Heart Valves Permit Forward Flow of Blood Through the Cardiac Chambers When Open and Prevent Backward Leakage When Closed

7/31/2019 Heart Valves Permit Forward Flow of Blood Through the Cardiac Chambers When Open and Prevent Backward Le

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Heart valves permit forward flow of blood through the cardiac chambers when open and prevent

backward leakage when closed. Mitral regurgitation is characterized by abnormal backflow ofblood through the mitral valve during the systolic period of the cardiac cycle. The left ventricle

(LV) must pump additional volume to compensate for the amount regurgitated. As mitral

regurgitation becomes severe, the continued hemodynamic burden may lead to ventricular

dysfunction, heart failure, and sudden death.

See the images below depicting mitral regurgitation.

Severe mitral regurgitation as depicted with color Doppler

echocardiography. Mitral regurgitation as seen with left

ventricular (LV) cineangiography.

Mitral regurgitation may be acute or chronic. Common causes of severe acute mitralregurgitation include ruptured chordae tendineae, ischemic papillary muscle dysfunction or

rupture, and infective endocarditis. Chronic severe mitral regurgitation is commonly caused bymyxomatous degeneration of the valve, rheumatic heart disease, or mitral annular calcification.

Echocardiography has emerged as the diagnostic imaging modality of choice. It can provide

vivid images of the LV and the mitral valve, and it may provide clues to the mitral-valve

abnormalities responsible for the regurgitation. The Doppler echocardiographic technique isexcellent for determining the severity of mitral regurgitation.

Acute mitral regurgitation often requires prompt surgical correction. However, symptomatic

patients with chronic mitral regurgitation may be initially treated with digitalis, afterloadreduction, and diuretics. After the LV function begins to deteriorate, clinical and

echocardiographic parameters may be used to determine the timing for surgical reconstruction or

replacement of the mitral valve.[1, 2, 3]

Electrocardiography
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The electrocardiogram (ECG) may exhibit an LA abnormality, LVH, and, in some patients, atrial

fibrillation. ECG evidence of LV enlargement occurs in about one third of patients with severemitral regurgitation. In approximately 15% of patients, the ECG shows evidence of RV

hypertrophy.

Chest radiography

Although the heart may not be enlarged in patients with acute mitral regurgitation, severepulmonary edema is frequently present as a result of left-sided cardiac failure. In cases involving

chronic mitral regurgitation, the LA and the LV border appears enlarged, and it may be massive

because of volume overload and increased pressure. When the LA is enlarged, it may extend

toward the right side, and it may appear as a double shadow along the right atrial border.Coexistent pulmonary arterial hypertension or tricuspid regurgitation may cause dilation of the

right atrium and ventricle, as well as enlargement of the pulmonary arteries.

Echocardiography

Echocardiography is the preferred examination. It demonstrates the extent of LA and LV

enlargement, as well as the presence and severity of mitral regurgitation. Two-dimensional (2D)echocardiography or transesophageal echocardiography (TEE) with Doppler echocardiography

and color flow Doppler imaging enables detailed assessment of the structure and function of the

mitral valve.

In the past, the use of echocardiography resulted in overestimations of the prevalence of MVP.

Early studies suggested a prevalence of as high as 21% in healthy young women. In earlystudies, normal bowing of the mitral valve was interpreted as representing an MVP.

Magnetic resonance imaging

MRI can demonstrate the abnormality of the valve apparatus, and it may be useful in evaluating

the amount of regurgitant flow with velocity encoding (VENC) and with model-independent

measurements of stroke volumes of RV and LV.

Cardiac catheterization

Cardiac catheterization is often needed. In patients older than 40 years or in those with symptoms

suggestive of coronary disease, cardiac catheterization should include coronary arteriography.

The main indications for catheterization include (1) the need to evaluate a discrepancy between

echocardiographic findings and the clinical presentation, (2) the need to detect other associatedvalvular lesions and to assess the severity of those lesions, and (3) the need to determine whether

coronary artery disease is present and, if so, to assess the extent of disease.

Limitations of techniques


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The limitations are minimal. Color-flow Doppler echocardiography of the valve helps in

determining the severity of regurgitation, but because this technique measures flow velocityrather than actual flow, it is subject to error in interpretation.

The Doppler technique is good for excluding mitral regurgitation and for differentiating between

mild and severe degrees of the condition. However, color-flow Doppler examination may not besufficient for more exact quantification of mitral regurgitation or for determining whether the

lesion is severe enough to cause LV dysfunction.

Chest radiography is useful in evaluating mitral regurgitation in several ways, but it mostly

reveals nonspecific findings.

Cardiomegaly

The chest radiograph usually shows an enlarged cardiac silhouette. The heart is increased in sizesecondary to enlargement of both the LA and the LV. The absence of cardiomegaly indicates that

the mitral regurgitation is either mild or acute.

The enlarged atrial appendage may be seen along the middle portion of the left cardiac border.

Also, a double shadow may be present on the right cardiac border, indicating an increase in thesize of the LA.

In patients with combined mitral stenosis and mitral regurgitation, overall cardiac enlargementand particularly LA dilatation are prominent findings. Relatively mild cardiomegaly and

clinically significant changes in the lung fields suggest predominant mitral stenosis. In

comparison, predominant mitral regurgitation is most likely when the heart is greatly enlarged

and when the changes in the lungs are relatively inconspicuous.

Calcification

Calcification of the mitral annulus, an important cause of mitral regurgitation in the elderly, is

most prominent in the posterior third of the cardiac silhouette. The lesion is best visualized on

chest radiographs in the lateral or right anterior oblique projections, on which it appears as adense, coarse, C -shaped opacity.

Pulmonary edema

Pulmonary interstitial edema with Kerley B lines is usually seen in patients with progressive LV

failure and chronic mitral regurgitation.

In acute mitral regurgitation, the chest radiograph reveals pulmonary edema, moderate or no

enlargement of the LA, and little if any cardiac enlargement.

CT can show the cardiac silhouette and chamber sizes with clarity. However, because of the widespread

use of echocardiography, CT is rarely performed in the evaluation of mitral regurgitation. The degree of

confidence is moderate in mitral regurgitation. False findings are rare in mitral regurgitation


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Accurate measurement of the degree of mitral regurgitation is critical. Doppler echocardiographyprovides an estimate of the area and depth of the regurgitant jet, but the finding is onlysemiquantitative. A direct quantitative, noninvasive measurement of the mitral regurgitant

volume can be precisely determined by using MRI.

Spin-echo MRI

Spin-echo (SE) images show structural consequences of mitral regurgitation, such as an enlargedLV and LA.

Cine gradient-echo MRI

Cine gradient-echo (GRE) images may be used to assess the severity of mitral regurgitation bycalculating the regurgitant fraction. The procedure involves mapping the area of the signal void

starting from the mitral valve and extending into the LA. The signal void of mitral regurgitation

is best seen on the 4-chamber and the coronal oblique views.

Another way to calculate regurgitant fraction involves estimation of the ventricular volumes.This method is usable only if the mitral valve is the sole regurgitant valve.

VENC MRI

VENC (encoding velocity) MRI is another method for determining the severity of mitral

regurgitation. In this method, the diastolic inflow across the mitral annulus is compared with

systolic outflow across the ascending aorta. In cases of mitral regurgitation, the LV inflow isincreased. As an alternative, regurgitant volume may be determined by measuring flows in the

ascending aorta and pulmonary artery. In fact, the best way to quantify the mitral regurgitant

volume is to combine the ventricular volume calculations obtained by using cine GRE sequenceswith the estimated forward flow in aorta obtained with VENC MRI.

Degree of confidence

The degree of confidence is high. MRI is the most accurate technique for measuring regurgitant

flow, and it provides measurements that are well correlated with those of quantitative Doppler

imaging. MRI is also the most accurate noninvasive technique that enables the measurement ofventricular EDV, ESV, and mass.

Errors may occur when cine GRE imaging is used to measure the area of the mitral annulus and

the mitral flow velocity, owing to the constant motion of the atrioventricular valves during eachcardiac cycle.

Two-dimensional echocardiography

In patients with severe mitral regurgitation, 2D echocardiography shows enlargement of the LA

and LV. The cause of mitral regurgitation may often be apparent on the transthoracicechocardiogram. Potential causes include rupture of the chordae tendineae; MVP; a flail leaflet;


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vegetations; and LV dilatation. Calcification of the mitral annulus, which appears as a band of

dense echoes, may be seen between the mitral valve and the posterior wall of the heart.

Three-dimensional echocardiography

Three-dimensional (3D) transthoracic echocardiography (TTE) and 3D color Doppler imagingmay be helpful in elucidating the mechanism of mitral regurgitation. The imaging of the mitral

valve is excellent on TEE, and the images offer clues to the mitral valve abnormalitiesresponsible for the regurgitation (see the image below).

Four-chamber apical view of a 2-dimensional transthoracicechocardiogram demonstrates mitral valve prolapse (MVP), a common cause of mitralregurgitation.

Color-flow Doppler imaging

Color-flow Doppler imaging of the valve helps in semiquantitatively determining the severity of

regurgitation (see the images below). This technique measures flow velocity rather than actual

flow; therefore, it is sometimes subject to error.

Severe mitral regurgitation as depicted with color Doppler echocardiography.
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Mitral regurgitation as seen with pulsed Doppler echocardiography.

Mitral regurgitation as seen with color Doppler echocardiography.

Left, Color Doppler apical 4-chamber view shows severe mitral regurgitation with theregurgitant jet hitting the distant wall of the left atrium and encircling it, as well as traversing

back into the pulmonary veins. Right, Pulsed Doppler images with a high-velocity jet in thesystolic phase of the cardiac cycle; this represents severe mitral regurgitation.

Mitral regurgitation in a patient with mitral valve prolapse (MVP). The regurgitant is

pointedposteriorly as a result of a prolapsing posterior mitral leaflet.

Acute severe mitral regurgitation in a patient with trauma. The mitral-regurgitation jet is wide, a

finding that semiquantitatively indicates severity. The normal size of the left atrium (LA) should

be noted, because the LA has not had sufficient time to adapt and enlarge, owing to the acutenessof the regurgitation.

The severity of mitral regurgitation is directly proportional to the size of the regurgitant jet

within the left atrium. The size of the jet is typically indexed to the size of the left atrium. Jets

that are peripheral impinge on a wall, rather than the center, causing predictable problems withassessment of severity. Owing to the Coanda effect, a regurgitant jet impinging on a wall results
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in a color-flow area smaller than an equivalent central regurgitant volume. A jet impinging on a

wall leads to underestimations of the regurgitant volume by approximately 40%.

In cases of moderate and severe mitral regurgitation, flow in the pulmonary veins may reverse

direction in systole. A variation on this finding is attenuation of normal forward flow in the

pulmonary vein during ventricular systole. Three-dimensional reconstruction of mitralregurgitation jets has been shown to be feasible. The incremental value of this method has not

yet been demonstrated.[4, 5, 6, 7, 8, 9, 10]

Doppler echocardiography

In cases of mitral regurgitation, Doppler echocardiography characteristically reveals a high-

velocity jet in the LA during systole. The severity of the regurgitation is a function of the

distance from the valve at which the jet can be detected and the size of the LA.

In estimating the severity of mitral regurgitation, both color-flow Doppler and pulsed Doppler

results are used. Color Doppler imaging involves measurement of the area of the mitral jet. If thearea of the jet is greater than 8 cm

2, the mitral regurgitation is considered severe. Findings that

indicate that mitral regurgitation is severe include reversal of flow in the pulmonary veins during

systole and a high peak mitral inflow velocity.

Transesophageal echocardiography

TEE is better than TTE in imaging the regurgitant mitral valve. Angiographic assessments ofmitral regurgitation are well correlated with the color-flow mapping obtained by using TEE

rather than TTE.

Mitral valve prolapse

Echocardiography is useful in diagnosing MVP, in determining the severity of associated mitral

regurgitation, and in showing the pathologic anatomy of the mitral valve. An extreme form ofMVP involves myxomatous degeneration of the valves with leaflet thickening (>3-5 mm),

marked symmetrical bowing of the valve behind the annular plane, and/or highly asymmetrical

buckling of 1 or both leaflets into the LA associated with mitral regurgitation. Because of the

eccentric leaflet buckling, the mitral regurgitation jet may be eccentric rather than central.

Acute mitral regurgitation after acute myocardial infarction

Two complications of myocardial infarction that produce confusing clinical signs are mitralinsufficiency caused by rupture of an infarcted papillary muscle and a ventricular septal defect

that occurs after infarction and necrosis of the septum. These are easily identified by noting the

intracardiac flow patterns seen on cine GRE images.



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The degree of confidence is high in mitral regurgitation. False findings are rare. Color-flow

Doppler examination may not be sufficient for exactly quantifying mitral regurgitation or fordetermining whether the severity of the lesion is sufficient to cause eventual LV dysfunction.

Radionuclide angiography may be useful in assessing mitral regurgitation, and gated blood-pool

nuclear imaging or first-pass angiography may reveal an increased EDV.

The regurgitant fraction may be estimated from the ratio of LV stroke volume to RV strokevolume. In patients with mitral regurgitation and impaired LV function, the ejection fraction fails

to rise normally during exercise.

Radionuclide angiograms are useful for interval follow-up, and progressive increases in

ventricular EDV and/or ESV often suggest that surgical treatment is necessary.

Radionuclide angiography is good for assessing LV function. False findings are unusual in mitral

regurgitation.

LV angiography may be performed to evaluate mitral regurgitation.

The immediate appearance of contrast material in the LA after its injection into the LV indicates

mitral regurgitation. The regurgitant volume may be determined from the difference between the

total LV stroke volume, which is estimated by using angiocardiography, and the simultaneousmeasurement of the effective forward stroke volume, which is determined by using the Fick

method.

In patients with severe mitral regurgitation, the regurgitant volume may approach the effective

forward stroke volume; in rare instances, it may even exceed this volume. Qualitative but

clinically useful estimates of the severity of mitral regurgitation may be made by means ofcineangiographic observation of the degree of opacification of the LA and the pulmonary veinsafter the injection of contrast material into the LV (see the image below).

Mitral regurgitation as seen with left ventricular (LV) cineangiography.

The cause of the regurgitation (eg, MVP) and a flail leaflet may often be distinguished by usingangiography. Mitral regurgitation secondary to rheumatic heart disease is angiographically

characterized by a central regurgitant jet and by thickened leaflets that have reduced motion. In

regurgitation resulting from other conditions, particularly dilatation or calcification of the mitral

annulus or ruptured chordae tendineae and papillary muscles, the systolic jet may be eccentric; insuch cases, the valves consist of thin filaments that display excessive motion.
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The degree of confidence in mitral regurgitation is excellent. False findings are rare in mitralregurgitation.

http://emedicine.medscape.com/article/349648-overview#a24

http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/cardiology/mitral-valve-

disease/

Mitral stenosis is characterized by restriction of blood flow from the left atrium (LA) to the leftventricle (LV) as a result of a narrowed mitral passage. It is an acquired valvular defect; it is

usually a consequence of rheumatic heart disease, though cases of congenital mitral stenosis are

occasionally encountered.

Extensive mitral annular calcification (MAC) may result in mitral stenosis, particularly in the

aged. Mitral stenosis is seen more often in women than in men, and it generally develops at anearlier age in developing countries than in Western societies. In the latter, the incidence ofrheumatic fever has declined precipitously over the past 4 decades.

See the images below depicting mitral stenosis.

Mitral stenosis as demonstrated with 2-dimensional (2D)

echocardiography. Rheumatic mitral stenosis with commissuralfusion and enlarged left atrium. Calcification of the subvalvular structures is minimal and has a

low Massachusetts General Hospital (MGH) score; this condition is potentially amenable to

balloon valvotomy.

Patients with mitral stenosis usually remain symptom-free for years. After the mitral orifice isreduced to one third of its normal size, symptoms typical of left-sided heart failure develop, such
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as dyspnea on exertion, orthopnea, and paroxysmal nocturnal dyspnea. Right ventricular (RV)

failure gradually ensues, causing ascites and edema.

Multiple imaging modalities may be used to diagnose mitral stenosis. Echocardiography has

become the most important diagnostic tool for confirming the diagnosis, for quantifying the

severity of mitral stenosis, and for determining the optimal timing for intervention.

Asymptomatic individuals with sinus rhythm on ECG need no treatment. After atrial fibrillationdevelops, pharmacologic agents may be administered to control the ventricular rate; in addition,

anticoagulation therapy may be initiated to prevent thromboembolism.

Symptoms of dyspnea and orthopnea improve with the use of diuretics. As symptoms worsen

and pulmonary hypertension occurs, mechanical correction of the stenosis, rather than medical

therapy, becomes necessary.

These surgical options, which include valvuloplasty and mitral valve replacement, have changed

the natural history of mitral stenosis, and terminally bedridden patients with mitral facies, cardiaccachexia, and end-stage congestive heart failure (CHF) are no longer encountered in everyday

clinical practice. Nonetheless, mitral stenosis is still endemic, and it continues to be a substantial

problem in many countries.[1, 2]

Echocardiography

Echocardiography, especially Doppler echocardiography, is the procedure of choice for

evaluating the degree of mitral stenosis; in most of the patients, echocardiography may be

adequate for the planning of therapeutic interventions.[3, 4, 5, 6, 7, 8]

Echocardiography generally provides sufficiently detailed images of the mitral valve and is themost important diagnostic tool in establishing the diagnosis. Doppler echocardiography is used

to accurately depict the severity of mitral stenosis. Typical 2-dimensional (2D)echocardiographic findings include thickening of the mitral valve cusps; enlargement of the LA,

with a normal or small LV; and a reduction in the size of the mitral valve orifice in diastole. A

diminished E-F slope is noted on M-mode images. Doppler studies demonstrate an increase inthe mean pressure gradient across the mitral orifice; Doppler studies are also helpful in

quantifying the severity of mitral stenosis.

Electrocardiography

If the patient is in sinus rhythm, the electrocardiogram shows abnormality of the LA. LAabnormality is manifested by prolongation of the P wave, with a double-saddleback contour (pmitrale) in limb lead II. This contour represents a right atrial p wave followed by delayed LA P

wave associated with an enlarged left atrium. LA abnormality is seen as a terminal negative

deflection following the initial upright p wave in the chest lead V1. The main rhythm is usually

sinus in the beginning. However, atrial fibrillation increases in frequency as mitral stenosisadvances. If pulmonary arterial hypertension has developed, electrocardiography may show signs

of RV hypertrophy.


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Patient selection for balloon mitral valvuloplasty by echocardiographic score

A widely adopted echocardiographic scoring system that Wilkins and colleagues developedhelps in patient selection.[9] In this system, 4 features of the mitral valve are identified, as

follows:

Valve leaflet mobility Valve thickening Valve calcification Subvalvular involvement

Each of these 4 features is then graded on a scale of 1-4, with the different grades representing

minimal, mild, moderate, and severe involvement, respectively. The highest total possible score

is 16. A score of 8 or less indicates high probability that balloon mitral valvuloplasty will be

successful.

Percutaneous balloon mitral valvotomy is the procedure of choice for patients who havesymptomatic, hemodynamically severe stenosis and whose echocardiographic score is 8 or lessand who are without LA thrombus. A score of 8 or less is generally associated with excellent

immediate and long-term results. For patients with scores exceeding 8, the results are less

impressive; in such patients, there is a risk of mitral regurgitation.

For patients with mitral stenosis, the chest radiograph may exhibit certain specific and

nonspecific findings that are generally a consequence of left atrial enlargement, mitralcalcification, pulmonary hypertension, and congestive heart failure (CHF).[10] The degree of

confidence is reasonably good for mitral stenosis. Findings are sometimes nonspecific.

Left atrial enlargement

The characteristic radiologic finding of mitral stenosis is selective left atrial enlargement.

An enlarged left atrial appendage, as shown by convexity at the left upper cardiac border just

below the left main bronchus, suggests a rheumatic etiology.

Generalized left atrial enlargement, particularly on the anteroposterior chest radiograph, altersthe left border of the cardiac silhouette so that it becomes straight, in contrast to the usual mildconcavity evident beneath the pulmonary artery shadow. A double contour or double convexity

may be discernible along the right cardiac border.

On the lateral chest radiograph, an enlarged LA is seen as posterior displacement of the uppercardiac border inferior to the tracheal bifurcation. In fact, a lateral chest radiograph obtained

during a barium swallow study may show a large left atrium impinging on the esophagus and

displacing it backward and to the left, in contrast with its usual rightward displacement.

Severe LA dilatation may cause aneurysmal enlargement; in addition, the left atrium approacheswithin a few centimeters of the chest wall on 1 or both sides, as seen in long-standing mitral


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regurgitation with atrial fibrillation. The LV is usually not enlarged in cases of isolated mitral

stenosis unless there is clinically significant mitral regurgitation.

Calcification

Calcification may be detectable on the plain radiograph. It may be either in the wall of the leftatrium or in a blood clot lining the atrial wall. This kind of calcification appears as a curvilinear

structure lying fairly high on the cardiac silhouette.

Fluoroscopy may be used to identify dystrophic calcification in the mitral valve cusps in patients

with long-standing rheumatic heart disease.

Mitral annular calcification (MAC) may appear in the shape of an ellipse, usually open medially

in a J, U, or horseshoe shape. In addition to causing mitral stenosis, the dense calcification may

interfere with valve closure and cause mitral regurgitation.

Pulmonary hypertension

In the presence of pulmonary arterial hypertension, the main pulmonary artery and central

pulmonary vessels appear enlarged, with pruning of the peripheral vessels.

Pulmonary congestion

Mitral stenosis causes pulmonary venous hypertension that appears as increased vascularity on

chest radiographs. Selective blood diversion to the upper lobes distends upper-lobe veins andconstricts lower-lobe veins.

Kerley septal costophrenic B lines represent interstitial edema. Pulmonary alveolar edema mayappear as confluent pulmonary shadows present mainly in the perihilar region.

The edematous interlobular septa of the lungs may be identified on the chest radiograph as

opaque lines of different lengths, depending on their location. Kerley first described these lines,

designated A, B, and C, which are known as Kerley lines. A lines are 5 to 10 cm long and arenonbranching; they fan radially upward and outward from the pulmonary hilum. B lines are best

seen in the lower lung zones, perpendicular to the pleural surface; these are shorter than 2 cm.

The combination of A and B lines creates a reticular pattern, called C lines, that are transient anddifficult to visualize.

All of the Kerley lines represent edematous interlobular septa. The pulmonary lobules tend to belarge and are oriented obliquely to the pleura in the upper lobes, whereas in the lower lobes, theyare shortened and are perpendicular to the pleural surface. This feature results in the

characteristic appearance of the B lines, which are the ones most readily identified on the chest

radiograph.

Miscellaneous findings


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Pulmonary hemosiderosis develops in long-standing mitral stenosis and pulmonary hypertension.

It is seen on the chest image as fine punctuate opacities throughout the lungs. They may alsooccur as recurrent hemorrhages seen as iron-containing deposits in the pulmonary tissue.

Pulmonary ossified nodules, defined as multiple discrete calcified opacities of up to 10 mm in

diameter, may be seen at the bases of the lungs as well.

CT scans occasionally depict calcification in the enlarged LA in patients with mitral stenosis. Itmay be seen to occupy the wall of the atrium, or it may appear within a thrombus attached to the

wall.

Whenever calcification is observed in the atrial appendage, it generally indicates associated

mitral stenosis. Calcification in the wall of the atrium or in the appendage is usually considered

an unfavorable prognostic sign.

When calcification in the atrium is suspected but is not positively identified on the chest

radiograph, fluoroscopy or CT may be used to confirm the diagnosis. In the current era, CTscanning is rarely performed; rather, echocardiography has gained widespread use, owing to its

portability and the fact that there is none of the risk associated with the use of radiation.

For patients with mitral stenosis, MRI may be helpful if Doppler echocardiographic findings are

insufficient or are inconsistent with clinical data.[11, 12]

This problem occurs in approximately

10% of patients because of air-tissue attenuation of ultrasound. MRI is often used in cases inwhich there is associated complex congenital heart disease because of its 3-dimensional (3D)

capabilities and high resolution.

MRI is of limited use in patients with atrial fibrillation, a common finding in mitral stenosis.

Irregular rhythm may be a potential source of error in the measurements.

Pulse sequences

With recent technological advances in magnetic resonance (MR) computer technologies, many

pulse sequences may now be used for cardiac MRI. The 2 main types of pulse sequences aredark-blood techniques and bright-blood techniques. With dark-blood techniques, such as spin-

echo (SE) and fast SE (FSE), fast flowing blood appears black and hypointense; dark-blood

techniques are useful for delineating the structure of cardiac chambers and the lumina of bloodvessels. In contrast, the bright-blood techniques, such as gradient-recalled echo sequences

(GRE), depict flowing blood as white and hyperintense. Bright-blood techniques are useful for

determining gradients and flows.

Imaging planes

Imaging planes for MRI of the thorax are the 3 orthogonal planes: transverse, sagittal, andcoronal. Because the cardiac axes are not parallel to the axes of the body, planes parallel and

orthogonal to cardiac axes (ie, the short and long axes of the heart) are used for cardiac imaging.


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For the mitral valve in particular, a long-axis view of the mitral valve is obtained through the LV

apex and the outflow tract for a 5-chamber view.

SE MRI

ECG-gated multisection SE and FSE MRI usually demonstrates thickening and bulging of theleaflets of the mitral valve. It may also show the sizes of the chamber, particularly in cases

involving an enlarged left atrium and a normal-size left ventricle.

Cine GRE MRI

Cine MRI is performed by using GRE pulse sequences at multiple phases of the cardiac cycle.

These may be used to determine the degree of mitral stenosis on the basis of the size and extentof the abnormal flow jet during diastole. The best planes for obtaining the signal void

representative of the abnormal flow jet are the 4-chamber view and the coronal oblique plane,

displaying the left atrium and the left ventricle.

Velocity-encoded cine MRI

With the help of velocity-encoded cine MRI, the maximum velocity of the mitral stenotic jet may

be calculated on planes perpendicular and parallel to the direction of the flow. This velocity

value may then be used in the modified Bernoulli equation (gradient = 4 X velocity2) to

determine the gradient across the stenotic mitral valve.

chocardiography is the most widely used imaging modality in the evaluation of mitral stenosis. Afull echocardiographic examination includes 2D transthoracic echocardiography (TEE), Doppler

echocardiography, and color-flow Doppler imaging. In most patients, echocardiography can

provide adequate information to formulate a therapeutic strategy without the need for cardiaccatheterization (see the images below).[13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28]


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Mitral stenosis as demonstrated with 2-dimensional (2D)

echocardiography. Prosthetic mitral valve in a patient with mitral

stenosis, as demonstrated with 2-dimensional echocardiography.

Two-dimensional (2D) echocardiogram (apical 4-chamber view) in a 29-year-old patient with

rheumatic mitral stenosis and mitral regurgitation shows fusion of commissures and vegetation.The echocardiogram was taken after the patient was hospitalized with sepsis (subacute bacterial

endocarditis).

General findings

In patients with mitral stenosis, characteristic findings on 2D echocardiography includethickening and reduced mobility of anterior and posterior mitral leaflets, with predominant

involvement of the commissures, especially in cases of rheumatic mitral stenosis. In advanced

mitral stenosis, substantial calcification occurs within the leaflet and the subvalvular tissues,

including the chordae tendineae and the papillary muscles.

Leaflet motion at the tips is decreased in the beginning, sparing the body and leading to the

characteristic doming of the mitral valve seen on 2D echocardiograms. The anterior leafletassumes a hockey-stick appearance. The actual restrictive orifice of the mitral valve may be

planimetrically measured in a parasternal short-axis view.

In the M-mode, the thickened leaflets may be seen. Because of their limited mobility, flattening

of the E-F slope is observed; the degree of flattening may be used to calculate the severity of

mitral stenosis.
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Assessment of the severity of mitral stenosis

Both continuous-wave and pulsed Doppler echocardiography may be performed with the patientat rest and during exercise to quantitate the transmitral gradient.

Pressure half-time method for calculating the area of the mitral valve

The pressure half-time (T) is the time in milliseconds required for the peak pressure gradient to

decline to one half of its original value. T may be calculated as follows: Mitral valve area = T 220 milliseconds.

This relationship may be yield somewhat inaccurate results in patients who recently underwent

balloon mitral valvotomy or in patients with concomitant mitral regurgitation, aorticinsufficiency, or decreased LV diastolic function.

Continuity equation for calculating the area of the mitral valve

The continuity equation for calculating the area of the mitral valve involves the determination of

quantitative mitral valve flow; the equation is as follows: A 1(V1) = A 2(V2), where A 1 is area1, A 2 is area 2, V1 is velocity 1, and V2 is velocity 2. Flow and dimensions at the level of the

mitral valve annulus or forward flow in the LV outflow tract may be used in this equation.

Regurgitation or multivalve disease may make the calculations inaccurate.

Assessment of other cardiac structures

LA dilatation is seen in mitral stenosis. With stasis of blood flow, especially in the presence ofatrial fibrillation, intramural or intra-appendage thrombus formation may be seen as an

echogenic mass. These findings are best delineated with TEE.

The most common clinically significant sequela of mitral stenosis is secondary pulmonary

hypertension with subsequent right-sided heart dysfunction and tricuspid regurgitation.

The tricuspid regurgitation jet may be measured, and the value may be substituted into the

Bernoulli formula to determine the PA systolic pressure. The pressure gradient is calculated as 4V

2, where V is the velocity jet measured in centimeters on the Doppler echocardiograph.


The degree of confidence is high. However, echocardiography has specific limitations. Becauseultrasound is not transmitted well through calcified structures or bone, an appropriate acoustic

window is necessary for optimal visualization. In adults, a noncalcified window must beobtained; this is typically done via the intercostal spaces or from the subxiphoid positions. In

patients with narrow intercostal spaces, imaging may be suboptimal. A greater limitation is the

degree to which the air-filled structures reflect ultrasound. In patients with obstructive lung

disease, intervening lung tissue may cause suboptimal or inadequate imaging results as well.


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Cardiac catheterization

Cardiac catheterization is usually unnecessary for assessing the severity of mitral stenosis.Nonetheless, coronary arteriography is performed in many patients with mitral stenosis who are

in an age group in which there is a relatively high incidence of coronary disease and for whom

heart surgery is anticipated or who have coexistent angina. In such cases, left- and right-sidedheart catheterizations are performed to evaluate the coronary arteries, to confirm the transmitral

gradient, and to determine the valve area. The valve area is determined by use of the Gorlin

equation: Mitral valve area = [CO(DFP X HR)]/37.6 X h), where CO is cardiac output (in

milliliters per minute), DFP is the diastolic filling period, HR is the heart rate, and h is the mean

gradient (see the image below).

Pulmonary capillary wedge pressure (PCW) and left ventricular(LV) end-diastolic pressure (LVEDP) gradient seen during cardiac catheterization.

Need for catheterization

Careful clinical evaluation and noninvasive assessment, particularly with 2D and Doppler

echocardiography, may provide sufficient information to permit an informed decision for the

majority of patients.

Preoperative catheterization is recommended for the following patients with mitral stenosis:

Patients for whom there is a discrepancy between clinical and echocardiographic findings Patients who have associated chronic obstructive pulmonary disease, for whom the

contribution of mitral stenosis to the symptoms must be determined

Patients for whom LA myxoma should be excluded Patients who have angina pectoris or anginalike chest pain for whom associated coronary

artery disease must be excluded

Men older than 40 years and women older than 50 years who have risk factors forcoronary artery disease or who have a positive result on stress testing and who are

candidates for surgery

Critical narrowing of 1 or more coronary vessels occurs in approximately 25% of all adults with

severe mitral stenosis. This finding is most common in men older than 45 years who have anginaand who have risk factors for coronary artery disease.

Angiocardiography in Lutembacher syndrome
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Angiocardiographic findings in Lutembacher syndrome are similar to those in atrial septal

defect. Other signs that may aid in the diagnosis include the following: enlargement of the RAand RV, as well as enlargement of the pulmonary artery; re-opacification of the right side of the

heart after left-sided opacification; and dilution in the RA in the presence of a large shunt.

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