ALWAYS ON EM, Season 1, Chapter 4: Pump it up!
Sarah Schettle, PA-C; Alexander Finch, MD; Venkatesh R Bellamkonda, MD
EPISODE LINK:
https://www.podbean.com/media/share/pb-65dn9-11b6ee3
OVERVIEW
LVAD is the acronym used for left ventricular assist devices. These are devices that serve to assist, not replace, the human heart functions – such as to augment the patient’s cardiac output. These devices support the left ventricular function. They involve both internal and external components: the pump, a controller, and batteries.
People who have advanced heart failure, such as New York Heart Failure Classifications IV, and have ejection fraction under 25%, or severely reduced cardiac index may qualify for an LVAD. The need for a temporary support with a balloon pump or Impella, or continuous inotropic medications may influence candidacy for these devices as well.
These devices are used as either:
- Destination Therapy (DT) – the LVAD is intended to be used for the life of the patient
- Bridge to Transplant (BTT) – the LVAD is being used to temporize the situation until a heart can be transplanted
Depending upon the specific device, there are key parameters that you may encounter:
- Power – measured in watts
- Flow – how much blood going across the device, rough estimate of cardiac output, measured in L/min (calculated, so can be erroneous)
- Speed – fixed, measured in RPMs
- PI – pulsatility index (HeartMate Devices only) – how much the native heart is contributing
- Waveform – unique to HeartWare devices
GENERAL CARE ISSUES
Pulses
The continuous flow of the device will not create a palpable pulse from the LVAD, however sometimes there can be some native heart function which creates pulsatility. Its more uncommon to feel a pulse than to not feel a pulse.
Doppler Blood Pressure
The lack of pulsatility can make the use of automated blood pressure cuffs inaccurate. Correlation of the mean arterial pressure (MAP= (systolic * 2 + diastolic)/3) from an automated blood pressure reading with a doppler pressure is recommended. Doppler pressure can be obtained by finding the best spot at the wrist or elbow to identify the sound of flow. Mark the area to be able to find it again. Inflate a manual cuff to find the point where the flow disappears. Continue for 20 or 30 mmHg more, and then slowly deflate, identify where the flow returns. Ideally this should be between 70 and 85 mm Hg – the goal for the majority of LVAD patients.
Buttons
There are only two or three buttons on a controller device, and none of them can harm the patient. These will help with accessing parameters, test alarms, etc, but safe to press.
Alarms
There are different categories of alarms. These are delineated similar to a traffic light:
Red Stop, and take action sooner rather than later
Yellow Take a pause, something that could be considered
Green Gives diagnostic information about the device, not likely to require immediate action
Common diagnostic testing:
- Chest Xray
- Echocardiogram
- Electrocardiogram
- Complete blood count
- Comprehensive metabolic panel
- Lactate dehydrogenase
- Prothrombin time / INR
- Magnesium
- AICD interrogation
- LVAD interrogation
Magnetic Resonance Imaging (MRI)
LVADs are not currently approved for MRI imaging. The future may hold a protocol for this, but nothing currently.
Prehospital Transport
Before transporting LVAD patients, bring backup equipment always, and consider bringing their skilled family member as they are often trained on the specific device.
Common Medications
Patients with LVAD are often prescribed anticoagulants, antihypertensives, antidysrhythmics, diuretics, electrolyte supplementation, and peptic ulcer disease prophylaxis.
Specific Devices
- Heartmate II – axial flow pump, initially approved for BTT 2008, DT 2010, not currently implanted
- Heartware – slightly different parameters, no longer approved; instead of PI, shows a waveform; two buttons, FDA has removed this device from the market
- Heartmate III – only one approved for use currently; three buttons
- With the Heartmate II and III devices, there are green arrows chasing each other on the controller when it is working correctly.
SPECIFIC SITUATIONS:
LVAD patient with bleeding
People with LVAD have several reasons they may bleed more than other people:
- Anticoagulant medications
- Mechanical trauma to clotting factors
- Acquired Von Willebrand Syndrome
- Predisposes to AVM formation
AVM formation is most commonly seen in the small bowel and large bowel.
Transfusions in these patients can increase the sensitization against a future donor organ and so if on the fence about a transfusion, consider holding off in BTT LVAD patients.
LVAD patient with clotting
These patients are at risk for clotting within the device itself or for having embolic syndromes such as stroke.
LVAD speed frequently drops below fixed mark
The devices are programmed with a slow speed setting which it can revert to in certain situations. These are often infrequent, however, if the device is frequently dropping down, there may be a situation where the LV wall or the septum can occlude the cannula creating a Suction Event. The slower speed can help the cannula to fall off the wall and restore flow. Echocardiography is helpful to diagnose this. The power may oscillate in this situation as well. Speed drops can also occur with arrythmias or significant fluid shifts (significant diuresis, significant blood loss).
LVAD power is elevated
The differential for this is broad and includes a few common situations, such as hypertension or hypervolemia – but can also be seen in situations of thrombosis of the pump or PE etc. LDH can be helpful in evaluating for LVAD thrombosis or hemolysis. 2.5 – 3 x the patient’s baseline is concerning for these diagnoses.
LVAD patients with arrhythmia
These patients can have very severe arrhythmias including life threatening rhythms like ventricular fibrillation but look quite okay because the device is maintaining a minimum level of flow. For this reason, keep arrhythmia on the differential even when the history of present illness may be inconsistent or not classic. Have a low threshold for AICD interrogation. The management of these arrhythmias is the same as in other scenarios but keep in mind the patient may be alert and may require sedation. However, hold off on performing chest compressions unless the patient’s LVAD is not working.
Death in patients with LVAD
Because the LVAD will be supporting left heart output, death is marked by respiratory failure, neurologic failure, right heart failure, etc. Keep in mind that the LVAD is an assist device so if there is no heart function at all underlying, then LVAD cannot serve as a life sustaining replacement for the heart.
The device will continue to pump blood until the blood clots off or the preload from the right heart drops. For this reason, will need to disconnect the cord from the controller. The controller device will alarm, but removing it from the environment and calling the specialty team for guidance on turning off the alarms is recommended.
LVAD patient with drive line infection
This can occur for many reasons but generally if the cord coming out of the patient’s torso is tugged or the dressing changes are not optimal, there can be risk of drive line infection. Look for foul smelling, or opaque colored drainage from the site. Take a culture from the drive line site before initiating antibiotic therapy. Consider ultrasound of the site to look for abscess, and blood cultures to evaluate for bacteremia.
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