Hardware for the Heart: The Increasing Impact of Pacemakers, ICDs, and LVADs

There are fewer adverse events overall with the continuous-flow LVADs compared with the pulsatile-flow LVADs. The number of LVADs implanted each year continues to increase, and more than 95% of these are continuous-flow. As more and more advanced heart failure patients are receiving these devices, emergency physicians should have a basic familiarity with their function and their common complications.⁴

There are several manufacturers and types of continuous-flow LVADs, but they generally consist of a pump that is surgically implanted into the abdominal or chest cavity of the patient with an inflow cannula positioned in the left ventricle and an outflow cannula inserted into the ascending aorta. The device draws blood from the ventricle and directs it to the aorta. There is a driveline connected to the internal pump that exits the body through the abdominal or chest wall and connects to a system controller. The controller is usually housed in a garment worn by patients that also includes the external battery that powers the LVAD. The controller can also be powered by a base unit that can be plugged into an electrical outlet.⁵ Patients with continuous-flow LVADs are anticoagulated with warfarin with a target international normalized ratio (INR) of 1.5 to 2.5 and will usually be on an antiplatelet agent as well.²

LVAD patients are typically managed by a team of providers that includes a VAD coordinator; a cardiologist and/or a cardiothoracic surgeon; and a perfusionist, who should be notified as soon as the patient arrives in the ED. Patients understand that it is vital that their LVAD be powered at all times and will usually arrive in the ED with their charged backup batteries. If a power base is available in the hospital, the LVAD can be connected to it to save battery life. If power is interrupted to the LVAD, the pump will stop working. This can be fatal to patients with severe aortic insufficiency who have had their outflow tract surgically occluded and are therefore completely dependent on the LVAD.²

With continuous-flow LVADs, blood is pumped continuously, and a constant, machine-like murmur will be heard on auscultation rather than the typical heart sounds. LVAD patients may not have palpable arterial pulses, and in that case a doppler of the brachial artery and a manual blood pressure cuff are used to listen for the start of Korotkoff sounds as the cuff is released. The pressure at which the first sound is heard is used as an estimate of the mean arterial pressure (MAP). Left ventricular assist device patients should have a MAP between 70 and 90 mm Hg. An accurate pulse oximetry reading may not be attainable, and some centers use cerebral oximetry to obtain oxygenation status.²

The EP should examine all of the connections from the percutaneous lead to the controller and from the controller to the batteries to ensure that they are intact. The exit site for the percutaneous lead should also be examined for evidence of trauma and signs of infection. The exit site is a potential nidus for infection, and even minor trauma from a pull or tug on the lead can damage the tissue and seed an infection. Emergency physicians should ask LVAD patients about any recent trauma to the driveline.^6,7

The ED evaluation for an LVAD patient should be focused toward the patient’s chief complaint, recognizing that often patients with LVADs presenting to the ED will have vague complaints of malaise or weakness that may represent a serious pathologic process. Infection, bleeding, thrombosis, and problems with volume status are common reasons for ED visits by LVAD patients.^3,5

Infection

In addition to infections in the lung, skin, and urinary tract, patients with LVADs are at risk for infectious complications relating to their device. Implantation of an LVAD involves a sternal incision, the creation of an internal pocket for the LVAD, and a driveline connecting the internal LVAD with an external power source. An infection in any one of these locations can lead to endocarditis, bacteremia, and sepsis.⁶

Driveline and/or pocket infections are very common, affecting up to 36% of patients with continuous-flow LVADs.⁸ The exit site for the driveline is an access point for the entry of pathogens, and can be the source of infections in the driveline or in the pump pocket. Pump pocket infections can also occur from exposure to pathogens during surgery or in the immediate postoperative period. In addition, the pump itself can become infected from similar sources, as well as from bacteremia or fungemia from infections in the urine, lung, or central catheters.⁶