Clinical Review

Troubleshooting the Left Ventricular Assist Device


 

References

Patient Responsibility

Following LVAD placement, patients are discharged from the hospital with extra batteries (usually four to six), a battery-charger station, a spare controller, and in certain models, a power base unit that can power the LVAD when they are at home and/or asleep. When patients are away from home, they should always have extra fully charged batteries, the spare controller, information about their device, and the complete names and contact information for their health care providers (ie, cardiologist, cardiothoracic surgeon, VAD coordinator) with them at all times.3,7,8

Patient Evaluation and Troubleshooting the Device

When a patient with an LVAD presents to the ED, regardless of reason or chief complaint, the emergency physician (EP) should begin assessing the patient while the unit secretary pages the patient’s LVAD coordinator and the hospital perfusionist. If the EP’s hospital does not routinely care for LVAD patients, an excellent resource is www.mylvad.com, which provides links to emergency medical service field guides for management of patients with all types of LVADs. The field guides provide step-by-step instructions for troubleshooting each type of LVAD, including instructions for replacing batteries and controllers.7,8

Perfusion and Mean Arterial Pressure
At presentation, the EP should evaluate the patient for signs of poor perfusion (eg, decreased mental status, pallor, cool skin) and, when indicated, provide a fluid bolus. Patients with an LVAD typically do not have palpable pulses due to the continuous flow of their devices.3-7 Therefore, a mean arterial pressure (MAP) using a Doppler and a manual BP cuff should be taken. The pressure at which the first sound is heard is used as the estimate of the MAP. The MAP for an LVAD patient generally should be between 70 and 90 mm Hg.3,4,7
Patients with an LVAD are afterload sensitive, and high BP must be addressed immediately to avoid morbidity. Elevated BP increases the work of the pump against increased peripheral resistance, which can lead to thrombus and stroke.7

Power and Connections
The EP should always check the controller to make sure the power light is on. Once this has been confirmed, she or he should auscultate over the patient’s chest and abdomen to detect the humming sound of the pump. If the pump is not powered or does not appear to be functioning, the controller should be replaced with the patient’s backup controller. Next, all connections to the power source and the connection between the driveline and the controller should be checked to confirm they are intact. After this has been completed, the connections should be disconnected and reconnected. Then the driveline should be evaluated for defects or damage.

Battery Assessment
While troubleshooting the LVAD for malfunction, the batteries on the device should be replaced with backup batteries or connected to the hospital’s power base unit (if one exists) or to the patient’s power base unit if it is present. If a battery replacement is required, before doing so, the patient should first be positioned flat on the stretcher or bed.7

Low-Flow Indicator
The EP should always check the controller to determine which alarms, if any, are flashing. Although the alarm buttons vary among the various LVAD devices, all types have a “low-flow” indicator. If the controller indicates low flow, the patient first should be given a fluid bolus. Patients with LVADs are preload dependent, and given their history of heart failure and fluid restriction, are often reluctant to maintain good fluid intake once an LVAD has been implanted.3,7
Another important etiology for a low-flow reading on the LVAD controller is pump thrombosis. Pump thrombosis should be considered when the MAP is low and the controller indicates a decreased pulsatility index and decreased flow. Often the RPMs (the speed) are increased as the controller attempts to adjust to the thrombosis with an increase in power. A bedside echocardiogram showing dilated right and left ventricles is consistent with a pump thrombosis. Treatment for pump thrombosis is anticoagulation with heparin or thrombolytics, and cardiothoracic surgery should be consulted.3

Suction Events
In addition to hypovolemia, another cause of hypotension is a “suction event” in which the left ventricle is not filling but the pump continues to attempt to pull blood from it and the walls of the ventricle suck in on themselves. Suction events can also be caused by cannula malposition, increased peripheral vascular resistance, and tamponade. A small left ventricle on bedside echocardiogram is consistent with a suction event. Often, the controller can sense this and will respond by slowing the pump speed and slowly bringing it back up to allow the ventricles to reaccumulate blood. Initial treatment consists of a fluid bolus and cardiothoracic surgery consultation.3,4

Next Article: