Chapter: Mitral Vlave

Stenosis Prolapse Regurgitation

Mitral Valve

An overview of mitral valve pathology and its assessment with POCUS

MITRAL STENOSIS (MS)

MS is uncommon in the primary care clinic because rheumatic mitral disease has become rare. Mitral annular calcification (MAC) is common in elderly patients and leaflet tips and chordae can thicken, but these infrequently cause clinically important stenosis. MAC and calcific aortic stenosis are often associated. Abnormal EPSS in a patient with otherwise normal left ventricular (LV) size and function suggests MS or aortic regurgitation.

Here is a PLAX clip of a patient with fairly extensive MAC and restricted movement of the mitral valve (MV). This patient was tachycardic, making analysis more difficult. This patient also had calcification and restricted movement of the aortic valve and the left atrium (LA) was enlarged.

This next patient was not tachycardic, which makes it easier to see both the restricted movement of the MV and the thickening and calcification, particularly of the posterior leaflet apparatus. As with the first patient, the aortic valve was also calcified and the LA was enlarged.

A final patient had thickening and sclerosis of the anterior leaflet, but it was only mildly restricted in movement, with an EPSS of 0.7 cm. However, the posterior MV leaflet seemed not to move in the PLAX. The aortic valve was sclerotic but opened fairly well. The LA was certainly enlarged.

A clip of the apical4 MV of this patient was then obtained and confirmed that the anterior leaflet had only mild restriction in opening, but the posterior leaflet didn’t move at all.

When the suspicion of MS exists, the additional IMBUS tools are only semi-quantitative. The key indicator is color Doppler (CD) in the apical views. Look for increased flow velocity towards the LV that results in a “candle flame” appearance because of the aliasing. It is appropriate to look for this in the apical4, apical2, and apical3 views because they each look at the LV inflow jet from a different angle.

Here is an apical CD clip from a clinic patient with heavy calcification of the MV and apparent restricted leaflet movement.

The jet toward the LV was heavily aliased, rather than the usual red flush.  There was also mild/moderate mitral regurgitation in this patient that will be discussed a little further in this chapter.

With a strongly aliased mitral inflow signal, CWD can evaluate the E wave. In rheumatic MS, the E velocity is high and never returns to the baseline off of the E. Here is a tracing from a clinic patient with rheumatic MS.

Notice the high E-peak velocity of 2.4 m/sec and the velocity never dropped to zero throughout diastole. Compare this rheumatic MS tracing to the mitral inflow tracing done with PWD in the previous MAC patient.

The shape of this spectrum looks similar, with the velocity never returning to the baseline. However, the measured peak E velocity was only 0.65 m/sec. Unless the PWD gate was sub-optimally positioned in the mitral inflow, such a low velocity indicates clinically insignificant MS.


 

MITRAL VALVE PROLAPSE (MVP)

This is a complicated, controversial, and sometimes over-diagnosed disease that occurs in 2-3% of the population, more often in women. But, it is a cause of mitral regurgitation, heart failure, infective endocarditis, and stroke. There are various genetic predispositions that can lead to MVP. In simplest terms, mild MVP without any mitral regurgitation (MR) needs infrequent follow-up. Once MR is present, follow-up needs to be more frequent because the progression of the MR and the consequences for the heart cannot be predicted. Ruptured chordal structures and even flail leaflets are definite possibilities.

In addition, as MR becomes significant, the risk of endocarditis becomes higher in relative terms but still very low in absolute terms. The ID and Cardiology societies recommendations against prophylaxis for MVP are based on older population estimates considering whether an MR murmur was heard or not. The presence or absence of a murmur is a poor surrogate for the severity of MR. Nevertheless, since the absolute incidence of endocarditis in MVP with even severe MR is probably not greater than about 1 in 2000, the societies recommendations against antibiotic prophylaxis probably make sense for most patients, but it is justified to worry about an MVP patient with substantial MR.

MVP isn’t just a little bowing of a leaflet back towards the LA in the apical4 view, because slight bowing can be normal. The whole valve apparatus in the PLAX and apical views should be evaluated. MVP should have increased thickening of the mitral leaflets and the sub-valvular apparatus without sclerosis. The chordae may also be floppy and elongated. A final characteristic feature is a rocking motion of the mitral annulus, which is what corresponds to mitral clicks. The following is a clip from 123sonography that is over a minute long, but nicely demonstrates these features in two different patients. There is no audio, but the arrow points to the characteristic things: increased tissue in the valve and the subvalvular apparatus and the rocking motion of the annulus. These are all more important than bowing of a leaflet back towards the LA. This is a pattern recognition diagnosis after enough normal mitral valves have been seen.

After identifying MVP, all that matters is looking carefully for MR. If a patient has just a little bowing but no thickness or excess tissue in the whole valve apparatus and there is no MR, we should be very reluctant to label the patient with MVP and should rarely recommend formal echocardiography.


 

MITRAL REGURGITATION (MR)

Trace MR is common and by itself has no impact on patient prognosis. Acute MR would almost never be seen in the clinic because these patients become acutely ill very quickly. The rest of this section focuses on chronic MR. Importantly, the severity category of an MR jet can vary substantially depending on a patient’s preload, afterload, and contractile state.

Chronic MR, as it progresses, is a volume overload on the LV, and the intermediate consequence is a somewhat hyper-contractile LV that eventually begins to dilate. Eventually, LA pressure increase is persistent and LA dilation and secondary pulmonary hypertension develops. In the final phase, LV function decreases and cannot keep up with the excess volume.

As with AR, careful attention must be paid to the consequences of MR by carefully measuring LV and LA diameters, LV systolic and diastolic function, and the systolic pulmonary artery pressure. The valve must be fixed before LV function drops below normal. LV function always looks visually better than it is because of the reduced afterload created by the MR and LV function after MV repair (or replacement) almost always deteriorates because the after-load acutely increases.

Quantification of MR is otherwise done equivalently to AR, looking for the presence and size of the flow convergence zone, the width of the vena contracta, and the length and width of the jet. The MR must be viewed in several planes because jets can be eccentric. As a simplification, functional MR from LV dilation and poor systolic function causes central MR jets while eccentric MR jets indicate structural disease of the MV. Eccentric jets that are wall-huggers (Coanda effect) always appear less severe than they are unless the most proximal part of the jet is analyzed. Here is a table to help assess MR severity.

 

MR Classification

Mild

Moderate

Severe

Flow convergence

Minimal to none

Detectable but small

Prominent

Vena contracta

< 0.3 cm

0.3 - 0.7 cm

> 0.7 cm

Jet area

 Small, < 20% of LA

In between

Large, > 40% of LA

 

Next is an example of moderate MR in an apical5 view. There was also modest AR in this view. The sector should have been narrowed and the depth decreased to maximize the frame rate. The image could then have been frozen and the proximal jet analyzed frame by frame. In this view, there definitely is a flow convergence zone, so this is at least moderate MR.

Here is the same patient in an apical3 view. In a few places, the flow convergence zone looks a little larger, suggesting that this might be moderate to severe MR.

Finally, here is a patient with rip-roaring severe MR. The LV is big, the LA is huge, the flow convergence zone is enormous, and the jet fills the whole LA.