Written by Sage Whitmore, MD
Here are some key points and pearls to take away with regard to management of the critical Left Ventricular Assist Device (LVAD) patient after a recent related simulation case.
|Ventricular Fibrillation||Defibrillate Early, even with LVAD. The LVAD is helping the LV but not the RV, so shock can occur.
Other arrhythmias, like VT, A-fib, flutter, etc. Can usually be treated with antiarrhythmics and watchful waiting
Chest compressions are NOT indicated unless there is a lack of pulses AND no measurable BP with Doppler AND a lack of LVAD function (out of battery, not whirring on auscultation, no flow). If there is any flow from the LVAD or measurable BP, conduct a “chemical code” without compressions. Compressions may dislodge the device and lead to rapid exsanguination (debatable). Alternative to chest compressions are LUQ abdominal compressions (debatable)
|Hypotension||BP should be obtained by manual cuff and Doppler of the brachial pulse. The first whooshing sound you hear is the MAP. Normal MAP is 70-90.
The differential for shock in the LVAD patient is the same for anyone. More details below
HYPOVOLEMIC—bleeding, overdiuresis, GI losses
CARDIOGENIC—RV overload, tamponade, arrhythmia, pump thrombosis, hypertensive crisis. (PE is relatively uncommon)
Bedside echo and then formal echo are absolutely essential to differentiating shock type and figuring out whether to give volume vs. pressors vs. inotropes
|Pump thrombosis||In our recent LVAD simulation case, our patient had cardiogenic shock with LV > RV overload on bedside echo, meaning his LV was not being drained or assisted by the LVAD. In the context of a warm battery pack, high power, and high flow, this points to pump thrombosis. If the LVAD was working properly, we might have seen the RV > LV with septum bowed from Right to Left, indicative of RV overload (which is how most of these guys walk around).
The treatment is immediate heparinization and discussion with CT surgery. At our institution, they tend to emergently replace the VAD rather than use tPA to open the thrombus.
|Hemolysis||Hemolysis is a common problem leading to anemia and poor O2 delivery, and is common with pump thrombosis. Every VAD patient needs the following labs added on to the usual labs/coags:
– Plasma (free) hemoglobin
– Urine Hgb/Mgb
|Mesenteric Ischemia||In our simulation case, our patient was is in cardiogenic shock from LVAD failure and had an elevated lactate and vague abdominal pain, suggestive of Mesenteric Ischemia. His CTAP would show thickened bowel walls.
One must ALWAYS think about gut ischemia in the LVAD patient. This may be due to shock/hypoperfusion in general, venous outflow diminished from RV failure, or from pump thrombosis flicking clots out into the mesenteric circulation.
Common LVAD settings and problems
|Speed (RPM)||This is the only setting that is actually “set” by the LVAD team. They set the RPM in the OR under TEE guidance, looking for the magic RPM that drains the LV adequately without allowing the RV to bulge too much. The best RPM is where the septum sits nicely between the RV and LV.||Normal RPM is 6000-15000 for Heartmate II||This value does not change|
|Power||The POWER is the wattage needed by the LVAD to maintain its set RPM. This is a variable.||Normal Power is <10 watts. The patient/family and LVAD team are told to watch this number over time for rising/falling||Increasing power (14 watts in our case) tells you that the LVAD is trying to overcome resistance to maintain the set RPM; think of pump thrombosis or hypertensive crisis (too much afterload in the aorta).
Decreasing power tells you the afterload is reduced, as in distributive shock (sepsis) or aortic insufficiency
|Pulsatility Index (PI)||The PI tells you in general about the equilibrium between the native cardiac function and the device (how much the heart squeezes compared to how much blood the LVAD is moving).
If the LVAD had a low speed, not much flow, but the heart was squeezing well, there would be a HIGH PI.
If the LVAD has a high speed, high power, cranking away and moving a lot of blood, and the heart is sick and not contracting, there is a LOW PI
|Normal PI is 3.5-5.5.||A low PI (1.5 in our case) tells you the heart is either not contracting at all, is underfilled, or the pump is thrombosed. Need an echo to figure it out.|
|Flow||In liters/min, the FLOW is a CALCULATED product of RPM and POWER. This is not the actual output of the device or the patient’s cardiac output||Normal Flow can be 4, 6, 8 LPM, anywhere in there.||In pump thrombosis, the flow is FALSELY elevated (power is high)
In bleeding, hypovolemia, or cardiogenic shock, the flows can be low.
Useful Head-to-Toe DDX for the sick LVAD Patient
|Intracranial Hemorrhage||High MAP, High INR|
|Embolic Stroke||Pump Thrombosis|
|Pump Thrombosis||High Power, High Flow, Big LV with shock, Hemolysis
INR might be subtherapeutic
Start heparin and inotropes (Dopamine, Epi, or Levophed+Milrinone)
|RV overload||Progressive RV failure, fluid overload, RV infarct
Edema, JVD, Liver tenderness, ascites
Huge RV with R > L septal bowing and obliterated LV cavity
Start Norepinephrine, Milrinone, 100% O2, INO, do not intubate
Otherwise, Amio is the usual go-to
|Suction Event||Bleeding or Hypovolemic patient has underfilled LV cavity, –OR–
Huge RV overload has obliterated LV cavity
Sudden drop in all parameters: RPM, PI, Flow, Power
Give fluids or treat RV failure, depends on echo
Team may adjust the speed
Suction events often present with sudden/recurrent syncopal episodes, usually associated with tachydysrhythmias
|Tamponade||Recent placement or instrumentation|
|Aortic Insufficiency||New appearance of big LV, pulmonary edema, low afterload state, hypotension and shock. The LVAD is essentially recirculating blood without moving it forward. Start inotropes (dopamine, epi) to increase heart rate and contractility and limit time spent regurgitating during diastole|
|Hypertensive crisis||Patient’s MAP is much higher than usual
Risk for head bleeds
Increased afterload will limit the LVAD flow
Afterload reduction (Nicardipine, Nitroprusside)
|Hemorrhage||GI bleed, retroperitoneal bleed, hypovolemic shock
Look for IVC variability on inspiration to know you can give fluids/blood
CAREFUL with transfusion—if patient is a potential heart transplant recipient, run the Hgb low and use Irradiated or Leuko-Reduced blood to reduce the chances of antibody formation
|Sepsis||Drive Line infection, Pocket infection, other typical sources|
|Mesenteric Ischemia||Maintain low index of suspicion. Fix hypotension. Think about scanning the belly|
|Limb Ischemia||Flickin’ clot|
|Hemolysis||Add those special labs|
Pratt et al. LVAD management in the ICU. Critical Care Medicine 2014
Higgins et al. LVAD Guidelines. Main Medical Center 2010.
MyLVAD.com, EMS Field Guide, 2012