Daniel Ziazadeh, Clauden Louis, and George Hicks
Background
Much has changed since Edler and Hertzin first reported on the use of ultrasound for cardiovascular diagnosis in 1954. With each iteration of technological improvement, the echocardiographic examination has progressively become more comprehensive and important for the cardiothoracic surgeon. The American Society of Echocardiography established standards for the two-dimensional transthoracic echocardiographic (TTE) exam and most recently updated them in 2018. A sequential series of two-dimensional images constitutes a complete TTE exam.
Transthoracic ECHO (TTE)
Parasternal Long Axis (PLAX Increased Depth + PLAX)
Beginning with the transducer in the left parasternal position (left of the sternum in the fourth intercostal space), the PLEX increased depth view provides visualization beyond the posterior wall of the left ventricle to look for pleural or pericardial effusions. A zoomed in view is then obtained to see the left atrium, both leaflets of the mitral valve, the LVOT and aortic valve, the left and right ventricle and the interventricular septum.
Adjustments can be made be in the PLAX view to obtain images of the RV inflow and outflow to allow for evaluation of the right atrium, tricuspid valve, right ventricle, RVOT, pulmonic valve, and pulmonary artery.
Parasternal Short Axis (PSAX)
Clockwise rotation of the probe by 90° from PLAX results in display of the PSAX view. The heart is viewed in cross-section at various levels including the great vessels, the apex, the papillary muscles, and the base of the heart. The first level allows for visualization of the aortic valve in the center surrounded by the left atrium, interatrial septum, right atrium, tricuspid valve, right ventricular outflow tract, and pulmonary valve. Moving inferiorly, the mitral valve and its anterior and posterior leaflet can be appreciated.
Continuing inferiorly to the mid-papillary view, the anterolateral and posteromedial papillary muscles can be seen which provides an excellent view at the mid-LV level to evaluate for LV wall motion abnormalities and estimate LV function. The final view as at the level of the LV apex.
Apical 4 Chamber (A4C)
Moving the transducer to the “point of maximal impulse” in the mid-clavicular line between the 5th and 6th intercostal spaces and imaging back into the cardiac plane within the chest allows a group of apical images to be obtained. The first image should encompass all four chambers with the myocardium uniformly visible from the apex to the atrioventricular valves. This allows for assessment of ventricular interdependence, septal motion abnormalities, and aneurysmal atria septal motion. An RV focused A4C can then be obtained by rotating the probe counterclockwise. This provides excellent visualization and assessment of RV strain, tricuspid valve annulus measurements, and tricuspid annular plane systolic excursion (TAPSE) and velocities.
Apical 5 Chamber (A5C)
By angling the transducer beam anteriorly in the chest, the A5c may be brought into the imaging sector which allows for evaluation of the LVOT, aortic valve, and proximal ascending aorta.
Apical 2 Chamber (A2C)
The next view of the standard TTE examination is the A2C, obtained by rotating the transducer approximately 90° counterclockwise. The A2C view shows only the LA, the mitral valve, and the LV in transverse axis.
Apical 3 Chamber (A3C)
Further counterclockwise rotation of the probe from the A2C position brings the apical long-axis view (also called the A3C) into the imaging sector. This apical view is roughly equivalent to the parasternal transverse section of the ventricles, and aortic and mitral valves in the PLAX view and provides further assessment of overall LV size and function, regional wall-motion of the anterior septum and inferolateral walls, and morphology of the aortic and mitral valves.
Subxiphoid (SC)
After completion of the apical views, the patient is moved into a supine position and the transducer is moved down below the rib cage and to the left side of the xiphoid process. This view is used to evaluate the pericardium, RV free wall, and abdominal vessels including the IVC, hepatic veins and abdominal aorta. The first view is a 4 chamber subxiphoid which provides excellent an examination of interatrial or interventricular septal pathology. The probe is then rotated 90* to obtain a short axis subxiphoid view which shows the liver and IVC in long axis as it enters the right atrium, to allow for evaluation of volume status and IVC collapsibility.
Supra Sternal Notch (SSN)
The final views that are obtained during the standard TTE involve placement of the transducer into the region just above the sternum at the base of the neck. This is called the suprasternal notch view and it allows for visualization of aortic structures (ascending, arch, and descending), and origins of the head vessels (innominate, left common carotid, and left subclavian artery). Finally, the right pulmonary artery is seen in cross section.
Transesophageal Echocardiogram (TEE)
Cardiothoracic surgeons and trainees should be familiar with basic intraoperative TEE examination to enable them to use this powerful non-invasive technique for immediate assessment of cardiac and vascular structures and heart function. The probe is progressively advanced down the esophagus to identify different structures of the heart at different levels.
The examination begins at the upper esophageal level to identify the trachea and bronchi as well as the great vessels (ascending aorta, main pulmonary artery, and its left and right PA branches). This view is critical for evaluate of aortic dissection or pulmonary embolism.
As the probe moves inferiorly in the esophagus, a mid-esophageal view can be appreciated. Rotation of the probe from 0-130 degrees allows to evaluation of the left and right atria and ventricles and aortic, mitral, and tricuspid valves.
Mid-Esophageal 4 Chamber (ME4C)
With the ME4C view, the imaging plane is directed through the left atrium, centering the mitral valve and apex of the heart. All four cardiac chambers including the left and right atrium and ventricles can be appreciated. Both atrioventricular valves (mitral and tricuspid) can be initially examined for pathology, coaptation, stenosis, and regurgitation. Interatrial and interventricular septal defects can be appreciated, as well as wall motion abnormalities of the inferoseptal and anterolateral LV walls. This view simulates a transthoracic A4C view and is one of the most useful for evaluating intracardiac anatomy and function.
Mid Esophageal 5 Chamber (ME5C)
A slight anteflexion of the probe provides a ME5C view, which allows for visualization of the LVOT, the subaortic membrane, and the aorto-mitral curtain. Color and spectral doppler can be applied over the aortic and mitral valve to evaluate for stenosis or regurgitation.
Mid-Esophageal 2 Chamber & Mitral Commissural (ME2C)
All surgeons should be familiar with the ME2C view to evaluate mitral pathology for consideration of repair or replacement. The imaging plane crosses both the anterolateral and posteromedial commissures of the mitral valve. Rotating the probe leftward allows for posterior leaflet imaging (P3, P2, P1) and rightward allows for anterior leaflet imaging (A3, A2, A1). Rotating the transduce angle allows for left atrial appendage (LAA) interrogation, evaluation of LV systolic function, and LV apex pathology.
Mid-Esophageal Long Axis (ME LAX)
The ME LAX view allows for excellent visualization of the LVOT, the aortic valve, Sinus of Valsalva, and the ascending aorta. The anterior (far field) aortic cusp is the right coronary cusp. The posterior (near field) cusp is either the left or non-coronary cusp depending on transducer rotation. A slight withdrawal and rotating of the probe allows for long axis view of the ascending aorta as well as the right pulmonary artery in cross section. This view is excellent for evaluating aortic valve insufficiency, pathology of the ascending aorta, supravalvular aortic stenosis and hypoplasia, or aneurysmal dilation.
Mid-Esophageal Short Axis (ME SAX)
The ME SAX view places the aortic valve in the center of the image providing excellent evaluation of aortic valve leaflet pathology and mobility, as well as right heart inflow and outflow (pulmonary valve, main pulmonary artery, right ventricle, and tricuspid valve). For a trileaflet aortic valve, the left coronary cusp will be posterior (near field) and to the left (2 o’clock), the right coronary cusp will be anterior (far field, 6 o’clock) and the non coronary cusp will be posterior (near field) to the right (10 o’clock). Adjustments of the probe can also show flow in the left and right coronary ostia.
Mid-Esophageal Bicaval
Every trainee should be familiar with this view for central line insertion and peripheral venous cannulation at the time of minimally invasive cardiac surgery or ECMO. The IVC (image left), right atrium (far field), right atrial appendage, SVC (image right), interatrial septum and left atrium (near field) can all be visualized with this view. Atrial septal pathology including defects or aneurysms can be seen with color doppler and 2D imaging.
Trans-Gastric Short Axis (TG SAX)
The TG SAX view allows for interrogation of mitral valve pathology and LV size and function (global and regional wall motion). The probe can be adjusted to evaluate various segments of the left ventricle including the base, mid-papillary, and apex. Left ventricular hypertrophy and the muscular interventricular septum can also be seen and measured.
Deep Trans-Gastric (DTG)
The DTG view is obtained by advancing the probe deep into the stomach with flexion to direct the probe posteriorly. Using 2D and Doppler imaging, multiple structures of the heart can be appreciated including the mitral vale, right ventricle, left ventricle, LVOT, aortic valve, IVS, and aortic root. Specifically, the IVS and its membranous and muscular portions can be interrogated for VSDs. An RVOT view can be obtained to evaluate for pulmonary insufficiency or stenosis. Lastly, this view is critical for aortic valve replacement to obtain gradients and search for paravalvular leaks.
Upper Esophageal (UE)
Withdrawal of the probe allows for the examiner to obtain upper esophageal views allowing for evaluation of the aortic arch in long and short axis as well as the pulmonary artery. The innominate vein can often be seen crossing superior and anterior to the arch. Color doppler can be applied to visualize for any patent ductus arteriosus between the aortic arch and main pulmonary artery.
Transesophageal Echocardiography
- Higher frequency due to a decrease tissue depth
- Higher resolution
Absolute Contraindications
- Stricture
- Tumor
- Diverticulum of the esophagus
- Current UGIB
- Esophageal perforation
- Esophageal fistula
Relative Contraindications
- Recent Upper GI surgery
- Varices
- Coagulopathy
- Cervical spine disease
- Large Type IV PEH
Pre-procedure
- 6-8 hours NPO
- Viscous lidocaine can be used with moderate sedation including fentanyl and versed. It is important to have flumazenil and naloxone close by if needed for reversal.
Right Heart
TR jet divided by 4 approximates right atrial pressure (i.e., 39/4 is ~10mmHg)
ESTIMATING RA PRESSURE (IVC <2.1cm in size is normal)
| IVC | RA Pressure |
| <2.1 cm with >50% collapse with sniff | 3-5 mmHg |
| <2.1 cm and not collapsible | 8 mmHg |
| >2.1 cm and not collapsible | 15 mmHg |
Use pulse wave doppler (PW) to assess TR
Grade of TR = 4V²
PASP (pulmonary artery systolic pressure) estimation is obtained by CW across the TV
PASP = 4V² + RAP (right atrial pressure)
PA pressures are not able to be estimated in severe TR because there is no gradient
Right heart enlarged
- Apex no longer basal but apical or similar to the LV apex
Right heart function
- Shortening with TAPSE
The Aortic Valve
Aortic Stenosis
| AS Severity | AVA (cm2) | MG (mmHg) | Velocity (m/s) |
| Mild | >1.5 | <25 | <3 |
| Moderate | 1-1.5 | 25-40 | 3-4 |
| Severe | <1.0 (AVAi <0.6) | >40 | >4 |
- Low Flow Low Gradient
- LVEF < 50%: true vs pseudo AS
- Paradoxical Low Gradient
- LVEF > 50%: Low stroke volume (LVH), severe MR, severe TR, high afterload (high SBP)
- For Low flow low gradient aortic stenosis, do a low-dose dobutamine stress test:
- True severe aortic stenosis with contractile reserve (reduced EF is secondary to severe AS)
- ↑↑Mean gradient
- ↔AVA = ↔LVOT A x ↑LVOT VTI / ↑AV VTI
- Pseudostenosis with contractile reserve (patient has depressed LVEF due to CMP)
- Mean gradient increases a little, but not much
- ↑AVA = ↔LVOT A x ↑↑LVOT VTI / ↔AV VTI
- True severe aortic stenosis with contractile reserve (reduced EF is secondary to severe AS)
Aortic Insufficiency
| AI Severity | ERO (cm2) | RV (mL) | RF (%) | PHT |
| Mild | <0.1 | <30 | <30 | |
| Moderate | 0.1-0.29 | 30-59 | 30-49 | |
| Severe | >0.3 | >60 | >50 | <250 ms |
| AI Severity by Jet | Jet Width (% LVOT) | Jet Area (% LVOT)* | Vena Contracta Width | Flow Reversal Descending Aorta |
| Mild | <25% | <5% | < 3 mm | Brief |
| Moderate | 25-64% | 5-59% | 3-6 mm | Intermediate |
| Severe | >65% | >60% | > 6 mm | Holodiastolic |
Patient Prosthesis Mismatch
| Aortic Valve PPM | Indexed EOA (cm2/m2) |
| No PPM | > 0.85 |
| Moderate | 0.66-0.85 |
| Severe | ≤ 0.65 |
The Mitral Valve
Mitral Stenosis
- MS Assessment: MV Gradient, MVA (PHT and Planimetry most important)
- Evaluate associated findings: LAE, LA thrombus, MR, and increased RVSP
- Key Distinctions
- Rheumatic – Thickening at the TIPS (hockey stick)
- Calcific – Thickening at base and annulus
- Congenital – Double orifice valve (owl eyes – don’t confuse with Alfieri/Mitraclip)
- Radiation – Pathognomonic calcification & stenosis of the AV & aorto-mitral curtain
- Mitral valvuloplasty for rheumatic MS
- Good results when crisp opening snap, loud S1, Wilkins score < 8, no calcium in commissures
- Contraindications: MR ≥ 2+, LA Thrombus
- Must get TEE prior to valvuloplasty
- Do not trust PHT MVA post valvuloplasty
Primary MR
- Myxomatous degeneration / MVP / fibroelastic deficiency
- Calcific / MAC
- Rheumatic
- Infective endocarditis
Secondary MR
- Dilated cardiomyopathy (Functional)
- Ischemic MR
- HCM
Mitral Valve Prolapse: PLAX View, >2mm systolic displacement of one or both leaflets below the plane of the mitral annulus. More specific with there is myxomatous thickening of the leaflets > 5 mm. MR Jet directed AWAY from the flail leaflet.
Ischemic MR: MR Jet directed toward ischemic pap/leaflet
| MS Severity | MVA (cm2) | MG (mmHg) | PA Pressure (mmHg) | Diastolic PHT (ms) |
| Normal | 4–6 | |||
| Progressive (“mild”) | >1.5 | <5 | <30 | <150 |
| Severe (“moderate”) | 1.0–1.5 | 5–10 | >30 | >150 |
| Very Severe | <1.0 | >10 | >30 | >220 |
Mitral Regurgitation
| MR Severity (Non-ischemic) | ERO (cm2) | RV (cc) | RF (%) | Specific Signs |
| Mild | <0.2 | <30 | <30 | VC <0.3 cm |
| Moderate | 0.20–0.39 | 30-59 | 30–50 | |
| Severe | ≥0.40 | ≥60 | ≥50 | VC >0.7 cm, large MR Jet >40% of LA area, large flow convergence, systolic reversal in the pulmonary veins, prominent flail leaflet |
NOTE: With ischemic MR, severe cut offs are lower: ERO ≥0.2 cm2, RV ≥30 cc
Mitral Valve Patient-Prosthesis Mismatch (PPM)
| Mitral Valve PPM | Indexed EOA (cm2/m2) |
| No PPM | > 1.2 |
| Moderate | 0.91-1.2 |
| Severe | ≥ 0.9 |
Pulmonic Stenosis
| PS Severity | Peak Velocity (m/s) (Peak Gradient) | Systolic valve doming | Other |
| Mild | <3 (36 mmHg) | yes | |
| Moderate | 3-4 | yes | |
| Severe | >4 (64 mmHg) | yes | RV hypertrophy >40 mm post-stenotic PA dilatation |
Hypertrophic CM
- Definition: LVH >15 mm without an identifiable etiology (differential ruled out)
- Required for diagnosis: LVH in any pattern (sigmoid septum, banana septum, neutral septum, apical hypertrophy etc)
- Not required for diagnosis: LVOT obstruction, SAM, asymmetric septal hypertrophy
- Differential: Hypertensive heart disease, aortic stenosis, sub-valvular membrane/stenosis, supra-valvular stenosis, infiltrative disease (amyloid)
- The degree of outflow obstruction does not correlate with risk of SCD. LVOT obstruction is highly dynamic
- LVOT Obstruction worsens: ↓Preload (dehydration, squat-to-stand, valsalva) ↓Afterload (ACEi, hydralazine, amlodipine) ↑Contractility (inotropes, exercise, post PVC: brockenbrough-braunwald-morrow sign)
- LVOT Obstruction gets better: ↑Afterload (hand-grips), ↑Preload (passive raising of legs)
| Athlete Heart | HCM | |
| Wall Thickness | RARELY ≥13 mm (only 1.7%) | Often >13 mm |
| Hypertrophy location | Wall thickness uniform | Usually not uniform |
| Diastolic Function | Normal E’ | Reduced E’ |
| Regression | LVH Regression with no exercise | No regression |
| LVEDD | >55 mm (volumes actually increase) | <45 mm |
Constrictive Pericarditis vs. Restrictive Cardiomyopathy
| Constrictive Pericarditis | Restrictive Cardiomyopathy | |
| Filling Pattern | Restrictive (E/A > 2, DT < 160) | Restrictive (E/A >2, DT <160) |
| E’ | Exaggerated E’ Medial E’ > Lateral E’ in 75% With CHF, strongly consider constriction if E’ >8 cm/s | Reduced E’ (≤6 cm/s) |
Suggested Readings
- Mitchell C, Rahko PS, Blauwet LA, et al. Guidelines for Performing a Comprehensive Transthoracic Echocardiographic Examination in Adults: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2019 Jan;32(1)v:1-64.
- 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. J Am Soc Echocardiogr. 2013 Sep;26(9):921-64.
- Vegas, A. (2018). Perioperative Two-Dimensional Transesophageal Echocardiography. Springer International Publishing. https://doi.org/10.1007/978-3-319-60902-7
- Kirkpatrick JN, Lang RM. Surgical echocardiography of heart valves: a primer for the cardiovascular surgeon. Semin Thorac Cardiovasc Surg. 2010 Autumn;22(3):200.e1-22.
- Cohn, L. H. (2018). Chapter 11. Echocardiography in Cardiac Surgery. In Cardiac surgery in the adult. New York: McGraw Hill Education.
