LVAD Management in the GI Bleed Patient
A 62-year old male presents to your community ED with brisk bright red blood per rectum. He had a prostate biopsy 2 days prior as part of a work-up for an elevated PSA. He had a left ventricular assist device (LVAD) placed due to severe left ventricular dysfunction 6 months ago following a myocardial infarction. His bleeding started 6 hours ago and he estimates passing a liter of blood per rectum.
His Medications are Ramipril, Atorvastatin, ASA, Warfarin and Lasix.
While previously a bridge to cardiac transplant in hospitalized patients, LVADs are now increasingly used as a form a definitive therapy for advanced heart failure. These patients are best cared for at their LVAD center, but they may present to your ED so it is critical to have a basic understanding of their function and the issues that can arise when caring for these patients.
All LVADs function as a separate circuit, pumping blood from the left ventricle to the aorta. The pump is connected via a driveline externally through the skin to a controller which houses the electronics and monitors pump function. This is often connected to two battery packs holstered on the patient’s shoulders.
On exam, the patient is alert but looks very unwell. He is diaphoretic and pale. Vitals are T 36.4, O2 Sat 95%, RR 20. The nurse was unable to get a BP at triage. There are absent pulses both peripherally and at the carotid. Cap refill is 2 seconds. You are unable to auscultate heart sounds but a mechanical hum is heard. Chest is clear. Abdominal exam is benign. Digital rectal exam reveals copious bright red blood with clots.
How does an LVAD change your physical exam? How do you measure blood pressure?
Current generation LVADs use a propeller-type mechanism (technically called an impellar) creating constant non-pulsatile blood flow through the circuit. As such, these patients often lack palpable pulses and essentially live in a hemodynamically stable pseudo-PEA state. Heart sounds are usually absent. Instead, listen for a hum over the precordium to confirm the pump is working. An absent hum would be incredibly concerning as it suggests pump failure.
Automated BP cuffs, which rely on biphasic blood flow, can only detect a BP half of the time. In stable patients, use a manual sphygmomanometer and a doppler probe. If a pulsatile sound is heard on doppler, the blood pressure obtained represents systolic blood pressure. If a non-pulsatile constant “swoosh” is heard, this number represents MAP and should be between 70-90 mmHg. Unstable patients need an arterial line, which will have to be placed using ultrasound guidance, as there will be no pulse to guide you. In the meantime, look for other perfusion indicators such as capillary refill, mottling, extremity temperature and mental status. Oxygen saturation probes similarly rely on pulsatile blood flow and may also be unreliable, however if you do obtain a normal Oxygen saturation it is likely accurate.
The community ER physician has assessed the patient and started a 1 L normal saline bolus while awaiting uncross matched blood from the blood bank. She estimates a liter of blood loss per rectum over the last 30 minutes and calls for transfer to tertiary centre, which is a 1-hour flight away.
What can go wrong with the LVAD pump that might be complicating this patient’s presentation? Thrombosis
Like patients with mechanical valves, LVADs are at risk of thrombosis. The presentation varies quite widely from increased pump power consumption and pump overheating to pump failure, cardiogenic shock, and death. Thrombosis can also present as distal embolization causing stroke, limb or intestinal ischemia. The presence of pump thrombosis can be assessed by echocardiogram but will also be suggested by poor pump performance and increased power requirements. Treatment options include IV heparin and thrombolytics.
During hypovolemia or dysrhythmias, the negative pressure generated by the LVAD that pulls blood from the LV to the aorta can cause collapse of the LV wall. This causes decreased flow through the LVAD and decreased cardiac output. The LVAD controller can often detect these events and will attempt to decrease the pump speed to account for this. In the meantime, the treatment is to optimize preload and get an ECG to identify any possible dysrhythmias that could be decreased cardiac output (ie. Vtach, Vfib).
An absent hum on auscultation suggests pump failure. Whether due to pump thrombosis or other mechanical failure, these patients will likely present in cardiogenic shock and should be treated with inotropes and vasopressors as if there was no LVAD present.