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Anesthesia & Analgesia:
doi: 10.1213/ANE.0b013e3182a0082f
Cardiovascular Anesthesiology: Echo Didactics

Transesophageal Echocardiography Imaging of the Total Artificial Heart

Mizuguchi, K. Annette MD, PhD, MMSc*; Padera, Robert F. Jr MD, PhD; Kowalczyk, Anna MD*; Doran, Matthew N. MD*; Couper, Gregory S. MD; Fox, Amanda A. MD, MPH*

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From the Departments of *Anesthesiology, Perioperative and Pain Medicine and Pathology, and Division of Cardiac Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts.

Accepted for publication May 28, 2013.

Published ahead of print August 19, 2013

Funding: None.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site.

Reprints will not be available from the authors.

Address correspondence to K. Annette Mizuguchi, MD, PhD, MMSc, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02215. Address e-mail to amizuguchi@partners.org.

A 57-year-old man presented with end-stage biventricular heart failure secondary to an infiltrative cardiomyopathy. Despite aggressive medical therapy, his health was deteriorating, and he was scheduled for a total artificial heart (TAH) implantation.

The Total Artificial Heart (SynCardia, Inc., Tucson, AZ; formerly known as CardioWest) has been Food and Drug Administration-approved since 2004 for use as a bridge to transplant in heart transplant–eligible patients who have irreversible end-stage biventricular heart failure. In April 2012, the TAH was also approved for destination therapy. Because the left ventricular assist device implantation rate nearly doubled with the approval of the HeartMateII device (Thoratec Corp., Pleasanton, CA) for destination therapy,1 it is possible that the frequency of TAH implants will also rise. In this article, we review key features of the perioperative transesophageal echocardiographic (TEE) examination of patients being evaluated for or undergoing TAH implantation.

To best use TEE to evaluate TAH patients, one must first understand the basic design of the TAH (Fig. 1). The TAH is an orthotopic pneumatic biventricular, pulsatile device that consists of 2 artificial ventricles. The native cardiac ventricles and arterioventricular valves are removed before implantation. Each artificial ventricle has a 27 mm inflow and a 25 mm outflow Medtronic-Hall single tilting disk valve (Medtronic, Inc, Minneapolis, MN)2 mounted on the rigid housings of the 2 artificial ventricles of the TAH. The inflow valve is attached via an atrial connector to the preserved native tricuspid or mitral valve annulus, and the outflow valve is attached to a short outflow graft that replaces the proximal segment of the aorta or pulmonary artery. Each TAH ventricle is connected to a pneumatically driven pump via a 4-layer polyurethane diaphragm. These diaphragms are interposed between a housing assembly superiorly and a base assembly inferiorly. After implantation, excursion of the air diaphragm via the pump allows the ventricles to fill and eject, thus moving blood in and out of the ventricles. Typically, output flows are maintained at 7 to 8 L/min with a central venous pressure of <15 mm Hg.2,3

Figure 1
Figure 1
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TEE EXAMINATION BEFORE CARDIOPULMONARY BYPASS

As with patients undergoing ventricular assist device implantation, a comprehensive TEE examination is helpful for guiding successful device implantation.4 Preoperative cardiac imaging and evaluation of the patient’s clinical status help determine whether TAH versus biventricular assist device (BiVAD) implantation is most likely to be successful. Cardiac pathologies that favor TAH versus BiVAD implantation include severe cardiomyopathies that result in biventricular hypertrophy with small intraventricular chamber size, failed Fontan procedure, myocardial infarction with related ischemic cardiomyopathy resulting in intractable biventricular failure coupled with pathologies such as postinfarct ventricular septal defects, large left ventricular apical aneurysm, or left ventricular thrombus, and severe aortic valve pathology such as aortic regurgitation or mechanical aortic valve prosthesis.2

Intraoperative TEE should be used for the following: (1) confirm that the tip of the patient’s central venous catheter is not in the right atrium (RA), as entrapment of a central venous catheter within the right TAH inflow valve can result in fatal malfunction of the TAH5; (2) assess the interatrial septum for a patent foramen ovale or atrial septal defect that could result in shunting or systemic embolic events after TAH implant; (3) check for thrombi in the atria and atrial appendages so that thrombus can be removed on cardiopulmonary bypass (CPB) to prevent thromboembolic events; (4) identify the inferior vena cava to establish a baseline size so that it can be readily compared to diagnose postoperative kinking or compression that could limit blood flow into the TAH. Kinking of the vena cava may be imaged as narrowing of the vena cava at the RA–caval junction (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A571); and (5) locate the pulmonary veins and assess for any pulmonary vein anomalies that could limit inflow to the TAH. Viewing the pulmonary veins pre-CPB can also facilitate ready localization of the pulmonary veins after TAH implantation (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A571).

Since all 4 native cardiac valves will be removed, presence of significant valvular regurgitation or stenoses is not concerning for TAH placement and may actually be the reason the TAH was selected for the patient rather than a BiVAD.2

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TEE EXAMINATION AFTER CPB

While mechanical valve malfunction after TAH implantation is unlikely, TEE can be used to confirm that all 4 mechanical valves are opening and closing well (Fig. 2; Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A572). The Medtronic-Hall valves show a dominant central regurgitant jet originating from the central orifice and 1 or 2 less pronounced peripheral jets originating along the border of the disk that can be evaluated by color-flow Doppler (CFD).6 Flow velocities across the TAH valves are not expected to be significantly higher than those observed across native heart valves. Although valve malfunction will unlikely occur in the operating room, establishing baseline values for 2-dimensional, color, and Doppler flow characteristics may be helpful in diagnosing future valve malfunction caused by thrombus or pannus formation.

Figure 2
Figure 2
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For the “mitral” position, the midesophageal (ME) 2-chamber, 4-chamber, and long-axis views, and for the “tricuspid” position, ME 4-chamber and right ventricular (RV) inflow–outflow views can be used to interrogate prosthetic valve function. The “pulmonic” valve can be interrogated using the ME–RV inflow–outflow and ascending aortic short-axis views. The upper esophageal aortic short-axis view can also be used to assess the gradient across the pulmonic valve (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A572). Evaluation of the aortic valve can be challenging because transgastric windows are limited secondary to acoustic shadowing (dropout) of the device. Thus, obtaining an aortic prosthetic gradient may not be practical. However, the ME aortic valve short- and long-axis views can show qualitative disk motion and postprosthesis CFD acceleration.

Using TEE to assess adequate de-airing of the TAH when separating from CPB can be challenging. TAH air diaphragms that drive blood out of the ventricles can appear similar on TEE to air that typically accumulates at the left ventricular apex at the end of open heart surgery. Reverberation and ring artifacts generated from the TAH mechanical valves can also hinder imaging of the internal ventricular chambers7 (Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A572). Also, the fast TAH ejection rate (typically 130 beats/min) generates echo contrast created by the rapid closure of the Medtronic-Hall mechanical valve. This echo contrast proximal to the valve can give an echodense appearance similar to air on 2-dimensional echo. Thus, because of the challenges of directly visualizing air within the TAH’s artificial ventricles and the limited TEE windows (i.e., transgastric windows are not helpful), the post-CPB TEE evaluation of TAH de-airing primarily consists of repeated assessment for air bubbles in the atria and pulmonary veins as well as air bubbles exiting the device into the ascending aorta and the main pulmonary artery (Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A573). Note also that after TAH implantation there will be no meaningful electrocardiogram waveform to denote systole. Visualization of the upward motion of the ventricular air bladders using TEE can help determine when the TAH is ejecting. CFD can be used to confirm pulsatile ejection into the main pulmonary artery and the ascending aorta.

Furthermore, because the artificial ventricles are rigid in construction, cardiac tamponade in the classical sense of RV diastolic compression cannot occur. However, cardiac “tamponade” manifested by decreased device output can occur from compression or kinking of the vena cavae (inferior vena cava compression is more common than superior vena cava compression) and/or pulmonary veins (left pulmonary vein compression is more common than right).3,8 Kinking or compression of the cava or pulmonary veins can also occur when the device is implanted in a relatively smaller thorax. Caval compression by TEE may show narrowing or compression of the cava near the caval–RA junction, possible collapsed RA, turbulent flow on CFD distal to the stenotic region, and a pressure gradient across the stenotic region.9

Doppler interrogation of obstructed pulmonary veins shows a turbulent continuous flow pattern (loss of phasic pattern) with high-velocity systolic and/or diastolic jets.10,11 Rapid heart rates as seen in TAH patients can show a similar continuous flow pattern (Fig. 3).10,11 Although Obeid and Carlson11 note that peak velocities ≥1.1 m/s are associated with stenosed pulmonary veins (normal Doppler flow is laminar and triphasic with peak velocities of 0.4–0.7 m/s), peak velocities as high as 2 m/s may be acceptable in TAH patients as long as TAH flows are adequate. Thus, TEE findings need to be correlated with clinical findings. Postoperative identification of the left upper pulmonary vein (seen lateral to the left atrial appendage) may be difficult after the left atrial appendage is ligated during the procedure. In the ME 4-chamber view with the probe withdrawn slightly to the level of the main pulmonary artery, identification of the ligament of Marshall (“Coumadin ridge”) is possible and will help identify the left upper pulmonary vein. The left lower pulmonary vein can be visualized by tilting the TEE probe further to the patient’s left (Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A573). Potential limitations of using TEE to assess for kinking of the pulmonary veins are possible difficulties in visualizing all 4 pulmonary veins, inability to align the Doppler beam completely parallel with the axis of primary blood flow in the pulmonary veins, or visualization of only the ostial regions of each pulmonary vein.12 E

Figure 3
Figure 3
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Teaching Points

* Before total artificial heart (TAH) implantation, baseline examination of characteristics of the vena cava and pulmonary veins may be useful for enabling identification and evaluation of kinking or compression of these vessels after TAH implant.

* TAH air diaphragms that drive blood through the artificial ventricles appear similar to air in the ventricular chamber. Therefore, evaluation of de-airing relies on repeated assessment for air bubbles in the atria and pulmonary veins as well as air bubbles exiting the device into the ascending aorta and the main pulmonary artery.

* Diagnosis of caval compression after TAH implant may be aided by transesophageal echocardiographic identification of narrowing or compression of the cava near the caval–right atrium junction, possible collapsed right atrium, turbulent flow on color-flow Doppler distal to the stenotic region, as well as a pressure gradient between the stenotic region.

* Doppler interrogation of obstructed pulmonary veins show a turbulent continuous flow pattern (loss of phasic pattern) with high-velocity systolic and/or diastolic pulmonary vein flow velocities (≥1.1 m/s), and associated spectral broadening (turbulence).

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DISCLOSURES

Name: K. Annette Mizuguchi, MD, PhD, MMSc.

Contribution: This author helped prepare the manuscript, figures, and videos.

Attestation: K. Annette Mizuguchi approved the final manuscript.

Name: Robert F. Padera, Jr., MD, PhD.

Contribution: This author helped prepare the manuscript, figures, and videos.

Attestation: Robert Padera approved the final manuscript.

Name: Anna Kowalczyk, MD.

Contribution: This author helped prepare the manuscript, figures, and videos.

Attestation: Anna Kowalczyk approved the final manuscript.

Name: Matthew N. Doran, MD.

Contribution: This author helped prepare the manuscript, figures, and videos.

Attestation: Matthew N. Doran approved the final manuscript.

Name: Gregory S. Couper, MD.

Contribution: This author helped prepare the manuscript, figures, and videos.

Attestation: Gregory Couper approved the final manuscript.

Name: Amanda A. Fox, MD, MPH.

Contribution: This author helped prepare the manuscript, figures, and videos.

Attestation: Amanda Fox approved the final manuscript.

This manuscript was handled by: Martin J. London, MD.

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REFERENCES

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2. Copeland JG, Smith RG, Arabia FA, Nolan PE, Sethi GK, Tsau PH, McClellan D, Slepian MJ. Cardiac replacement with a total artificial heart as a bridge to transplantation. N Engl J Med. 2004;351:859–67

3. Arabia FA, Copeland JG, Pavie A, Smith RG. Implantation technique for the CardioWest total artificial heart. Ann Thorac Surg. 1999;68:698–704

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6. Flachskampf FA, O’Shea JP, Griffin BP, Guerrero L, Weyman AE, Thomas JD. Patterns of normal transvalvular regurgitation in mechanical valve prostheses. J Am Coll Cardiol. 1991;18:1493–8

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10. Smallhorn JF, Gow R, Freedom RM, Trusler GA, Olley P, Pacquet M, Gibbons J, Vlad P. Pulsed Doppler echocardiographic assessment of the pulmonary venous pathway after the Mustard or Senning procedure for transposition of the great arteries. Circulation. 1986;73:765–74

11. Obeid AI, Carlson RJ. Evaluation of pulmonary vein stenosis by transesophageal echocardiography. J Am Soc Echocardiogr. 1995;8:888–96

12. Jander N, Minners J, Arentz T, Görnandt L, Fürmaier R, Kalusche D, Neumann FJ. Transesophageal echocardiography in comparison with magnetic resonance imaging in the diagnosis of pulmonary vein stenosis after radiofrequency ablation therapy. J Am Soc Echocardiogr. 2005;18:654–9

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