You are in: eMedicine Specialties > Radiology > CARDIAC Mitral StenosisArticle Last Updated: Sep 17, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Vibhuti N Singh, MD, MPH, FACC, FSCAI, Director, Suncoast Cardiovascular Center; Chair, Cardiology Division and Cath Labs, Department of Medicine, Bayfront Medical Center; Clinical Assistant Professor, Division of Cardiology, University of South Florida College of Medicine Vibhuti N Singh is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Heart Association, American Medical Association, and Florida Medical Association Coauthor(s): Rakesh K Sharma, MBBS, FACC, FACP, Interventional Cardiologist, The Heart and Vascular Institute of Florida; Hanumanth K Reddy, MD, FACC, Clinical Professor of Medicine, St Louis University Medical School; Associate Chief, Department of Cardiovascular Services, Three Rivers Healthcare; Kul Aggarwal, MD, FACC, Professor of Clinical Medicine, Department of Internal Medicine, Division of Cardiology, University of Missouri School of Medicine; Chief, Cardiology Section, Harry S Truman Veterans Hospital Editors: Justin D Pearlman, MD, PhD, ME, MA, Director of Dartmouth Advanced Imaging Center, Professor of Medicine, Professor of Radiology, Adjunct Professor, Thayer Bioengineering and Computer Science, Dartmouth-Hitchcock Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Robert M Steiner, MD, Professor of Radiology, Temple University School of Medicine, Clinical Professor of Radiology, Medical School of the University of Pennsylvania; Consulting Radiologist, Temple University Hospital, Temple University Children's Medical Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Clinical Assistant Professor of Radiology, University of Washington Medical School Author and Editor Disclosure Synonyms and related keywords: mitral stenosis, MS, mitral valve stenosis, mitral valve, rheumatic mitral stenosis, mitral commissural stenosis, mitral annular calcification, MAC, Lutembacher syndrome, congenital mitral stenosis, atrioventricular valve, rheumatic heart disease, rheumatic fever, acute rheumatic fever, carditis, pancarditis, cor triatriatum, submitral ring INTRODUCTIONSection 2 of 12
  BackgroundMitral stenosis is characterized by restriction of blood flow from the left atrium (LA) to the left ventricle (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 an earlier age in developing countries than in Western societies. In the latter, the incidence of rheumatic fever has declined precipitously over the past 4 decades. Patients with mitral stenosis usually remain symptom-free for years. After the mitral orifice is reduced to one third of its normal size, symptoms typical of left-sided heart failure develop, such 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 fibrillation develops, 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, cardiac cachexia, 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 PathophysiologyNormal and stenotic mitral valves In a normal heart, an initial pressure gradient between the LA and LV exists at the onset of diastole that starts the LV filling. At a certain point in the diastolic filling period, as LV continues to receive blood, LA and LV pressures become equal, terminating LV filling. At the end of diastole in patients with sinus rhythm, atrial contraction causes additional (presystolic) filling. In contrast, when mitral stenosis is present, obstruction at the LV inlet increases LA pressure. As a result, a constant pressure gradient between the LA and the LV exists, and filling occurs continuously throughout diastole. Pulmonary venous pressure also rises because of the backup of pressure from the LA into the pulmonary vasculature. In addition, the restriction of flow into the LV reduces overall forward cardiac output. Cardiac performance In patients with mitral stenosis, the myocardium itself is usually normal. In one third of patients, however, the LV ejection fraction is low despite normal muscle function. This condition usually results from reduced preload caused by LV inflow obstruction, along with augmented afterload as a consequence of reflex vasoconstriction that occurs to compensate for the reduced forward cardiac output. RV pressure overload The RV is responsible for generating most of the contractile force that pushes blood across the pulmonary circulation and through the mitral valve. The back pressure from mitral stenosis that causes pulmonary venous hypertension leads to backward pressure overload all the way back to the RV. Initially, reversible pulmonary vasoconstriction develops. This causes an increase in the pulmonary arterial pressure and further burdens the RV, which begins to dilate; in addition, the central pulmonary artery enlarges. As mitral stenosis worsens, pulmonary vascular changes become fixed, RV failure sets in, and signs of CHF begin to develop. FrequencyUnited StatesBecause of widespread and effective use of antibiotics in the treatment of streptococcal infections, the incidence of rheumatic endocarditis with subsequent valvular heart disease, including mitral stenosis, has greatly decreased in the United States. At present, most patients are elderly individuals who initially develop degenerative MAC and subsequent mitral stenosis. Rheumatic mitral stenosis is still encountered, but it occurs at an older age, and it progresses more slowly than previously. Among immigrant populations, trends similar to the those seen in their native countries are seen. InternationalMitral stenosis is still prevalent in developing nations where rheumatic fever is common. Both economic and genetic conditions may play a role. Mortality/MorbidityThe prognosis for patients with untreated congenital mitral stenosis is poor. With medical treatment, the 10-year survival rate is approximately 80% for mildly symptomatic patients with rheumatic mitral stenosis who have New York Heart Association (NYHA) class II disease. The 10-year survival rate is 38% for patients with NYHA class III disease. The 5-year survival rate for patients with class IV disease may be as low as 15%. RaceThe progression of mitral stenosis is most rapid in tropical and subtropical areas and in patients of Polynesian or Alaskan Inuit descent. In India, critical mitral stenosis tends to occur at an early age; it may occur in children as young as 6-12 years of age. SexRheumatic mitral stenosis occurs more frequently in women than in men; the female-to-male ratio is 3:1. Age
AnatomyProper function of the mitral valve requires the orchestration of many different components. Adequate mitral leaflet function requires a mobile mitral annulus; intact chordae tendineae; normal-size atria that do not displace the orientation of the leaflets; well-functioning papillary muscles to maintain chordal tension as LV volume shrinks in systole; and a normal-size ventricle that does not disorient the mitral leaflets or papillary muscles. The circumference of the normal ring of the mitral valve is generally 10 cm. The mitral valve is a bicuspid valve consisting of a large anterolateral cusp and a posteromedial cusp that is shortened by half. The area of the normal mitral orifice is approximately 5-6 cm2. Mitral stenosis is generally classified as mild if the area is less than 4 cm2, moderate if it is less than 2 cm2, and severe if it is less than 1 cm2. Causes of mitral stenosis
Differential diagnoses
Rheumatic fever and carditis Approximately 60% of patients with isolated mitral stenosis have rheumatic fever; approximately 90% of patients with multivalvular disease have isolated mitral stenosis. One of the critical consequences of acute rheumatic fever is pancarditis, which occurs in 40-50% of patients; pancarditis progresses gradually, causing chronic abnormalities. The mitral valve is frequently involved; the free edges of the commissures become fused, giving the mitral valve a characteristic fish-mouth appearance. Subvalvular structures, such as the chordae tendineae, gradually thicken and become calcified, leading to further restriction of leaflet mobility. The mean latent period between the occurrence of acute rheumatic fever and mitral stenosis is usually 20 years. Another 7-10 years pass before patients become significantly disabled. Atrial septal defect with mitral stenosis In some patients, atrial septal defect (ASD) is associated with acquired mitral stenosis. In this syndrome, called Lutembacher syndrome, the RV workload is higher than that associated with an isolated ASD because of left-to-right shunting of blood with an increase in LA pressure. An enlarged pulmonary artery is the characteristic feature on chest radiographs. Congenital anomalies of the mitral valve Congenital mitral stenosis is rare. Some patients may have a single mitral papillary muscle in which all chordae attach to 1 spot, making the valve functionally stenotic (parachute mitral valve). The clinical presentation is similar to that of rheumatic mitral stenosis. Some patients who have cor triatriatum present with features similar to those of mitral stenosis. Such patients have a submitral membrane in the LA that may obstruct blood flow. Transthoracic echocardiography may show the membrane; however, in most instances, transesophageal echocardiography (TEE) is needed. Clinical DetailsHistory Patients with mitral stenosis usually remain asymptomatic until the area of the valve is reduced to about one third of its normal size of 4 cm2. After the area is decreased to less than 4 cm2, symptoms may begin to develop. Symptoms Symptoms include dyspnea on exertion and fatigue. As mitral stenosis worsens, dyspnea on exertion (NYHA class II) progresses to orthopnea and paroxysmal nocturnal dyspnea (NYHA class III and IV, with the symptoms associated with LV failure). Subsequently, RV failure manifests itself as ascites and dependent edema. Physical examination Although mitral stenosis produces characteristic findings on physical examination, the diagnosis is frequently missed because the auscultatory findings may be subtle on inspection. Mitral facies may be seen in some patients (see Image 8). Palpation of the precordium reveals a quiet apical impulse. In pulmonary hypertension and RV hypertrophy, an RV parasternal lift may be encountered. On auscultation, a loud S1 is present because the transmitral gradient holds the mitral valve open throughout diastole until ventricular systole closes the fully opened valve with a loud closing sound (S1). In advanced mitral stenosis, as the mitral leaflets become so damaged that they neither open nor close well, S1 eventually becomes quiet. S2 is physiologically split, with a loud pulmonic component (P2) in the presence of pulmonary hypertension. S2 is usually followed by another early diastolic sound, called the opening snap (OS). The interval between S2 and the OS provides a good estimate of LA pressure and thus the severity of the mitral stenosis. When LA pressure is high, the OS closely follows S2 (0.06 s); when it is normal, the OS occurs later (0.12 s), and it may mimic the S3 gallop. As mitral stenosis worsens, the S2-OS interval shortens. The OS is followed by the characteristic low-pitched early-diastolic murmur. This murmur may be soft in patients with low cardiac output. In such patients, modest exercise, such as isometric handgrip, may cause an increase in the intensity of the murmur. A presystolic accentuation of the mitral stenosis murmur is also heard coincidentally with the atrial contraction. In the presence of pulmonary arterial hypertension, another diastolic murmur of blowing quality, associated with resultant pulmonary regurgitation (Graham Steell murmur), often becomes audible. Mitral stenosis with atrial fibrillation Patients with mitral stenosis and atrial fibrillation frequently present with decompensated congestive heart failure (CHF). The rapid ventricular rate shortens the diastolic filling time to a period insufficient to allow the LA to empty. As a consequence, the LA pressure rises and the forward cardiac output decreases. Congenital mitral stenosis Symptoms of mitral stenosis usually appear within the first 2 years of life. Infants have delayed development and breathlessness, caused by heart failure. Cyanosis and pallor may be noted. The heart is enlarged as a result of dilatation and hypertrophy of the RV and LA. Rumbling apical diastolic murmur is usually audible, followed by a loud first sound. The OS is usually absent. Preferred ExaminationEchocardiography, 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 Echocardiography generally provides sufficiently detailed images of the mitral valve and is the most 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 in the 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. LA abnormality is manifested by prolongation of the P wave, with a double-saddleback contour (p mitrale) 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 stenosis advances. If pulmonary arterial hypertension has developed, electrocardiography may show signs of RV hypertrophy. Limitations of TechniquesFalse findings on echocardiography are uncommon in mitral stenosis. DIFFERENTIALSSection 3 of 12
Other Problems To Be ConsideredRheumatic mitral stenosis
RADIOGRAPHSection 4 of 12
FindingsFor patients with mitral stenosis, the chest radiograph may exhibit certain specific and nonspecific findings that are generally a consequence of left atrial enlargement, mitral calcification, pulmonary hypertension, and congestive heart failure (CHF).9 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, alters the left border of the cardiac silhouette so that it becomes straight, in contrast to the usual mild concavity 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 upper cardiac 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 approaches within a few centimeters of the chest wall on 1 or both sides, as seen in long-standing mitral 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 left atrium 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 and constricts lower-lobe veins. Kerley septal costophrenic B lines represent interstitial edema. Pulmonary alveolar edema may appear 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 are nonbranching; 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 and difficult to visualize. All of the Kerley lines represent edematous interlobular septa. The pulmonary lobules tend to be large and are oriented obliquely to the pleura in the upper lobes, whereas in the lower lobes, they are 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 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 also occur 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. Degree of ConfidenceThe degree of confidence is reasonably good for mitral stenosis. False Positives/NegativesFindings are sometimes nonspecific for mitral stenosis. CT SCANSection 5 of 12
FindingsCT scans occasionally depict calcification in the enlarged LA in patients with mitral stenosis. It may 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. Degree of ConfidenceWhen 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, CT scanning 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. False Positives/NegativesFalse findings are rare in mitral stenosis. MRISection 6 of 12
FindingsFor patients with mitral stenosis, MRI may be helpful if Doppler echocardiographic findings are insufficient or are inconsistent with clinical data.10, 11 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 are dark-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 blood vessels. 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, and coronal. 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. 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 the leaflets 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 extent of 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. Degree of ConfidenceMRI may be used if echocardiographic visualization is inadequate. This problem occurs in approximately 10% of patients because of air-tissue attenuation of ultrasound. MRI is often used in cases in which 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. False Positives/NegativesFalse findings are rare in mitral stenosis. ULTRASOUNDSection 7 of 12
FindingsEchocardiography is the most widely used imaging modality in the evaluation of mitral stenosis. A full 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 cardiac catheterization (see Images 1, 3-7).12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 General findings In patients with mitral stenosis, characteristic findings on 2D echocardiography include thickening 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 leaflet assumes 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. Assessment of the severity of mitral stenosis Both continuous-wave and pulsed Doppler echocardiography may be performed with the patient at 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 (T½) is the time in milliseconds required for the peak pressure gradient to decline to one half of its original value. T½ may be calculated as follows: Mitral valve area = T½ ÷ 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, aortic insufficiency, 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: A1(V1) = A2(V2), where A1 is area 1, A2 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 of atrial 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 4V2, where V is the velocity jet measured in centimeters on the Doppler echocardiograph. Degree of ConfidenceThe degree of confidence is high. However, echocardiography has specific limitations. Because ultrasound is not transmitted well through calcified structures or bone, an appropriate acoustic window is necessary for optimal visualization. In adults, a noncalcified window must be obtained; 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. False Positives/NegativesFalse findings are uncommon in mitral stenosis. ANGIOGRAPHYSection 8 of 12
FindingsCardiac 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: (1) patients for whom there is a discrepancy between clinical and echocardiographic findings; (2) patients who have associated chronic obstructive pulmonary disease, for whom the contribution of mitral stenosis to the symptoms must be determined; (3) patients for whom LA myxoma should be excluded; (4) patients who have angina pectoris or anginalike chest pain for whom associated coronary artery disease must be excluded; and (5) men older than 40 years and women older than 50 years who have risk factors for coronary 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 angina and who have risk factors for coronary artery disease. Angiocardiography in Lutembacher syndrome 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 RA and 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. Degree of ConfidenceThe degree of confidence is good in mitral stenosis. False Positives/NegativesFalse findings are rare in mitral stenosis. INTERVENTIONSection 9 of 12
The prophylaxis, evaluation, and treatment of mitral stenosis may involve medical approaches and surgical or percutaneous approaches, such as balloon mitral valvotomy (balloon mitral valvuloplasty). The prognosis for patients with untreated congenital mitral stenosis is poor. The results of surgical valve replacement are mixed. A mitral valve prosthesis is usually required; in children, the prosthesis must be replaced as the child grows. Patients must undergo anticoagulation therapy with warfarin for the prevention of stroke and prosthetic valve thrombosis. Complications of overanticoagulation or underanticoagulation are common. Balloon mitral valvuloplasty has been used as a palliative procedure; the results have been mixed and depend on the structure of the valve and the papillary muscles.28, 29, 30, 31, 32, 33, 34, 35, 36, 37 Medical treatmentProphylaxis Patients with mitral stenosis caused by rheumatic heart disease should receive penicillin prophylaxis for beta-hemolytic streptococcal infections and prophylaxis for infective endocarditis. In patients with valvular heart disease, concomitant conditions, such as anemia and infections, should be treated promptly and aggressively. Adolescents and young adults with severe valvular heart disease should be advised to avoid occupations that require strenuous exertion. Asymptomatic patients with moderate mitral stenosis should be reevaluated yearly. Heavy exertion is contraindicated in symptomatic patients. General drug treatment In symptomatic patients with mitral valve disease, considerable improvement may be achieved with the use of oral diuretics and the restriction of their sodium intake. Digoxin does not affect the hemodynamics and usually does not benefit patients with mitral stenosis and a sinus rhythm. However, it is useful in reducing the heart rate in those with atrial fibrillation, with or without right-sided heart failure. In patients with a sinus rhythm or atrial fibrillation, beta-blocking agents and rate-slowing calcium antagonists may increase exercise capacity by reducing the heart rate. Hemoptysis is managed by use of measures designed to reduce pulmonary venous pressure. These include sedation, upright positioning, and aggressive diuresis. Anticoagulant therapy is helpful in preventing venous thrombosis, stroke, and pulmonary embolism in patients who have had 1 or more episodes of pulmonary emboli. Such patients include those in whom the risk of systemic embolization is high (eg, those with persistent or transient atrial fibrillation, especially patients older than 70 years) and those with previous systemic emboli. Treatment with warfarin is indicated to maintain an international normalized ratio (INR) of 2.5-3.5. No firm evidence suggests that anticoagulation reduces the incidence of pulmonary or systemic emboli in patients with a sinus rhythm who have no history of embolization. Treatment of atrial fibrillation As an overview, patients with mitral stenosis and atrial fibrillation usually experience decompensation. Decompensation occurs because the rapid heart rate reduces the diastolic filling time and, in turn, increases LA pressure and decreases cardiac output. The heart rate must be controlled promptly. In cases of acute atrial fibrillation, an infusion of diltiazem or esmolol is preferred; for patients with chronic atrial fibrillation, oral digoxin, a beta-blocker, or a calcium channel blocker are the agents of choice. Anticoagulation and conversion to sinus rhythm should be undertaken either pharmacologically or with synchronized direct-current (DC) countershock. Premature atrial contractions frequently precede atrial fibrillation. After atrial fibrillation develops, antiarrhythmic drugs may be ineffective in restoring a sinus rhythm because of the pathologic changes that occur in the atrium secondary to increased pressure, as well as the changes associated with the arrhythmia itself. After electrical cardioversion, a sinus rhythm may often be maintained with antiarrhythmic agents. This approach is especially effective in young patients with mild mitral stenosis, provided the LA is not markedly enlarged and provided the atrial fibrillation is of less than 6 months' duration. In most adults, conversion to a sinus rhythm is rarely achieved. Immediate treatment of atrial fibrillation should include anticoagulation and rate control. For anticoagulation, intravenous heparin should be started as a bridging therapy, followed by oral warfarin to achieve an INR of 2.0-3.0. For rate control, the ventricular rate should be slowed with intravenous digoxin and a beta-blocking agent or a rate-slowing calcium antagonist. An effort should be made to reestablish a sinus rhythm through the use of a combination of pharmacologic treatment and cardioversion. If cardioversion is planned for a patient who has had atrial fibrillation for more than 24 hours before the procedure, anticoagulation with warfarin for more than 3 weeks is indicated. As an alternative, if no atrial thrombus is apparent on TEE, immediate cardioversion may be performed using intravenous heparin. Paroxysmal atrial fibrillation and repeated conversions, spontaneous or induced, pose a risk of embolization. In patients in whom conversion of heart rhythm cannot be achieved or in whom a sinus rhythm cannot be maintained, digitalis should be used to achieve a resting ventricular rate of approximately 60 bpm. If it is not possible to achieve this rate, small doses of a beta-blocking agent, such as atenolol, 25 mg/d, may be added. Multiple repeat cardioversions are not indicated if a sinus rhythm cannot be maintained while the patient is receiving adequate doses of an antiarrhythmic. Patients with chronic atrial fibrillation who undergo open mitral valve repair or replacement may undergo the Cox maze procedure (atrial compartment operation). In more than 80% of patients undergoing this procedure, a sinus rhythm is maintained postoperatively; in most patients, normal atrial function is reestablished. The latest trials have shown that the 2 strategies for atrial fibrillation—conversion to sinus rhythm and rate control with anticoagulation—are equivalent with regard to outcomes. Surgical treatmentThe prognosis of patients with mitral stenosis worsens once symptoms progress beyond early NYHA functional class II, unless the stenosis is relieved by intervention. Balloon mitral valvotomy (balloon mitral valvuloplasty) In most instances, an excellent result may be obtained with percutaneous balloon mitral valvotomy. Unlike aortic stenosis, mitral stenosis involves fusion of the valve commissures. Balloon dilatation produces a commissurotomy; in addition, the valve area is increased substantially, and that increase is maintained for a period of 10 years or longer. Whether balloon valvotomy is suitable for a patient is partially determined during echocardiography by use of the Wilkins criteria (see Patient selection by echocardiographic score). However, even when the valve anatomy is not ideal, valvotomy may be attempted in patients who are of advanced age or for patients who have severe comorbid risk factors. Valvular procedural treatment must be individualized. For example, surgery might be deferred in a mildly symptomatic and sedentary elderly person with a mitral valve orifice of 0.8 cm2/m2 body surface area, whereas a 30-year-old laborer might be an excellent candidate for mechanical relief of obstruction, even if the mitral valve orifice size is 1.2 cm2/m2 body surface area. The following Table summarizes the advantages and disadvantages of some valvotomy procedures. Table 1. Advantages and Disadvantages of Some Valvotomy Procedures
Indications for balloon mitral valvotomy Balloon mitral valvotomy is indicated for symptomatic patients with moderate to severe mitral stenosis (ie, area of the mitral valve orifice < approximately 1.0 cm2/m2 body surface area <1.5-1.7 cm2 in normal-sized adults). Balloon mitral valvotomy is also indicated for patients with mild stenosis (orifice area of 1.0-1.5 cm2/m2) who are symptomatic during ordinary exertion, whose pulmonary arterial systolic pressure exceeds 60 mm Hg, or whose mean pulmonary capillary wedge pressure exceeds 25 mm Hg with exercise. LA thrombus must be excluded. Balloon mitral valvotomy yields acceptable results in patients with accompanying mild or moderate aortic regurgitation and in those who experience mitral restenosis after surgical valvotomy. It may also be used in patients with unfavorable valves who are unsuitable for surgery because the risk of surgery is high. Patient selection by echocardiographic score A widely adopted echocardiographic scoring system that Wilkins and colleagues developed helps in patient selection.38 In this system, 4 features of the mitral valve are identified, as follows:
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 have symptomatic, hemodynamically severe stenosis and whose echocardiographic score is 8 or less and 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. Good patient selected is associated with a decrease in cost and less morbidity. Contraindications to balloon mitral valvotomy Balloon mitral valvotomy is contraindicated in patients with severe mitral regurgitation, severe aortic regurgitation, or LA thrombus. In addition, balloon mitral valvotomy should not be performed in patients with stenotic bioprosthetic valves. Fluoroscopically visible calcium and coexisting mitral regurgitation are additional important predictors of an adverse outcome. Transesophageal echocardiography (TEE) enables accurate evaluation of mitral valve structure and function; it also allows assessment of concomitant mitral regurgitation and LA thrombus, which are contraindications to balloon mitral valvotomy. Three-dimensional echocardiography is useful in assessing indications for balloon mitral valvotomy. The findings on echocardiography predict the outcome of both open and closed surgical valvotomy equally. Procedure for balloon mitral valvuloplasty For balloon mitral valvuloplasty, the percutaneous approach consists of advancing a small balloon flotation catheter across the interatrial septum through a transseptal puncture, enlarging the opening of the mitral valve, positioning a large (23-25 mm) hourglass-shaped balloon (Inoue balloon), and inflating it within the orifice of the mitral valve. Sometimes, 2 small (12-18 mm) balloons may be used for simultaneous inflation. The mechanism includes commissural separation and fracture of the nodular calcium. In terms of the hemodynamic results, the transmitral pressure gradient decreases from approximately 18 mm Hg to 6 mm Hg; cardiac output increases by about 20%; and the area of calculated mitral valve doubles from 1.0 to 2.0 cm2 on average. An improvement in exercise tolerance occurs proportional to the favorable hemodynamic effects. The mortality rate associated with balloon mitral valvuloplasty is 1-2%. Complications include cerebral emboli (1%), cardiac perforation (1%), and mitral regurgitation severe enough to require surgery (another 2%, approximately 15% have a lesser degree of mitral regurgitation). Approximately 5% of patients have a small residual ASD associated with the septotomy, but this closes or decreases in size in most. In patients with favorable anatomic findings, the survival rate without functional disability or the need for surgery or repeat balloon mitral valvuloplasty is 70% at 7 years. Excellent results are also reported in children and adolescents in developing nations, where patients tend to be young. These young patients usually have pliable valves, which are ideal for balloon mitral valvuloplasty. Valvulotome procedure In developing countries, where financial resources are limited, the cost of the balloon catheter is relatively high; in response, a reusable metallic valvulotome has been developed. Early results appear to be similar to those of balloon mitral valvuloplasty. Mitral valve replacement Mitral valve replacement is indicated in 2 groups of patients with mitral stenosis whose valves are not suitable for valvotomy: (1) those with a mitral valve area less than 1.5 cm2 who have NYHA class III or IV disease and (2) those with severe mitral stenosis (mitral valve area <1.0 cm2) who have NYHA class II disease and who have severe pulmonary hypertension (pulmonary artery systolic pressure >70 mm Hg). This procedure is often required in the following patients: those with combined mitral stenosis and moderate or severe mitral regurgitation; those with extensive commissural calcification, severe fibrosis, or subvalvular fusion; and those who have previously undergone valvotomy. The surgical mortality rate after isolated mitral valve replacement is 3-8% in most centers; in 13,936 patients with mitral stenosis and/or mitral regurgitation reported in the national database of the Society of Thoracic Surgeons, the surgical mortality rate was 6.4%. Regarding morbidity, bioprosthetic valves mechanically deteriorate faster in the mitral position than in the aortic position because of the increased transvalvular gradient. Patients with mechanical prostheses have a lifelong hazard of anticoagulation. Because the surgical mortality risk in patients in NYHA class IV disease may be high (10-20%), surgery should be contemplated before the disease reaches this stage. Such patients should not be denied valve replacement surgery unless comorbid conditions preclude surgery or an acceptable outcome. Medical/Legal Pitfalls
FURTHER READINGSection 10 of 12
ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to update the 1997 guidelines for the clinical application of echocardiography). MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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