CONTENTS
- Impella monitoring
- Hematology of Impella:
- Suction alarms
- RV failure in the context of LV Impella
- Complications
- Weaning off Impella
- Indications & contraindications
- Ecpella (ECMO + impella)
- Impella RP
[#1/5] laboratory monitoring
- [1] Complete blood count (anemia may reflect hemolysis or hemorrhage).
- [2] Hemolysis labs:
- Plasma-free hemoglobin is the best test for real-time identification of active hemolysis. Plasma-free hemoglobin >40 mg/dL warrants intervention. (35184086, 37607271)
- Many laboratory chemistry analyzers automatically measure the hemolysis index (to evaluate for artifactual hyperkalemia due to in vitro hemolysis). The hemolysis index correlates closely with plasma-free hemoglobin and may be used as a surrogate for plasma-free hemoglobin.
- Other hemolysis labs include lactate dehydrogenase, bilirubin, and haptoglobin. These are less useful for real-time evaluation of intravascular hemolysis. Haptoglobin has a slow turn-around time. Bilirubin and lactate dehydrogenase can be affected by numerous factors, so they often don't accurately reflect hemolysis.
- Some centers check hemolysis labs q6-12 hours, with other articles recommending daily monitoring. (35474971, 35184086)
- ⚠️ Many labs cannot distinguish between in vivo and in vitro hemolysis (due to laboratory artifacts). For example, plasma-free hemoglobin and hemolysis index are accurate indices of hemolysis – but don't prove whether it's occurring in the body or within the blood tube. When in doubt, repeat the laboratory draw.
- Related topics:
- [3] Evaluation of coagulation status:
- Monitor heparin infusion per institutional protocols.
- Follow platelet levels.
- [4] Perfusion indicators:
- Lactate.
- Renal function.
- Transaminase levels.
[#2/5] Foley catheter
- [1] Urine output may serve as a perfusion monitor (in the absence of acute kidney injury).
- [2] Hemolysis is suggested by pink/red urine. (37607271)
[#3/5] Impella console settings
Impella parameters
- Power level (P-level).
- Note: Don't drop below P2 (retrograde blood flow can occur). (35248330)
- Flow level (L/min).
Impella waveforms
- Green motor current:
- Measures the resistance to blood flow through the Impella over time.
- It should be pulsatile. A non-pulsatile motor current indicates that the Impella's inlet and outlet are on the same side of the aortic valve, or the patient's left ventricle isn't contracting.
- Red placement signal:
- Estimates the pressure near the Impella outlet.
- It should resemble an aortic pressure waveform.
- This isn't an accurate arterial pressure. Management of BP should be based on a separate arterial line or blood pressure cuff. (35248330)
- White LV pressure waveform:
- Estimates the pressure near the Impella inlet.
- It should resemble a left ventricular pressure waveform.
- (Only available in some Impellas that have Smart Assist).
[#4/5] POCUS to evaluate Impella position & cardiac function
confirm device position
- [1] Ideal depth from the aortic annulus (distance from the annulus to the Impella inlet at the “end of the railroad tracks”): (35184086)
- Impella CP or 5.0: 3 +/- 0.5 cm.
- Impella 5.5: 4.5 +/- 0.5 cm.
- [2] The catheter should bend away from the mitral apparatus (it has an intrinsic 30-degree bend) and avoid intracardiac structures. (35184086)
- [3] On Doppler ultrasonography, the motor will cause a broad mosaic color pattern. This pattern should be limited to the aortic side of the valve. (35184086)
- [4] If microbubbles are seen in the left ventricle, this suggests cavitation, which is causing hemolysis. (32240102) The differential diagnosis of left-sided microbubbles includes a right-to-left shunt causing microbubbles generated from intravenous infusions to enter the left-sided cardiac chambers.
- (Suboptimal location may cause hemolysis, valvular damage, and ventricular arrhythmias.)
additionally, evaluate for
- Valvular complications.
- Hemodynamic status (e.g., preload, RV function, LV function).
[#5/5] right heart catheter parameters & hemodynamics
filling pressures
- CVP:
- Ideally, it would be relatively low (target CVP <15 mm). (37345215)
- CVP >8-12 may indicate right ventricular decompensation (see PAPi below).
- Wedge pressure & PA diastolic:
- Reasonably high left-sided filling pressures are needed to avoid suction alarms. If the LV pressure waveform on the console shows normal systolic pressure but low diastolic pressures, this suggests inadequate Impella preload. However, decongestion is also desirable.
- Pulmonary capillary wedge pressure of ~10-15 mm could be reasonable, which may correlate roughly with a PA diastolic pressure of ~15-20 mm. (35474971)
- A dynamic PEEP test (lowering or increasing PEEP) may provide additional information about preload. (37495347)
perfusion indices
- Cardiac output (targeting a CI >2-2.2 L/min/m2 may often be reasonable). (35184086)
- SvO2 should remain >50-60% if it is measured. (35474971, 37345215)
PAPi (pulmonary artery pulsatility index) 📖
- PAPi = (PA systolic – PA diastolic)/CVP.
- Target PAPi >~1. (37345215)
- PAPi <1 implies significant RV failure.
- (RV failure in the context of LV Impella is discussed further below: ⚡️)
CPO (cardiac power index) 📖
- CPO = [(MAP-CVP)(CO)]/451
- Normal CPO is 0.8-1.1 Watts.
- Target CPO >~0.6 (37345215)
- CPO <0.6 Watts suggests the patient is undersupported.
Bp & afterload
- Target MAP >60 mm, but not excessively high.
- Pulsatility may reflect native LV function.
- Hypertension will decrease the pump flow rate of the Impella (it is afterload-sensitive). (35120198)
- Vasopressor doses should be limited to the minimal amount required to support perfusion.
- Excessive afterload should be addressed. 📖
numerous coagulation derangements occur
- Therapeutic anticoagulation:
- Heparin infusion is often used for the Impella (discussed above).
- Antiplatelet agents are often utilized after coronary stenting.
- Thrombocytopenia:
- The Impella may cause thrombocytopenia.
- This is especially problematic if there are numerous devices (e.g., Impella + CRRT).
- Acquired von Willebrand syndrome:
- Impella pump shearing and reduced pulsatile blood flow may reduce the levels of high molecular-weight von Willebrand factor multimers and factor VIII.
- This may be exacerbated by Impella malpositioning (e.g., malrotation towards the mitral valve). (37495347)
- Acquired von Willebrand syndrome occurs in most patients within one day of Impella insertion and resolves rapidly after Impella discontinuation. (35550692)
- DIC due to systemic illness can occur in some patients.
- Hepatic failure with depletion of factors II, V, VII, IX, and X may occur less frequently. (37495347)
- Plastic surface adherence may deplete factors XI and XII. (35550692) This causes PTT prolongation, without causing substantial clinical coagulopathy.
indications for anticoagulation
- Generally, systemic anticoagulation with heparin or an analogous anticoagulant is utilized (e.g., bivalirudin or argatroban for patients with HIT). Additional anticoagulation may be delivered via the purge solution (depending on local protocols).
- In severe bleeding or absolute contraindication to anticoagulation, anticoagulation can be held.
monitoring heparin anticoagulation in patients on mechanical cardiac support
- Discussed in the chapter on ECMO here: 📖
diagnosis
- Hemolysis labs in relationship to Impella are briefly discussed above: ⚡️
- The diagnosis of device-related hemolysis is discussed in the chapter on ECMO: 📖
causes of hemolysis
- Higher pump support levels (hemolysis correlates directly with P-level). (37495347)
- Suction events:
- Inadequate preload.
- Right ventricular dysfunction (PAPi <1.3 correlates with more hemolysis). (37495347)
- (Suction events are discussed further in the section above.)
- Impella misplacement (e.g., partial obstruction of the inlet or outlet). (35184086)
- Pump thrombosis (thrombus formation within the Impella).
- Obstruction to the purge flow (if this stops flowing, erythrocytes will be directly exposed to the motor).
consequences of hemolysis
- Acute kidney injury (free hemoglobin is toxic to the kidneys).
- Systemic vasoconstriction (hemoglobin scavenges nitric oxide).
- Thrombosis (hemolysis causes platelet activation and arterial thrombosis). (35550692)
management of hemolysis
- [1] Confirm correct placement using POCUS. ⚡️ Causes of hemolysis may include:
- Impingement of the inlet on cardiac structures (including malrotation of the Impella towards the mitral apparatus).
- The Impella is inserted too deep, so the aortic valve obstructs the outlet.
- [2] Reduce the level of Impella support if possible.
- If lower P-levels are tolerated, consider weaning off the Impella entirely.
- [3] Consider optimizing LV preload:
- Fluid administration.
- Treatment of RV failure (discussed below: ⚡️)
- [4] Consider pump thrombosis (may be suggested by elevated purge pressures, recent interruption in anticoagulation). Treatment requires replacing the Impella.
- [5] Consider if the patient's anatomy is inadequate for Impella support:
- A small left ventricular chamber size makes hemolysis more likely. One small study found that an angle <126 degrees between the aortic and mitral annulus in the apical 3-chamber view on transthoracic echocardiography predicts refractory hemolysis (figure below). (32410011)
- [6] Consider weaning off the Impella or transitioning to VA ECMO.
trigger of a suction alarm
- A suction alarm occurs when the calculated ventricular diastolic pressure is below -40 mm. (37607271)
causes of suction alarm may include
- Volume depletion (reduced LV end-diastolic pressure).
- Vasoplegia with impaired venous return.
- Right ventricular failure of any etiology (e.g., RVMI, PE) (discussed in the section below).
- Tamponade.
- Ventricular arrhythmias.
- Malpositioning of the Impella (with the inlet area obstructed).
- Excessively high pump speed.
- Aspiration of thrombus (may cause a motor current spike, followed by motor current instability and hemolysis). (35120198)
investigation
- Reduce device flow until the etiology of the suction event is identified and managed. (35120198)
- Evaluate the Impella console: (37607271)
- Deviation between the ventricular and aortic pressures in systole or continuously suggests Impella positional abnormality (including a continuous suction alarm).
- Deviation between the ventricular and aortic pressures in diastole (i.e., diastolic suction) suggests hypovolemia or inadequate preload.
- POCUS, if possible.
- Right heart catheterization parameters, if these are available.
physiology
- If a patient has underlying BiV failure, LV support may increase the RV preload and exacerbate RV failure.
clinical manifestations of RV dysfunction
- Suction alarms:
- RV dilation may compress the LV chamber.
- Reduced RV output may decrease the LV preload.
- Reduced cardiac output.
diagnosis of RV dysfunction
- Echocardiography:
- RV dilation.
- Reduced TAPSE (tricuspid annular plane systolic excursion).
- Systemic congestion (e.g., IVC dilation, VEXUS scan).
- Right heart catheterization data:
- PAPi <1.
- CVP >8-12 mm.
management of RV dysfunction may involve
- Fluid removal with diuresis/dialysis.
- Inotropes (e.g., epinephrine, milrinone).
- Reduction in Impella speed (if possible). In BiV failure, support of the LV can overwhelm the right ventricle and precipitate RV failure (with elevations in CVP).
- Inhaled pulmonary vasodilators.
- Avoid excessively high mean airway pressures among patients who are intubated.
- (More on the management of RV failure: 📖)
relationship of different devices & speeds to complications
- Impella 5 and 5.5 may reduce the risk of hemolysis but increase the risk of vascular complications.
- Faster Impella speed may decrease the risk of thrombosis while increasing the risk of hemolysis.
vascular complications
- Vascular complications occur in ~10% of patients, roughly half of whom may require vascular surgery. (37926367)
- Types:
- Access-site bleeding.
- Limb ischemia.
- Risk factors for vascular complications:
- Older age.
- Female sex.
- Obesity.
- Peripheral artery disease. (35550692)
hemolysis & acute kidney injury
- Discussed in the section above on hemolysis: ⚡️
other complications
- Valvular damage:
- Structural damage to the mitral or aortic valves.
- Functional regurgitation of the mitral or aortic valves.
- Ventricular arrhythmias (as high as 18%). (35184086)
- Thrombocytopenia & coagulopathy (discussed above: ⚡️).
- Line infection.
- Ischemic stroke.
There is no high-quality evidence on Impella weaning in cardiogenic shock. The following may be considered rough suggestions only.
optimal conditions for Impella weaning
- Recovery of the underlying problem that necessitated Impella insertion.
- The patient doesn't require high-dose inotropic support.
- Lactate level <2-3 mM.
- No signs of active cardiogenic pulmonary edema.
- Adequate hemodynamic parameters (discussed above: ⚡️)
approach to Impella weaning
- Flow rate may be decreased over several hours with ongoing clinical attention to the following parameters:
- Monitoring right heart catheterization parameters as discussed above.
- Urine output.
- Lactate level (should remain <3 mM).
- MAP.
- Absence of tachycardia or arrhythmia.
- No development of cardiogenic pulmonary edema.
- Adequate LV function on echocardiography.
- In some cases, it might be reasonable to up-titrate inotropic therapy somewhat to facilitate the removal of the Impella. (35474971)
- Once the patient is stable on P2, the Impella can be removed.
indications for LV Impella
- Cardiogenic shock (SCAI C-D stages). (39200728)
- SCAI B: Not ill enough to benefit.
- SCAI E: Impella may not provide sufficient support; consider VA ECMO.
- ECMO patients with LV distension (ECPELLA).
- High-risk PCI.
contraindications to Impella
- Unusually high bleeding risk:
- Uncontrolled coagulopathy.
- Inability to tolerate heparin anticoagulation.
- Biventricular failure may not be adequately supported by an LV Impella alone.
- LV thrombus.
- Ventricular septal defect (weak contraindication; there were concerns that Impella could worsen right-to-left shunting, but this doesn't seem to be a huge problem). (37926367)
- Aortic valve disease:
- Moderate to severe aortic regurgitation.
- Significant aortic stenosis (Impella 5 or 5.5 may provide higher flow rates than the native cardiac output, so insertion of Impella 5 or 5.5 may be feasible even if it essentially obstructs the valve). (37926367)
- Mechanical aortic valve.
- Hypertrophic obstructive cardiomyopathy.
- Aortic dissection.
- Tamponade.
- Severe peripheral arterial disease. (35184086, 35120198, 37926367)
DanGer Shock trial 🌊
- This was the first study to show the benefits of Impella (reduction in mortality at 180 days).
- STEMI patients in the SCAI C-E class were randomized to Impella CP versus standard care.
- Notable exclusion criteria:
- Post-cardiac arrest patients.
- Patients with right ventricular failure (RV larger than LV, TAPSE <1 cm, or septal shift).
- Shock duration >24 hours.
- Other causes of shock.
- Shock due to mechanical complications of MI.
- Severe aortic regurgitation or stenosis.
- Aspects that may have contributed to the success of the trial:
- Early Impella insertion (before reperfusion).
- Safe vascular access and closure techniques.
- Standardized weaning and removal protocols. (39200728)
- Impella may be utilized to decompress the left ventricle in the context of VA-ECMO.
- The systolic LV pressure may continuously be lower than the aortic pressure due to the left ventricle's inability to contract. This may mimic a malpositioned Impella (i.e., a continuous suction alarm). (37607271)
- In this context, Impella settings may be titrated primarily to achieve LV decompression (rather than against systemic cardiac output, which is largely provided by the ECMO circuit).
- ECMO is often weaned off first, with Impella subsequently weaned off. (35184086)
indications for Impella RP
- Right heart failure is an indication, but this is difficult to quantify.
- PAPi <0.9 may suggest a benefit from Impella RP. (35474971)
- Before placement of Impella RP, less invasive interventions to improve RV function should be trialed (e.g., pulmonary vasodilators). 📖
To keep this page small and fast, questions & discussion about this post can be found on another page here.
Guide to emoji hyperlinks
- = Link to online calculator.
- = Link to Medscape monograph about a drug.
- = Link to IBCC section about a drug.
- = Link to IBCC section covering that topic.
- = Link to FOAMed site with related information.
- 📄 = Link to open-access journal article.
- = Link to supplemental media.
References
- 32240102 Quevedo HC, Abi Rafeh N. Impella-Induced Left Ventricular Microbubbles, A Potential Sign for Hemolysis. J Invasive Cardiol. 2020 Apr;32(4):E101 [PubMed]
- 35120198 Wu IY, Wyrobek JA, Naka Y, Dickstein ML, Glance LG. Perioperative Management of Patients Receiving Short-term Mechanical Circulatory Support with the Transvalvular Heart Pump. Anesthesiology. 2022 May 1;136(5):829-842. doi: 10.1097/ALN.0000000000004124 [PubMed]
- 35184086 Papolos AI, Barnett CF, Tuli A, Vavilin I, Kenigsberg BB. Impella Management for the Cardiac Intensivist. ASAIO J. 2022 Jun 1;68(6):753-758. doi: 10.1097/MAT.0000000000001680 [PubMed]
- 35248330 Gottula AL, Shaw CR, Milligan J, Chuko J, Lauria M, Swiencki A, Bonomo J, Ahmad S, Hinckley WR, Gorder KL. Impella in Transport: Physiology, Mechanics, Complications, and Transport Considerations. Air Med J. 2022 Jan-Feb;41(1):114-127. doi: 10.1016/j.amj.2021.10.003 [PubMed]
- 35474971 Zein R, Patel C, Mercado-Alamo A, Schreiber T, Kaki A. A Review of the Impella Devices. Interv Cardiol. 2022 Apr 8;17:e05. doi: 10.15420/icr.2021.11 [PubMed]
- 35550692 Vandenbriele C, Arachchillage DJ, Frederiks P, Giustino G, Gorog DA, Gramegna M, Janssens S, Meyns B, Polzin A, Scandroglio M, Schrage B, Stone GW, Tavazzi G, Vanassche T, Vranckx P, Westermann D, Price S, Chieffo A. Anticoagulation for Percutaneous Ventricular Assist Device-Supported Cardiogenic Shock: JACC Review Topic of the Week. J Am Coll Cardiol. 2022 May 17;79(19):1949-1962. doi: 10.1016/j.jacc.2022.02.052 [PubMed]
- 37345215 Pietrasik A, Gąsecka A, Jasińska-Gniadzik K, Szwed P, Grygier M, Pawłowski T, Sacha J, Kochman J. Roadmap towards an institutional Impella programme for high-risk coronary interventions. ESC Heart Fail. 2023 Aug;10(4):2200-2213. doi: 10.1002/ehf2.14397 [PubMed]
- 37495347 Van Edom CJ, Gramegna M, Baldetti L, Beneduce A, Castelein T, Dauwe D, Frederiks P, Giustino G, Jacquemin M, Janssens SP, Panoulas VF, Pöss J, Rosenberg A, Schaubroeck HAI, Schrage B, Tavazzi G, Vanassche T, Vercaemst L, Vlasselaers D, Vranckx P, Belohlavek J, Gorog DA, Huber K, Mebazaa A, Meyns B, Pappalardo F, Scandroglio AM, Stone GW, Westermann D, Chieffo A, Price S, Vandenbriele C. Management of Bleeding and Hemolysis During Percutaneous Microaxial Flow Pump Support: A Practical Approach. JACC Cardiovasc Interv. 2023 Jul 24;16(14):1707-1720. doi: 10.1016/j.jcin.2023.05.043 [PubMed]
- 37607271 Balthazar T, Van Mieghem NM, Raes M, Van Loo I, Verbrugge FH. Short-term percutaneous mechanical circulatory support: no promise without positioning! Eur Heart J Acute Cardiovasc Care. 2023 Dec 21;12(12):869-877. doi: 10.1093/ehjacc/zuad097 [PubMed]
- 37926367 Saito S, Okubo S, Matsuoka T, Hirota S, Yokoyama S, Kanazawa Y, Takei Y, Tezuka M, Tsuchiya G, Konishi T, Shibasaki I, Ogata K, Fukuda H. Impella – Current issues and future expectations for the percutaneous, microaxial flow left ventricular assist device. J Cardiol. 2024 Apr;83(4):228-235. doi: 10.1016/j.jjcc.2023.10.008 [PubMed]
- 39200728 Masiero G, Arturi F, Panza A, Tarantini G. Mechanical Circulatory Support with Impella: Principles, Evidence, and Daily Practice. J Clin Med. 2024 Aug 6;13(16):4586. doi: 10.3390/jcm13164586 [PubMed]