Pathology of the Cardiac Valves

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Pathology of the Cardiac Valves

F. Luke Aldo and Enrique Pantin

Cardiac valves… hopefully somewhere somebody talked about normal valves…

Cardiac valves are like any other valve, they help direct flow in the desired direction, and the cardiac ones have to do this about 3–3.5 billon times without failing. I want the same warranty for my car!!! Simply, they have to open completely and then close completely.

NORMAL VALVE AREA CM2
Aortic valve 3–4
Mitral valve 4–5
Pulmonic valve 3.5–4.5
Tricuspid valve 5–8

No matter which one we are talking about, the four cardiac valves all have to do the same thing, open and close and nothing else… talk about a boring job. The valves can only work if there is blood being pumped through the heart, usually by the heart, but sometimes by a superhero trying to save a life by pumping on the chest. There are only two main problems with valves: insufficiency/leaky/open when it should be closed and stenosis/narrowed/somewhat closed when it should be open. There are however several reasons why they get messed up. Blood pumped through relatively narrow holes (which the valves are) causes certain blood velocity increases.

Normal systolic blood velocities through the valves are:

Aortic valve <1.4 m/s
Mitral valve <1.2 m/s
Pulmonic valve <1 m/s
Tricuspid valve <0.8 m/s

Valves and their supporting structures can sustain several types of damage that can cause them to malfunction. For simplicity, valve dysfunction has been categorized as stenosis or insufficiency. Before we continue any further we must always make sure in cases of valvular stenosis that the problem is at the valve level and not a sub- or supra-valvular stenosis. It takes years to develop tight valves, and thus it takes a while to cause problems. Leaky valves can occur over years, but also acutely. As you can imagine, acute valve leakage is not well tolerated by the heart. This often needs immediate medical intervention and usually surgical repair as the heart has no time to compensate for the extra volume load.

Aortic valve stenosis due to senile calcific degeneration is the most common valve problem in the elderly (>65 years old). Is this really that old?!? In the figure below we see a short-axis view of a normal aortic valve (A). How nice and secure it looks closed, and when it opens a truck can drive through its orifice! This figure is drawn anatomically correct, but as you know when we do TEE, the top will be on the bottom, and the left will be on the right. Unfortunately a lot of stuff in echo is not done anatomically correct because some genius a long time ago decided to be fancy!

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Rheumatic heart disease (B) is the most common cause of mitral stenosis in general, and is a common cause of aortic stenosis in less developed countries. Rheumatic disease starts with commissural fusion at the leaflet coaptation points and works its way outward towards the perimeter of the valve. This early commissural calcification often gives the so-called “hockey stick” appearance. As we mentioned earlier, in developed countries nobody beats senile calcific aortic stenosis (C). Here calcification starts at the perimeter of the valve and works its way in toward the leaflet edges, which is the exact opposite of rheumatic disease progression. Congenitally defective aortic valves (bicuspid, unicuspid, etc.) can get tight much sooner. A bicuspid aortic valve (D) is the most common cause of aortic stenosis in patients less than 55 years old. Note the upper and larger lower valve leaflets fused with a clearly seen raphe, and the smaller left coronary cusp. The valve comes defective from the factory and you can’t return it. Where is the consumer protection! Nature is definitely smarter than us because they have no lawyers involved in their business!

Too much, just see the table below for a list of causes of valvular problems, not necessarily in any particular order.

We are going to concentrate on the two valves that most commonly develop problems, the aortic and the mitral. When assessing valves we use 2-D imaging and Doppler-related measurements: continuous wave Doppler (for faster velocities, usually greater than 2–2.5 m/s), pulsed-wave Doppler (for slower velocities, anything less than 2–2.5 m/s), and color flow Doppler (will give us an idea about what the blood flow pattern is). We can also use 3-D, but this is a bit esoteric for us. We know what the normal velocities through the valves are and that if the valve gets narrower, in order to allow the passage of the same stroke volume the blood velocity through the smaller orifice will increase proportionally. This is valve stenosis in action. That is it, you’ve got it! End of chapter, we can stop writing! You wish! Valvular regurgitation is diagnosed when we see diastolic valvular flow in the opposite direction it should be going.

Now we are really done! Just kidding, we will explore stenosis and regurgitation a bit more.

You already have read that there are several formulas used to calculate blood velocity using the Doppler effect. Well it is quite simple and we really only need to memorize two Doppler-derived formulas:

Simplified Bernoulli equation

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Continuity equation

In a tube with an area of focal stenosis:

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Integrating the area under the velocity curve obtained by Doppler we get the Velocity Time Integral (using VTI gives us a more accurate result than just the velocity).

This can also be written as:

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There are a bunch of images and numbers used to categorize the degree of valvular dysfunction. You should always look at the supra-valvular, valvular, and infra-valvular areas. For the aortic valve the mid esophageal long and short axis, and then the deep transgastric views are ideal. The first two will provide a lot of anatomical data and the last one is the best for Doppler measurements. In the ME AV LAX view (during systole and diastole) the areas above, below, and at the level of the valve can be examined in 2-D and then color flow Doppler. The first image below is named Mid Esophageal Aortic Valve LAX (Long Axis) view and is usually obtained at a multiplane angle of about 130 degrees. The image was taken in ventricular diastole; note that the mitral valve is open, and the aortic valve is closed. LA = left atrium; P = posterior mitral valve leaflet; A = anterior mitral valve leaflet (the anterior mitral leaflet is always the closest to the aortic valve); LV = left ventricle; AO = ascending aorta. The anterior mitral leaflet in this image corresponds to a segment of the mitral leaflet called “A2”. “A2” length measurement correlates very closely with the ideal mitral valve ring size that needs to be used when a surgeon performs a mitral valve repair in cases of mitral regurgitation. Hey, you can teach this to your surgeon! The second image is in ventricular systole. Notice the closed mitral valve and the amount of mitral leaflet coaptation (arrow), usually greater than 8 mm. A measurement of the aortic valve annulus is taken during systole (white line). This is the best view to measure the aortic annulus.

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At the valvular region, the annulus and leaflets must be closely examined. You also must take a look at the chamber above and below the valve to see the effects of the valvular problem on these chambers. Finally, in cases of mitral or tricuspid insufficiency you must see how the regurgitation affects the pulmonary or hepatic venous flow into the left or right atrium. If the venous flow is reversed into the pulmonary or hepatic veins during systole, there is a high chance that the valvular insufficiency is pretty bad!

Because we know you have such an open mind, we are going to talk about the two valve problems at once! Not really talk, but just put some stuff into a table. What do you expect? Don’t you know by now we want to finish writing this stuff! Just take a look at the table below, and then take a deeper look. Dissect it, enjoy it, and try to make sense of it! We show you several ways, but not all the ways the valve pathology can present. For example, there could be aortic insufficiency due to calcified leaflets or annular dilation. We will not talk about cardiac symptoms or speed of development of the valvular problem, otherwise we’ll be here forever and most likely you will fall asleep!

Now that we have an idea of what to look for we will try to grade the severity of the valvular problem. PLEASE always make sure to set your CFD scale ≥50 cm/s to avoid over reading flow patterns and scaring the s#@* out of your surgeon after a mitral valve repair! It might be humorous to try on April Fools day, but I wouldn’t make a habit out of it unless you:

Ok, here we go!

We start by having practiced enough 2-D imaging to be able to obtain the 20 standard ASE TEE views. If you can’t, please STOP, and go back until you can identify them and their components. Otherwise, you will say our chapter stinks, when in fact it is you.

The following TEE web page is an AMAZING teaching tool, go there and study it:

http://pie.med.utoronto.ca/tee/TEE_content/TEE_standardViews_intro.html

Done? Can you obtain the 20 standard views? Can you do more? Excellent, then let’s move on! We will start at the Mid Esophageal Four-Chamber (ME4C) view that is obtained at a multiplane angle of ZERO degrees. In this view we can see the atria (size, smoke, clots, appendage, and veins draining into them), mitral and tricuspid valves, and both ventricles all in one shot. Are we efficient or what?!? Below is the ME4C view in ventricular diastole: RA = right atrium; AS = tricuspid valve (A = anterior leaflet; S = septal leaflet); RV = right ventricle; LA left atrium; AP = mitral valve (A = anterior leaflet segment “A3”; P = posterior leaflet segment “P1”); and LV = left ventricle.

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From there we have to decide if we want to start with the mitral or tricuspid valve. Whatever valve we decide to check first, we turn our TEE probe to make sure we place it in the middle of the screen. Then we take a look at all its components in 2-D first. You want to see if the valve looks normal, if it opens and how much, if there is motion restriction, and if things are hanging from it or ruptured. After the 2-D exam a CWD to measure the maximum velocity across the valve should be done. This is super important in stenosis. Let’s talk a bit more about mitral/tricuspid stenosis. With the CWD information we can calculate the mean pressure gradients across the valve, by tracing and integrating (with the TEE machine software) the area under the curve for the mitral or tricuspid diastolic pressure tracing.

Mitral inflow patterns obtained with CWD can be seen below. All tracings shown below the baseline mean that flow is moving away from the transducer, and all shown above, duh, mean that flow is moving towards the transducer! You feel pretty smart, don’t you? We decided to place several patients in one drawing. “A” and “B” demonstrate normal CWD tracings through the mitral valve in diastole and systole. The Doppler cursor is placed running through the middle of the mitral valve. Take a look at a normal valve tracing during ventricular diastole “A”. You did notice the two peaks of the “A” tracing right? The early one called the “E wave” represents passive ventricular filling, and the late one, the “A wave”, represents additional ventricular filling due to the atrial kick. Yes indeed, the “A wave” is named after the atrial kick. When the mitral valve closes, during ventricular systole, we see a normal mitral valve tracing “B” (no Doppler signal in diastole because the valve is 100% competent). The next patient is Mr. C with a typical severe mitral stenosis tracing “C”. Note the increased velocity, the little “E wave” deceleration slope, and the large area under the curve for “C”. This is reflective of a high gradient across the mitral valve, all indicative of significant mitral stenosis. Finally, in the case of mitral regurgitation we see patient “D”.

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A mean pressure gradient >5 mmHg is suggestive of severe tricuspid stenosis and an area of <1 cm2.

Another calculation we can do with the aid of the TEE machine software is the pressure half time. The deceleration slope of the mitral “E” wave is traced from the mitral inflow envelope generated by CWD and the machine calculates a pressure half time number. The longer, slower, and less complete it takes the atria to empty, the flatter the slope will be and thus the smaller the valve size. Mitral valve area = 220/mitral pressure half time, and tricuspid valve area = 190/TV pressure half time.

Mitral and tricuspid regurgitation is much easier, especially to differentiate between none or mild (we all can have a bit of leaking in these valves) and severe leakage! The most helpful tool is the CFD. Remember to set the color flow Doppler scale to ≥50 cm/s, otherwise we will be over reading and calling things severe that are not. Starting from the ME4C view, we look at the valve and multiplane to see all sides of the valve. In the 2-D image below, obtained in ventricular systole, it is pretty clear someone bit a piece off of the mitral valve leaflets and a gap can be seen. We then turn on our secret weapon, CFD, and a large, gigantic, humongous flare of color can be seen across the mitral valve. This is severe mitral regurgitation. A wimpy barely visible flare across the tricuspid valve is seen as well. This qualifies for trace tricuspid insufficiency. Please do not panic, we all have a bit of tricuspid regurgitation and other flares as well.

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Before you decide to make any “TEE diagnosis” make sure you interrogate the whole darn heart! Too often, we stand up with our heads held high and announce to the world with a loud and proud voice that there is no valvular problem or that the heart function is great! Then, a nanosecond later we realize we missed the view that showed severe regurgitation or that the patient had a humongous apical aneurysm and its effective ejection fraction is only 5%!!!!!!!!!!!!!!

Before we go into fancy methods of valve assessment in the mid esophageal 4-chamber view we need to center the mitral valve in the middle of the screen and at zero degrees scan the entire valve. First, we slowly pull out the TEE probe until the valve disappears and then advance it back in until the valve disappears again. What we just did was scan the valve from the most superior area of the valve, the so-called “Area 1”, then as we reinserted the probe we passed through “Area 2”, and finally before we lost the view of the valve we saw “Area 3”. The posterior mitral valve usually has three clearly differentiated scallops, the most superior numbered “1”, the middle, “2”, and the most inferior, “3”. The corresponding opposing portions of the anterior leaflet are named the same way. This mitral valve nomenclature allows for uniform communication among surgeons, cardiologists, and anesthesiologists. From the Transgastric Basal SAX (short-axis) view of the LV, we can see these three mitral valve segments as well. This view is obtained at ZERO degrees as well with the probe inside the stomach and moderate degree of ante-flexion of the probe tip.

R = right ventricular outflow track; A = anterior leaflet of the mitral valve with segments 1 (the most superior), 2, and 3 (the most inferior), and P = posterior leaflet of the mitral valve. This view is great to localize regurgitant jets, but not to grade them as the color Doppler is almost perpendicular to blood flow.

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A few common ways to grade the severity of mitral and tricuspid regurgitation are vena contracta measurements, regurgitant jet area, continuous wave Doppler of the regurgitant jet, and pulmonary venous and hepatic venous flows. If you want to get even sexier we can even obtain a PISA (no, this has nothing to do with the Leaning Tower of Pisa…it stands for proximal isovelocity surface area), which will be explained in another section of this book, but if not then go read a more sophisticated echo book. Vena contracta is simply a measurement of the narrowest portion of the regurgitant jet, usually at the level of the leaflets. Obviously, the larger the vena contracta the worse the regurgitation. The regurgitant jet area can be obtained by simply tracing the jet with our magic trace button and track ball on the TEE machine and the computer will spit out a number. It’s that simple! CWD as we mentioned above will show different waveforms depending upon the severity. A mild MR jet will have a soft density and will be parabolic in shape, whereas a severe MR jet will be a very dense triangular one. Lastly, we can explore flow reversal. If regurgitation is severe enough it will affect even the veins draining into the cardiac chamber it is leaking into. For example, normally during systole blood is flowing from the pulmonary veins into the left atrium, but with severe MR, the regurgitant jet is so powerful that it is actually reversing this flow and not allowing the pulmonary veins to empty. Makes sense right? Of course it does! The exact same thing applies to the hepatic venous flow when grading tricuspid regurgitation. Now be careful, echocardiography is not about discovering one finding in one specific view and slapping on a diagnosis. No! Echocardiography is more like a murder mystery. You are Sherlock Holmes and you are gathering as many clues as possible to solve the crime or in this case make the diagnosis. The more clues you discover the more confident you can be in your diagnosis.

The pulmonic valve for TEE is like the red-headed step child that no one likes. Why is this the case? The pulmonic valve is the furthest away from our TEE probe and as a result, the hardest to image. In the case of pulmonary regurgitation, there are no quantitative measurements to grade the severity. We are left with making a qualitative assessment of the valve and regurgitation. A thin jet with a narrow origin is likely mild and a large jet with a wide origin is likely severe. Not very scientific we know. As for pulmonary stenosis, a CWD can be shot down the valve to obtain a peak gradient.

Pulmonary stenosis can be graded depending on the PEAK pressure gradient as:

Mild <36 mmHg
Moderate 36–64 mmHg
Severe >64 mmHg

The best view to shoot a CWD through the pulmonic valve is the upper esophageal aortic arch short-axis view obtained at 90 degrees. One of those 20 standard views that you are an expert at by now! This view is nice because it allows for near parallel alignment of the CWD down the pulmonic valve.

Wow, so many words! Finally we can discuss Mr. aortic valve. After getting the valve in view we do the same stuff again. We evaluate the valve with 2-D, look at the valve in a short and long axis, the annulus, and the chamber before and after (LV and aorta). The Mid Esophageal Aortic Valve SAX view of the aortic valve is obtained around 45 degrees of multiplane and allows for a pretty good view of the tricuspid and pulmonic valves (“P”). Because the tricuspid is almost parallel to the Doppler cursor, this view is commonly used to evaluate insufficiency or stenosis. The aortic valve has 3 leaflets: a left coronary cusp (“L”), a right coronary cusp (“R”), and a non-coronary cusp (“N”). Yes indeed, all are named based upon the coronary arteries that originate from their location. LA = left atrium; RA = right atrium; RV = right ventricle; and P = pulmonic valve and main pulmonary artery.

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Then again place the CFD over the valve. We will see systolic turbulent flow after the valve in aortic stenosis, and diastolic blood flow across the aortic valve if insufficient. In the picture below, we see the Mid Esophageal Aortic Valve LAX view during ventricular systole. The two following images are of the same patient, both in ventricular systole. On your left, there is an aortic valve that does not visibly open, not even with a microscope can we see an opening! We see that the mitral valve is closed because… yes, you’re correct: the heart is in ventricular systole, because the aortic valve does not open… not because it is lazy, but the leaflets are stuck together… yes, correct again: this is how severe aortic stenosis looks! The aortic valve leaflets are thickened and have areas of calcification (top arrow) with posterior echo shadowing as the ultrasound has trouble seeing beyond the calcified area and thus the machine just shows a black long triangular area after the severely calcified area (bottom arrow). All of this is typical of senile calcific aortic stenosis. To the right, color Doppler demonstrates a mosaic flow pattern after the valve. This is typical of turbulent flow, and flow speed above the flow scale limit aka the Nyquist limit.

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In our next set of two images, aortic valve insufficiency is seen after placing the CFD interrogation box over the aortic valve. In the image on the left, obtained during ventricular diastole, trace insufficiency is seen. The image at the right demonstrates a large color pattern (we know there is no color in this book, but imagine it!) starting immediately from the subvalvular area and extending into the left ventricle occupying the entire CFD box. Look closely and you will also notice that the anterior leaflet of the mitral valve has been pushed into the semi-closed position by the regurgitant jet. We can see this more so on the right image in severe cases of AI.

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Wider and longer color usually correlates with a more severe problem. If the ventricular function is poor, systolic flow will be decreased as well. Now that we are done with 2-D and CFD, it’s time to do CWD across the valve. The transgastric views are the best views to shoot a CWD across the aortic valve, as they allow parallel alignment of the Doppler beam with the valve. The Deep Transgastric LAX view, obtained at ZERO degrees, is shown below with the Doppler cursor in ideal position across the aortic valve; RV = right ventricle, LV = left ventricle, LA = left atrium, and A = aorta.

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CWD cursor is seen across the LV, aortic valve, and proximal ascending aorta.

CWD systolic envelope with a peak velocity greater than 1.5 m/s is seen in stenosis.

Aortic stenosis can be classified depending on the degree of peak velocity by CWD as:

Mild >1.5 m/s, but<3 m/s
Moderate 3–4 m/s
Severe >4 m/s

These velocities correlate with aortic valve areas of:

>1.5 cm2 = Mild AS

1.5–1 cm2 = Moderate AS

<1 cm2 = Severe AS

These peak velocities are all nice, but if the ventricle is half dead (has poor/crappy function) he is not able to generate large gradients even in the presence of severe stenosis. One easy way to tell, besides looking at the valve, is to measure the PWD at the LVOT and the CWD through the valve. A ratio of LVOT velocity/aortic valve velocity close to 100% is normal, >50% is indicative of mild stenosis; 50–25%, moderate, and <25% is indicative of severe aortic stenosis. These Doppler measurements along with a measurement of the LVOT cross sectional area (which is easily obtained in the ME AV LAX view by measuring the diameter of the LVOT and having the computer figure it out) can also be plugged into the continuity equation, which we reviewed earlier, and an aortic valve area can be calculated. Another quick and dirty measurement could be made using planimetry in the ME AV SAX view. Planimetry is just a fancy word used for tracing the aortic valve orifice and having the machine calculate an area. It has tons of potential for error, especially in a stenotic valve, and is no-where near as impressive as the all great and powerful continuity equation!

Aortic insufficiency is best evaluated by looking at CFD in the ME AV LAX and ME AV SAX views. It is considered mild aortic insufficiency if the amount of color through the valve in relation to the LVOT is <25%; mild/moderate if 25–45%; moderate/severe if 46–64%; and severe if >65%. With the CWD the slope of the regurgitation waveform can also be measured, usually using the deep transgastric window. The insufficiency is considered severe if the slope is >3 m/s2. A pressure half-time of >500 ms = mild, 500–200 ms = moderate, and <200 ms = severe aortic insufficiency. Again we can use vena contracta measurements to grade the valvular insufficiency. A vena contracta <0.3 cm is mild AI, 0.3–0.6 cm is moderate, and >0.6 cm is severe. In severe AI, we will also see LV dilation from volume overload. Yet another diagnostic clue for severe AI would be holodiastolic aortic flow reversal in the descending aorta. This is simply done by obtaining a long-axis view of the descending aorta and shooting a PWD down it, just as we looked for reversal in the pulmonary veins for MR and the hepatic veins for TR. Wow, this is all coming together and starting to make sense!

The following diagram contains CWD tracings through the aortic valve from various patients, all bunched into one graph. Tracing “A” and “B” correspond to one whole cardiac cycle in an aortic valve that is working normally. We just like to make learning this stuff a bit more confusing for you. Not really, we are just trying to save some space.

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Tracings below the baseline represent systolic flow across the aortic valve, and above, diastolic flow. Note also the “double envelope” in all systolic flow patterns. The larger tracing of the “double envelope” represents flow across the aortic valve and the smaller one represents flow at the LVOT. “A” and “B” = a normal systolic and diastolic (no flow across the valve) flow pattern. “C” = severe aortic stenosis, with a peak velocity of 6 meters/second, which is equivalent to a calculated peak pressure gradient using the simplified Bernoulli equation of 144 mmHg! Yikes! The double envelope relationship, LVOT/AV Doppler, is called the dimensionless index as it is pretty independent of ejection fraction. Normally it is >50%. An index <25% is considered criteria for severe aortic stenosis. “D” = mild aortic insufficiency. The deceleration slope is almost flat. “E” = systolic flow across the aortic valve at 3 m/s, equivalent to a peak gradient of 36 mmHg and moderate aortic stenosis. Finally “F” = severe aortic insufficiency. Note the steep deceleration curve reaching the baseline demonstrating rapid diastolic equilibration between the ascending aorta and the left ventricle. This can only happen if there is a BIG hole across the aortic valve in diastole, or just no aortic valve at all!

Well, well, well. If you are still awake and were able to get to this point you will be happy to know we just decided to end it right here.

Final word: take it easy, learn what is normal very well, and then when you see abnormal you will know something is cooking! Now we are done! Out-freakin’-standing!!! You deserve a pat on the back!

Questions

1. What is the most common cause of aortic stenosis in patients <70 years old?

2. What is the most common cause of mitral stenosis?

3. Which Doppler mode is used for velocities >2–2.5 m/s?

4. Which of the following is NOT necessary to calculate the aortic valve area using the continuity equation?

5. Which view is best for doing a CWD measurement through the aortic valve?

6. When evaluating mitral regurgitation and you see systolic flow reversal in the pulmonary veins, how would you grade the MR?

7. When evaluating valvular dysfunction with CFD, what should your scale be set to in order to avoid overreading regurgitation or stenosis?

8. What is the best view to evaluate for subvalvular and supravalvular causes of aortic stenosis?

9. When grading the severity of aortic stenosis using peak jet velocities in a patient with an ejection fraction of 10%, how would you expect your findings to compare to the true severity of the stenosis?

10. An IV drug abuser with endocarditis is most likely to have which valve affected?

Answers

Bibliography

Armstrong WF, Ryan T. Feigenbaum’s echocardiography, 7th edn. Lippincott: Williams & Wilkins;, 2009.

Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice. J Am Soc Echocardiogr. 2009;22:1–23.

Brown JM, O’Brien SM, Wu C, et al. Isolated aortic valve replacement in North America comprising 108687 patients in 10 years: changes in risks, valve types, and outcomes in the Society of Thoracic Surgeons national database. J Thorac Cardiovasc Surg. 2009;137:82–90.

Kisslo J.A., Adams D.B. Doppler evaluation of valvular stenosis #3. <http://www.echoincontext.com/doppler03.pdf>

Mathew J, Madhav Swaminathan M, Ayoub Chakib. Clinical manual and review of transesophageal echocardiography, 2nd edn. McGraw-Hill Professional, 2010.

Shanewise JS, Cheung AT, Aronson S, et al. ASE/SCA Guidelines for performing a comprehensive intraoperative multiplane transesophageal echocardiography examination: recommendations of the American Society of Echocardiography Council for Intraoperative Echocardiography and the Society of Cardiovascular Anesthesiologists Task Force for Certification in Perioperative Transesophageal Echocardiography. J Am Soc Echocardiogr. 1999;12:884–900.

Toronto TEE website: <http://pie.med.utoronto.ca/TEE/index.htm>

Zoghbi WA, Enriquez-Sarano M, Foster E, et al. Recommendations for evaluation of the severity of native valvular regurgitation with two-dimensional and Doppler echocardiography. A report from the American Society of Echocardiography’s Nomenclature and Standards Committee and The Task Force on Valvular Regurgitation, developed in conjunction with the American College of Cardiology Echocardiography Committee, The Cardiac Imaging Committee Council on Clinical Cardiology, the American Heart Association, and the European Society of Cardiology Working Group on Echocardiography. J Am Soc Echocardiogr. 2003;16:777–802.

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