Overview
Mechanical circulatory support systems, or assist devices, are used in advanced heart failure that is refractory to medical therapy. Various centrifugal pumps are used to support the left heart.
These centrifugal pumps can be implanted in the pericardium and are connected to the control unit via a thin control cable that is led out through the skin in the area of the abdomen. This is carried by the patient in a bag, which also contains two batteries that supply the control unit with energy. This makes the patient completely mobile and able to perform all the usual activities of daily living.
If, in addition to the left heart, the right heart also needs to be supported, so-called paracorporeal biventricular cardiac assist devices are used, in which both the right and the left heart are connected and supported via an inflow and outflow cannula to one pump chamber each. The two pump chambers are located outside the body on the patient’s abdomen. They are connected to a pneumatic drive unit that the patient carries on a small transport cart. Patients are also completely mobile with these systems.
In recent years, more than 100 cardiac assist devices have been implanted at the USZ.
Risks and complications
While these systems are very effective in supporting circulation and can pump high volumes of blood up to 6-7 l/min, on the other hand, complications can occur. The contact of blood with non-body materials of the systems can cause the formation of blood clots, which on the one hand can impair the function of the pump and on the other hand can embolize into the body organs. To prevent this, patients are treated with drugs to thin the blood and inhibit platelets. This in turn increases the risk of bleeding. The “control cable” routed through the abdominal wall from the implanted pump to the outside, which in particular ensures the power supply to the pump, and, in the case of biventricular support systems, the cannulas routed to the outside, lead to a connection of the inside of the body with the skin and its germs, which represents an increased risk of infection of the system. In extremely rare cases, a mechanical or electronic defect can also occur with subsequent device failure.
Cardiac assist devices have traditionally been used as a bridge to heart transplantation when patients would otherwise be highly unlikely to survive the wait for a matching donor organ to become available.
In recent years, implantable left ventricular assist devices have also been used as definitive, lifelong treatment (so-called “destination therapy”); this is primarily the case for patients for whom heart transplantation is no longer an option for age or medical reasons. Heart transplantation continues to be the only longer-term treatment option for many patients in the late stages of heart failure.