Transesophageal Echocardiography (TEE)

Language quoted from Centers for Medicare and Medicaid Services (CMS), National Coverage Determinations (NCDs) and coverage provisions in interpretive manuals is italicized throughout the policy. NCDs and coverage provisions in interpretive manuals are not subject to the Local Coverage Determination (LCD) Review Process (42 CFR 405.860[b] and 42 CFR 426 [Subpart D]). In addition, an administrative law judge may not review an NCD. See Section 1869(f)(1)(A)(i) of the Social Security Act.

Unless otherwise specified, italicized text represents quotation from one or more of the following CMS sources:

Title XVIII of the Social Security Act (SSA):

Section 1862(a)(1)(A) excludes expenses incurred for items or services which are not reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member.

Section 1833(e) prohibits Medicare payment for any claim which lacks the necessary information to process the claim.

Section 1862(a)(7) of Title XVIII of the Social Security Act excludes routine physical examination, unless otherwise covered by statute.

Code of Federal Regulations:

42 CFR, Section 410.32, indicates that diagnostic tests may only be ordered by the treating physician (or other treating practitioner acting within the scope of his or her license and Medicare requirements) and the results must be used in the management of the patient.

42 CFR, Section 410.33c, describes qualifications required for non-physician practitioners used by an IDTF.

CMS Publications:

CMS Publication 100-02, Medicare Coverage Issues Manual, Chapter 15:

80 Requirements for Diagnostic X-Ray, Diagnostic Laboratory, and Other Diagnostic Tests

CMS Publication 100-04, Medicare Claims Processing Manual, Chapter 9:

100 General Billing Requirements

CMS Publication 100-04, Medicare Claims Processing Manual, Chapter 12:

30.4 Cardiovascular System (Codes 92950-93799)

CMS Internet-Only Manual (IOM), Publication 100-04, Medicare Claims Processing Manual, Chapter 13:

20 Payment conditions for radiology services

National CCI Manual, version 13.3, Chapter II: CCI editing for anesthesia services; accessible at http://www.cms.hhs.gov/NationalCorrectCodInitEd/

Abstract:

Transesophageal echocardiography (TEE) is ultrasonic examination of the heart performed by placing the transducer in the esophagus which allows different views of the heart than transthoracic echocardiography (TTE). TEE is particularly useful for posterior structures, such as the pulmonary veins, left atrium, and mitral valve and provides better visualization of the aortic root, valve and the ascending and descending aorta and arch.

TEE is frequently performed because TTE was not technically adequate. In addition, there are a number of medical conditions for which TEE is preferred over transthoracic echocardiography (see indications below). TEE is considered medically necessary when there is a reasonable expectation that it will both provide information not available with TTE or other less invasive forms of imaging and significantly contribute to management decisions regarding treatment of the patient.

In order to qualify as a valid echocardiographic service, the study must be done for an accepted clinical indication by a properly trained examiner and must include a permanent record of the findings, data sufficient to support the conclusions and an appropriate interpretation and written report.

This policy addresses the medically necessary and appropriate application of TEE. Transthoracic echocardiography (TTE) is the subject of a separate policy statement.

Indications:

Mitral valve disease:
TEE is indicated for the following:

1. When needed to assess the etiology of mitral regurgitation
2. When needed to assist in the decision making: mitral valve repair vs. replacement
    

Endocarditis:
TEE is indicated for the following:

1. When the suspicion of endocarditis is high (persistent febrile state, negative cultures, preexistent valvular pathology) and TTE does not document endocarditis. TEE may define small vegetative masses and more completely delineate local complications (e.g., ring abscesses, aneurysm, fistulae).
2. Re-evaluation in complex endocarditis;
3. Evaluation of bacteremia without known source;
4. Evaluation of suspected or actual prosthetic valve endocarditis otherwise obscured because of reverberations and other image artifacts related to mechanical or other non-native valves during TTE.

Valvular Prostheses (mechanical and bioprostheses): TEE is indicated in the evaluation of suspected prosthetic valve dysfunction when therapeutic decisions are critical and TTE is inconclusive and/or when the left atrium must be well-visualized. TEE is not routinely indicated in all patients with prosthetic valves.

Suspected Cardiac Thrombi and Emboli:
TEE is indicated for the following:

1. Evaluation of the left atrium and atrial appendage for clot, when clot is not visualized on TTE;
2. Evaluation for an ASD, patent foramen ovale or atrial septal aneurysm with clot; and
3. Evaluation of the mitral valve in patients with a history of emboli.

Cardiac/Pericardial Masses and Other Pericardial Disease:
TTE and TEE have comparable sensitivity in the assessment of right heart masses. Therefore, TEE is indicated for the following:

1. Visualization of left atrial masses when needed to provide therapeutic direction (cystic vs. solid, attachment, infiltration);
2. When cardiac mass lesions (including tumors on cardiac valves) are suspect and cannot be visualized on TTE, and TEE is needed for development of a management strategy;
3. To assess pericardial effusion when surface studies do not provide adequate information. "The risk of pericardiocentesis may be reduced by the use of echocardiographic guidance and monitoring of needle aspiration, particularly for loculated or small effusions." (ACC/AHA/ASE 2003 Guideline Update, pg. 39).

Aortic Pathological Conditions and Diseases of the Great Vessels:

1. TEE may be indicated when adequate visualization of the aortic root is not sufficient with TTE.
2. TEE may be indicated for identification of aortic dissection, aortic ulceration, atherosclerotic plaque, and mural thrombotic material.
3. TEE has a particularly high degree of sensitivity and specificity for aortic dissection. TEE is the technique that is indicated in examination of the entire aorta, especially in emergency situations.
4. Because descending thoracic aortic aneurysms are difficult to visualize using TTE, TEE is recommended for this condition.
5. Visualization of the superior vena cava and diagnosing various congenital and acquired abnormalities, such as vena caval thrombosis;
6. Visualization of the proximal inferior vena cava, vena caval dilation and detection of thrombosis or extension of tumors from the inferior vena cava to the right-heart chambers;
7. Visualization of all four pulmonary veins;
8. Evaluation of the heart and great vessels following blunt trauma to the chest (e.g., rupture or transsection of the aorta, acute dissection, hematoma, etc.)
9. When needed to assist in the decision making prior to aortic valve operative intervention.

Congenital Heart Disease:
TEE is indicated for the following:

1. Patients with congenital heart disease postoperatively where fibrosis, echo opaque patches and prostheses, inadequate penetration, and acoustical shadowing can result in incomplete TTE data;
2. Patients in which TTE is technically inadequate or anatomic definition is incomplete;
3. Patients in whom a more precise definition of atrial, outflow tract and proximal pulmonary vascular anomalies by TEE can be critical to management strategies;
4. To assess complications of congenital heart surgery, visualization of shunt flow across atrial-septal defects, guidance of clamshell device to close atrial-septal defects, diagnosis of cor triatriatum, and detection of pulmonary valve abnormalities.

Critically Ill Patients:
TEE is indicated for the following:

1. Management of the critically ill patient when TTE is otherwise contraindicated (e.g., chest or other major trauma) or inadequate (e.g., patient on a ventilator or with COPD, or in postoperative patients who are unable to be positioned for TTE);
2. Patients with persistent hypoxemia having suspected right-to-left shunt;
3. Patients with complications of myocardial infarction (ruptured septum, papillary muscle, or free wall);
4. Hemodynamically unstable patients in whom TTE images are suboptimal;
5. Evaluation of brain-dead patients being considered as cardiac donors;
6. Persistent unexplained fever when endocarditis or myocardial abscess is suspected and TTE is non-diagnostic.

Interventional and Surgical TEE:
TEE is indicated for the following:

1. Guidance during percutaneous cardiac interventions such as during the creation of shunts, placement of septation devices, valvuloplasty procedures, endomyocardial biopsy, electrophysiologic studies/procedures, placement of septal or atrial appendage occluders or during percutaneous valve replacement;
2. Intraoperative evaluation to assess prosthetic or repaired/reconstructed valve function, or the integrity/function of complex congenital heart repairs;
3. Intraoperative evaluation to assess the integrity of the cardiopulmonary circulation in patients during lung or heart-lung transplants; and
4. Intraoperative assessment for presence and/or severity of outflow tract obstruction or presence/repair of an intracardiac shunt;
5. Intraoperative assessment of wall motion abnormalities in the case of acute deterioration in the patient's status, once the chest has been closed;
6. Only TEE done for specific diagnostic purposes may be separately payable during intraoperative use (TEE used for monitoring purposes is not separately payable). The results of the test must be used in making management decisions on the patient's intraoperative treatment. A covered service must include a complete interpretation/report by the performing physician, and must be available if requested.

Doppler Color Flow Velocity Mapping:

1. Spectral Doppler echocardiography and Doppler color flow-velocity mapping may be necessary in addition to an echocardiogram when the examination could contribute significant information to the patient's condition or treatment plan. Typically, Doppler is indicated in the evaluation of some heart murmurs, valvular problems, shunts, suspected congenital heart disease, complications of myocardial infarction, or cardiomyopathy. Doppler should be medically necessary for the evaluation and management of the patient.
2. "Color/spectral Doppler may not be useful or appropriate in certain relatively small and well-defined patient populations when there is a recent comprehensive examination and the test is being ordered for re-evaluation of a limited problem." (ASE comment).
3. The use of the Doppler is inherent in the ultrasonic cardiac evaluation. However, if the test reports fail to document the use of this technique to assess these structures and function (e.g., measurement of valvular insufficiency or stenosis, myocardial diastolic function, etc. as described by the ASE), or if the medical records fail to document that the examination was "clinically necessary" (e.g., follow-up of pericardial effusion size) then the Doppler portion of the test may be considered medically unnecessary and denied.
   
   

3-Dimensional Echocardiography
When billed with TEE, it is indicated for:

1. The pre-operative planning of valve repair for multiple etiologies of mitral regurgitation;
2. Assessment of mitral stenosis and in the accurate calculation of mitral valve area;
3. Pre-operative planning for diagnosis and treatment of atrial septal defects;
4. Pre-operative and intraoperative planning for interventional cardiac procedures (e.g., transcatheter placement of occluders for atrial septal defects or patent foramen ovales, or paravalvular dehiscence or leaks;
5. Intraoperative mapping for atrial ablation procedures.
6. The evaluation of tricuspid valve disease.

While three-dimensional echocardiography may provide improved calculation of volume when compared to 2D echocardiography, its value in affecting clinical outcomes is not yet proven and it is therefore not medically necessary.

TEE is indicated for cardioversion in patients:

1. Requiring urgent (not emergent) cardioversion for whom extended pre-cardioversion anticoagulation is not desirable;
2. Who have had prior cardioembolic events thought to be related to intra-atrial thrombus;
3. For whom anticoagulation is contraindicated and for whom a decision about cardioversion will be influenced by TEE results;
4. For whom intra-atrial thrombus has been demonstrated in previous TEE. (ACC/AHA/ASE 2003 Guideline Update, pgs. 49-50)

Limitations:

Screening examinations to identify structural cardiac abnormalities in the absence of established diagnoses, signs or symptoms, are not considered reasonable and necessary.

TEE does not provide incremental information over that obtained by TTE in the serial assessment and management of pericardial pathology. Therefore, it will not be covered, unless there are loculated posterior effusions or adequate visualization of the pericardium is not possible by TTE.

In general, TTE provides accurate and serial noninvasive assessment of global and regional left ventricular function. Unless TTE is technically inadequate and clinical data is insufficient for a management decision, TEE will not be covered. Transthoracic echocardiographic assessment of left ventricular function is considered preferable to TEE in all other circumstances.

Intraoperative TEE is reimbursable to a qualified cardiologist, cardiac surgeon, anesthesiologist or other qualified physician but only when performed as a significant, separately identifiable diagnostic test, with a formal written report, and not for monitoring purposes. 

In aortic root dilation in Marfan Syndrome or other connective tissue syndromes, the ACC AHA/ASE 2003 Guideline Update recommends TTE over TEE as the first choice for examination. "TEE should only be used if the examination is incomplete or additional information is needed." (pg. 42.)

In most patients with valvular prostheses TTE provides diagnostic functional information and noninvasive serial follow-up. However, in some patients, acoustical shadowing can decrease data acquisition. If TTE provides adequate information for diagnosis and management, then TEE is not covered. The medical record should document any need for additional information.

In general, TTE can reliably diagnose or exclude evidence of potentially embolic material located in a ventricle. The TEE may complement TTE, particularly to assess for left atrial thrombus and patent foramen ovale or atrial septal aneurysm. The additional information that can be provided by TEE should be reasonably anticipated to be of therapeutic relevance before the patient is subjected to TEE, otherwise the TEE is not covered.

Training Requirements:

Medicare expects a satisfactory level of competence from providers who submit claims for services rendered for these services to be considered medically necessary. Tests performed by providers not meeting these levels of competence will be denied.

The acceptable levels of competence are outlined as follows:
a. For the technical portion, an acceptable level of competence is fulfilled when the image acquisition is obtained under any one of the following conditions:

1. The service is performed by a physician; or
2. The technical portion of the service is performed by a technician who is credentialed as either a Registered Diagnostic Cardiac Sonographer (RDCS) through the American Registry of Diagnostic Medical Sonographers or as a Registered Cardiac Sonographer (RCS) through the Cardiovascular Credentialing International; or
3. Any non-physician personnel used by an IDTF to perform tests must demonstrate the basic qualifications to perform the tests in question and have training and proficiency as evidenced by licensure or certification by the appropriate State health or education department. In the absence of a State licensing board, the technician must be certified by an appropriate national credentialing body. The IDTF must maintain documentation available for review that these requirements are met. (42 CFR, Section 410.33c)
4. b. For the professional portion, an acceptable level of competence is fulfilled when the interpretation is performed by a physician meeting any one of the following requirements:
   1. The physician is board certified in Cardiovascular Diseases or Perioperative Transesophageal Echocardiography (National Board of Echocardiography); or
   2. The physician has Level II training in transesophageal echocardiography (including documentation of the performance of 25 esophageal intubations and 50 supervised interpretations), as defined by the American College of Cardiology/American Heart Association/ American College of Physicians Task Force on Clinical Competence in Echocardiography, or the equivalent of Level II training as set forth in that document, or has been credentialed for this procedure by the hospital where the physician performs this service.
   3. The submission of claims for transesophageal echocardiography will be considered an attestation that both the technical and professional components of the service were provided within the context of the above stated credentials.
      
      The requirements have been in effect in New York and Connecticut since prior to 2011 and are effective in Illinois (for Part B providers), Maine, Massachusetts, Minnesota, New Hampshire, Rhode Island, Vermont and Wisconsin (for Part B providers) as of January 1, 2017.

The National CCI Manual, version 13.3, Chapter II: CCI editing for anesthesia services; accessible at http://www.cms.hhs.gov/NationalCorrectCodInitEd/ 

Based on a Reconsideration Request to clarify language regarding the provision of intraoperative TEE when performed by an anesthesiologist, NGS has revised the following paragraph: “ Intraoperative TEE is reimbursable to a cardiologist or other physician who is not part of the surgical/anesthesia team but only when performed as a diagnostic test and not for monitoring purposes (TEE for intraoperative monitoring is included in the anesthesia care)” and has clarified the language accordingly: “Intraoperative TEE is reimbursable to a qualified cardiologist, cardiac surgeon, anesthesiologist or other qualified physician but only when performed as a significant, separately identifiable diagnostic test, with a formal written report, and not for monitoring purposes."

This bibliography presents those sources that were obtained during the development of this policy. National Government Services is not responsible for the continuing viability of Web site addresses listed below.

ACC/AHA Task Force Report, ACC/AHA Guidelines for the Clinical Application of Echocardiography, JACC. 1990;16(7):1505-28.

AdminaStar Federal and other Medicare contractors' policies.

AHA Medical/Scientific Statement (Feinberg WM, chair) Guidelines for the management of transient ischemic attacks. From the ad hoc committee on guidelines for the management of transient ischemic attacks of the stroke council of the American Heart Association. Stroke. 1994;25:1320-1335.

Ansari A, Transesophageal two-dimensional echocardiography: current perspectives. Prog Cardiovasc Dis. 1993;35(5):349-397.

Besson G, Bogousslavsky J, Hommel M, et al. Patent foramen ovale in young stroke patients with mitral valve prolapse. Acta Neurol Scand. 1994;89:23-26.

Biner S, Rafique AM, Kar S, et al. Live three-dimensional transesophageal echocardiography-guided transcatheter closure of a mitral paraprosthetic leak by amplatzer occluder. JASE. 2008;21(11):1282.e7-1282.e9. (published online 15 August 2008).

Blanchard D, Kimura BJ, Dittrich HC, DeMaria AN. Transesophageal echocardiography of the aorta. JAMA. 1994;272(7):546-551.

Braunwald E. ed. Heart Disease, A Textbook of Cardiovascular Medicine. 4th ed. WB Saunders, Philadelphia, PA. 1992.

Carrier Medical Directors' Cardiology Clinical Workgroup.

Cerebral Embolism Task Force. Cardiogenic brain embolism. Arch Neurol. 1986;43:71-84.

Cheitlin MD, Alpert JS, Armstrong WF, et al. ACC/AHA Guidelines for the clinical application of echocardiography: executive summary. a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Clinical Application of Echocardiography). J Am Coll Cardiol. 1997;29:862-79.

Cheitlin MD, Armstrong WF, Aurigemma GP, et al. ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to Update the 1997 Guidelines for the Clinical Application of Echocardiography). 2003. http://www.acc.org/clinical/guidelines/echo/index.pdf. Accessed: March 14, 2006.Updated URL: http://www.acc.org/qualityandscience/clinical/guidelines/echo/index.pdf. Accessed: October 27, 2006.

Cigarroa JE, Isselbacher EM, DeSanctis RW, Eagle KA. Diagnostic imaging in the evaluation of suspected aortic dissection. Old standards and new directions. N Engl J Med. 1993;328(1):35-43.

Daniel WG, Mhgge A. Transesophageal echocardiography. N Engl J Med. 1995;332(19):1268-1279.

Daniel WG. Transcatheter closure of patent foramen ovale. Therapeutic overkill or elegant management for selected patients at risk? Circulation. 1992;86(6):2013-2015 (editorial.)

deBelder MA, Lovat LB, Tourikis L, Leech G, Camm AJ. Limitations of tranosesophageal echocardiography in patients with focal cerebral ischaemic events. Br Heart J. 1992;67:297-303.

deBelder MA, Tourikis L, Leech G, Camm J. Risk of patent foramen ovale for thromboembolic events in all age groups. Am J Cardiol. 1992;69:1316-1320.

Demopoulos LA, Tunick PA, Bernstein NE, et al. Protruding atheromas of the aortic arch in symptomatic patients with carotid artery disease. Am Heart J. 1995;129:40-44.

DeRook FA, Comess KA, Albers GW, Popp RL. Transesophageal echocardiography in the evaluation of stroke. Ann Intern Med. 1992;117:922-932.

Dhandheria B. Transesophageal echocardiography; concise review for primary-care physicians. Mayo Clinic Proc. 1994;69:856-863.

Hanna JP, Sun JP, Furlan AJ, et al. Patent foramen ovale and brain infarct. Echocardiographic predictors, recurrence, and prevention. Stroke. 1994;25:782-786.

Homma S, DiTullio MR, Sacco RL, et al. Characteristics of patent foramen ovale associated with cryptogenic stroke. A biplane transesophageal echocardiographic study. Stroke. 1994;25:582-586.

Hung J, Lang R, Flachskampf F, et al. 3D echocardiography: a review of the current status and future directions. J. Am. Soc Echocardiography. 2007;20:213-233.

Isselbacher KJ, Braunwa E, Wilson JD, Martin JB, Fauci AS, Kasper DL. Eds. Harrison's Principles of Internal Medicine. 13th ed. McGraw Hill, New York 1994.

Jones EF, Calafiore P, Donnan GA, Tonkin AM. Evidence that patent foramen ovale is not a risk factor for cerebral ischemia in the elderly. Am J Cardiol. 1994;74:596-599.

Khoury AF, Afridi I, QuiZones MA, Zoghbi WA. Transesophageal echocardiography in critically ill patients: feasibility, safety, and impact on management. Am Heart J. 1994;127:1363-1371.

Kronzon I, Sugeng L, Perk G, et al. Real-time 3D-transesophageal echocardiography in the evaluation of post-operative mitral annuloplasty ring and prosthetic valve dehiscence. Submitted for publication October 2008.

Kronzon I, Tunick PA. Transesophageal echocardiography as a tool in the evaluation of patients with embolic disorders. Prog Cardiovasc Dis. 1993;36(1):39-60.

Lindower PD, Gutterman DD. Detection of cardioembolic sources with echocardiography. Comprehensive Therapy 1994. 20(3):174-180.

Louie EK, Konstadt SN, Rao TLK, Scanlon PJ. Transesophageal echocardiographic diagnosis of right to left shunting across the foramen ovale in adults without prior stroke. J Am Coll Cardiol. 1993;21:1231-1237.

Lucas C, Goullard L, Marchau Jr M, et al. Higher prevalence of atrial septal aneurysms in patient with ischemic stroke of unknown cause. Acta Neurol Scand. 1994;89:210-213.

Mitusch R, Stierle U, Tepe C, et al. Systemic embolism in aortic arch atheromatosis. Dur Heart J. 1994;15:1373-1380.

Mügge A, Daniel WG, Haverich A, Lichtlen PR. Diagnosis of noninfective cardiac mass lesions by two-dimensional echocardiography. Comparison of the transthoracic and transesophageal approaches. Circulation. 1991;83:70-78.

Otto, Catherine M. Textbook of clinical echocardiography. 2nd ed., W.B. Saunders Co., 2000.

Pearlman AS. Detecting prosthetic valve dysfunction. ACCEL. 1995; 27(10):tape B, side 3 (interview with Holmes, Jr DR.)

Pearson AC, Nagelhout D, Castello R, et al. Atrial septal aneurysm and stroke: a transesophageal echocardiographic study. J Am Coll Cardiol. 1991;18:1223-1229.

Pepi M, Tamborini G, Maltagliati A, et al. Head-to-head comparison of two-and three-dimensional transthoracic and transesophageal echocardiography in the localization of mitral valve prolapse, J Am Coll Cardiol. 2006;48:2524-2530.

Perk G, Lang RM, Garcia-Fernandez MA, et al. Transcatheter interventions use of real time three dimensional transesophageal echocardiography in intracardiac catheter based interventions. Journal of the American Society of Echocardiography. 2009;22(8).

Petty GW, Orencia AJ, Khandheria BK, Whisnant JP. A Population-based study of stroke in the setting of mitral valve prolapse; risk factors and infarct subtype classification. Mayo Clin Proc. 1994;69:632-634.

Sansoy V, Abbott RD, Jayaweera AR, Kaul S. Low yield of transthoracic echocardiography for cardiac source of embolism. Am J Cardiol. 1995;75:166-169.

Stratton JR, Lighty, Jr GW, Pearlman AS, Ritchie JL. Detection of left ventricular thrombus by two-dimensional echocardiography: sensitivity, specificity, and causes of uncertainty. Circulation. 1982;66:156-166.

Sugeng L, Shernan SK, Salgo IS, et al. Live 3-dimensional transesophageal echocardiography initial experience using the fully-sampled matrix array probe. J Amer Coll Cardiol. 2008;52(6):446-9.

Sugeng L, Shernan SK, Weinert L, et al. Real-time 3D transesophageal echocardiography in valve disease: comparison with surgical findings and Evaluation of prosthetic valves. J Am Soc Echocardiography. 2008;21:1347–1354.

Wiet SP, Pearce WH, McCarthy WJ, et al. Utility of transesophageal echocardiography in the diagnosis of disease of the thoracic aorta. J Vasc Surg. 1994;20:613-620.

Sources reviewed for reconsideration request of July 17, 2017:

Hahn RT. State of the art review of echocardiographic imaging in the evaluation and treatment of functional tricuspid regurgitation. Circ Cardiovascular Imaging. 2016;9:1-15.

Hahn RT. Transcatheter valve replacement and valve repair: review of procedures and intraprocedural echocardiographic imaging. Circulation Research. 2016:341-356.

Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. Journal of Amer Soc. of Echocardiog. 2013;26:921-964.

Lang RM, Badano LP, Tsang W, et al. EAE/ASE recommendations for image acquisition and display using three-dimensional echocardiography. Journal of Amer Soc. of Echocardiog. 2012;25:3-46.

Rodes-Cabau J, Hahn RT, Latib A, et al. Transcatheter therapies for treating tricuspid regurgitation. JACC. 2016;67(15):1829-1845.

Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography. J Am Soc Echocardiogr. 2010;23:685-713.

Zoghbi WA, Adams D, Bonow RO, et al. Recommendations for noninvasive evalulation of native valvular regurgitation. Journal of Amer Soc. of Echocardiog. 2017;30(4):303-371.