Harvard Medical School Mitral Regurgitation 2008 David M. Leder, MD 8/20/08.

Harvard Medical School

Mitral Regurgitation 2008

David M. Leder, MD

8/20/08


Outline

• Anatomy• Etiology of mitral regurgitation• Management strategies for chronic severe MR• Quantification of MR severity on

echocardiography• Advances in mitral valve repair


Anatomy

• Functionally includes:– Left ventricular myocardium

– Subvalvular apparatus (papillary muscles and chordae tendinea)

– Mitral annulus

– Mitral valve leaflets

– Left atrium


Anatomy:



Etiology of Mitral Regurgitation:

• Primary:

-Myxomatous

-Endocarditis

-Rheumatic

-Trauma

-Anorexic drugs

• Functional (Secondary):-LV systolic dysfunction

-Ischemic heart disease

-Hypertrophic CM


Functional (Carpentier) Classification:

• Type I = normal leaflet motion but with annular dilatation or leaflet perforation

• Type II = leaflet prolapse (eg myxomatous disease) or papillary muscle rupture

• Type III = restricted leaflet motion.

IIIa = rheumatic disease

IIIb = ischemic or idiopathic cardiomyopathy.


Copyright ©2006 American College of Cardiology Foundation. Restrictions may apply.Bonow, R. O. et al. J Am Coll Cardiol 2006;48:598-675

Management strategy for patients with chronic severe mitral regurgitation


Management – Symptomatic patients:


Management – Asymptomatic patients:

>90%


How to measure severity of mitral regurgitation:


I. Hemodynamic Determinants of MR

• RgV = Regurgitant volume.

• ROA = Regurgitant oriface area.

• Cd = Discharge coefficient

• MPG = Mean systolic pressure gradient b/t the LV and LA

• T = Duration of MR during systole.


Regurgitant Oriface Area (ROA)

• Typically fixed in rheumatic MR b/c the valve is fibrotic, calcified, and immobile.

• In DCM and myxomatous disease, it is often dynamic and load dependent.

• ROA is a fundamental determinant of MR severity and therefore its measurement/calculation is critical.


Discharge coefficient (Cd)

• Is a constant.• Accounts for contraction of the flow stream as it

passes through the anatomic orifice.• It is dependent upon orifice geometry, flow, and

fluid viscosity.• Is not affect by clinical variations in loading

conditions.


Mean systolic pressure gradient (MPG)

• Is a primary determinant of MR severity, but its effect on echo variables is mitigated by 2 factors:1. Hemodynamic changes tend to move LV and LA

pressures in the same direction, thus the net effect is blunted.

2. It is a function of its square root. eg. a 144mmHg gradient compared to a 100mmHg gradient only results in a 20% difference in the calculated MR volume.

(ie. 12 v. 10)


Duration of MR during systole (T)

Particularly important in myxomatous degeneration, where late systolic MR may lead to overestimation of MR severity by techniques that rely on single frame measurements (eg PISA or vena contracta).


II. Mitral Valve Anatomy

• Includes the leaflets, annulus, chordae, papillary muscles, and left ventricle.

• Severe MR seldom occurs when the mitral valve and left ventricle are anatomically normal.

• LA size and LV function provide clues to the severity and chronicity of MR.


III. Doppler Color Flow Mapping

• Represents an image of the spatial distribution of velocities within the imaging plane.

• It can be profoundly affected by instrument settings and hemodynamic variables.

• Since spatial distribution of velocities is not a primary determinant of MR severity according to the Gorlin equation, some argue it should not be heavily relied upon to grade MR severity.

• That being said, it does offer several potential ways to assess MR severity.


Color Flow Jet Area

• Generally, larger jets which extend deep into the LA represent more MR than small thin jets.

• However, the correlation b/t jet area and MR severity is poor due to technical and hemodynamic limitations.

• Therefore avoid grading MR severity by “eyeballing” the color flow jet area.– Exception: a small central jet w/ an area <4.0cm2 or

<10% of LA area, is almost always mild MR.


Vena Contracta Width

• Represents the smallest, highest velocity region of a flow jet and is typically located at or just downstream from the regurgitant orifice.

• Should be measured in a plane perpendicular to mitral leaflet closure (eg PLA).

• If the regurgitant orifice is circular, then vena contracta width should be an excellent marker of the ROA.

• However, the regurgitant orifice in MR is often elongated along the coaptation line…ie, like a smiley face.



Long-axis Short-axis



• Has been shown to be accurate in assessing the severity of MR.

• According to ASE:<0.3cm = mild MR

>/=0.7cm = severe MR

• A strength of this method is that it works equally well for central and eccentric jets.


Proximal Isovelocity Surface Area (PISA)

• Based on the hydrodynamic principle that the flow profile of blood approaching a circular orifice forms concentric, hemispheric shells of increasing velocity and decreasing surface area.

• In MR, color flow mapping is usually able to image one of these hemispheres that corresponds to the aliasing velocity of the instrument.

• The aliasing velocity should be adjusted to identify a flow convergence region with a hemispheric shape.

• The radius of this hemisphere is then measured and flow rate is calculated as the product of the surface area of the hemisphere and the aliasing velocity.




• Assuming that the maximal PISA radius occurs at the time of peak regurgitant velocity, the maximal EROA can be derived as:

• PkVreg = the peak velocity of the regurgitant jet by continuous wave Doppler.

• Generally, an EROA >/=0.4cm2 is considered to be severe MR. <0.2cm2 is mild MR




EROA = [6.28 x (.8)(.8) ml/s] / [480 cm/s] = 0.3cm2


Limitations of PISA

• It is more accurate for central jets.• In MR, the orifice shape is often elliptical rather

circular/hemispheric.• Any error is determining the location/radius of the

orifice is squared.– Therefore PISA is more accurate if the aliasing velocity

can be adjusted to obtain a radius of >/=1cm.

• For determination of EROA, it is essential that the CW signal by well aligned with the regurgitant jet.


IV: Quantitative Doppler Volumetric Measurements:

• In the absence of regurgitation, stroke volume should be equal at different sites, eg the mitral and aortic annulus.

• In the presence of regurgitation (assuming the absence of an intracardiac shunt), the flow through the affected valve is larger than through other competent valves.


Quantitative Doppler Volumetric Measurements:


Quantitative Doppler Volumetric Measurements:

• Common errors:1. Failure to measure the valve annulus properly.

2. Failure to trace the modal velocity of the pulsed Doppler tracing.

3. Failure to position the sample volume correctly, at the level of the annulus.


V. Adjunctive Findings

• Continuous wave Doppler-the density of the CW signal is a useful qualitative index of MR

severity (a dense signal suggests worse MR)

-an unusually low maximum velocity may indicate hemodynamic compromise (high LA and low LV systolic pressures)

• Pulsed Doppler-patients with severe MR usually exhibit dominant early filling

(E>1.2m/s); an A-wave dominant inflow pattern virtually excludes severe MR.

• Pulmonary vein flow-with increasing severity of MR, systolic velocity in the pulmonary

veins progressively decreases and reverses in severe MR.


Summary


Summary


Evolving Concepts and Technologies in Mitral Valve Repair


Key Concept: the fibrous skeleton of the heart is fixed and its length does not change with mitral valve disease.


Valvular-Ventricular Interactions

• The collagenous matrix elements within the chordae tendineae and papillary muscles are histologically continuous with the collagen network of the heart at one end and the mitral valve annulus and leaflets at the other end.

• Removal of the papillary muscles and chordae results in ventricular dilatation, increased wall stress and afterload, and decreased contractile fxn.

• Late survival after MVR can be enhanced with the use of chordal-sparing techniques.


Annuloplasty Rings

• The annulus is a dynamic, saddle-shaped structure.

• The original Carpentier ring was flat and rigid.

• Newer mitral rings have attempted to replicate this normal saddle shape and flexibility.


Annuloplasty Rings• Despite a more “normal” valve physiology, superior long-term

clinical results with flexible rings have not been demonstrated.• The most recent annuloplasty rings are cause-specific, geometrically

shaped to accommodate the underlying pathology and not to replicate the “normal” mitral annulus.


Commercially Available Rings and Band


Novel (Percutaneous) Approaches to Mitral Valve Repair


Coronary Sinus Approaches

• Concept: – Place a device in the coronary sinus to push against the posterior

portion of the mitral annulus and ideally improve coaptation of the posterior and anterior mitral valve leaflets

• Anatomic limitations:– Often the coronary sinus does not lie directly adjacent to the

posterior mitral valve annulus.

– The CS is an atrial structure and not in the same plane as the mitral valve annulus

– The left circumflex artery may lie in between

– The distance between the CS and posterior mitral annulus increase with chronic ischemic MR


Coronary Sinus Approaches


Annular Approaches

• Include annular shrinking via magnets or heating.• The Mitralign device approaches the posterior

annulus directly from the LV and positions stitches to allow annular cinching.

• The PS3 system approaches the posterior annulus from the atrial septum and tethers a device from the P2 vicinity toward the atrial septum.


Alfieri Revisted:• Edge-to-edge surgical concept modified for a percutaneous approach.

• Feasibility study completed in the US and a randomized phase 2 trial is ongoing.

• Surgical experience with

the technique demonstrated

significant recurrent MR if

it was not accompanied by

an annuloplasty

• Reoperation at 5 years =

30% v. 8%, p=0.02


Subvalvular Approaches

• Developed to treat complex ischemic mitral valve disease:

1. Approximate the papillary muscles (papillary muscle sling)

2. Pull the papillary muscles toward the annulus to release leaflets tethering.

3. Cut secondary chords to reduce tethering of the leaflets.

• All have been used with some success but the need is uncommon, as the majority of patients with MR undergoing coronary bypass are treated with simple annuloplasty rings.


Coapsys and i-Coapsys

• Evolved from the concept of moving the ventricle, rather than the annulus, to increase leaflet coaptation and eliminate functional MR.

• Can be placed off pump w/ echo guidance or via a minimally invasive approach w/ fluoro guidance.

• Employs a transventricular splint


Coapsys and i-Coapsys• The pads are tightened gently to pull the ventricle into the

region of the papillary muscles and also to move the posterior leaflet to better coapt with the anterior leaflet.


The End: Questions?

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Harvard Medical School Mitral Regurgitation 2008 David M. Leder, MD 8/20/08.

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