Mitral Valve Disease

Welcome back to Behind the Knife. My name is Jessica Millar, PGY5 General Surgery Resident at the University of Michigan. And I'm Aaron Williams, a third year cardiothoracic surgery fellow here at Duke. And I'm Nick Tiemann, cardiac surgeon at the University of Virginia. As the cardiac surgery subspecialty team for Behind the Knife, we are so excited to be back with another high yield episode.

We hope you all have enjoyed our previous episodes and that you're just as excited about cardiac surgery as we are. Or that you've been able to use our episodes to help dominate your time on a cardiac surgery rotation or while taking care of cardiac surgery patients. For this episode, we have another high yield and common topic that you're likely to encounter in the OR, ICU, and emergency department, mitral valve disease.

Mitral valve disease is a topic that applies to both cardiac and non cardiac surgery patients and in this episode, we'll help navigate some of the important physiologic differences in patients with mitral valve disease, common surgical techniques and approaches for addressing mitral valve disease, and even some of the most common mitral valve consults you're likely to come across in

the ED.

Now Nick, since you're also an ICU intensivist, why don't you start us off with the important physiologic differences that patients with mitral valve disease often have. Sure thing. Great. Thanks, Jess. Patients with mitral valve disease have pretty significant alterations in their physiology that need to be recognized and managed in the perioperative period.

Before we get into specifics, let's quickly review some basic cardiac physiology. Remember that the vasculature around the heart is essentially just one long pipe with blood coming in through the SVC and IVC, out the pulmonary artery and into the lungs, back into the left side of the heart, and finally out into the systemic circulation.

Any resistance in this pipe will cause blood to back up, and similarly, backwards flow or regurgitation will also cause blood to back up within the system. Okay, with that in mind, let's start with mitral regurgitation. These patients can be profoundly fluid overloaded, with resultant pulmonary edema and hypertension, as well as RV overload and tricuspid regurgitation.

Prior to operating on these types of patients, they need to be medically optimized. Aaron, how would you go about doing that? So first you want to

remove some of the extra fluid the patient has to reduce the stretch and strain of the heart. Now, oral diuretics should do the trick here, although patients in a decompensated heart failure would often benefit from inpatient admission and diuresis.

Now, you want to also reduce the afterload of the heart, which is the resistance the heart is facing as it ejects blood to the body. Now, in this case, this is the systemic vascular resistance, or SVR, which is manifested as systolic blood pressure. Now, you don't want to overdo it and cause hypotension, but if you can lower the resistance across the aortic valve, blood will preferentially be ejected to the body rather than back across the mitral valve into the left atrium.

Now, ultimately, these patients may require inotropic or mechanical support if they're in heart failure. That's right, and the acuity of this process is also important. If this is a chronic process, the heart has time to adapt and compensate for the increased volume, and this can slowly worsen over years until the patient develops symptoms.

But if it's an acute process, for example from a ruptured papillary muscle as a result of myocardial infarction, the heart hasn't had this time to compensate. You get a sudden decrease in cardiac output

because all of it is regurgitating back through the mitral valve, coupled with a large amount of volume refluxing into a non compliant left atrium, which causes flash, pulmonary edema, and right ventricular dysfunction.

So Jess, what about mitral stenosis? So, similar to mitral regurgitation, patients with a narrowed or stenotic mitral valve have increases in their left atrial pressure, as the left atrium has to do more work to push blood across the stiff mitral valve, and that can cause blood to pool in the left atrium or even back up into the lungs, causing pulmonary congestion and pulmonary hypertension.

They can also develop pulmonary vasoconstriction, which can worsen this pulmonary hypertension, and if you continue this backwards flow through the pipes, you can also cause right ventricular strain. Now, unlike mitral regurgitation, the left ventricle is not volume overloaded because the flow across the mitral valve is restricted.

However, the decrease in cardiac output can cause a compensatory rise in your systemic vascular resistance and your left ventricular afterload, which then can cause left ventricular remodeling as the left ventricle has to

get stronger to be able to push the blood into the high pressure, high resistance systemic vasculature.

And so this can ultimately also lead to LV failure. It's important to keep these patients from becoming tachycardic and keeping them out of atrial fibrillation because these will decrease the amount of time for the left ventricle to fill during diastole and decreases the volume of blood which can be emptied from the left atrium.

Exactly. When it comes to mitral stenosis, you want to avoid tachycardia as this will decrease the filling time of the heart. You also wanna avoid a high afterload as this will increase the amount of work the heart has to do, and you wanna avoid hypovolemia as this will decrease your stroke volume and your cardiac output.

Yeah, so as you can see, mitral valve disease can affect a lot of the normal physiology we're used to seeing and can make management of these patients in the ICUA bit more complex. However, let's move on to a topic that's a bit more fun for us surgeons, obviously the surgical management of mitral valve disease.

Now, Jess, can you walk us through how you surgically help manage these patients? Absolutely, but before we do that, it may be helpful to review some quick

anatomy of the mitral valve. That way, all of our listeners kind of have this rough picture in their head of what the different parts of the mitral valve are before we start talking about some of those surgical techniques to repair or replace them.

Erin, when you think about the mitral valve, what are the main anatomical components you're thinking of? Yeah, so the main things that I think about is the mitral valve consists of an annulus, or a saddle shaped ring. It has two leaflets, an anterior and a posterior, and then three types of chordae tendineae, which are based on where they insert onto the leaflet, and two papillary muscles.

That's great. Now, there's a lot of reasons why someone may develop mitral valve disease, and the cause can sometimes influence our surgical approach. Nick, what are some of the most common causes of mitral valve disease? All right, so let's start with degenerative disease. This is when the valve itself undergoes degenerative changes such as thickening or prolapse and is most commonly associated with mitral regurgitation.

This is in contrast to ischemic disease in which mitral regurgitation is due to underlying coronary artery disease. Myocardial infarction can

result in changes of the geometry and function of the left ventricle and the mitral angulus, leading to angular dilatation and leaflet dysfunction. In other words, the leaflets and cords of the mitral valve are normal, but regurgitation occurs due to chronic ischemia and remodeling of the left side of the heart.

I'll jump ahead a little here and say that in these cases, concomitant revascularization with CABG is often performed to correct the underlying ischemic disease rather than just addressing the mitral valve dysfunction. Great. Now, Aaron, can you think of any other causes of mitral valve disease? Yes. Yeah, absolutely.

So while not as common in the U. S., rheumatic disease is one of the leading causes about the heart disease worldwide and it's most commonly associated with mitral stenosis. However, as a side point rheumatic disease still exists and accounts for up to 23 percent of mitral valve disease in the U. S.

Also, infectious etiology, such as endocarditis, can often result in mitral valve dysfunction. And then we'd also consider surgical intervention for those patients with active, infective endocarditis, complicated by congestive heart failure, intracardiac extension of the infection like

an abscess, sepsis and responsive to antibiotic therapy, systemic embolism, or even if there are really large vegetations.

Perfect. So when it comes to surgical intervention for mitral valve disease, there are two main approaches. You can either repair or you can replace the mitral valve. Now, repair is regarded by some as like the optimal surgical procedure to treat mitral valve dysfunction, and it's currently the most commonly performed surgical procedure for mitral valve regurgitation in North America.

Nick, what are some of the advantages of repair that make it maybe a little bit more favorable compared to replacement? Well, repair of the mitral valve is associated with lower operative mortality and improved preservation of left ventricular function compared to replacement. And we don't have to worry about prosthetic valve related complications such as thromboembolism, stroke, anticoagulation related hemorrhage, and endocarditis.

Yeah, and it's important to remember that repair may not be appropriate for all patients, and you must consider every component of the mitral valve. Including the size of the annulus, the anatomy, and the mobility of the leaflets,

as well as the quality of the subvolvular apparatus, that is the cordae and the papillary muscles, when deciding which approach to pursue.

For example, in patients with infective endocarditis, if there is extensive tissue destruction and large amounts of grossly infected tissue, these must be removed and repair may not be possible. But, that's a really good point, Erin. Now, deciding repair versus replacement is often a very nuanced decision, and, like Erin mentioned, can be dependent on the cause, the anatomy of the mitral valve.

However, let's just review both approaches and the common techniques for each. Now, as a disclaimer, both surgical and transcatheter options are available for both mitral valve repair and replacement. However, for this episode, we're just going to focus on the surgical approaches. So, let's start with mitral valve repair.

In order to keep these different repair techniques organized, I often find it helpful to remember the main components of the mitral valve that Erin had mentioned earlier. So, you have the annulus, the two leaflets, and the chordae tendineae. Each of our repair techniques will focus on repairing one of these main components.

So,

Nick, what are our options for mitral valve repair if mitral valve dysfunction is due to a segment of diseased leaflet? If mitral valve dysfunction is due to a segment of diseased leaflet, then we have lots of options, including leaflet resection, leaflet placation, or even leaflet repair. For resection, the diseased portion of the leaflet is excised and the cut edges are re approximated, effectively reducing the amount of tissue in the mitral valve.

For placation, portions of the leaflet may be folded and sewn together to reduce redundancy or prolapse. Finally, some cases of mitral valve dysfunction may be due to a small hole or tear within the leaflet of the mitral valve. In these cases, leaflet repair can be performed using primary closure or by a patch with bovine pericardium.

Awesome. Now, Aaron, what can we do if the cause of our mitral valve dysfunction is, say, due to damage of the chordae tendineae? Yeah, so in these cases, we can perform either a repair or replacement, but you'll probably see replacement perform most often. Now, ruptured cords or elongated cords are often replaced with artificial cords made of cortex, and

you'll probably hear them referred to as neocords.

Now, these cords can be sewn in the papillary muscle in the mitral valve leaflet in order to restore proper function. Now, one more important consideration during this repair technique is that the length of the cords must be adjusted appropriately to ensure proper function after the repair. And so, in some of these cases, we also perform cord transfer.

And, for example, if a cord is elongated on the anterior leaflet, a corresponding opposing cord from the posterior leaflet can then be transferred to the anterior leaflet to help out. Okay, so we've covered what you can do to replace the leaflets, the chordae, I guess that leaves our last main component of the mitral valve, which is the annulus.

So Nick, how can we repair the mitral valve annulus, and bonus question, should we always repair the annulus? Yeah, so ring annuloplasty can help repair the normal size and geometric shape of the mitral valve annulus, and in almost all cases of mitral valve repair, ring annuloplasty will be performed.

There are currently multiple types of rings in the market, and some are in the shape of a complete circle, while

others are in the shape of semicircles. However, all of them are flexible with a slight 3D shape to conform to the normal saddle like shape of the mitral annulus. When you're performing an annular opacity, one of these rings will be sewn in around the annulus.

This is to help re establish the normal geometric shape and size of the annulus. Now this may be utilized as the sole repair technique, or in conjunction with the other types of repairs that we've discussed. Alright Aaron, when might we be able to use ring annuloplasty by itself for mitral valve repair?

Yeah, so you'll often use ring annuloplasty by itself or in isolation for cases of pure mitral annular dilation, causing mitral valve dysfunction. Now in these cases, reducing the annulus size with an annuloplasty ring helps to bring the leaflet edges closer together and causes a better coaptation.

Great. Now, there's one more mitral valve repair technique that you may hear about in the cardiac OR, and that is the edge to edge repair. Nick, can you describe to us what that is? Sure, so probably one of the oldest techniques for mitral valve repair is the edge to edge repair,

also called the Alfieri technique.

This technique attempts to re approximate the edges of the mitral valve leaflets in cases of mitral valve gravitation. To do this, a clip or stitch is placed in the middle of the anterior and posterior leaflet, effectively suturing the middle of the two leaflets together. Now, it's worth pointing out that a lot of the transcatheter repairs for mitral valve disease invoke this procedure to basically bring the leaflets together to reduce the regurgitation.

Absolutely. Now, again, just keep those different components of the mitral valve in mind, so again, the annulus, the leaflets, and the chordae, and that should help make remembering all of those different repair techniques a little easier. However, as Aaron mentioned earlier, repair is not always possible and sometimes the mitral valve just needs to be replaced.

Our options for replacement are a little bit more limited, so Aaron, can you tell us what the two biggest options for mitral valve replacement are? Absolutely. So for replacement, our options are either To implant a bioprosthetic valve, which is either a pig valve or a valve made with bovine pericardium, or a

mechanical valve.

And so they each have their own pros and cons, and which one you use will largely be dependent on the patient's age and comorbidities. Alright, well, Nick, can you tell us what some of those pros and cons are for, say, a bioprosthetic valve? Absolutely. So bioprosthetic valves have the advantage of being less thrombogenic since they're made with natural tissues, and they do not require lifelong anticoagulation.

That being said, many surgeons will still anticoagulate their patients for the first three months. after implantation of a bioprosthetic valve. Now, this is ideal in patients in which anticoagulation is contraindicated. However, these valves have limited durability due to degenerative changes and tissue fatigue and most bioprosthetic valves have a lifespan of 10 years or so.

Therefore, they are often not recommended for patients less than 65 years of age. Due to the high risk of valve degeneration and the need for re operation later in life. Yeah, it's important to note that the lifespan of a bioprosthetic valve is also dependent on the position in which they're implanted.

An implantation in the mitral valve position is often associated with decreased durability

compared to when they're implanted in aortic valves. Now, I will add one important disclaimer to the age recommendation for implantation of bioprosthetic mitral valves. So previously, open surgery with redo valve replacement was the only treatment option for people with failed bioprosthetic valves.

However, some centers are now performing percutaneous valve in valve procedures in which a transcatheter valve is placed within a previously placed surgical valve. This procedure still carries risks with it, including the need to place a smaller valve inside the previous valve which can cause patient prosthesis mismatch, which is when a valve is too small for the patient's body size.

That's a great point, Nick. Bioprosthetic valves are a great choice for older individuals where the expected lifespan of the patient and the valve are roughly similar. Now, Erin, on the flip side, can you tell us the pros and cons of our other option, which are mechanical valves? Yeah, so mechanical valves are often made of materials such as carbon or titanium, and as a result, they are extremely thrombogenic, and patients with mechanical valves are also at high risk of thromboembolism,

and therefore require lifelong anticoagulation with Coumadin, and for patients with mechanical mitral, we'll often target an INR goal of 2.

5 to 3. 5, although there's a Other ongoing trials to see if we can reduce that for certain valves. And bonus points for those taking the abset, you should never stop anticoagulation in patients with mechanical heart valve. If they need any type of procedure, it should always be bridged with, with heparin, okay?

And unlike bioprosthetic valves, mechanical valves will last the patient's entire lifetime, and are pretty ideal in younger patients requiring mitral valve replacement. However, this can get a little bit tricky for women of childbearing age. We want to have children, but we're in a coagulation, their pregnancy could be a little bit dangerous.

One other thing I want to point out as a strange consequence of mechanical valve implantation is the associated sound. Many patients will complain or will acknowledge being able to hear their valve, especially at night when it's quiet. So if you're a medical student on a rotation, you have a patient with a mechanical valve, definitely see if you can hear it.

Now one thing that's critical for mitral valve replacement, regardless of whether we're doing a bioprosthetic or a mechanical valve implantation, is the size. And Nick, can you talk to us why implanting the right size valve is so important? Yeah, so as I mentioned earlier, appropriate sizing of the implanted valve is critical to avoid patient prosthetic mismatch.

This is when the implanted valve is too small in relation to the patient's body size, essentially resulting in a iatrogenic mitral stenosis. Now, the nice thing about the mechanical valves is that they have better flow characteristics than the bioprosthetic valves. So, usually you can get away with putting a smaller mechanical valve in and have less risk of having a mismatch with the patient's size.

Alright. So, we've talked about our different options for surgery. Aaron, can you just take us through some other important surgical considerations when we're talking about taking a patient to the operating room for mitral valve surgery? Yeah, so remember that for most mitral valve surgery, regardless of whether or not you're performing a repair or replacement, full cardiopulmonary bypass and arrest are used.

Now be sure to check out our previous episodes to learn more about bypass. Surgical approaches for both can consist of median sternotomy, which is typically best for planning to perform other bypasses. Associated procedure like a cabbage or an A. V. R. You can also end up performing thoracotomy or robot assisted surgery for mitral valve disease.

And during the procedure, you may see the surgeon injecting cold saline in the left ventricle to assess the valve prior to making a definitive decision regarding whether you can repair or replace. Essentially, at this point in the case, you're getting an up close, live look at what is functionally wrong with the valve, rather than relying on shadows from the echocardiography.

Now, intraoperative TEE is essential to help us better define the anatomy of the mitral valve and to confirm a successful procedure. And if post procedure mitral valve dysfunction is demonstrated on TEE, we can quickly make corrections while we're still in the operating room. Now let's take a few minutes to chat about some other scenarios you may encounter clinically or on the boards or as just part of some pimp session with your

attendings on your rotation.

This will often include mechanical complications after acute MI. Now in relation to mitral valve disease, this often involves acute papillary muscle rupture resulting in severe MR. So acute severe MR can really be a life threatening surgical emergency, and there's definitely improved outcomes with early surgical intervention.

After an MI, about 12 to 45 percent of patients will develop mild to moderate chronic MR, but this is usually pretty well tolerated. However, acute severe MR, which occurs less than 1 percent of the time, has an in hospital mortality rate of up to 80%. With surgery, the long term survival at five years can be around 75 percent when compared to 20 percent without surgery.

Often, these patients will require CABG as well, which will further improve their survival when combined with addressing the mitovalve from up to 65 percent compared to about 20 percent without. All right. So Jess, what's the physiology behind acute severe MR with papillary rupture? Well, as you mentioned, acute severe mitral

regurgitation happens from an acute papillary rupture, which occurs at about 75 percent of the time with an inferior MI.

This specifically targets the posterior medial papillary muscle, which has a single blood supply coming from the right coronary artery in right dominant patients, or the circumflex system in patients that have left dominance. An anterior lateral papillary muscle rupture can also occur, but that's a little less common because it gets duals blood supply from the left anterior descending artery and the circumflex system.

Either way, this can happen pretty early, with a median time to rupture of just 12 6 hours following an MI, and it's typically not diagnosed until about 2 7 days after someone's had an MI. And some of the risk factors for mortality in this patient population includes advanced age, duration of preoperative shock and other comorbidities as well as time to operating delay.

And Nick, how do these patients typically present and how would you go about diagnosing them? Yeah, so patients with severe MR from acute papillary muscle rupture will often present with acute dyspnea due to

pulmonary edema. as well as cardiogenic shock. The classic physical exam sign that often gets asked about is a new pansystolic murmur that is heard loudest at the apex of the heart and can radiate to the axilla.

This is in contrast to an acute post infarct ventricular septal defect that can be heard at the left sternal border. On EKG, you may see evidence of an inferior wall MI, and on chest x ray, you will see bilateral pulmonary edema or infiltrates. On echo, you will see partial or complete rupture of the papillary muscle or cords, Leaflet eversion, severe mitral regurgitation, a hyperdynamic left ventricle, and possibly signs of pulmonary hypertension.

If the patient has a pulmonary artery catheter or undergoes a right heart catheterization, they'll have prominent V waves and increased pulmonary artery pressures. All right, now Jess, these patients are often seen by the ED or cardiology at the time of their MI way before they see the surgical team.

Tell us a little bit more about that. Yeah, so these patients will oftentimes present and undergo a left heart cath at the time of their initial diagnosis of their MI. This will usually

occur a couple of days before the papillary muscle ruptures like we mentioned earlier. These patients will often undergo stent or angioplasty in order to relieve their MI.

However, if these patients with acute MR present in a delayed fashion, they may get their left heart cath time at the time of their presentation, and in this case, they would urgently need to also get their coronaries as well as their mitral valve disease addressed urgently. And because this is a surgical emergency, it's really important to act quickly.

So you want to start out by stabilizing these patients the best you can. Nick, what kind of early things do you think about? Yeah, so these patients can be very sick when they present, and they often have pulmonary edema and multi system organ failure. It is important to start these patients on inotropes and vasodilators that can help stabilize the patient's hemodynamic.

Diuretics may be helpful as well, but should not be overdone. Intubation and mechanical ventilation will often be required for these sick patients who often have respiratory failure. Great points, Nick. Now, some of the other points to be made aware of for these patients are that they often require mechanical circulatory support.

And this is either through a

balloon pump or even ECMO, depending on their degree of shock. Now, the patients that usually end up on ECMO have severe end organ dysfunction. And sometimes there are even questions about whether these patients are salvageable with an operation. Now, in terms of the surgical intervention itself, the best intervention undoubtedly is mitral valve replacement with cortal preservation.

And the valve choice itself obviously is dependent on a lot of factors mentioned earlier in this podcast. Now, some may ask about the possibility or the likelihood of repairing the valve but given the etiology is ischemic in nature, I'd say there's definitely concern about ongoing necrosis or progression of the failing mitral valve apparatus when compared to just doing a straightforward mitral valve replacement.

However, there are reports of people re implanting a papillary muscle or using neocords, but I would say for, for PIMP questions, the boards, these are exceptions to the rule. And oftentimes trying to repair these techniques may often result in repair failure or even prolonged bypass times. Out of curiosity, how often do you guys see these as a consult on your cardiac surgery service?

I've probably seen four or five since I've been a fellow. Yeah. It happens a couple of times a year. I mean, we definitely saw more of all of the like mechanical complications of MI kind of during the COVID era when people weren't going to seek care. So, I mean, like we've seen more post infarct PSDs and ruptured patent muscles and even free wall ruptures in the last.

You know, four years than we have in the previous eight years that I was a fellow or whatever. Well, that's all the time we have today. We hope that mitral valve disease now maybe makes a little bit more sense. So when you're in the operating room and seeing these consults, you have a better understanding of the repair replacement strategies, as well as how to take care of these patients.

Until next time, Dominate the day. That's right.

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