TRANSESOPHAGEAL ECHOCARDIOGRAPHIC EVALUATION OF NATIVE VALVULAR DISEASE AND REPAIR
1996; Elsevier BV; Volume: 12; Issue: 2 Linguagem: Inglês
10.1016/s0749-0704(05)70251-7
ISSN1557-8232
Autores Tópico(s)Cardiac Structural Anomalies and Repair
ResumoSurgery for valvular heart disease corrects systolic or diastolic dysfunction of the mitral, aortic, or tricuspid valves. The surgery typically involves repair of the native valve, replacement with a bio-or mechanical prosthesis, or a combined procedure with insertion of a prosthetic valve or annular ring while retaining a surgically corrected or modified native valve. Surgery for primary pulmonic valve disease is rare. The advent of the Ross procedure with transfer of the pulmonic valve and pulmonary artery to the aortic position, however, has prompted the intraoperative echocardiographer to study the pulmonic valve to assess its suitability. The intraoperative echocardiographic assessment of the native heart valve is aimed at defining the pathology of valve disease, determining the mechanism of valve dysfunction, and quantitating the degree (grade) of valvular stenosis or insufficiency.MITRAL VALVEThe mitral valve permits laminar diastolic blood flow from the left atrium to ventricle, prevents regurgitant systolic flow via a valve andsphincter action, and contributes to ventricular contraction. The elements of the mitral valve are a funnel-shaped atrioventricular membrane, two leaflets, and subvalvular attachments to ventricular myocardium. The mitral annulus directs diastolic blood flow inferiorly, anteriorly, and toward the left side of the heart.112Van Mierop L.H.S. Kutsche L.M. Embryology of the heart.in: Hurst J.W. The Heart. ed 6. McGraw-Hill, New York1986: 3-16Google Scholar The mitral annulus has a sphincter action with circumferential fiber shortening.27Davis P.K.B. Kinmonth J.B. The movements of the annulus of the mitral valve.J Cardiovasc Surg (Torino). 1963; 4: 427-431PubMed Google Scholar Chordae tendineae pull the annulus and the base of the heart during systole toward the ventricular apex and shorten the longitudinal axis of the left ventricle. The anterior and posterior leaflets develop from evaginations of muscular ventricular wall. The early quadricuspid mitral valve is attached via muscular tendineae to four papillary muscles. The two posterior and two anterior papillary muscles fuse to form the bifid anteriolateral and posteriomedial papillary muscles of the adult heart. The two commissure cusps of the early quadricuspid valve retract and are vestigial in the adult. The large triangular anterior mitral leaflet is continuous at its attachment with the noncoronary and left coronary cusps of the aortic valve.111Van Mierop L.H.S. Embryology of the canal region and pathogenesis of cushion defects.in: Feldt R.H. Atrioventricular Canal Defects. WB Saunders, Philadelphia1976: 1-12Google Scholar, 112Van Mierop L.H.S. Kutsche L.M. Embryology of the heart.in: Hurst J.W. The Heart. ed 6. McGraw-Hill, New York1986: 3-16Google Scholar During systole, the "bare edge" of the anterior leaflet is apposed by a broad, crescent-shaped posterior leaflet. During diastole, the anterior leaflet forms the separation between the left ventricular inflow and outflow tracts. The posterior leaflet is comprised of the medial, middle, and lateral scallops. Although the surface area of the anterior and posterior mitral leaflets is nearly equal, the annular attachment of the posterior leaflet renders it shorter and less mobile.The subvalvular apparatus of the mitral valve is comprised of the papillary muscles and chordae tendineae. First-, second-, and third-order chordae are defined according to their attachment to the valve leaflets. First-order chordae attach to the edges of the valve leaflets giving the mitral valve its typical serrated appearance in the basal short-axis view. Second-order chordae attach to the ventricular surface of the leaflets and third-order chordae attach near the mitral annulus. The anterolateral and posteromedial papillary muscles have chordal attachments to both leaflets.Blood flow across the mitral valve during diastole is biphasic. Early diastolic filling (E phase) begins when the ventricular pressure is less than the left atrial pressure. Although early diastolic filling is governed primarily by the pressure gradient between the left atrium and ventricle, diastolic "suction" produced by ventricular relaxation can augment early diastolic filling when transvalvular pressures are low.103Suga H. Goto Y. Igarashi Y. et al.Ventricular suction under zero source pressure for filling.Am J Physiol. 1986; 251: H47-H55PubMed Google Scholar Late diastolic or active filling (A phase) follows atrial contraction. Left atrial enlargement or loss of since rhythm decreases the atrial contribution to left ventricular filling. Blood flow velocities across the mitral valve generally are low because the normal transvalvular pressure gradient is small and the mitral valve orifice is large. The average value for the peak velocity of blood flow through the normal mitral valve is 0.9 m/s in the adult and can be measured by pulsed-wave Doppler echocardiography.45Hatle L. Angelsen B. Doppler Ultrasound in Cardiology, Physical Principles and Clinical Application. ed 2. Lea and Febiger, Philadelphia1985Google ScholarThe normal adult mitral valve area ranges from 4 to 6 cm2. A mitral valve area of 2 cm 2 is considered mild mitral stenosis, 1 to 2 cm 2 is moderate mitral stenosis, and less than 1 cm 2 is severe mitral stenosis. The diastolic transvalvular pressure gradient increases with progressive decrease in the mitral valve area. Severe mitral stenosis can produce transvalvular diastolic gradients of greater than 20 mm Hg. The transvalvular pressure gradient is dependent on the transvalvular flow rate.39Gorlin R. Gorlin S.G. Hydraulic formula for calculation of the area of stenotic mitral valve, other cardiac valves and central circulatory shunts.Am Heart J. 1951; 41: 1-29Abstract Full Text PDF PubMed Scopus (1136) Google Scholar When cardiac output is low, the diastolic transvalvular pressure gradient decreases and may underestimate the severity of valvular stenosis.The normal mitral valve is exquisitely competent despite a left ventricle to left atrium systolic pressure gradient that typically exceeds 120 mm Hg. Mitral regurgitation is prevented by the coaptation of the left atrial surfaces of the mitral valve leaflets. Small increases in annular size do not necessarily produce mitral regurgitation because the leaflets appose each other along their left atrial surfaces.Mitral StenosisRheumatic carditis produces exudative and proliferative inflammatory lesions in any part of the heart. A verrucous acute valvulitis, most commonly involving the mitral and aortic valves, causes valve edema and deformity.102Stollerman G.H. Acute rheumatic fever and its management.in: Hurst J.W. The Heart. ed 6. McGraw-Hill, New York1986: 1306-1313Google Scholar Rheumatic involvement of all four heart valves is unusual.3Bandin M.A. Vargas-Barron J. Keirns C. et al.diagnosis of rheumatic cardiopathy affecting all four cardiac valves.Am Heart J. 1990; 120: 1004-1007Abstract Full Text PDF PubMed Scopus (14) Google Scholar Fibrous thickening of the valve leaflets, fusion of the posteromedial and anterolateral commissures, shortening of chordae, and calcification of the valve apparatus are the morphologic features of rheumatic mitral stenosis. The extent of calcification is variable and inversely related to the size of the stenotic orifice.120Wooley C.F. Baba N. Kilman J.W. Ryan J.M. Thrombotic calcific mitral stenosis: Morphology of the calcific mitral valve.Circulation. 1974; 49: 1167-1174Crossref PubMed Scopus (13) Google Scholar Calcium deposits begin in the commissures and extend to the leaflet bodies, subvalvular apparatus, and valve annulus. Inflammation and calcium deposits erupt through the leaflet endothelium causing surface ulceration and thrombosis. Systemic embolization associated with rheumatic mitral stenosis traditionally has been attributed to left atrial thrombi, but may also result from valve surface thrombi and fragmentation.Mitral stenosis impairs diastolic emptying of blood from the left atrium and produces and increase in left atrial, pulmonary venous, and pulmonary artery pressures. Interstitial and alveolar pulmonary edema occur when pulmonary venous hydrostatic pressure exceeds the pulmonary capillary oncotic pressure. Chronically increased pulmonary venous pressure leads to right ventricular hypertrophy and dilatation. Right ventricular pressure overload in combination with right ventricular dilatation may render the tricuspid valve incompetent. Left atrial dilatation caused by chronic increases in left atrial pressure produces a high volume, low flow chamber with increased risk for clot formation. Left atrial mural thrombi are more common than free-ball thrombi, but the latter are more likely to cause acute mitral valve obstruction, systemic embolization, and sudden death.13Chow W.H. Lee W.T. Tai Y.T. Cheung K.L. Free-floating ball thrombus in left atrium after mitral valve replacement: Surgical removal following embolization to the aorta.Am Heart J. 1990; 120: 1463-1465Abstract Full Text PDF PubMed Scopus (3) Google Scholar Dilatation of the left atrium decreases the effect of atrial systole to augment left ventricular filling and increases the risk of developing atrial flutter or fibrillation.Left ventricular regional wall motion abnormalities, a decreased ejection fraction, decreased left ventricular stroke work, and increased left ventricular end-diastolic pressure can be detected in as many as 50% of patients with significant mitral stenosis.9Carabello B. Timing of surgery in mitral and aortic stenosis.Cardiol Clin. 1991; 9: 229-238PubMed Google Scholar, 69Mohan J.C. Khalilulla M. Arora R. Left ventricular intrinsic contractility in pure rheumatic mitral stenosis.Am J Cardiol. 1989; 64: 240-242Abstract Full Text PDF PubMed Scopus (49) Google Scholar, 94Silverstein D.M. Hansen D.P. Ojiambo H.P. Griswold H.E. Left ventricular function in severe pure mitral stenosis as seen at the Kenyatta National Hospital.Am Heart J. 1980; 99: 727-733Abstract Full Text PDF PubMed Scopus (29) Google Scholar Potential causes include rheumatic carditis, which may impair the systolic function of the ventricle, independent of valve disease. Chronic decreases in left ventricular preload produced by mitral stenosis may cause ventricular remodeling and an atrophic ventricle. Pulmonary hypertension is associated with abnormal contraction of the interventricular septum, a dilated and hypertrophied right ventricle, and tricuspid regurgitation. A rigid immobile rheumatic mitral valve and annulus restrict the normal contraction and relaxation of adjacent myocardium.62Liu C.P. Ting C.T. Yang T.M. et al.Reduced left ventricular compliance in human mitral stenosis.Circulation. 1992; 85: 1447-1456Crossref PubMed Scopus (78) Google Scholar Regional wall motion abnormalities of the posterobasal myocardium in patients without coronary artery disease occur with severe rheumatic mitral stenosis and suggest a mechanical "tethering" of the myocardium caused by a scarred mitral valve. The regional wall motion abnormality is similar to that associated with prosthetic mitral valve replacement and suggests that the mechanical properties of the mitral valve leaflets, annulus, and subvalvular apparatus are important for normal ventricular contraction.34Gaasch W.H. Folland E.D. Left ventricular function in rheumatic mitral stenosis.Eur Heart J. 1991; 12: 66-69Crossref PubMed Google Scholar, 62Liu C.P. Ting C.T. Yang T.M. et al.Reduced left ventricular compliance in human mitral stenosis.Circulation. 1992; 85: 1447-1456Crossref PubMed Scopus (78) Google ScholarMost patients with mitral stenosis who present for mitral valve surgery have clinical symptoms. The clinical evaluation determines the appropriateness for operation, the risk of perioperative mortality, and the anticipated improvement in postoperative function. The most common symptoms associated with mitral stenosis are limitations in physical activity, dyspnea, cough, orthopnea, and paroxysmal nocturnal dyspnea. Symptoms are exacerbated with conditions that demand an increase in cardiac output, such as exercise, pregnancy, anemia, fever, orthyrotoxicosis. A subjective method of categorizing patients based on the severity of their symptoms uses the New York Heart Association (NYHA) classification.Echocardiographic Assessment of Mitral Stenosis: Anatomy and FunctionThe Gorlin equation is the standard for comparison of echocardiography-based methods for the estimate of mitral valve area. The Gorlin equation is applied to data collected at catheterization:The accuracy of the Gorlin equation is usually limited by the measurement of cardiac output (e.g., thermodilution or Fick equation).Two-Dimensional EchocardiographyWith the long-axis view of the heart, the mitral valve leaflets can be examined in their entirety by scanning from the posteromedial to the anterolateral commissure. Calcifications produce focal echogenic densities that cast far-field shadows (Fig. 1). Leaflet calcifications cause irregular leaflet surfaces that can ulcerate, cavitate, and generate thrombus. The excursion and separation of thickened valve leaflets are restricted (Fig. 2) Fusion of the leaflet edges produces diastolic doming of the anterior leaflet as the increased left atrial pressure displaces the usually more pliable body of the anterior leaflet toward the left ventricle. The diastolic displacement of the broad midportion of the anterior leaflet retracts the fused posterior leaflet in a paradoxical anterior direction.32Feigenbaum H. Acquired valvular heart disease.in: Feigenbaum H. Echocardiography. ed 5. Lea and Febiger, Philadelphia1994: 239-349Google Scholar The basal short-axis image of the mitral valve suggests a loss of the normal open fish-mouth appearance of the mitral orifice. The serrated edges of the valve leaflets may be obscured by multiple areas of focal calcifications.Figure 2Mitral stenosis: four chamber long-axis image of a rheumatic mitral valve with restricted leafletseparation. LA = left atrium; RA = right atrium; RV = right ventricle; LV = left ventricle.View Large Image Figure ViewerDownload (PPT)Left atrial dilatation and bowing of the interatrial septum toward the right atrium are caused by chronic increases in left atrial pressure. The normal range of left atrial dimensions measured by transesophageal echocardiography (TEE) (anteroposterior and mediolateral) is 39 ± 6 mm, which is consistent with the atrial dimensions measured by transthoracic echocardiography of 40 mm.16Cohen G.I. White M. Sochowski R.A. et al.Reference values for normal adult transesophageal echocardiographic measurements.J Am Soc Echocardiogr. 1995; 8: 221-230Abstract Full Text PDF PubMed Scopus (49) Google Scholar, 117Weyman A.E. Normal cross-sectional echocardiographic A.in: Weyman A.E. Principles and Practice of Echocardiography. Lea & Febiger, Philadelphia1994: 1289-1298Google Scholar Spontaneous echo contrast has the appearance of "smoke" in the left atrium and can be detected by TEE in greater than 50% of patients with mitral stenosis. Spontaneous echo contrast suggests blood stasis and is associated with mitral stenosis, left atrial dilatation, atrial fibrillation, the absence of significant mitral regurgitation, and an increased risk of thromboembolism.6Black I.W. Hopkins A.P. Lee L.C. Walsh W.F. Left atrial spontaneous echo contrast: A clinical and analysis.J Am Coll Cardiol. 1991; 18: 398-404Abstract Full Text PDF PubMed Scopus (373) Google Scholar, 19Cormier B. Influence of percutaneous mitral commissurotomy on left atrial spontaneous contrast of mitral stenosis.Am J Cardiol. 1993; 71: 842-847Abstract Full Text PDF PubMed Scopus (40) Google Scholar, 70Movsowitz C. Movsowitz H.D. Jacobs L.E. et al.Significant mitral regurgitation is protective against left atrial spontaneous echo contrast and thrombus as assessed by transesophageal echocardiography.J Am Soc Echocardiogr. 1993; 6: 107-114Abstract Full Text PDF PubMed Scopus (81) Google Scholar, 113Vigna C. de Rito V. Criconia G.M. et al.Left atrial thrombus and spontaneous echocontrast in non-anticoagulated mitral stenosis. A transesophageal echocardiographic study.Chest. 1993; 103: 348-352Crossref PubMed Scopus (35) Google Scholar Thrombus appears on TEE as an abnormal echogenic density within the left atrium, often residing in the left atrial appendage (Fig. 3). It frequently is difficult to distinguish mural thrombus in the atrial appendage from hypertrophied pectinate muscle or normal reflections in the wall of the atrium. Thrombus can be free, adherent to left atrial wall (mural thrombus), or pedunculated. Thrombus may have irregular borders. A dark, less echogenic, central region within the thrombus suggests central liquification.Figure 3Left atrial thrombus. Thrombus completely fills appendage.View Large Image Figure ViewerDownload (PPT)The left ventricle of patients with mitral stenosis typically is small. Nonischemic posterobasal regional wall motion abnormalities often are present and attributable to rheumatic disease. Fractional area change is mildly decreased or normal. Severe left ventricular dysfunction is unusual, but if present suggests coexisting disease (e.g., aortic valve disease, severe mitral regurgitation, rheumatic carditis). The usually crescent-shaped right ventricle increases in size and becomes more spherical and wall thickness may exceed that of the left ventricle. Increased right ventricular systolic pressures may cause paradoxical interventricular septal motion.Orifice area can be measured directly by manual planimetry of the mitral leaflet edges imaged en fosse. Transthoracic planimetric mitral valve area measurements are reproducible and accurate compared with valves derived from cardiac catheterization.65Martin R.P. Rabowski H. Kleiman J.H. et al.Reliability and reproducibility of two-dimensional echocardiographic of the stenotic mitral valve orifice area.Am J Cardiol. 1979; 43: 560-568Abstract Full Text PDF PubMed Scopus (170) Google Scholar, 74Nichol P.M. Gilbert B.W. Kisslo J.A. Two-dimensional echocardiogaphic assessment of mitral stenosis.Circulation. 1977; 55: 120-128Crossref PubMed Scopus (146) Google Scholar The measurement is performed by acquiring a short-axis tomographic image of the limiting mitral valve orifice and manually tracing its edges (Fig. 4). Measured orifice areas of less than 2, less than 1.5, and less than 1 cm 2 are graded as mild, moderate, and severe mitral stenosis, respectively; however, measured valve area using this method is dependent on the skill of the operator and equipment settings. A true tomographic image plane across the narrowest mitral valve opening often is difficult to obtain, especially with TEE. Mitral stenosis is underestimated if the apex of the funnel-shaped mitral valve is not sampled. Increased instrument gain settings increase the echogenicity of the borders of the mitral valve opening, especially if the valve is extensively calcified, and may lead to underestimation of the true mitral valve area and overestimation of the severity of mitral stenosis.65Martin R.P. Rabowski H. Kleiman J.H. et al.Reliability and reproducibility of two-dimensional echocardiographic of the stenotic mitral valve orifice area.Am J Cardiol. 1979; 43: 560-568Abstract Full Text PDF PubMed Scopus (170) Google Scholar Commissurotomy usually renders the mitral valve orifice irregular and difficult to quantify by planimetry.97Smith M.D. Handshoe R. Handshoe S. et al.Comparative accuracy of two-dimensional and Doppler pressure half-time methods in assessing severity of mitral stenosis in patients with and without prior commissurotomy.Circulation. 1986; 73: 100-107Crossref PubMed Scopus (115) Google Scholar Using the width of the color Doppler jet across the mitral valve in two different planes (the short-axis and long-axis view) may aid in identifying the borders of the mitral orifice and has been used for direct estimation of the stenotic mitral valve orifice area.56Kawahara T. Yamagishi M. Seo H. et al.Application of Doppler color flow imaging to determine valve area in mitral stenosis.J Am Coll Cardiol. 1991; 18: 85-92Abstract Full Text PDF PubMed Scopus (35) Google ScholarFigure 4Planimetry measurement of the mitral valve area from TEE in a patient with mitral stenosis.View Large Image Figure ViewerDownload (PPT)a = jet width in short-axis viewb = jet width in long-axis view.Doppler EchocardiographyDoppler transmitral blood flow velocity permits the estimate of mitral valve area and valve gradient. The transesophageal long-axis view of the heart aligns transmitral blood flow along the same axis as the ultrasound transmission. The locus of flow velocity measurement is positioned between the tips of the open mitral leaflets. Transmitral blood flow velocities normally are between 0.50 and 0.80 m/sec and are within the bandwidth of pulse-wave Doppler. A stenotic or distorted mitral orifice causes turbulent flow and an increase in the peak transmitral blood flow velocity (Vmax). An increased distribution of flow velocities produces a widening of the spectral bandwidth on pulsed-wave Doppler and a mosaic of colors on the color-Doppler variance flow map. The increased peak velocities may exceed the Nyquist.Range-gated pulse-wave Doppler with a high pulse repetition frequency, upward shifting of the baseline velocity, or continuous-wave Doppler frequently are required for accurate estimation of the peak blood flow velocity across the stenotic valve. Peak blood flow velocity of greater than 1 m/sec is a sensitive but not specific indicator of mitral stenosis. The peak blood flow velocity may be increased in the absence of significant mitral stenosis by increased cardiac output, tachycardia, increased inotropic state, the presence of a ventricular septal defect, or mitral regurgitation.54Kandath D. Nanda N.C. Conventional and color Doppler assessment of mitral and tricuspid stenosis.in: Nanda N.C. Textbook of Color Doppler. Lea and Febiger, Philadelphia1989: 168-177Google Scholar An aortic regurgitant jet crossing the path of the continuous-wave ultra-sound beam may be misinterpreted as an increase in the peak blood flow velocity and can falsely suggest mitral stenosis.The diastolic pressure gradient across the mitral valve is estimated from the transmitral blood flow velocities using the modified Bernoulli equation. The transvalvular pressure gradient calculated by Doppler correlates with direct measurements obtained by cardiac catheterization. Valve pressure gradients usually are expressed as peak or mean gradients. The instantaneous peak transmitral pressure gradient ‡P max is calculated by:Peak blood flow velocity equal to 2 m/sec produces a ‡P max equal to 16 mm Hg. Calculation of a mean-valve gradient requires integration of the spectral velocity and temporal averaging. The development of "user-friendly" software in echocardiography machines facilitates velocity flow analysis. The mean diastolic pressure gradient across the mitral valve is obtained by tracing the spectral velocity over time throughout diastole and using the mean blood flow velocity to calculate the mean pressure gradient. The major limitation of using the transvalvular pressure gradient to estimate the severity of mitral stenosis is that pressure gradients are dependent on blood flow. A decrease in cardiac output decreases the transmitral pressure gradient.Mitral stenosis impedes left atrial emptying and the rate of decay of the diastolic transmitral pressure gradient. The rate of deceleration of diastolic transmitral blood flow velocity is a function of the instantaneous transvalvular pressure gradient. The normal transmitral blood flow velocity decays rapidly during diastole because the left atrial pressure decreases rapidly on opening of the mitral valve. The impedance to left atrial emptying in patients with mitral stenosis causes a sustained transvalvular pressure gradient throughout diastole and a more gradual decay in the transvalvular blood flow velocity.107Thomas J.D. Weyman A.E. Doppler mitral pressure half-time: A clinical tool in search of theoretical justification.J Am Coll Cardiol. 1987; 10: 923-929Abstract Full Text PDF PubMed Scopus (142) Google Scholar The rate of diastolic blood flow velocity decay measured by Doppler echocardiography provides a functional estimate of the mitral valve area (Fig. 5). The methodology is based on determining the pressure half-time, which is the time elapsed for the peak diastolic pressure gradient to decrease by 50%. The E phase of the transmitral flow velocity is used in the calculation of the peak transmitral pressure gradient and the pressure half-time. The A phase of mitral inflow is not included in the pressure half-time calculation and may be absent if the rhythm is atrial fibrillation (Fig. 6). Postoperative restoration of sinus rhythm is more likely when the duration of atrial fibrillation has been less than 1 year.84Probst B. Goldschlager N. Seltzer A. Left atrial size and atrial fibrillation in mitral stenosis: Factors influencing their relationship.Circulation. 1973; 48: 1281Crossref Scopus (118) Google Scholar The pressure half-time is determined by measuring the time for the peak E phase velocity (Vmax) to decrease to 0.7 peak blood flow velocity.Figure 5Transmitral flow velocity in mitral stenosis: sinus rhythm produces biphasic filling of the left ventricle.View Large Image Figure ViewerDownload (PPT)Figure 6Continuous-wave Doppler measures of transmitral pressure gradient (peak and mean velocities) and mitral valve area (pressure half-time). Rhythm is atrial fibrillationView Large Image Figure ViewerDownload (PPT)Derivation of the Pressure Half-TimeDefinitions:GivenDerivation:The estimated mitral valve area can then be calculated from the Pt1/2 with the following equation:In patients with atrial fibrillation, the estimation of mitral valve area customarily is based on the average Doppler measurements obtained over five cardiac cycles.The shape of the transvalvular blood flow velocity profile is determined not only by the mitral valve orifice size but also by left atrial and ventricular compliance, the transvalvular pressure gradient, aortic valve regurgitation, and cardiac output.108Thomas J.D. Wilkins G.T. Choong C.Y. et al.Inaccuracy of mitral pressure half-time immediately after mitral valvotomy. Dependence on transmitral gradient and left atrial and ventricular compliance.Circulation. 1988; 78: 980-993Crossref PubMed Scopus (222) Google Scholar Left atrial and ventricular compliance may change after valvuloplasty and cardiopulmonary bypass. Aortic regurgitation produces retrograde filling of the left ventricle from the aorta and increases left ventricular diastolic pressure and decreases the transmitral pressure gradient. Aortic regurgitation decreases the pressure half-time and leads to an overestimation of mitral valve area (underestimation of the severity of mitral stenosis). Aortic regurgitation also decreases left ventricular diastolic compliance.31Fachskampf F.A. Weyman A.E. Gillam L. et al.Aortic regurgitation shortens Doppler pressure half-time in mitral stenosis: Clinical evidence, in vitro simulation, and theoretical analysis.J Am Coll Cardiol. 1990; 16: 396-404Abstract Full Text PDF PubMed Scopus (90) Google Scholar, 67Mego D.M. John J.P. Rubal B.J. Pharmacodynamic Doppler determination of mitral valve area in patients with significant aortic regurgitation.J Am Soc Echocardiogr. 1993; 6: 142-148Abstract Full Text PDF PubMed Scopus (3) Google Scholar, 75Oh J.K. Hatle L.K. Sinak L.J. et al.Characteristic Doppler echocardiographic pattern of mitral inflow velocity in severe aortic regurgitation.J Am Coll Cardiol. 1989; PubMed Google Scholar Changes in the rate of decay of the diastolic transmitral blood flow velocity cause a corresponding change in the pressure half-time, which may be independent of the mitral valve orifice size.Pressure half-time and peak inflow velocity measurements are also affected by changes in the cardiovascular status. Pressure half-time measurements can overestimate the mitral valve area by 50% to 100% during exercise.7Braverman A.C. Thomas J.D. Lee R.T. Doppler estimation of mitral valve area during changing hemodynamic conditions.Am J Cardiol. 1991; 68: 1485-1490Abstract Full Text PDF PubMed Scopus (59) Google Scholar, 114Voelker W. Regel B. Dittmann H. et al.Effect of heart rate on transmitral flow velocity profile and Doppler measurements of mitral valve area in patients with mitral stenosis.Eur Heart J. 1992; 13: 152-159PubMed Google Scholar Exercise-induced increases in heart rate, inotropy, and cardiac output increase the transmitral pressure gradient and peak inflow velocity, which decreases the pressure half-time independent of the actual mitral valve orifice area because the pressure half-time is a function of the peak inflow velocity. The correlation between mitral valve area estimated from the pressure half time, two-dimensional echocardiography, and cardiac catheterization data is variable and in the range of r = 0.70 to r = 0.90. The application of the pressure half-time method to calculate mitral valve area after cardiopulmonary bypass or mitral surgery has not yet been validated.The continuity equation, based on the conservation of mass, permits the calculation of mitral valve area because the net antegrade blood flow through the mitral valve must be eq
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