LV & Mitral Quantification for Real - Time 3D TEE - SD

Introduction

Hello, I'm Dr. Ivan Algo. I'm chief of cardiovascular investigations for ultrasound research and development within Phillips Healthcare, and I've been asked to speak to you about quantification of the mitral valve for mitral valve repair.

I'll first give you a brief overview of quantifying LV function and then I'll talk about some common and also some not so common measurements that can be made on mitral valve anatomy, which should prove to be useful in performing mitral valve repair.

Let's get started.

LV and Mitral Quantification Using 3D Transesophageal Echocardiography

In this segment we're going to talk about LV and mitral quantification using 3D trans esophageal echocardiography.

We're actually going to talk about those aspects of quantification, which are useful in assessing patients for potential mitral valve repair.

And we're going to start talking about LV volume first.

In fact, LV volume is an important physiologic variable to be measured in patients who are candidates for mitral valve repair in the face of mitral regurgitation.

In fact, it's well known and well-established in the literature that 3D echocardiography is superior to 2D echocardiography in measuring LV volumes.

And in fact, we typically think of decreasing LV function as an indicator of decreasing myocardial performance and helping us time the golden hour for mitral valve surgery.

Cautionary Note on Ejection Fraction in Mitral Regurgitation

In fact, though, I want to give you a cautionary note in using EFS for assessment of LV function in the face of mitral regurgitation.

In fact, on this diagram we see elastin and actually we see an LV pressure volume loop.

But it's important to note that with patients with mitral regurgitation all is not necessarily well.

In fact, we see patients may have an increased end diastolic volume and in fact patients have an end systolic volume and we may see in fact ejection fraction, quote unquote total ejection fraction and total stroke volume may be maintained.

But stroke volume is not the total story.

In fact, in patients with severe mitral regurgitation, what we're interested in is forward stroke volume.

What might appear to be normal LV function may actually have decreased LV function in the face of regurgitation.

So in fact, as now we move forward, the next segment we're going to talk about after differentiating EF and forward EF is looking at the total LV in mitral valve.

In fact, as I mentioned, the LV can enlarge over time.

It can adversely remodel in the face of mitral regurgitation.

And it's also important to notice that the mitral valve is more than simply leaflets.

It actually consists of an apparatus and in fact, mitral regurgitation can cause over time a feedback loop which can worsen mitral regurgitation, for example, as the ventricles enlarge, they can pull and create cordal forces, which actually retract the mitral leaflets and cause worsening mitral regurgitation as well as increasing mitral annular dilatation depending on the pathophysiology.

Mitral Valve Anatomy

So let's review.

Of course, the mitral valve is more than just leaflets.

It consists of an annulus, it consists of an anterior and posterior leaflet.

It consists of coaptation point and actual cordal attachments to these coaptation areas.

And it also consists of cordal attachments to the papillary muscles.

Now, in fact, it doesn't end with the papillary muscles.

Normal mitral valve function depends on normal wall motion as well, especially in the face of ischemic mitral regurgitation.

So let's take a look in more detail at quantifying these various aspects of mitral valve anatomy.

It's done today conventionally by 2D Echo, and as you see up there on the upper left, we see there at least a moderate to severe jet of mitral regurgitation centrally directed.

Now, while the echocardiographer sees what's on the upper left, the surgeon sees what's on the lower right, and in fact, delineating the portion of diseased leaflet and physiologic defect can be challenging.

And in fact, one must take multiple sweeps through annular planes to find out and localize where the defect is.

That's important because the surgeon in his or her mind wants to understand what to do in terms of correcting annular size, what to do in terms of correcting leaflet prolapse, and will this be a simple repair related to, for example, fibroelastic disease or will this be a complex repair related to barlow's disease?

So the key then in the operating room with the 2D Echo is the game is let's play, where's the defect?

And in fact, that can be more challenging as we move forward into the new devices that are being developed, new annular prosthesis that are being developed to hopefully simplify mitral valve repair for the surgeon, but with which nonetheless increase the complexity of mitral valve geometry.

So again, let's review.

If we look at the images on the top portion and we look at the 2D echo, they really don't tell us things about the three dimensional nature of the annulus, the relation of the leaflets to the annulus and of the defect.

Importance of Mitral Valve Repair

Now, why is understanding mitral valve repair important?

Actually at the 2007 heart valve summit, which was held in Boston, David Adams provided some very important insights into that.

David Adams is chair of cardiac surgery at the Mount Sinai School of Medicine, and as he frequently ask, why is it a 50 50 proposition for patients with mitral valve disease to receive replacement versus repair?

In fact, replacement has with it decreased longevity and also the need for chronic anticoagulation.

So the question is why don't more patients get repair?

And in fact, evaluating the nature of the defect is important in appropriately selecting patients.

So let's talk a little bit about how quantification and live 3D TE can help assess the nature of the repair and help a surgeon assess whether a patient might be better with replacement or repair.

Now, as I mentioned before, multiple vendors are actually developing newer types of mitral valve annular prosthesis to deal with different physiologic problems.

For example, the mixer ring is designed to help reduce the need for sliding valvuloplasty by actually having an elongated posterior annular aspect.

Geo formm ring is designed to be used in patients with ischemic mitral regurg regurgitation.

Now these are not the conventional types of rings which have been used before, but again, look at the simple 2D measurements that can be made in echo.

There are limitations to the type of measurements can be made, and you should ask yourself, how do you know that with a caliper, you're actually measuring the important aspect of the leaflet, which is going to change with the nature of placing an annular prosthetic ring in.

So in fact, this is where 3D comes in.

In 3D, we look at the whole nature of the mitral valve as nature sees it as the fluid dynamic sees it, and as the surgeon sees it when the patient is on cardiopulmonary bypass, you can see here that the annulus actually is has a complex nature to it.

And actually you can see there on the lower right the relationship of the annulus sitting within the volume rendered 3D assessment or 3D echo image of the mitral valve and apparatus.

3D Calculations of Mitral Valve Quantification

So let's talk a little bit about some aspects related to 3D calculations of mitral valve quantification.

What you can see there labeled A is that aspect of the anterior annulus.

And actually we can see just below that since it's very close with the aorta mitral continuity, we see that the aortic root is very close to the attachment of the anterior leaflet.

We can see below there marked ao, the other aspect of the aortic annulus.

And you'll see in a later image why that's important.

Other things that we can see here, for example, are the posterior annulus and that's labeled P and we can see the angles of the takeoff of the leaflets from both the anterior and posterior aspects of the leaflet.

So we can start first just doing some simple measurements.

And simple measurements include diameters, but diameters which are actually stationed in 3D with more certainty than just with 2D because of variations in cross-sectional planes.

So some simple calculations that can be performed using mitral valve quantification include annular measurements, for example, the diameter of the ant lateral to posterior medial aspect.

We can also find the AP diameter that from the aortic root down to the posterior aspect of the annulus.

In this image that is measured at 44 millimeters.

We can also find the angle of the aortic te mitral annular reference planes and we'll talk about that shortly.

So let's start with a simple measurement.

The diameter of the anterior to posterior annulus in this measurement called DAP, it measures that to be 44 millimeters.

And actually if you use Q lab, you can actually hover over the measurement and that actually brings up a display of the leaflet and it actually shows using that green marker specifically what is being measured.

And specifically in 3D notice here in 3D, we've actually found the maximal extent of that annular diameter so that we don't have to worry are we to the left, are we to the right, are we more to the A one side?

Are we more to the A three side?

And so that is one of the key benefits of 3D actually showing exactly where one is in three dimensions with relationship to the mitral valve.

Annular Height

Now let's talk a little bit about height.

Several years ago, while I was at the University of Pennsylvania, my colleagues and I published a paper on looking at the nature of mi, the mitral annulus and the fact that it is non planar and its effects on leaflet stress.

In fact, nature has not made the mitral annulus planar.

As you can see in this diagram, it is actually assumes a saddle shape.

And what you see enclosed in that box there is the three dimensional height that is to say from the top mosts to the bottom most aspect of the mitral annulus, if you will.

If that was the edges of a Pringles potato chip and we put the Pringles potato chip in a box, you could actually see what that height is of the box.

And that height actually changes depending on things such as annular dilatation and LV remodeling.

In this case, the height is measured to be 6.7 millimeters.

Now the annulus is not as simple ellipse.

So actually, if one goes from a basic mode to a standard mode, in looking at the annulus, one actually can use more points to be localized around the annulus to create the true nature of the annulus besides those simple diameters that I showed before.

And that's what we see here.

We actually see the true annulus as measured by 3D echocardiography, and I'll show you how that's quantified in a moment.

We also see an aspect of the coaptation line between the anterior and posterior leaflets.

On that lower left NPR view, you can begin to see the nature of the defect, and I'll call that out in subsequent slides.

In fact, what we see in mitral anatomic quantification, we can see the defect on the volume rendered image on the left with that arrow.

And it's actually in the A three aspect, and it's actually just above the coaptation line.

And actually to the right we can see where we've quantified both the annulus and the leaflets.

We can actually see on a topographic map where the location is of the leaflet billowing or prolapse, and in fact, that's demarcated by the arrow and it's what I call what you see is what you get.

So with one simple view, now one can see where the nature of the defect is located on the mitral apparatus in this aspect as you see towards the posterior medial aspect.

Aortic to Mitral Angle

Okay, let's talk about another measurement.

The aortic to mitral angle.

This is an area of research that some hypothesis, some physicians hypothesize actually can help be used to predict the nature and likelihood of systolic anterior motion of the mitral valve after leaflet repair and annulus reduction.

So what we see here is actually the nature of the annular line to the aortic line, and in this case we measure 108 degrees.

Leaflet Measurements

Now let's move to another leaflet measurement in this case on the anterior leaflet.

And actually many surgeons are beginning to hypothesize and hypothesize that the measurement of this length, especially in its true 3D nature, can potentially be used to understand what the effects are of mitral leaflet resection and annular reduction, and how much coaptation will be left after repair.

It's important for me to say that what you see here is not the total mitral leaflet or the leaflet segments, but the exposed or functional leaflet segments that is the closed door between the left atrium and the left ventricle.

And what you see there on the green line is not a simple line, but actually a three dimensional line, which goes from the top of the annulus through the anterior leaflet all the way to the coaptation.

And that true length in 3D can be measured.

Leaflet Surface Area Measurements

Now let's talk about some measurements which are simply impossible to do from a 2D image.

And these are leaflet surface area measurements.

These obviously are not commonly done today because up until now it's been typically impossible or extremely unlikely to do a leaflet measurement on an ultrasound system because it takes so much effort.

But because of the live 3D acquisition is very quick, one can actually do a reconstruction of a leaflet online on a system.

So what you see here on the mesh is actually an example of an anterior functional anterior leaflet surface area and a posterior leaflet surface area.

Again, just functional, not total, but just that exposed.

And you can see there that the prolapsed segment can increase the leaflet leaflet area.

Future Directions and Summary

So winding down, why is this important?

Where do we think things are going?

Well, in fact, the ability to reconstruct leaflets has many types of bioengineering research labs looking at what contributes to leaflet durability with different types of leaflet stress and the ability to do not only the types of quantification at talk today, but also new types and future types of quantification, that should allow us to help predict what should be a durable repair and what is the best possible repair for a patient.

So in summary, I'd like to first say that mitral repair is changing that patients more and more patients should be receiving repair, that newer repairs and newer rings are increasing the complexity of mitral quantification and that needs newer methods and measures that can be made in three dimensions.

I'd also like to add that better image quality provides for more accurate information.

If you can't see what you're measuring, then your caliper or your 3D measurement or 2D measurement aren't going to be appropriate necessarily if you're just trying to measure through fuzz.

That's why increased image resolution, for example, with 3D TE helps position calipers and quantification tools with more certainty for the user.

Even if you're just doing conventional caliper measurements, you can see as I've shown in this talk, that you can lay down that caliper measurement with better position in precision in 3D and in fact there are newer 3D measures such as leaflet surface area and aortic mitral angle, which are emerging, which will have potential applications for increasing the engineering certainty of mitral valve repairs.

And hopefully these can improve patient outcome.

So I'd like to say that with 3D and with mitral valve quantification done in three DI echo is anything but boring.

Thank you very much.