are removed.

Your blood hemoglobin level (a measure of red blood cells that carry oxygen) will also be monitored.

If needed, you may receive transfusions of platelet concentrate, red blood cell concentrate, or fresh frozen plasma. You may also receive blood-derived medications such as fibrinogen, prothrombin complex concentrates, or recombinant activated factor VII.

Your time on mechanical ventilation in the intensive care unit will be recorded.

Any bleeding events, blood clot formation in veins or arteries, infections, or problems with organ function will be monitored and recorded.

Blood tests may be performed at the hospital or, if you are discharged before day 7, they may be done outside the hospital.

Monitoring will continue until the 28th day after your surgery. During this period, your platelet count and hemoglobin levels will continue to be checked.

Any additional transfusions or blood-derived medications given during this time will be recorded.

Your length of stay in the intensive care unit and total hospital stay will be documented.

Any complications, bleeding events, blood clots, infections, or organ problems occurring during this period will be monitored.

You will be followed for up to 3 months after your surgery to monitor for any bleeding events, blood clots in veins or arteries, and infections.

During the first month after surgery, you will receive medication to prevent blood clots. This will be either medication that prevents platelets from sticking together or medication that prevents blood from clotting, or both types.