Ventricular assist devices (VADs)
General considerations
- Ventricular assist devices (VADs) are mechanical pumps that are used to improve cardiac output in the setting of severe heart failure or cardiogenic shock. They work by unloading the ventricle and delivering blood flow directly to the aorta or pulmonary artery.
- As the number of heart transplants performed each year declines, more and more patients with cardiac failure are having VADs inserted as bridging therapy.
- As of 2015, there were two patients living in the Geelong region with VADs in place.
- The remote management of these patients is becoming easier and we are likely to see increasing numbers of Geelong residents and holidaymakers with these devices.
- The models being used in Victoria include the Heartmate II LVAS and the Heartware HVAD.
- Avoid chest compressions where possible as these can dislodge the grafts.
- Always liaise with the treating team when you encounter a patient with a VAD in place.
Essential reading
Community Management of Ventricular Assist Devices (VADs) (PDF)
Review article: Ventricular assist devices in the emergency department (PDF)
- Note that there is also a hard copy resource folder in Staff Base 4.
The anatomy of a ventricular assist device
- Each brand of ventricular assist device differs slightly but the overall configuration is the same, as shown.
- The pump.
The pump is grafted into the heart with both an inflow graft at the ventricle and an outflow graft at the aorta. These can be pulsatile or (more commonly) continuous and are usually a form of Archimedes screw or centrifugal pump.
- The controller.
The controller monitors the system and generates alarms when faults are detected. It ‘controls’ the speed at which the pump runs automatically, but pump settings cannot be programmed via the controller.
- The power source.
The system must be plugged into two power sources at all times. Generally this means two batteries however patients also have access to power modules running off wall power supply.
- The percutaneous line, also known as the ‘perc line’ or ‘drive line’.
The drive line is tunneled under the skin and connects the controller to the pump itself. It ‘drives’ the pump, therefore if the drive line is disconnected or damaged the ventricular assist device will stop altogether.
- Patients are instructed to carry spare batteries and a spare controller with them at all times.
How to check the pump is on
- When the pump is functioning it can be heard as a continuous humming sound on auscultation over the epigastric area.
How to measure the patient’s vital signs
- Patients with continuous flow VADs do not have pulsatile cardiac output, therefore they will have no palpable pulses and no detectable blood pressure at first glance.
- Pulse oximetry is also unreliable in these patients due to the lack of pulsatility.
- A handheld Doppler can be used to measure the mean arterial pressure, which should be kept between 70 and 85mmHg for optimal VAD function. Alternatively an arterial line can be inserted.
- If necessary, blood gas sampling can provide an accurate oxygen saturation.
- Always document the patient’s VAD parameters in your notes.
The importance of preload and afterload
- VADs are preload-dependent and afterload-sensitive.
- If the preload is too low or the afterload is too high then the pump output will be inadequate.
- Unlike a typical cardiac failure patient, a patient with a VAD generally needs to drink additional fluid (often 2-3L per day) to maintain adequate preload for effective pump function.
- Bedside echocardiography can be used to help differentiate issues of preload and afterload.
- a small RV suggests inadequate preload
- a small LV suggests suckdown
- a large RV and a small LV suggests RV failure or pulmonary hypertension
- a large RV and a large LV suggests pump thrombosis or obstruction
What to look for in these patients
- Infection
- Mandates early aggressive management of bacteraemia. High risk of endocarditis and mediastinitis.
- MANAGEMENT: treat for Staphyloccocus and Streptococcus +/- Pseudomonas; swab drive line exit site.
- Low flow
- CAUSES: dehydration; postural hypotension; right heart failure; arrhythmia; high afterload; aortic regurgitation.
- MANAGEMENT: increase venous return (ie. filling); reduce MAP (ie. diuretics, antihypertensives); consider fludrocortisone; reduce VAD speed; correct right heart failure (ie. inotropes, sildenafil, nitrous oxide).
- Suckdown
- Suckdown occurs when the inflow catheter sucks against the opposing ventricular wall resulting in ventricular collapse. It can result in low flow and arrhythmias.
- CAUSES: hypovolaemia; small ventricular size; right heart failure.
- MANAGEMENT: increase preload (ie. filling); reduce VAD speed.
- Thrombus
- Clot can form within the device itself or result in partial obstruction of the inflow or outflow catheters. It is associated with up to 50% mortality. Look for signs of peripheral embolisation and haemolysis. Check for spikes in power consumption.
- CAUSES: sepsis; low pump flows (eg. due to arrhythmia); subtherapeutic INR.
- MANAGEMENT: consider thrombolysis; discuss with treating team.
- Arrhythmias
- Arrhythmias are common (up to 50% of patients). Ventricular tachycardia and ventricular fibrillation can be well tolerated. Take your time.
- CAUSES: suckdown, mechanical irritation, migration, electrolyte disturbances.
- MANAGEMENT: amiodarone as first line therapy; can shock these patients if needed.
- Stroke
- Risk of stroke increases exponentially with mean arterial pressure >90mmHg, and these patients need aggressive blood pressure management.
- CAUSES: thromboembolism; uncontrolled hypertension.
- MANAGEMENT: activate stroke call (if appropriate); discuss with treating team.
- Right heart failure
- Check for evidence of a dilated right ventricle or right atrium on bedside echocardiography.
- MANAGEMENT: inotropes (eg. milrinone); sildenafil; nitrous oxide.
- Bleeding
- Higher rates of gastrointestinal bleeding are seen with continuous-flow VADs due to lower pulse pressures with resultant hypoperfusion of the bowel wall resulting in angiodysplasia.
- CAUSES: anticoagulation (eg. warfarin); acquired von Willebrand disease; gastrointestinal angiodysplasia.
- MANAGEMENT: anticoagulation can be withdrawn if needed.
How to get further advice
- VAD Coordinator / VAD Clinic Nurse (The Alfred)
mobile 0408 561 160
via switch (03) 9076 2000
- Nurse-in-charge of the Cardiac Unit (3CTC) (The Alfred)
phone (03) 9076 3635
via switch (03) 9076 2000
- Cardiology Registrar on call for heart failure (The Alfred)
via switch (03) 9076 2000
- Transplant Cardiologist on call (The Alfred)
*For urgent out of hours assistance only
via switch (03) 9076 2000
Manuals and documentation