Indications for a VAD
In order to qualify for a ventricular assist device, one must have serious problems:
- Cardiogenic shock
- Cardiac arrest
- Fulminant myocarditis
- Failure to wean off bypass
There are also situations in which you might anticipate a VAD might be needed, and would have one on standby:
- High-risk PTCA
- High-risk cardiac surgery with poor preoperative function
Contraindications for a VAD
- Aortic regurgitation
- Aortic aneurysm or dissection
- Left heart thrombus
- Uncontrolled bleeding
- Uncontrolled sepsis
Basic physics of VAD
- They are either an axial (Archimedes' screw) or a centrifugal pump; flow is non-pulsatile, which results in poor end-organ function
- The action of pumping blood in this way provokes haemolysis
- The insertion usually requires a sternotomy
- It can be implanted for up to a month, but you cant walk around with this thing. You need to stay in hospital, largely confined to your bed.
Anticoagulation during VAD
- Heparin is the poison of choice
- APTT is used to monitor the level of anticoagulation; an APTT of 150-200 is aimed for.
Major complications of VAD
- Infection is the major cause of morbidity; something like 50% of the implated devices get infected.
- The LV gets (understandably) irritated by the presence of an LVAD, and in 25% of patients ventricular arrhythmias develop
- Thrombi form on the walls of the device in spite of anticoagulation, and 10-16% of people have thrombotic complications.
- Some degree of haemolysis and thrombocytopenia occur in everybody