– A look at Left Ventricular Assist Devices (LVADs) and how they may change your Patient Care, Assessment and Treatment Plan as a Prehospital Care Provider.
You may have come across one out on the road, or you may have never even heard of one. A Left Ventricular Assist Device (LVAD) is a mechanical pump that is implanted inside a person’s chest to help a poorly functioning heart to pump blood. The first implantation of such a device occurred back in 1984. LVADs are often named a ‘bridge to transplant’, in that they are used to give the heart a rest after open-heart surgery, or utilised for patients awaiting heart transplantation. LVADs may also be the definitive therapy for patients whose long-term condition prevents the opportunity for a total heart transplant. These devices are available in most heart transplant centres. The majority of patients with a Ventricular Assist Device (VAD) have an ejection fraction (the percentage of blood pumped from the left ventricle with each contraction) of less than 25%. A normal ejection fraction is 55–65%.
The intracorporeal LVAD is a pump that is surgically implanted inferiorly to the heart. Blood enters the LVAD through an inflow cannula placed within the left ventricle, which then passes through an impeller pump (a magnetically levitated rotor which can turn at speeds of >3000rpm to generate up to 10 litres per minute of blood flow), and then into the outflow graft into the ascending arch of the aorta. There is an external driveline cable that passes from the internal LVAD pump to the external controller device and power source (often passed through the patients epigastrium or right-upper quadrant). The external controller and batteries are found as part of an external unit on a belt or harness. Be extremely careful not to cut, twist or bend this wire; this is the patient’s ‘lifeline’!!
LVADs are often used for weeks to months, and patients with them fitted can be discharged from hospital with an acceptable quality of life, while waiting for a donor heart to become available. Patients’ lives depend on their LVADs working properly, therefore the device needs to be extremely reliable with thorough safety systems. The average time that a single LVAD battery lasts is 4-6 hours, therefore most external belts have a backup battery with a portable charger (some include USB and car cigarette lighter chargers for long journeys). A low battery will sound an alarm to prompt the change of batteries, and to put one on charge.
Here is an example of an LVAD controller showing the pump rotor RPM, the battery life, cardiac output and power usage. Alarms will be shown on this screen. Remember that the patient will be, or should be, the expert in their own device!
Serious problems with LVADs include situations of ACS and Dysrhythmia. Although the LVAD can maintain LV function, deficits in the right side of the heart can be very problematic. Hypovolaemia can lead to fluid drawn out of the LV in excess of the flow entering the LV; therefore if the speed of the pump remains the same, the ventricular walls will ultimately collapse on themselves. Luckily for prehospital care providers, LVADs are designed to deal with this situation by decreasing the rotor speed until flow has returned.
Assessing the VAD Patient & Device Troubleshooting
At the earliest opportunity, contact the local VAD co-ordination centre, or heart transplant centre, for assistance and/or to transfer the patient to their most appropriate destination. In the event that you are unable to get in touch with the emergency VAD co-ordinator, consult with your Trust on-call Medical Incident Commander (MIC), or find out if you can be connected with an on-call cardiologist.
* Always stabilise the patient prior to transport *
Arrhythmias – Treatment of arrhythmia is not too different to that of patients without a VAD. Consider IV amiodarone as a first-line agent for treatment of Ventricular Arrhythmia. Cardioversion/Defibrillation is best performed with an Anterior-Posterior placement of the pads. Some VADs, however, may be able to internally defibrillate (or an ICD may be fitted at the time of LVAD with documented VT/VF). Ventricular Tachycardia IS a major problem with an LVAD patient (as the RV will be subsequently affected, therefore reducing LV filling pressures) – Refractory VT is not such a problem in a patient with a BiVAD. Patients who go into VT/VF with an LVAD generally remain to be fully supported on the left side of their heart. Typically, these patients will not acutely crash, but they will feel horrible due to the decreased forward flow/preload, as a result of a lack of RV support.
Assessing the VAD Device – Auscultate the epigastrium/chest for a continuous noise (hum); this is the sound of the pump operating. Check the controller for 1) Battery Function 2) Flow 3) Power. Are all of the wires in tact? Are there any messages on the screen? Are there any fluctuations in Flow and/or Power?
Bleeding – One of the most common reasons for a VAD patient to present to EMS is a result of bleeding or pump rotor thrombosis. Reasons are multifactorial, considering the fact patients are often put on anti-coagulation/anti-platelet therapy to reduce risks of thromboembolic events. In addition to this, Patients often get an acquired von Willebrand deficiency due to the shear forces created by the VAD itself. Consider Tranexamic Acid ONLY after discussion with a VAD specialist/Trust MIC.
Blood Pressure – Due to diminished, and sometimes completely absent, peripheral pulses in continuous-flow VADs, NIBP is difficult to obtain (LVADs can be either pulsatile or continuous flow designs). With a manual blood pressure cuff, gradually reduce the cuff pressure until a constant brachial artery sound is heard; this approximates mean arterial pressure (MAP). Target MAP is 75-85 mmHg (* >90 mmHg higher risk of CVA).
Cardiac Arrest – ABCs are paramount for oxygenation, ventilation and fluid resuscitation. CPR should only be performed if absolutely necessary, keeping in mind that this might lead to damage of the VAD itself and significant internal haemorrhage. It is especially important to use the guidance of the VAD coordinator before initiating CPR. However, in a small retrospective case series, standard chest compressions in patients with LVADs did not cause cannula dislodgment or VAD damage in all of the study’s 8 patients; with 4 surviving with neurologically good outcomes. However, more research is necessary to determine the utility of chest compressions in the LVAD population (Shinar, Z. et al., 2014).
Infection – If you suspect infection, treatment is in no way different to that of normal protocols. However, ensure that the patient is transferred to the nearest VAD facility for more definitive treatment (i.e. VAD investigation/replacement).
Pulse Oximetry – This can be another barrier to normal assessment due to weak or absent pulses. It is most helpful in these case to assess the Patient’s mental status, warmth, colour, tone, lips and capillary bed refill.
Suction Events – With negative pressure in the left side of the heart (as a result of continuous rotor speed with decreased filling pressures), the left ventricle can collapse. This can be due to multiple reasons including: hypovolaemia, tamponade, arrhythmia and displacement of the inflow cannula. Treatment should begin with IV Fluids and early discussion with a VAD specialist.
Key Points in Conclusion
- ALWAYS contact the closest VAD coordinator or cardiac transplant centre at the earliest opportunity.
- ALWAYS listen to the VAD; auscultate and hear for an internal ‘hum’.
- A 12-Lead ECG can give you your physiological ‘heart rate’ and should be performed on all patients with VADs (However, note that LVADs are ECG Independent in their own function). Arrhythmia can affect LVAD function. New 12-Lead ECGs are used for comparison with previous traces.
- Many LVADs will not present with a carotid or femoral pulse. Patients will therefore have reduced, or non-existent pulse pressure. Mean Arterial Pressure (MAP) is therefore a key parameter. MAP is assessed with a Manual NIBP cuff, looking for a ’normal parameter’ of 75-85 mmHg.
- A decrease in pump power may be due to; Increased Blood Pressure, LVAD Thrombus, Dehydration/Bleeding and/or Tamponade.
- VADs are preload dependant (Consider this especially if thinking of administering Nitrates).
- It is possible for a patient to be in VT or VF while awake and talking, if the pump is working properly. If a patient requires antiarrythmics, defibrillation or synchronised cardioversion, these interventions can be performed as normal; Anterior/Posterior placement is acceptable. DO NOT stop the VAD prior to delivering a shock.
- Let the patient, or the patient’s carer, lead . They are the experts in their own devices.
- Be careful not to cut through the power cord of the pump when/if cutting through clothing!!
Remember that VAD patients often call for problems unrelated to their VAD, so do not get distracted from your usual approach to patient care.
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