INTRODUCTION — Temporary short- and intermediate-term mechanical circulatory support (MCS) devices may be used as an escalation strategy to manage cardiogenic shock or cardiorespiratory failure refractory to optimal medical therapy in settings such as failure to wean from cardiopulmonary bypass (CPB). These devices may also be used for temporary support during high-risk interventional cardiology and electrophysiology cases. This topic addresses the role of transesophageal echocardiography (TEE) to guide insertion and positioning of MCS device cannulae in these settings, as well as initial assessment of device function and patient response.
Indications for short-term MCS devices and management of patients receiving such support are addressed in a separate topic. (See "Short-term mechanical circulatory assist devices".)
Other topics address extracorporeal membrane oxygenation (ECMO). (See "The role of TEE in the management of extracorporeal membrane oxygenation" and "Extracorporeal membrane oxygenation (ECMO) in adults".)
GENERAL CONSIDERATIONS — Selection of an MCS device depends on the specific indication for hemodynamic support, urgency of need, patient-related or device-related risks or contraindications, as well as variable availability and institutional experience with specific device(s) (table 1). General contraindications to all temporary MCS devices include uncontrolled sepsis, irreversible neurologic disease, contraindication to anticoagulation, or refusal by patient or proxy.
TEMPORARY SUPPORT FOR THE LEFT VENTRICLE
Overview of LV support — MCS for the left ventricle (LV) with an intra-aortic balloon pump (IABP), temporary axillary flow device (Impella), temporary percutaneous axillary-femoral artery system (TandemHeart), or similar devices may be initiated in various settings, most commonly [1,2]:
●Low cardiac output (CO) syndrome after cardiopulmonary bypass (CPB). Postcardiotomy cardiogenic shock occurs in 0.2 to 6.0 percent of patients after cardiac surgery with CPB, with inability to maintain oxygenation, adequate CO, or end-organ perfusion [3,4]. Temporary MCS with IABP counterpulsation, percutaneous or implantable ventricular assist device (VAD), or, in some cases, extracorporeal membrane oxygenation (ECMO) may be employed to treat refractory ventricular dysfunction with persistently low CO [3]. This may allow time for myocardial recovery [5]. Efficacy of short-term MCS for management of cardiogenic shock has been demonstrated in case reports and small clinical trials after cardiac surgery [6-8]. Less commonly, the MCS device has been inserted to serve as a bridge to urgent cardiac transplantation [5,8,9]. (See "Intraoperative problems after cardiopulmonary bypass", section on 'Cardiogenic shock'.)
●Refractory cardiogenic shock in the setting of acute myocardial infarction [10]. (See "Prognosis and treatment of cardiogenic shock complicating acute myocardial infarction", section on 'Other mechanical devices'.)
●Very high-risk percutaneous valvular or coronary interventions [11]. (See "Short-term mechanical circulatory assist devices", section on 'Indications'.)
●As a bridge to durable LV assist devices (LVAD) or heart transplantation. (See "Treatment of acute decompensated heart failure: Specific therapies", section on 'Mechanical cardiac support'.)
Theoretical advantages of initiating MCS in these settings include decreased myocardial oxygen consumption and improved LV unloading, with increased CO and coronary perfusion to provide an opportunity for myocardial recovery [12].
Echocardiography before initiating LV support — When immediately available, transesophageal echocardiography (TEE; or transthoracic echocardiography [TTE]) is often used to help assess the need for a MCS device to support the left or right ventricle, and to determine whether contraindications for use are present in an individual patient (table 1) [1,13]. However, use of echocardiography is not always necessary for emergency implantation of some temporary MCS devices. For example, IABP and percutaneous axial flow devices are often inserted in the cardiac catheterization suite using fluoroscopy to guide placement of cannulae.
Standard echocardiographic views are employed to assess for the presence of:
●Aortic regurgitation (AR), which limits the effectiveness of a temporary MCS device since a significant amount of the blood delivered to the aorta would be directly returned to the LV, resulting in LV distention and possibly pulmonary edema if left atrial (LA) pressures are persistently elevated. Notably, AR may occur intermittently, during diastole, or throughout the entire cardiac cycle in the case of continuous flow devices (even in the absence of LV ejection) [14]. Assessment of severity of AR is primarily based on the width of the color-flow Doppler (CFD) AR jet vena contracta or the ratio of vena contracta width to LV outflow tract (LVOT) diameter.
●Intracardiac shunting via an atrial septal defect (ASD), ventricular septal defect, or patent foramen ovale (PFO), which may worsen when blood is drawn from the LV with consequent exacerbation of right-to-left shunting. Recognition of the presence of an ASD or PFO may be facilitated by elevating right atrial pressure with a "Valsalva," maneuver, injection of agitated saline, or use of a lower setting of the Nyquist limit during TEE examination with CFD.
●Significant right ventricular (RV) dysfunction that may impair flow from RV to LV. In addition, increased venous return to the RV which occurs with effective LV mechanical support may precipitate acute RV distention and failure. In some cases, an RV support device is added to manage this.
●Left atrial or ventricular thrombi, which may become dislodged and embolize into the systemic circulation or into the MCS device and occlude the outflow cannula (figure 1).
●Aortic dissection, which creates a false lumen where a wire or catheter may be placed during attempts to insert device cannulae. This may result in extension of the dissection.
●Severe aortic disease indicated by large (>5 mm) or mobile atheroma on TEE, which may result in embolization to mesenteric vessels or peripheral arteries.
Echocardiography for specific LV support devices
Intra-aortic balloon pump
●Overview of IABP support – IABP counterpulsation is the most widely used temporary MCS device [15-17]. Approximately 15 to 30 percent of all IABP use occurs after cardiac surgery with CPB [18-24].
The balloon pump is positioned in the proximal descending aorta. Inflation of the balloon during diastole displaces blood toward the aortic root and into the coronary arteries, thereby augmenting diastolic blood pressure (BP) to increase coronary blood flow and improving coronary perfusion [16]. In addition, rapid deflation of the balloon during the systolic phase of the cardiac cycle (just prior to aortic valve opening) reduces LV afterload and LV end-diastolic pressure, thereby decreasing myocardial oxygen consumption and myocardial work through a reduction in the isovolumic phase of ventricular systole. Although IABP counterpulsation does not directly increase systemic blood flow, the resulting increase in myocardial performance typically increases CO by approximately 20 percent. Proper timing for inflation and deflation of the IABP balloon is shown in the figures (waveform 1 and figure 2). (See "Intraaortic balloon pump counterpulsation".)
●TEE imaging for peripheral cannulation to insert the IABP – An IABP is typically placed through a sheath in the femoral artery using a Seldinger technique [25]. Contraindications to insertion and use of an IABP include AR that is more than mild, aortic dissection or aneurysm, active bleeding, and severe peripheral arterial disease [15,16].
Echocardiography is not always used for initial IABP placement, but TEE guidance should be used in the OR when available. Final positioning of an IABP is confirmed as soon as possible after initial insertion with a chest radiograph. The IABP tip should lie between the anterior portion of the second intercostal space at the level of the carina at least 2 cm below the aortic arch (image 1) [26].
•TEE imaging prior to insertion – TEE is typically used in intubated patients immediately before IABP placement to evaluate for contraindications to the use of an IABP including moderate or severe AR, aortic dissection, and severe peripheral arterial disease or mobile atheroma in the descending aorta [27]. TEE views typically obtained include midesophageal (ME) aortic valve two dimensional and CFD short-axis (SAX) and long-axis (LAX) views, which allow assessment of the degree of AR or presence of aortic dissection. Pulse-wave interrogation of the proximal descending aorta will assess the presence of diastolic flow reversal with high grade AR. Imaging of the descending aorta SAX and LAX views may reveal grade III (>5 mm) or mobile atheroma increasing the risk of atheroma embolizing in the systemic circulation.
•TEE imaging during insertion – TEE is used during IABP placement to confirm positioning of the guidewire in the descending thoracic aorta using both LAX and SAX views. The IABP is then threaded over the guidewire, the wire removed, and the balloon is advanced until positioned 2 to 5 cm below the left subclavian artery and aortic arch. This is determined by identifying the descending aorta, then withdrawing the TEE probe until the aortic arch appears.
Before initiation of counterpulsation, proper position of the IABP is reconfirmed by identifying the tip of the IABP and making sure it is positioned below the takeoff of the left subclavian artery and aortic arch. Once filled with gas, the IABP balloon will create significant acoustic shadowing and reverberation artifacts during each diastolic inflation phase [25,27].
●Alternative cannulation sites for IABP insertion – In rare circumstances, an IABP may be placed via a graft directly into the aortic arch or the left axillary artery [28,29]. Such insertion sites may be selected in situations of severe peripheral vascular disease or after repair of an aortic dissection. TEE use for IABP placement after surgical repair of an aortic dissection facilitates confirmation of IABP position in the true lumen [30].
●Monitoring IABP support – After initiation of balloon assistance, expected changes in hemodynamic variables include increased CO and mean arterial pressure, with decreased systolic BP, increased (augmented) diastolic BP, reduced heart rate (HR), and decreased mean pulmonary artery wedge pressure (PAWP) [16]. TEE may be used to reassess ventricular function, alterations in the degree of AR, changes in previously identified atheroma locations, or presence of aortic dissection (which is rare after IABP placement) [31].
●Weaning IABP support – Weaning of support from an IABP is generally accomplished by monitoring hemodynamic variables and laboratory measures of adequate circulatory function and appropriate adjustment of inotropic and vasoactive medications while decreasing IABP support ratios from 1:1 to 1:2, then 1:3 prior to discontinuing support. Echocardiography is not a key component of weaning, but is often used to assess ventricular function as support is withdrawn.
Impella device for LV support
●Overview of Impella devices – Use of miniaturized-percutaneous axial flow LVADs such as the Impella device has become more common to treat postcardiotomy shock. These devices are also employed to manage high-risk percutaneous coronary interventions [11,12,15]. An Impella device may be used to support the left or right ventricle, or used in tandem to support both ventricles [7,32,33]. Occasionally, an Impella device is used for LV assistance during venoarterial ECMO to reduce distention of the LV caused by AR [34]. (See "Short-term mechanical circulatory assist devices", section on 'Left ventricle to aorta' and 'Overview of RV support' below and 'Temporary biventricular support' below.)
Impella devices for LV support include the 2.5, CP (cardiac power), 5.0, 5.5, and LD (left direct) devices, which provide different levels of hemodynamic assistance. However, all require the same positioning across the aortic valve to achieve optimal effectiveness as blood is withdrawn from the LV cavity and expelled via the outflow port into the aortic root.
Versions of this device that generate blood flow of up to 2.5 L/minute are typically placed percutaneously through the femoral artery or via a surgically placed graft to the axillary artery, then across the aortic valve to be positioned in the LV (Impella Recover LP 2.5 (figure 3)). Larger percutaneous versions of the Impella device may generate flows up to 4.3 L/minute (Impella CP 3.5) or up to 5.0 L/minute (Impella Recover 5.0). The Impella 5.5 which can generate up to 6.0 L/minute is inserted via a graft attached to the ascending aorta or the axillary artery.
●TEE imaging for peripheral cannulation to insert an Impella device – Although Impella devices are usually placed with the use of fluoroscopy, supplemental information is often obtained from TEE imaging [1,35]. Successful bedside placement with TEE alone has been reported [36]. Comparison of placement with fluoroscopy versus placement with TEE alone revealed that placement was successful in all cases even though patients undergoing bedside placement with TEE alone had a higher rate of refractory hemodynamic collapse [36]. Notably, the time required for placement of an Impella device is longer than for an IABP or initiation of ECMO.
•TEE imaging prior to insertion – Preimplantation TEE is used to confirm the diagnosis and need for MCS, and to evaluate for contraindications which include severe aortic stenosis or severe AR, presence of a mechanical aortic valve, thrombus in the LV, aortic dissection, severe peripheral vascular disease, or the presence of an atrial or ventricular intracardiac shunt [27]. Relative contraindications include asymmetric septal hypertrophy or a myxomatous mitral valve.
TEE imaging from the ME level includes the 4 or 5 chamber view (4C/5C) as well as SAX and LAX views of the aortic valve, ascending aorta, and descending aorta. Transgastric (TG) views (deep TG 5 chamber or TG LAX) with CFD allow additional assessment of aortic stenosis or regurgitation.
•TEE imaging during insertion – During a femoral approach for Impella device insertion, TEE is used to confirm wire positioning within the aortic lumen of the descending thoracic aorta with no evidence of aortic dissection [1].
Both an SAX and LAX view of the descending aorta are imaged for accurate confirmation. The ME aortic valve LAX view is used to confirm guidewire passage through the aortic valve into the LV cavity, but not too deep into the cavity (to avoid arrhythmias). The tip of the wire should be directed towards the apex of the ventricle. After passage of the wire, competency of the aortic valve should be reassessed, as well as the degree of mitral regurgitation (MR) since this may increase if the wire distorts the mitral subvalvular apparatus.
The Impella device is then placed over the guidewire, through the aortic valve, and is positioned with the tip in the middle of the LV cavity. The distance from the aortic valve to the inlet should be approximately 3.5 cm for all Impella devices, with the exception of Impella 5.5 for which this distance should be 5 cm. Placement too far into the LV may result in the outlet port remaining in the LV and failure to improve systemic blood flow. Final positioning of the device should show it curving toward the apex of the LV and away from the mitral valve, with the outlet positioned distal to the aortic valve.
Immediately after Impella placement, a comprehensive TEE examination should be performed including CFD imaging to evaluate for proper ventricular assist device (VAD) flow into the inlet in the LV and from the outlet into the aorta. The TEE should confirm proper function of the mitral and aortic valves with no evidence of aortic or mitral valve perforation, significant aortic or mitral insufficiency, aortic dissection, or pericardial effusion [35]. Subsequently, device positioning is also checked with a chest radiograph (CXR).
●Monitoring Impella device function – During LV support with an Impella device, TEE imaging is used to ensure that proper positioning has been maintained, and to monitor for adequate device function [1]. A malpositioned Impella device will cause recirculation and ineffective circulatory support because the inlet and outlet ports are located on the same side of the aortic valve. This may result from either device positioning that is too far into the LV or migration outside the LV into the aorta [37].
●Weaning and removal of Impella support – Removal of the Impella device is considered in patients with evidence of hemodynamic and myocardial recovery, which include increased systemic arterial pulsatility and increased native CO with only low levels of inotropic, vasopressor, and device support, as well as end-organ recovery. After removal of an Impella device, performance of a complete echocardiographic examination with either TEE or TTE is accomplished to establish a new "baseline," of ventricular and valvular function. In particular, the aortic and mitral valves are re-evaluated to detect new or worsened aortic or mitral regurgitation that can occur due to direct damage from the device [27].
TandemHeart device for LV support
●Overview of TandemHeart system – The TandemHeart is a percutaneous LA-to-aorta LVAD with a centrifugal pump containing a spinning impeller (figure 4) [38-40]. The venous 21 Fr cannula is inserted into the LA by transseptal puncture, and the 15 to 19 Fr arterial cannula is inserted into the iliofemoral arterial system. Oxygenated blood is then withdrawn from the LA into a peripheral centrifugal pump and returned to the systemic circulation via the cannula in the iliofemoral artery. Flows of 3.5 to 4.0 L/minute can be generated. However, adequate function of the RV is critical in order to drive blood through the pulmonary system and achieve effective support. (See "Short-term mechanical circulatory assist devices", section on 'Left-atrium-to-aorta assist device'.)
●TEE imaging for peripheral cannulation and insertion of a TandemHeart device
•Venous cannula placement – The venous cannula of the TandemHeart is introduced into the femoral vein and guided into the LA via a transseptal puncture across the interatrial septum (IAS). This procedure is commonly performed with fluoroscopy, but TEE may be used to guide the initial transseptal puncture and subsequent cannula positioning [41].
The anatomy of the IAS must be visualized and understood by the echocardiographer [42]. The posterior border of the IAS consists of a fold of pericardium between the left and right atria. The superior border is the superior vena cava (SVC). The anterosuperior border is the non-coronary sinus of Valsalva, while the anterior border is the septal tricuspid annulus. At the anteroinferior border is the opening of the coronary sinus and the inferior vena cava (IVC) is at the inferior border.
An ME bicaval view is used to visualize guidewire placement from the femoral vein into the RA and SVC [43]. Then the guidewire is removed and replaced with a transseptal puncture needle which remains within the catheter tip. An ME RV inflow-outflow view or ME aortic valve short axis view (40 to 50°) will demonstrate the thinnest part of the IAS. Needle contact with the IAS will demonstrate "tenting," of the IAS, then penetration of the needle into the LA. A wire is placed through the puncture needle into the LA and directed into the left upper pulmonary vein. This may be visualized starting from a ME four chamber view and then rotating the omniplane angle to approximately 70°. A sheath and dilator are advanced into the LA after dilation of the hole in the IAS. The inflow cannula is then positioned such that all of its holes are visualized within the LA.
Complications occur in approximately 1 percent of transseptal punctures; these include the most common complication (creation of an iatrogenic ASD), as well as tamponade due to perforation of the atrium, pulmonary veins, or aortic root, which can be identified using TEE [44]. Stroke may also occur, but its incidence does not appear to be higher in those with a new ASD. By six months most iatrogenic ASDs have closed, although 7 percent remain at 12 months [45]. Transient ST elevation is another reported complication [46].
•Arterial cannula placement – After venous cannula placement, TEE is employed to assist with guidewire placement via the iliofemoral arterial system into the descending aorta, followed by introduction of the arterial cannula. However, TEE cannot be used to demonstrate the final placement of the TandemHeart arterial outflow cannula because its location is below the diaphragm within the descending aorta and beyond the limits of TEE imaging.
●Monitoring TandemHeart device function – Device flow is initiated in the centrifugal pump after placement of these cannulae. CFD should demonstrate flow into the cannula from the LA without entrainment of blood from the right atrium [43,47].
It is paramount to maintain LV ejection and aortic valve opening during support by the device in order to prevent LV blood stasis and formation of clot in the LV apex or in the aortic root.
●Weaning and removal of TandemHeart support – Similar to weaning from other MCS, removal of the TandemHeart device should be considered in patients who show signs of hemodynamic and myocardial recovery. These include increased systemic arterial pulsatility and native CO at low levels of inotropic, vasopressor, and device support, as well as end-organ recovery. Upon removal of the device, TTE or TEE may be employed to perform a complete echocardiographic examination in order to establish a new "baseline," of ventricular and valvular function.
CentriMag implantable device for LV support
●Overview of CentriMag device for LV support – The CentriMag is a continuous flow centrifugal blood pump with a console and motor, flow probe, and tubing which may be used to provide support with a variety of different cannulas or cannula configurations. Such devices may be selected for patients likely to need a longer duration of support than can be provided by IABP, Impella, or TandemHeart devices. The CentriMag VAD can generate flows up to 9.9 L/minute at 5500 rotations per minute, and is approved for left, right, or biventricular support for up to 30 days [48-50]. (See "Short-term mechanical circulatory assist devices", section on 'Nonpercutaneous centrifugal pumps'.)
Most commonly, the CentriMag is used to treat low CO syndrome after CPB or as a bridge to transplantation in patients who do not qualify for more durable ventricular devices. During cardiac surgery, the surgical median sternotomy allows direct access to the heart and great vessels for central cannulation.
●Imaging during CentriMag device placement for LV support – The LV inflow cannula of the CentriMag device is placed into the LA via a pulmonary vein (or a graft to a pulmonary vein) [51] or into the apex of the LV. The arterial outflow cannula may be placed directly into the ascending aorta or into a graft to the ascending aorta.
TEE is used just before initiation of CentriMag flow to guide removal of air that may be present in the LV, seen as hyperechoic white speckles. Air tends to accumulate in areas of the heart that are nondependent (more superior in a supine patient). Although several different TEE views should be obtained, air is typically best demonstrated in the ME views at the LV apex or along the interventricular septum [52]. Immediately after initiation of the CentriMag function, CFD is used to demonstrate blood inflow into the atrial cannula, as well as outflow exiting either the cannula or the graft into the ascending aorta. Outflow velocities are generally <2 m/second, although smaller aortic graft sizes may result in higher velocities [27].
●Monitoring CentriMag device function during LV support – The LV should appear decompressed on TEE imaging after flow is initiated. A shift of the interventricular septum and dilatation of the RV may indicate excessive LV unloading and RV dysfunction.
During ongoing CentriMag support, assessment with TEE is used to determine causes of inability to achieve adequate flows [53]. These include RV dysfunction, graft kinking, outflow obstruction, cardiac tamponade, hypovolemia, severe tricuspid regurgitation, and aortic dissection.
●Removal of CentriMag LV support – Removal of the cannulae used with the CentriMag LVAD is generally accomplished in the operating room (eg, electively after recovery of LV function, or urgently at the time of heart transplantation). TEE is used to assess ventricular function of the native heart after device removal or the donor heart after transplantation.
TEMPORARY SUPPORT FOR THE RIGHT VENTRICLE
Overview of RV support — MCS of the right ventricle (RV) in isolation or in addition to support of the left ventricle (LV) may be necessary due to (see "Short-term mechanical circulatory assist devices", section on 'Right ventricular assist devices'):
●Pressure overload resulting from advanced left-sided heart failure, pulmonary hypertension, or acute pulmonary embolus
●Volume overload resulting from right-sided valvular insufficiency or left-to-right shunts
●Decreased contractility in acute myocardial infarction or myocarditis
●RV failure after durable LV assist device (LVAD) placement
●Postcardiotomy shock following inadequate myocardial protection or heart transplantation
An RV assist device (RVAD) works by pumping blood from the inferior vena cava (IVC), superior vena cava (SVC), or right atrium (RA) to the pulmonary artery (PA), thereby bypassing the RV [54]. When optimal medical therapy is insufficient to treat RV failure (eg, inotropic agents [dobutamine, epinephrine, milrinone], optimization of volume status to ensure adequate filling while avoiding overdistension, maintenance of coronary perfusion pressure, and reduction of RV afterload with inhaled or intravenous pulmonary vasodilators), such support can unload the RV, ensure adequate LV preload, and optimize end-organ perfusion. (See "Intraoperative problems after cardiopulmonary bypass", section on 'Right ventricular dysfunction' and "Anesthesia for noncardiac surgery in patients with pulmonary hypertension or right heart failure", section on 'Hemodynamic management'.)
Echocardiography before initiating RV support — Transesophageal echocardiography (TEE) is used before initiation of RV MCS support in order to:
●Confirm the need for device placement
●Rule out the presence of abnormalities which may contraindicate device placement or interfere with device functioning. These include:
•Thrombi or other masses in the RA or PA that may impede cannula drainage or flow.
•Strictures or thrombi in the SVC or IVC that may preclude placement of the device or impede adequate venous drainage. The presence of a stricture in the cavae may be indicated by turbulent or flow acceleration with color-flow Doppler (CFD).
•An intracardiac shunt (eg, large patent foramen ovale [PFO], atrial septal defect [ASD]) that may result in significant left-to-right shunting when the RA is unloaded.
•Severe tricuspid valve (TV) or pulmonic valve (PV) stenosis.
•Tricuspid regurgitation (TR) or pulmonic regurgitation (PR). While TR is typically well-tolerated during RVAD support, the presence of more than mild PR may limit the efficacy of device outflow delivered to the PA.
•Presence of a mechanical TV or PV prosthetic valve.
•Presence of an IVC filter or congenital interruption of the IVC (rare) [55].
Echocardiography for specific RV support devices
Impella right percutaneous device — Percutaneous placement of MCS devices enables rapid deployment of RV support without the need for surgery.
●Overview – The Impella right percutaneous (RP) microaxial flow pump is placed via the femoral vein. The inflow port is positioned at the IVC cavoatrial junction, and the distal outflow (return) cannula opening located near the tip of the catheter which is positioned beyond the pulmonic valve (PV) within the main PA [56-58]. Thus, the microaxial pump positioned within the catheter is able to drain blood from the IVC and pump it into the PA.
The Impella RP Catheter can provide up to 5.0 L/min of flow. It can provide temporary RV support for up to 14 days in patients with a body surface area ≥1.5 m2.
●TEE imaging for peripheral cannulation – Placement of a percutaneous RV support device is typically achieved using both fluoroscopic and echocardiographic guidance [1,58].
TEE is used to confirm proper positioning of the inflow port of the Impella RP cannula at the inferior cavoatrial junction (modified midesophageal [ME] bicaval view to visualize the opening of the IVC into the RA) and the outflow cannula opening beyond the PV within the main PA (ME RV inflow-outflow view or upper esophageal [UE] aortic arch short-axis [SAX] view).
●Monitoring percutaneous RVAD function – TEE may be used to monitor the degree of RV unloading and troubleshoot device low flow during RV support [58]. Inadequate decompression in the presence of normal flows can occur due to:
•Migration of the distal tip of the device below the PV into the RV outflow tract. In this situation, the device should be advanced and repositioned under fluoroscopic or echocardiographic guidance.
•Presence of clot partially occluding the inflow or outflow cannulas.
•Hypovolemia.
•External compression of RV chambers by the accumulation of clot or pericardial effusion. Careful TEE examination in multiple views is necessary to rule out the presence of clot or blood in the pericardium since these effusions can be loculated.
●Weaning and removal of a percutaneous RVAD – Myocardial recovery can be evaluated with TEE during weaning of RV support in conjunction with monitoring hemodynamic values. The adequacy of RV function is also assessed after removal of the RVAD, and the possibility of iatrogenic tricuspid or pulmonic valve injury should be ruled out [59].
CentriMag implantable device for RV support
●Overview – Similar to use of the CentriMag for LV support (see 'CentriMag implantable device for LV support' above), this device may be used for RV support, typically when LVAD implantation is complicated by RV failure. Central cannulation is through a sternotomy or a left thoracotomy, with direct inflow cannula insertion into the RA, and outflow cannula insertion into the PA (either directly or through a graft attached to the main PA through which the device outflow cannula is passed) [60,61]. Alternatively, the cannulae can be inserted percutaneously via femoral venous cannulation.
●Echocardiography during CentriMag insertion
•Inflow cannula – The atrial inflow cannula is placed anteriorly at the level of the RA appendage for RV support and is best visualized in the ME modified bicaval view to note entry into the RA, as well as orientation and depth of device insertion. Both two dimensional imaging and CFD should be used. While spectral Doppler can be employed to measure blood flow velocities, there are no recognized velocity guidelines, thereby limiting the utility of Doppler measurements.
If the RA cannula is placed through percutaneous femoral venous cannulation, the presence of the guidewire should be confirmed advancing from the IVC into the RA, then the cannula should be observed advancing over the wire in the RA. Very rarely the RVAD inflow cannula may be placed in the RV; both the ME four chamber view and ME RV inflow-outflow view can be used to visualize the cannula in this configuration.
•Outflow cannula – The CentriMag outflow cannula is implanted at the level of the main PA for RV support. Visualization of this cannula can be achieved in the UE aortic arch SAX view , ME ascending aorta SAX view, or a modified ME RV inflow-outflow view. The cannula should not be abutting the PA walls and should not be directed unilaterally toward either the left or right PA to avoid preferential flow to one lung.
●Monitoring CentriMag function during RV support – During support, the most common causes of low flow include:
•Presence of clot partially occluding the inflow or outflow cannulas.
•Hypovolemia.
•External compression of right heart chambers due to accumulation of clot or blood in the pericardium. As with other devices, careful TEE examination in multiple views is necessary to rule out the possibility of loculated effusion(s).
●Removal of CentriMag RV support – Similar to removal of a CentriMag LVAD, removal of a CentriMag RVAD is generally accomplished in the operating room TEE is used to assess RV (and LV) function after removal.
TEMPORARY BIVENTRICULAR SUPPORT
●Overview of biventricular support – Presence of biventricular failure should prompt consideration of placement of biventricular MCS devices or initiation of venoarterial extracorporeal membrane oxygenation (ECMO) (table 2) (see "Extracorporeal membrane oxygenation (ECMO) in adults"). Biventricular support can be achieved through many configurations of MCS devices:
•Durable left ventricular (LV) assist device (LVAD) and a surgically implanted temporary right ventricular (RV) assist device (RVAD)
•Surgically implanted temporary RVAD and LVAD
•Percutaneous temporary support of both the LV with an Impella CP device and the RV with an Impella RP or PROTEK Duo cannula
Excessive flow from the RVAD can lead to a variety of pulmonary complications including pulmonary edema and hemoptysis caused by pulmonary circulation overload. On the other hand, inadequate RV mechanical support can lead to under filling of the MCS device on the left side, with reduced systemic output and inadequate end-organ perfusion. Therefore, proper balancing of right and left ventricular MCS is critical.
●Echocardiography for biventricular support – For biventricular support, echocardiographic monitoring is critical for managing VAD flows and balancing right and left circulations. Unique echocardiographic considerations for biventricular support include assessment of [53]:
•Position of the interventricular septum and interatrial septum. Ideally both septae are midline indicating a balanced circulation.
•Relative size of the LV and RV chambers.
•Degree of decompression of the LV and RV, noted by assessing the change in severity of mitral and/or tricuspid regurgitation, as well as the frequency of aortic valve and pulmonic valve opening with initiation of support.
SUMMARY AND RECOMMENDATIONS
●Transesophageal echocardiography (TEE) is useful before, during, and after mechanical circulatory support (MCS) for the left ventricle (LV) or right ventricle (RV) and may include assessment prior to implantation to confirm need and identify contraindications (table 1), guidance for initiation of flow, assessment of malfunction during device operation, and assessment of the patient’s response to the weaning process before and after device explanation. (See 'General considerations' above.)
●Uses of TEE for specific MCS devices for LV support include the following (see 'Echocardiography for specific LV support devices' above):
•Intra-aortic balloon pump (IABP) (see 'Intra-aortic balloon pump' above):
-Identify specific contraindications (eg, moderate or severe aortic regurgitation [AR], aortic dissection, severe peripheral arterial disease, mobile atheroma in descending aorta)
-Confirm positioning of the guide wire in the descending thoracic aorta 1 to 2 cm below the left subclavian artery
-Assess ventricular function, alterations in the degree of AR, changes in previously identified atheroma location, or presence of aortic dissection during IABP use
-Assess ventricular function after IABP removal
•Impella device (see 'Impella device for LV support' above):
-Identify specific absolute contraindications (severe AR or aortic stenosis [AS], presence of a mechanical aortic valve, thrombus in the LV, aortic dissection, severe peripheral vascular disease, presence of an atrial or ventricular intracardiac shunt) and relative contraindications (eg, asymmetric septal hypertrophy, myxomatous mitral valve).
-Confirm wire positioning within the aortic lumen of the descending aorta with no evidence of new aortic dissection during a femoral approach, then observe passage through the aortic valve into the LV cavity.
-Assess device positioning during insertion over the guidewire through the aortic valve with the tip in the middle of the LV cavity and the inflow port located 3.5 to 4.5 cm from the aortic valve annulus. Final positioning is with the device curving toward the apex of the LV and away from the mitral valve, with the outflow port positioned distal to the aortic valve.
-Evaluate proper device flow and functioning without significant AR or mitral regurgitation (MR), tethering of valve leaflets, aortic valve perforation, aortic dissection, or pericardial effusion.
-Reassess device positioning during Impella support (ie, not too far into the LV or migration outside the LV into the aorta causing inadequate function).
-Evaluate for new or worsened AR or MR after device removal.
•TandemHeart device (see 'TandemHeart device for LV support' above):
-Visualize the venous cannula of the TandemHeart placed via a wire introduced into the femoral vein and guided into the left artery (LA) via a transseptal puncture across the intra-atrial septum (although fluoroscopy is often used). Final positioning is with all inflow holes visualized within the LA.
Visualize guidewire placement into the descending aorta for introduction of the arterial cannula into the iliofemoral arterial system.
-Demonstrate blood flow into the arterial outflow cannula with color-flow Doppler (CFD) (although final placement of this arterial cannula cannot be visualized with TEE).
-Identify thrombus formation in the LV during support.
•CentriMag implantable device for LV support (see 'CentriMag implantable device for LV support' above):
-Guide removal of air during initiation of CentriMag flow and demonstrate blood inflow into the atrial cannula using CFD, as well as outflow exiting either the cannula or the graft into the ascending aorta immediately after placement.
-Demonstrate decompression of the LV after flow is initiated, without dilatation of the RV or shift of the interventricular septum (indicating RV dysfunction).
-Determine causes of inability to achieve adequate flows during ongoing LV support (eg, RV dysfunction, graft kinking, outflow obstruction, cardiac tamponade, hypovolemia, severe tricuspid regurgitation, aortic dissection).
-Assess function of the ventricles and identify the presence of new or worsened cardiac valve disease during weaning and after removal.
●TEE is used before initiation of RV MCS support to rule out the presence of lesions which may contraindicate device placement or interfere with device functioning. These include presence of thrombi or other masses in the right atrium (RA) or pulmonary artery (PA), strictures or thrombi in the inferior vena cava (IVC) or superior vena cava (SVC), intracardiac shunt, severe stenosis or regurgitation of the tricuspid valve (TV) or pulmonic valve (PV), mechanical TV or PV prosthesis, or an in situ IVC filter. (See 'Echocardiography before initiating RV support' above.)
●Uses of echocardiography for specific MCS devices for RV support include the following (see 'Echocardiography for specific RV support devices' above):
•Impella for RV support (see 'Impella right percutaneous device' above):
-Assess device positioning during insertion of an Impella RP cannula, with the inflow port positioned at the at the IVC cavoatrial junction and the outflow cannula opening is positioned beyond the PV within the main RA.
-Monitor the degree of RV unloading and troubleshoot device low flow during RV support.
-Evaluate myocardial recovery during weaning of RV support and adequacy of RV function after removal of the device.
•CentriMag for RV support (see 'CentriMag implantable device for RV support' above):
-Visualize CentriMag inflow cannula placement anteriorly at the level of the RA appendage, and outflow cannula placement at the level of the main PA.
-Determine causes of inability to achieve adequate flows (eg, presence of clot partially occluding the inflow or outflow cannulas, hypovolemia, external compression of the RV chamber).
●During biventricular support, TEE is used to evaluate position of the interatrial septum and interventricular septum (ideally both septae are midline indicating balanced circulation) and degree of decompression of the LV and RV. (See 'Temporary biventricular support' above.)
