the abcs of left ventricular assist device echocardiography - ehj

REVIEW PAPER

The ABCs of left ventricular assist deviceechocardiography: a systematic approachKhawaja A. Ammar1, Matt M. Umland1, Christopher Kramer1, Nasir Sulemanjee1,M. Fuad Jan1, Bijoy K. Khandheria1, James B. Seward2, and Timothy E. Paterick1*

1Aurora Cardiovascular Services, Aurora Sinai/Aurora St. Luke’s Medical Centers, University of Wisconsin School of Medicine and Public Health, 2801 W. Kinnickinnic RiverParkway, #845, Milwaukee, WI 53215, USA; and 2Professor Emeritus, Mayo Clinic, 200 1st St. Southwest, Rochester, MN 55905, USA

Received 9 February 2012; accepted after revision 3 April 2012; online publish-ahead-of-print 10 May 2012

Echocardiography is an important imaging modality used to determine the indication of left ventricular assist device (LVAD) implantation forpatients with advanced heart failure (HF) and for serial follow-up to make management decisions in patient care post-implant. Continuousaxial-flow LVAD therapy provides effective haemodynamic support for the failing left ventricle, improving both the clinical functional statusand quality of life. Echocardiographers must develop a systematic approach to echocardiographic assessment of LVAD implantation and post-LVAD implant cardiac morphology and physiology. This approach must include the evaluation of left and right heart chamber morphologyand physiology and the anatomy and physiology of the inflow and outflow cannulas and the rotor pump, and the determination of the degreeof tricuspid regurgitation and the presence of interatrial shunts and aortic regurgitation. Collaboration among the echocardiography and HF/transplant teams is essential to obtain this comprehensive evaluation. We outline a systematic approach to evaluating patients with HF whohave failed conventional therapy and require LVAD therapy as a bridge to cardiac transplantation or destination therapy.- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Keywords HeartMate 2 † Left ventricular assist device † Echocardiography pre- and post-implant † Bridge to transplantation

† Destination therapy

IntroductionHeart failure (HF) is a major cause of death, morbidity, and health-care expenditures in the USA, despite routine clinical use of scien-tifically proved therapies that reduce mortality and improve qualityof life.1 In patients unresponsive to aggressive HF therapy, a leftventricular assist device (LVAD) is an option to provide mechanicalcirculatory support as a bridge to cardiac transplantation or destin-ation therapy. LVAD therapy is effective in supporting cardiovascu-lar circulation for weeks to years.2– 5 The continuous axial-flowLVAD is designed to minimize the operative risk, improve durabil-ity, and lower the risk of device-related adverse events.6– 8 Con-tinuous axial-flow LVAD provides effective haemodynamicsupport for greater duration with both an improved clinical func-tional status and quality of life.9,10

Increased use of LVAD therapy for patients with HF has resultedin a knowledge gap for practising physicians treating such patients,and created a growing need for evaluation of how these devicesimpact cardiac morphology, physiology, and function. Echocardiog-raphy is the most important imaging modality for LVAD assess-ment pre- and post-implantation and for long-term follow-up.

It facilitates serial, non-invasive evaluations before and after im-plantation to document cardiac morphology and physiology,guide management decisions, and identify mechanical dysfunction.This review will identify a comprehensive approach for sonogra-phers and echocardiographers in their evaluation of patients forthe appropriateness and timing of LVAD implantation and post-LVAD implant evaluation using echocardiography.

New technology for cardiacanatomyThe HeartMate IIw, developed by Thoratec Corp. (Pleasanton, CA,USA), is a continuous axial-flow pump that consists of a propellerin a pump. The main advantage of this LVAD is that it can be easilyadjusted to run at low-flow/high-pressure and high-flow/low-pressure settings by changing the pitch on the propeller. Theparts of the HeartMate II are positioned in succession—spinneyrotor pump, inflow cannula, outflow cannula, and a single driveline that exits percutaneously towards the electronic control-ler—to act as the left ventricle (LV).7,8

* Corresponding author. Tel: +1 414 649 3909; Fax: +1 414 649 3278, Email: [email protected]

Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2012. For permissions please email: [email protected]

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The inflow cannula is inserted into the apex of the LV; theoutflow cannula is anastomosed to the right anterior aspect ofthe ascending aorta. The LVAD pump is placed within the periton-eal cavity. The percutaneous lead carries the electrical cable to anelectronic controller and battery pack that are worn on a beltand shoulder holster. The spinning of the rotor draws bloodfrom the inflow cannula through cardiac diastole and systole intothe ascending aorta (Figure 1).

Echocardiography caveats inpatients with left ventricularassist devices

Tips and tricksEchocardiographic assessment of patients undergoing LVADimplantation must include morphological and physiologicalparameters that delineate the benefits and risks of proceeding.This review will focus on specific imaging concerns pertainingto patients undergoing LVAD implantation. The four types ofechocardiographic LVAD evaluations are:

(i) pre-operative transthoracic echocardiography (TTE);(ii) perioperative transoesophageal echocardiography (TEE);(iii) post-operative echocardiography TEE/TTE;(iv) serial TTE, post-operatively.

Examining the heart structure and function pre-LVAD implant-ation has two main purposes: (i) to determine the suitability of

LVAD treatment for a patient with HF, and (ii) to identify cardiacabnormalities that could predict post-surgical complications. Spe-cifically, the pre-operative echocardiographic examination shouldinclude the assessment of the structure and function of the leftheart chambers, right ventricular (RV) function and degree of tri-cuspid regurgitation (TR), and presence of intracardiac clots,interatrial shunts, and degree of aortic regurgitation (AR).

Function of left heart chambersDuring pre-operative echocardiographic examination, identify LVchamber dimensions, diastolic and systolic functions, left atrial(LA) volume and pressure, mitral annulus dimension, tethering ofmitral valve leaflets secondary to geometrical changes of the LVand papillary muscles, and degree of mitral regurgitation.11–14 Thepersona of restrictive diastolic physiology is reflected by increasedLV and LA pressures and, when severe, supports the indicationfor LVAD implantation (Supplementary data online, Video S1).

Right ventricular function and degreeof tricuspid regurgitationThe RV is a complex structure and not completely visualized in anysingle echocardiographic imaging window. Several methods arecommonly applied to evaluate RV functions pre-LVAD implant-ation. First, imagers obtain semi-quantitative assessment of theRV dimensions/function using four-chamber and inflow views viaTTE. Additionally, the mid-oesophageal four-chamber and trans-gastric short- and long-axis views via TEE can be used. Thissemi-quantitative assessment is based on the usual appreciationof longitudinal and radial motions.15 Semiquantitation haslimitations.

Additionally, the RV systolic function can be measured byseveral alternative approaches. These include global fractionalarea change (FAC), tricuspid annular plane systolic excursion(TAPSE), tissue Doppler-derived lateral annular systolic velocity(S′), isovolumic acceleration, RV outflow tract (RVOT) fractionalshortening using M-mode echocardiography, and longitudinalstrain and strain rate.16,17 Commonly, FAC is used as a quantitativemeasure and represents a surrogate of the RV ejection fraction.

The calculation of RV FAC (Figure 2) is:

(RV diastolic area − RV systolic area) / RV diastolic area.

The RV diastolic and systolic areas are traced in the apical four-chamber view.18

RV FAC ≥ 40% is considered normal. A typical LVAD candidatehas an RV FAC between 20 and 30%. Patients with an RV FAC ,

20% are at risk for RV failure with the initiation of LVAD therapy.A more quantitative evaluation of RV myocardial performance is

the Tei index. The Tei index is reproducible, independent of ven-tricular geometry, and not significantly impacted by heart rate orblood pressure.16 Ventricular loading conditions do not appearto affect the index to a meaningful clinical extent.16 The Teiindex obtained by echocardiographic assessment is concordantwith invasive measures of systolic and diastolic function.19 The cal-culation for the Tei index using the tricuspid valve (TV) annular

Figure 1 HeartMate IIw (Thoratec Corp., Pleasanton, CA,USA): Volume-rendered dual-source computed tomographyimage in a 70-year-old man showing locations of the inflowcannula (red arrow), drive line (green arrow) and outflowcannula (blue). (Reproduced with permission from Carr CMet al. CT of left ventricular assist devices. RadioGraphics2010;30:429–44.)

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velocity (Figure 3) (where a is the TV opening to closure time and bis the ejection time) is:

Tei index = (a − b) / b.

A result ≤0.4 is normal. Limitations of the Tei index includepseudonormalization and the fact that it cannot be measured inpatients with first-degree atrioventricular block.

TAPSE is a methodology to measure the distance of systolic ex-cursion of the RV annular segment along its longitudinal plane from

a standard apical four-chamber view. As with other regional meth-odologies, it assumes that the displacement of the basal and adja-cent segments in the apical four-chamber view is representative ofthe function of the entire RV, an assumption that is not valid inmany disease states. A TAPSE cut-off value of ,17 mm yieldshigh specificity to distinguish abnormal from normal systolic func-tion (Figure 4).20

The RV S′ (systolic excursion velocity) is another measure of RVsystolic function that is easy to measure, reliable, and reproducible.To perform this measurement, an apical four-chamber window isused with a tissue Doppler mode region of interest highlighting

Figure 2 Measurement of right ventricular (RV) function: the RV fractional area change (RV FAC). Right ventricular diastolic (A) and systolic(B) areas traced in the apical four-chamber view facilitates calculation of RV FAC, which equals: (RV diastolic area – RV systolic area/RV diastolicarea). This measurement is a quantitative assessment of RV function.

Figure 3 Tei Index: a measurement of right ventricular (RV)function independent of loading conditions. Illustration demon-strating the calculation of the Tei index. (A), tricuspid valveopening to closure time; (B), ejection time; IVCT, interventricularcontraction time; IVRT, interventricular relaxation time; TVCO,tricuspid valve cardiac output.

Figure 4 Measurement of tricuspid annular plane systolicexcursion.

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the free wall. S′ , 10 cm/s is indicative of RV systolic dysfunction. Itis important to maintain the RV basal segment and keep theannulus aligned with the Doppler cursor to preclude measurementerrors (Figure 5).

Myocardial acceleration during isovolumic contraction is avail-able as a method to measure RV systolic function, but there arelimited normative data.21 Additional methods include RVOT frac-tional shortening using M-mode echocardiography17 and longitu-dinal strain and strain rate, but these techniques are evolving atthis time.

Functional TR is a common finding in patients with HF. Signifi-cant post-operative TR contributes to RV dysfunction and is a con-tributor to the development of a low output state. LVADimplantation has competing beneficial and adverse effects on theseverity of TR (Supplementary data online, Video S2).

Factors increasing TR are the following:

(i) Leftward shift of the interventricular septum (IVS);(ii) Decreased RV function post-LVAD implant; and(iii) LVAD function increasing RV preload to an already dysfunc-

tional RV.

The factor blunting TR is as follows:

(i) TR may be blunted or absent when the right atrial (RA) pres-sure is very high.

The following is a beneficial effect whereby TR is reduced:

(i) Unloading of the LV decreases TR and pulmonary arterypressure.

The competing beneficial and aggravating effects of LVADimplant have variable effects on different patients.18,22,23 The left-ward IVS shift is more pronounced in LVAD patients who arehypovolaemic, have reduced RV function, or significant TRpre-LVAD implant. Additionally, patients with elevated LVADflow will demonstrate an IVS shift culminating in a spiral ‘suctionevent’. This finding mandates decreasing the pump speed with a

resultant reduction of TR and improved RV function (Figure 6).An additional clinical caveat is recognition that the absence ofTR does not imply that the TV orifice is free from abnormality. Sig-nificant TV annular dilation represents a risk factor for post-LVADimplant TR.24

All these variables reinforce the importance of a meticulousexamination of RV size and function and TV pre-LVAD implant-ation. The mechanism of TR is extremely important to define.TR determined to be moderate or greater may require surgicalcorrection at the time of LVAD implantation.25

Intracardiac clotsThe risk of thrombosis formation is 9 to 16% in patients receivingan LVAD.26 Left heart chamber thrombosis increases the risk ofembolic events during cannulation. The axial LVAD impeller is asubstrate for thrombosis formation, which may precipitate cata-strophic pump malfunction in addition to common clinical compli-cations such as stroke, myocardial infarction and mesenteric, renal,and peripheral ischaemia. An apical thrombus is often located insmall pockets next to the inflow cannula orifice and IVS inferiorwall.27,28 Pre-operative and post-operative interrogations of theLV and the LA for the presence of thrombosis are essential. Intra-venous contrast injection increases the sensitivity and specificity ofdetecting an LV apical29 and LA appendage thrombus (Figure 7).The stitched-closed aortic valve creates a substrate for stasis ofblood flow, and becomes a potential site for clot formation (Sup-plementary data online, Video S3).

Interatrial shuntsIdentification of a patent foramen ovale (PFO) is clinically import-ant (pre- and post-cardiopulmonary bypass) prior to LVAD im-plantation. The prevalence of a PFO in the USA population is25%.30 The LVAD has important cardiopulmonary physiologicaleffects: unloading of the LV results in a decrease in LA pressure,and RA pressure is maintained or increased through increasedvenous return resulting from an increased systemic flow.31 Thosehaemodynamic results may elicit two detrimental consequencespost-LVAD implant: paradoxical embolization and hypoxaemia.Paradoxical embolism can result in immediate thrombosis with im-mediate or delayed LVAD malfunction. The development of severehypoxaemia may occur acutely upon activation of the LVAD,32,33

or several months post-LVAD implantation (Supplementary dataonline, Video S4).34

A meticulous search for a PFO must be performed during thepre-LVAD implant echocardiogram. The identification of a PFOmay be difficult in intubated or uncooperative patients and patientsin respiratory distress. Agitated saline and colour-flow DopplerTEE are highly sensitive and specific methods for identifying aPFO.35 The variable physiological status of the patient pre-LVADimplant can make the identification of a PFO elusive. The LA pres-sure may be greater than in the RA. This situation may result in aleft-to-right shunt; however, a bubble study may not demonstratethe shunt even with an appropriate Valsalva manoeuvre. In the caseof biventricular failure, the elevated biatrial pressure may reduce/eliminate any gradient and that may interfere with PFO detectionby colour-flow Doppler and agitated saline. The imaging teammust be aware of these variable physiological states (Figure 8).

Figure 5 Tissue Doppler of the tricuspid valve anomalies in apatient with normal right ventricular systolic function. Thearrow points to the tricuspid valve annular systolic velocity.


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Aortic regurgitationRecognition of pre- and post-operative AR is critical to the man-agement of patients with an LVAD (Supplementary data online,

Video S5). Managing AR at the time of an LVAD implantation is chal-lenging. The approach is variable depending on the severity of theAR and the experience of the institution. Options include: aortic

Figure 6 The ‘spiral suction’ event leading to significant tricuspid regurgitation (TR) and right ventricular (RV) failure. Patients with an ele-vated left ventricular (LV) assist device flow will demonstrate an interventricular septum shift and decreased LV volume, which culminates in aspiral ‘suction event’ (A). This ‘suction event’ leads to increased TR (green arrow) and depressed RV function (B). These findings mandate de-creasing the pump speed with a resultant reduction of TR and improved RV function. RA, right atrium; TV, tricuspid valve.

Figure 7 Identification of an inflow cannula clot. The apical four-chamber view on a transoesophageal echocardiogram demonstrates a clot(green arrow) on the inflow cannula (white arrow) (A). The inflow cannula (A) was explanted and the pannus and the clot were found(B). A clot inside the inflow cannula (C). The surgeon extracting the clot from the inflow cannula (D). LV, left ventricle.


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valve replacement with a bioprosthesis, aortic valve patching withpolytetrafluoroethylene, or primary closure. A simple coaptationstitch placed at the central portion of the main aortic cusps canbe performed through a small lateral aortotomy incision. Correc-tion of the AR is important because the regurgitation volumeincreases as the LVAD preload increases and causes secondaryup-regulation of the pump flow volume, resulting in increasedblood flow into the ascending aorta. The pump spirals to highlevels with the systemic flow decreasing. Thus, a ‘futile cycle’

Figure 8 Pre- and post-interatrial shunting. Pre-left ventricular assist device (LVAD) implantation, transoesophageal echocardiography (TEE)revealing no right-to-left shunt (A). Post-LVAD implantation, TEE demonstrating a right-to-left shunt (B). The patient, a 60-year-old man, under-went ablation for atrial fibrillation prior to an LVAD implant for treatment of heart failure. Ablation did not lead to recovery from heart failure.After the LVAD implant, the patient experienced oxygen desaturation as evidenced by the right-to-left atrium low-flow shunting (B). He thenunderwent surgery to close the atrial defect and regain normal oxygen saturation.

Table 1 Preoperative echocardiographic evaluationof the potential LVAD patient: ASSESS

LV and RV chamber dimensions

LV and RV systolic function

LA volume, mitral annulus dimension, geometry of the leaflets andpapillary muscles, and degree of MR

Diastolic function

Degree of TR, TV annulus dimension, and PASP

AV morphology degree of AR, and size of ascending aorta

Clots

Shunts

AR, aortic regurgitation; AV, aortic valve; LA, left atrial; LV, left ventricular; LVAD,left ventricular assist device; MR, mitral regurgitation; PASP, pulmonary arterysystolic pressure; RV, right ventricular; TR, tricuspid regurgitation; TV, tricuspidvalve.

Figure 9 Inflow cannula alignment. Apical four-chamber trans-oesophageal echocardiography demonstrating the correct align-ment of the inflow cannula (white arrow) in relationship to themitral valve. A perpendicular line (green) drawn from theinflow cannula should bisect the mitral valve leaflets. LA, leftatrium; LV, left ventricle; RV, right ventricle.


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occurs, resulting in a high pump flow, low stroke volume, andelevated LA and LV pressures (Table 1).

Post-surgical evaluationPost-surgical evaluation has two purposes: (i) to evaluate the surgicalresults of the LVAD implant, and (ii) to assess and troubleshoot post-operative haemodynamics. Specifically, the echocardiography teammust evaluate the de-airing, structure and function of left and rightheart chambers, degree of TR, presence of interatrial shunts, andinflow and outflow cannula placement.

The TEE operator must detect air bubbles in the immediatepost-LVAD implant period before the device is activated. The airbubbles are observed as white refractors (Supplementary dataonline, Video S6). Inspection should include the ascending and des-cending aorta using the mid-oesophageal aortic valve long-axis,mid-oesophageal ascending aorta long-axis, and descending aortashort- and long-axis views. The cannulas, as well as anastomoticsites, and the LV apex should be inspected (Figures 9 and 10; Sup-plementary data online, Video S7). This is extremely importantbecause air is lighter than blood and will migrate towards theanterior chest of the supine patient with preferential embolizationto the right coronary artery.36 This can result in RV ischaemia/in-farction, which can have a deleterious impact on LVAD functionsbecause of the decreased preload to the LV.

Function of left heart chambersLVAD activation should result in unloading of the LV and the LAwith a reduction in each chamber’s size.37 Slightly leftward inter-ventricular and interatrial septal positions indicate adequate LVand LA decompression (Figure 11). Lack of decompression post-LVAD implant with a rightward shift of the septum should raisethe possibilities of suboptimal LVAD support, abnormal devicefunction, or cannula obstruction. Alternatively, an extreme left-ward shift rouses the suspicion of excessive unloading due tohigh pump speed, significant TR, or RV dysfunction. Evidence ofspontaneous echocardiographic contrast in the LV or LA is asign of an LVAD malfunction (Supplementary data online, Video S8).

Right ventricular function and degreeof tricuspid regurgitationThe RV function and the degree of TR must be carefully evaluated.The post-bypass examination should follow the same protocolas the pre-LVAD examination. The examination must identifywhether RV assist device support will be necessary.

Interatrial shuntsThe haemodynamic changes associated with LVAD implants maysurface a detectable PFO in 20% of patients with no evidence ofa PFO on pre-implant echocardiographic examination.38 The

Figure 10 Parasternal long-axis view of the left ventricle demonstrating the inflow cannula at the apex (A). Demonstration of laminar flow inthe inflow cannula (B). An apical four-chamber three-dimensional (3D) transoesophageal echocardiogram demonstrating the inflow cannula atthe apex (C). A 3D zoomed view of the inflow cannula (D).


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decrease in the LA pressure associated with unloading the LV andthe maintained increased RA pressure can create a gradient thatproduces a shunt. The search for a PFO should occur while reco-vering from cardiopulmonary bypass because early detection leadsto re-institution of cardiopulmonary bypass and PFO closure. Thepost-implant TEE must include agitated saline administration.

Although rare in our experience, it is important to identify anyshunting across the IVS. Recently, we identified an apical ventricu-lar septal defect in a follow-up LVAD evaluation (Figure 12; Supple-mentary data online, Video S9).

Inflow cannulaInflow cannula orientation within the LV apex should be alignedwith the mitral valve opening (Figure 9). Doppler assessmentshould be performed in the mid-oesophageal four-chamber viewto evaluate deviation towards the IVS, and a two-chamber viewto evaluate antero posterior direction (Figure 13). A properlyaligned inflow cannula should have laminar flow from the ventricleto the device (Figure 14). Turbulence and elevated Doppler vel-ocity suggest obstruction of the inflow cannula (thrombus/

intermittent obstruction by LV wall; Figure 15).39 Pulsed-waveDoppler should reveal low velocity, laminar flow without regurgi-tation. Elevated velocities via continuous-wave Doppler shouldraise a suspicion of cannula obstruction, and regurgitation flow sug-gests an LVAD pump malfunction. The normal filling velocity isbetween 1 and 2 m/s depending on the preload and the intrinsicLV function.37,40 Acoustic shadowing on TTE may limit Doppler in-terrogation of the inflow cannula and require TEE to obtain valid,reliable velocities.

Outflow cannulaThe outflow cannula is best visualized in the high, long-axis view ofthe ascending aorta at the level of the right pulmonary artery. Theascending aorta should be interrogated for the presence of plaque,calcification, and dilation. The outflow cannula will be localizedmost commonly at the right anterolateral aspect of the ascendingaorta concordant with an end-to-side anastomosis. Computedtomography imaging is frequently used to assess for kinking ofthe outflow cannula (Figure 16).

Figure 11 Left ventricular assist device (LVAD) activation should result in the unloading of the left ventricle (LV) and the left atrium (LA) witha reduction in the chamber size. Panels A and B demonstrate a dilated LV and LA. LVAD activation results in slightly leftward interventricular andinteratrial septal positions and indicate adequate LV and LA decompression (C and D).


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Colour-flow and pulsed- and continuous-wave Doppler are usedto evaluate flow patterns of the outflow cannula. The pulsed-wavesample volume should be 1 cm proximal to the aortic anastomosis.Peak velocity usually ranges from 1 to 2 m/s with unidirectionaland slightly pulsatile flow (Figure 17).37,40 Flow patterns of the

outflow cannula are affected by the insertion angle of the cannulainto the native aorta.41 Acoustic shadowing may limit Doppler inter-rogation of the outflow cannula, resulting in a need for TEEevaluation.

Post-operative troubleshootingPost-operative haemodynamic instability should prompt a differen-tial thought process:28

† hypovolaemia;† acute RV dysfunction;† cardiac tamponade;† pulmonary embolism; and† LVAD malfunction, most commonly secondary to an impella

thrombosis.

Echocardiography allows for an immediate assessment and de-tection of the underlying aetiology of haemodynamic instability.Hypovolaemia should be considered when the RV and LV cavitiesare small. Acute RV dysfunction will manifest as a dilated, hypocon-tractile RV with significant functional TR, small LV, and intermittentinflow cannula obstruction by the collapsed LV (Figure 18). Cardiactamponade is an elusive diagnosis post-LVAD. The typical approachfor assessing interventricular independence is not possible. The op-erator must diligently search for subtle blood collections compres-sing a particular chamber as RA and LA tamponade can occur withsmall collections of blood. The RV tamponade may be the conse-quence of a loculated substernal thrombus (Figure 19).28 LVADdysfunction/thrombosis should be suspected when there is a com-bination of a rightward deviation of the IVS (reduced unloading ofthe LV), functional mitral regurgitation with annular dilation, aorticvalve opening each cardiac cycle, spontaneous contrast in the LAand/or LV, and regurgitant flow through both cannulas. Animpaired LVAD output allows the diastolic aortic pressure toexceed the LV diastolic pressure, resulting in a reverse flow from

Figure 12 Identification of a ventricular septal defect. Parasternal long-axis view of the inflow cannula (A) and the colour-flow jet from theright to left ventricle through the ventricular septum defect (B).

Figure 13 Alignment of the inflow cannula. Misalignment ofthe inflow cannula (yellow arrow) towards the interventricularseptum (red arrow). A perpendicular line (blue) drawn fromthe cannula should bisect the mitral valve (MV). The anglebetween the blue and green lines reflects the degree of misalign-ment. LA, left atrium; LV, left ventricle.


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the ascending aorta through the outflow and inflow cannulas. Theventricular septal motion is complex in LVAD patients anddepends on the electrical conduction system, LV and RV loadingconditions, and the ‘unloading’ capacity of the LVAD. The typicalfeatures of the ventricular septum when there is interventricularinterdependence (tamponade/constriction) are not present post-LVAD implantation. Neutral or slight leftward shift of the interven-tricular and interatrial septum is indicative of adequate LV and LAcompression. A rightward shift of the septum should raise the sus-picion of inadequate LV decompression and considerations includea device malfunction or inlet obstruction. Alternatively, a leftwardshift may indicate excessive decompression due to high pumprevolutions per minute, significant TR, or RV systolic dysfunction.Understanding the ventricular septal motion is crucial to LVAD as-sessment (Table 2).

Follow-up transthoracicechocardiographyThe two main purposes for follow-up TTE are: (i) comprehensiveroutine evaluation of optimal LVAD function, and (ii) assessment ofpotential aetiologies of recurrent HF. The critical variables to care-fully evaluate include the structure and function of left heart cham-bers and IVS position, RV function and TR, evaluation of inflow andoutflow cannula position and flow, degree of AR, status of aorticvalve opening, and LVAD setting in relationship to haemodynamicfindings.

Function of left heart chambersThe LV cavity at end-systole and end-diastole should remain stablewith a decreased dimension secondary to LV unloading.37

Figure 14 The inflow cannula Doppler profile. Doppler profile demonstrating a normal laminar flow in the inflow cannula. The normal vel-ocity range is 1 to 2 m/s. There is flow towards the cannula during systole as the cannula comes out of the left ventricular apex. The flow ispulsatile as the heart is still contracting. No minimal velocity. The maximum velocity should be ,2 m/s, otherwise suspect a problem.

Figure 15 The inflow cannula Doppler profile demonstrating an obstruction to the flow. Doppler profile demonstrating a turbulent flow inthe inflow cannula (A). The turbulent flow raises the concern of an obstruction. The clot (green arrow) on the inflow cannula (white arrow) wasidentified as causing the velocity to be 4 m/s (B). LV, left ventricle.


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Increased dimensions should alert the clinician to a possible mal-function. Alternatively, a leftward shift of the IVS, marked decreasein LV dimension, and enlarged RV should alert the clinician to

excessive decompression due to a high pump speed or suggest adeterioration in RV functions and increased TR. The LV ejectionfraction is not a valid measure of LV function because the LVAD

Figure 16 Cardiac computed tomography of the outflow cannula in a patient with a left ventricular assist device malfunction. The inflowcannula was functioning normally. The outflow cannula was not visualized on transthoracic or transoesophageal echocardiography. A computedtomography scan identified that the outflow cannula (yellow arrow) was not the cause of obstruction as no kinking was identified (A and B).

Figure 17 Location and Doppler profile of the outflow cannula. The outflow cannula inserted in the normal position of the ascending aorta(A). Colour-flow Doppler profile of the outflow cannula demonstrating laminar flow (B). Doppler profile with velocities reinforcing a normalflow pattern (C).


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promotes non-physiological LV unloading. To assess the LV func-tion, there must be temporary LVAD interruption. Under thesecircumstances, the LV ejection fraction, LV end-diastolic diameter,and ejection period divided by the ejection time can be measuredin an attempt to assess intrinsic LV function.42– 44 Assessment mustbe individualized to the patient’s haemodynamic status.

Right ventricular function and degreeof tricuspid regurgitationRV dysfunction can present months or years post-LVAD implant.Routine evaluation should include apical four-chamber, parasternal

short-axis at the level of aortic root and apex, parasternal RVinflow, and subcostal four-chamber views. Semi-quantitative as-sessment should be based on the visual appreciation of longitudinaland radial RV motions.15 Quantitative approaches using global RVFAC, TAPSE, S′, and the Tei index are advised. Mechanical para-meters will be part of future assessment. The estimation of TR isvisually estimated by colour-flow Doppler using the TR jet areaand RA areas on the same image, with the TR area/RA area(ratio) being quantitative. Also, the peak systolic TR velocity inend expiration is integrated into the estimation of the RV function.The RA pressure is estimated by the inferior vena cava diameterand its response to respiration (Figure 20).45

RV systolic pressure = 4 × (TR velocity)2 + RA pressure

Aortic regurgitationDuring normal LVAD function, the aortic valve is closed. Theretrograde aorta-to-LV gradient is high. This gradient makes theaortic valve susceptible to deterioration over time. The AR cancreate ‘futile cycles’ and ineffective LVAD function, as discussedpreviously. The estimation of the AR severity is essential. Themost commonly used methods are by colour-flow Doppler andthe vena contracta, measuring the width of the regurgitate jet atits origin relative to the dimension of the LV outflow tract in theparasternal long-axis view. To be quantitative, it is recommendedto use the proximal isovelocity surface area method when feasible.

Inflow and outflow cannula locationand flowThe inflow cannula should be aligned with the mitral valve openingand should not have any contact with the LV walls. Colour-flowDoppler should demonstrate laminar, unidirectional flow fromthe LV to the inflow cannula. Misalignment can lead to an obstruc-tion of the inlet flow at rest and with activities. The misalignmentcan lead to clinical symptoms. Post-LVAD placement, a patientexperienced syncope every time he coughed. Imaging with TEErevealed an obstruction to the flow at the level of the inletcannula; the cannula was misaligned and coughing caused the ob-struction to the inlet flow, causing ‘sucking down’ on the LVADfrom 9400 to 8000 rpm concomitant with the patient experiencingsyncope lasting 8 to 10 s (Supplementary data online, Video S10).Turbulent flow suggests an obstruction at the cannula and the

Figure 18 Right ventricular (RV) failure resulting in an inflowobstruction. A dilated RV with significant tricuspid regurgitationresulted in a collapsed left ventricle (LV) that obstructed theinflow cannula. RA, right atrium; TV, tricuspid valve.

Figure 19 A localized apical thrombus resulting in tamponade.Post-left ventricular assist device implantation there was haemo-dynamic compromise. An apical thrombus (green arrow) com-pressing the left ventricular (LV) cavity resulted in cardiactamponade. The clinical condition required surgical removal ofthe thrombus to restore normal haemodynamics. LA, leftatrium; RA, right atrium; RV, right ventricle.

Table 2 Perioperative echocardiographic analysis:TEE

Detection of air bubbles and de-airing prior to LVAD activation

Inspection of the ascending and descending aorta using amid-oesophageal aortic valve long-axis view, and long- andshort-axis views of the descending aorta

Evaluate the location of the cannulas, anastomotic sites and LV apex

LVAD flow and power interrogation

LV, left ventricular; LVAD, left ventricular assist device; TEE, transoesophagealechocardiography.


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regurgitant flow suggests a pump malfunction. Pulsed-waveDoppler assessment should reveal a laminar, low velocity flowno more than 2 m/s with no regurgitation. TTE interrogation canbe technically challenging. Optimal views are a high left parasternallong-axis view, demonstrating an end-to-side anastomosis of theoutflow cannula to the mid-ascending aorta, and right parasternalview with the patient lying on the right side, showing the long-axisview of the outflow cannula traversing from the pump towards the

ascending aorta. Colour-flow and pulsed- and continuous-waveDoppler are used to the evaluate flow patterns; the peak velocitiesin the outflow graft range from 1 to 2 m/s.27 The angle of insertionof the LVAD outflow cannula into the native aortiac can influenceflow patterns and velocities (Table 3).41

Extracorporeal membraneoxygenation and left ventricularassist devicesExtracorporeal membrane oxygenation (ECMO) is temporarysupport of the heart and lung functions by partial cardiopulmonarybypass in critically ill patients. It has a potential role as a bridge tocardiac transplantation, to recover from early graft failure post-cardiac transplantation, and as a bridge to a bridge (ECMO toLVAD) in cardiac transplantation. ECMO may provide short-termhaemodynamic and oxygenation support to patients with severehaemodynamic instability, permitting recovery from multi-organinjury. It allows time to complete a transplant evaluation beforelong-term circulatory support with an implantable LVAD.46 Therole of ECMO must be individualized on a case-by-case basis inthis subset of patients.

Assessment of recurrent heartfailure associated with leftventricular assist devicedysfunctionLVAD malfunction can be broadly characterized into three maingroups: (i) low pump flow with increased power, (ii) low pumpflow with normal power, and (iii) high pump flow with lowcardiac output.

Figure 20 The calculation of the right ventricular systolic pressure. Doppler profile of a tricuspid regurgitant (TR) jet used to calculate theright ventricular systolic pressure (RVSP), which equals: 4 (TR velocity)2 + right atrial (RA) pressure (A). Subcostal assessment of the inferiorvena cava dimension and respiration variability used to estimate the RA pressure (B).

Table 3 Post-operative and follow-upechocardiographic examination: TTE

LV and RV chamber dimensions

LV and RV systolic function

LA volume, mitral annulus dimension, geometry of the leaflets andpapillary muscles, and degree of MR

Diastolic function

Degree of TR, TV annulus dimension, and PASP

AV morphology, assessing for the opening of the valve, degree of AR,and size of the ascending aorta

Evaluate for clots, particularly surrounding the inlet cannula

Shunts

Inflow cannula location, colour-flow pattern, and Doppler analysisassessing for laminar flow and normal velocities

Outflow cannula location, colour-flow pattern, and Doppler analysisassessing for laminar flow and normal velocities

Interventricular septal location and AV opening assessing the adequacyof the LVAD function

LVAD interrogation of flow and power

AR, aortic regurgitation; AV, aortic valve; LA, left atrial; LV, left ventricular; LVAD,left ventricular assist device; MR, mitral regurgitation; PASP, pulmonary arterysystolic pressure; RV, right ventricular; TR, tricuspid regurgitation; TTE,transthoracic echocardiography; TV, tricuspid valve.


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Low pump flow with increased powerThe differential for low pump flow with increased power includespump failure and an increased afterload.

Pump failure can be attributed to thrombosis and mechanicalmalfunction. Echocardiographic findings include a rightward devi-ation of the IVS, functional mitral regurgitation, aortic valveopening each cycle, spontaneous echocardiographic contrast inthe LV and/or LA, and regurgitant flow through both cannulas.Controller device interrogation will identify the LVAD settings.The differential is crucial as an LVAD thrombosis or malfunctionmay require urgent surgery for pump replacement.

When there is diminished or loss of Doppler signal in theoutflow cannula, the differential thought process should includean outflow cannula obstruction and increased afterload.27,28

Low pump flow with normal powerThe combination of a low pump flow with normal power is theresult of a reduced LVAD preload, which is encountered withRV failure, significant TR, or hypovolaemia. Additionally, oneshould consider an inflow cannula obstruction.

High pump flow with low cardiac outputCalculated total cardiac output less than an LVAD output shouldraise the suspicion of ‘futile cycles’. This could represent underlyingsignificant AR.

SummaryEchocardiography is essential to evaluate the need for an LVADimplantation in patients with advanced HF and to assess theLVAD performance post-implant. Standard echocardiographicimaging allows for optimal LVAD programming immediately post-implantation and during routine follow-up, and rapid and accurateidentification of mechanical or systemic malfunctions. All echocar-diography laboratories evaluating patients with an LVAD mustunderstand the ABCs of LVAD echocardiographic assessment.

Communication between the clinician providing patient care andthe echocardiology team is crucial in directing the focus of theechocardiographic evaluation.

Supplementary dataSupplementary data are available at European Heart Journal -Cardiovascular Imaging online.

AcknowledgementsThe authors gratefully acknowledge Barbara Danek, Joe Grundle,and Katie Klein of Aurora Cardiovascular Services for the editor-ial preparation of the manuscript, and Brian Miller and BrianSchurrer of Aurora Sinai Medical Center for their help in prepar-ing figures.

Conflict of interest: none declared.

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the abcs of left ventricular assist device echocardiography - ehj

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