Mitral Stenosis

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5 Mitral Stenosis

Valid Methods for Mitral Valve Area Determination (Need ≥2 Concordant)

Continuity (if < mild AI)

Pressure half time (PHT), if no factors are present that alter left ventricle (LV) compliance, such as left ventricular hypertrophy, left ventricular wall motion abnormalities, LV dysfunction, recent CBV, or more than mild AI

Proximal isovelocity surface area (PISA)

Planimetry

Real-time three-dimensional (3D) echocardiography

Scanning Notes

Planimetry

Optimize the gain settings for planimetry—over-gain results in a falsely low estimation of mitral valve area (MVA) due to “blooming” of the margins.

Measure the area at the narrowest part of the funnel-like orifice of MS—this may be at the level of the leaflet tips or at the subvalvar level.

Be cautious if there was a prior commissurotomy—planimetry underrepresents area if the orifice has deep “splits” into the commissures (or leaflets), which are difficult so see by ultrasound, especially if they extend off the plane of imaging.

Pressure Half Time

Do not accept PHT estimates of MVA if any of the following are present:

• Left ventricular hypertrophy

• Left ventricular wall motion abnormalities

• LV dysfunction

• Recent commissurotomy

• More than mild AI

All are factors that reduce the accuracy of the PHT relation to MVA.

Proximal Isovelocity Surface Area

where r = PISA radius.

The PISA method is based on the assumption that there is a hemisphere of flow acceleration such as would occur with a planar orifice. This often is not the case in mitral stenosis, however, particularly when the greatest stenosis is subvalvar. To adjust for the effect of the orifice on the volume of the PISA, use of an angle correction factor has been suggested (Fig. 5-1), multiplying the preceding calculation by α/180°. Not all echo systems carry angle measurement software.

where α = the measured angle of the “plane” of the orifice and r = PISA radius.

Transesophageal echocardiography (TEE) generally affords excellent depiction of PISA in mitral stenosis.

Reporting Issues

The mean gradient is the gradient seen, by the left atrium, on average, through diastole and is, as with AS, the only suitable expression of the physiologic pressure burden on the downstream chamber. Many MS profiles have an initial, brief, higher velocity/gradient that is not borne out through the rest of diastole. Therefore, emphasize the mean gradient, and avoid mentioning the peak gradient. It is clinically useful to offer the heart rate and rhythm, both of which are apparent on echocardiography, when stating the mean gradient: “The mean gradient was 13 mm Hg at an average heart rate of 75 bpm (atrial fibrillation).” When reporting, compare gradients, areas and RVSP, and rhythm to any previously recorded measurements.

Area Issues

Place less emphasis on the valve area, which is invariably calculated (other than by the planimetry method) and, therefore, is subject to larger error.

Ensure MVA is concordant by at least two suitable methods.

Pressure Half Time Method

The PHT relation (220) was validated in a relatively small series and is best applied for MVA between 1 and 1.5 cm²; r = 0.75.¹ The actual precision of the correlation is less than has been thought.

The 220 constant is actually different for both MVA <1 cm² and MVA >1.5 cm²; therefore, use of the relationship at higher or lower areas is essentially an extrapolation of the known relationship, and assumes that a known variable (220) is a constant, which it is not.

In the presence of AI, there are two ventricular inflows determining the spectral inflow:diastolic relationship. The PHT relation, therefore, is less representative of MS alone, in the presence of more than moderate AI. Correlation and SEE for MVA by PHT (vs. Gorlin) for patients both without and with AI are as follows:

• r = 0.69, SEE = 0.44 cm² for patients with AI

• r = 0.91, SEE = 0.24 cm² for patients without AI.²

PHT is less accurate in patients older than 65 years of age, because of effects of hypertension on the ventricular diastolic properties, leading to overestimation of MVA.³

PHT is less accurate for 3 months after CBV,⁴ because passive ventricular diastolic properties and atrial diastolic properties are adapting to the changes in load (i.e., less atrial/more ventricular).

Planimetry Method

When images are amenable to planimetry, it is an accurate technique. It requires attention to scan extensively along the short axis of the orifice, to ensure sampling at the narrowest part. This may be at the leaflet tips, or in the subvalvar zone, which is important not to miss.

Correlation for MVA by planimetry (vs. cardiac catheterization): r = 0.92 – 0.95.^5,⁶

Planimetry of MVA is an AI-independent technique.

Planimetry is less accurate with prior commissurotomy,^3,^7,⁸ because the split often is eccentric: it may lead out onto another plane of imaging and be missed, or may go into a bright commissure that is difficult to visualize.

Continuity Method

MVA by the continuity method is less accurate when the ideal reference site (the LVOT) has more than mild AI. The tricuspid reference site is harder to use, and is at least as likely to have TR. For all-comers, the correlation of continuity is very good: r = 0.91, SEE = 0.24 cm²,² especially in the absence of AI: r = 0.93.² However, in the presence of AI it is less: r = 0.84.²

Real-Time Three-Dimensional Echocardiography

The real-time 3D technique allows depiction of the mitral orifice on any plane, and thus should assist with the task of planimetry. Although studies are limited to date, real-time 3D echocardiography shows very good correlation with Gorlin (average difference of 0.08 cm²), and low inter- and intraobserver variability (κ of 0.84 and 0.96, respectively), which in comparative studies was better than with other methods.¹⁰

Descriptors of Mitral Stenosis Severity

After it has been established that MS is present, the next important task is to determine its severity. This involves a composite assessment of symptoms, physical findings, and hemodynamics. It must be recalled that MVA < 1 cm² always indicates severe MS, but larger patients or those with higher cardiac output (CO) needs are commonly “severe” above an area of 1 cm² and receive intervention for average MVAs of 1.2 or 1.3 cm².

Distinguishing moderate from mild is really of little consequence, as both are “nonsevere” and would not prompt intervention.

“Severe” = mean gradient >12 mm Hg at rest, and an area of <1.3 cm².

• A subset of clinically severe cases have MVA > 1 cm² (1.2–1.3 cm²).

“Critical” = mean gradient > 12 mm Hg at rest, and an area of <1.0 cm²

Moderate = mean gradient < 12 mm Hg at rest, and an area of ≥1.3 cm²

Surgical Issues

Establish the degree of submitral (annular) calcification. There is a greater risk of periprosthesis (paravalvar) MR when submitral (annular) calcification is severe.

Determine the degree of AI: in severe MR, IABP should not be used if there is concurrent AI ≥2+.

Describe the RV in detail (RVH/systolic dysfunction/size), as well as the RVSP.

RA size is a reasonable descriptor of RV diastolic function, if neither TR nor atrial fibrillation is present.

Provocative Testing to Enhance Transmitral Gradients and Right Ventricular Systolic Pressure

Simple bedside maneuvers (e.g., a few sit-ups) or more sophisticated ones (e.g., supine bicycle, upright treadmill testing, or dobutamine) may be used to increase the heart rate and cardiac output, and thereby enhance the mitral gradient and RVSP. The role of such testing is unclear: in mitral stenosis the gradient would be expected to increase, and generally it does, about two-fold, when patients are subjected to a Bruce or modified Bruce protocol: from 9 ± 7 mm Hg at rest to 17 ± 8 mm Hg, as does the RVSP, from 41 ±1 9 mm Hg to 70 ± 32 mm Hg.¹¹ The optimal interpretation of the provoked hemodynamics is unclear. Advocates suggest that it better describes the basis of exertional symptoms and may be contributory when the resting hemodynamics are less striking than the (exertional) symptoms and findings.

Dobutamine stress echo (a gradient cut-off of 18 mm Hg) has been shown to predict clinical events (90% sensitivity, 87% specificity, and 90% accuracy) over a 5-year period, and increases the detection of medium- and higher-risk cases.¹² Dobutamine stress echocardiography may assist with the evaluation of patients whose symptoms are out of proportion to the calculated valve area, and who may benefit from “medical or invasive intervention.”¹³

Notes on Mitral Stenosis

Pathophysiology

The normal mitral valve area is 4.5 to 6 cm². A diastolic transmitral valve gradient occurs with loss of about half of the original area. There is increased left atrial pressure at rest with MVA of 1.5 cm².

Two thirds (at least) of MS cases occur in women. Of all cases of rheumatic heart disease, 25% are pure MS and 40% are mixed MS/mitral insufficiency.

The course of disease proceeds as follows:

• There is a 5- to 15-year latent period after rheumatic fever before early findings (auscultatory abnormalities) become apparent.

• Usually, a decade of asymptomaticity (with auscultatory abnormalities) passes before symptoms develop.

• Over 5 years, most patients with NYHA Class 2 symptoms progress to Class 3 to 4.

• Ten-year survival of patients with NYHA Class 2 symptoms is about 80%; for patients with NYHA Class 3 symptoms, it is about 38%. A more rapid progression has been noted among certain groups, such as in the subtropical areas of India and the Philippines, and among the Inuit.

Role of Transthoracic and Transesophageal Electrocardiography in Mitral Stenosis

Transthoracic Echocardiography

Nearly all cases of MS can be hemodynamically assessed using TTE alone. Both apical and lower esophagus sampling sites are, however, ideally aligned for Doppler interrogation, and generally generate accurate estimates of gradient. However, if the plane of the mitral orifice is oblique (because of LA dilation), TEE may struggle to achieve optimal alignment for sampling.

Mitral valve scoring is better performed by TTE than TEE, because posterior long-axis and apical views show subvalvar (chordal) involvement better than TEE does. TEE images from the esophagus, acquired through thickened (and potentially calcified) leaflets, fail to clearly depict subvalvar disease. Transgastric long-axis views may afford adequate views of the important subvalvar apparatus.

TEE is better than TTE for the following:

Detection of LAA and LA thrombus, which is necessary information when contemplating CBV

Estimation of MR severity (TTE may underestimate MR severity)

The rare truly technically difficult study case

TEE is not superior for the evaluation of subvalvar disease. The thickened and often calcified leaflets impair subvalvar imaging from the esophagus. Transgastric views are helpful to circumvent this imaging problem.

Cardiac Catheterization for Assessment of Mitral Stenosis

Usual Technique

Pulmonary artery (PA) catheter(s) for right-sided pressures and thermodilution-estimated CO

Femoral arterial access for retrograde cannulation into the LV via the aorta

• LV to aortic (femoral) pressure gradients

• Diastolic filling period (DFP): the average width (time) of the gradients

Verification of pressure waveforms (see later discussion)

Gorlin Equation

The Gorlin equation is employed, using the following variables: CO, DFP, HR, gradient. These variables are readily obtained at cardiac catheterization.

Historically, the Gorlin equation constant was developed for MS, because there is less flow dependence with MS than for AS.¹⁴

In a small initial validation (11 cases), variation of serial measurements averaged ±0.0 cm², but ranged from +0.2 to –0.4 cm².¹⁵

In the initial series, autopsy standard was ±0.5 to ±0.1 cm² and the variation against autopsy was ≤0.2 cm².¹⁴

The Gorlin equation purportedly estimates anatomic, not effective, orifice, because it was validated against surgery and autopsy, but there is evidence that it does not truly reflect anatomic area.

The Gorlin equation is less accurate in the presence of the following:

• MR. Therefore, in the presence of mixed mitral disease, echocardiographic measures (2D, planimetry) are superior to Gorlin.¹⁶

• Atrial fibrillation

• Tachycardia

• Other valve lesions

• Abnormal LV function

Gorlin works best in the context of normal LV systolic function.

Areas should be calculated from 10 beats.¹⁶

Gorlin Equation Considerations

Cardiac Output Issues

By any technique, CO is not reproducible within 15%.

Thermodilution is rendered less accurate by significant TR, which may not be known to be present, and is fairly common in advanced mitral disease.

The Fick technique is not likely more accurate in the real world, but does offer a “cross-check.” 3 mL/kg is an estimate of oxygen consumption, and has its own variance.

Gradient Issues

Ideally, the mitral gradient is recorded by catheters directly on either side of the valve (LA catheter via transseptal puncture and LV catheter), but this is not actual practice, and would confer additional risk if performed universally. Instead of an LA catheter, a pulmonary capillary wedge pressure (PCWP) recording is generally used, because it is easier and carries lower risk, but it is subject to artifacts that tend to increase the measured gradient.

In most patients, the PCWP is the same as the left atrial pressure, but delayed by 40 to 120 msec. To attempt to account for this, the peak of the V-wave is shifted (“phase corrected”) onto the downslope of the LV pressure tracing.

When the data by PCWP tracings are in doubt, a transseptal puncture for direct LA pressure should be considered.

Gradients will vary with atrial fibrillation, which is common with MS, and more beats than usual should be averaged, ideally 10.¹⁶

Catheterization–Echocardiographic Discordance of Hemodynamic Parameters of Mitral Stenosis

Some cases of MS have discordance with catheter-derived estimates. The most common scenario that begets case discussion occurs when the case is not (quite) severe by echocardiography, but is severe as assessed by the wedge technique at catheterization. In most cases, this type of discordance reflects only lack of familiarity with wedge technique errors.

Reasons for Discordance with Catheterization–Echocardiography

The 95% CI Doppler mitral valve gradient versus catheter (wedge technique) gradient is 3 mm Hg.

Echocardiography Estimates Mitral Valve Area Less Than Catheterization

Planimetry: over-gain results in smaller depiction of orifice

PHT: if DT is prolonged due to LV properties

Within the SEE

Echocardiography Estimates Mitral Valve Area Greater Than Catheterization

Under-sampling of MS jet (alignment, poor signal intensity, poor planimetry)

Echocardiography Estimates Mitral Valve Gradient Greater Than Catheterization

Within the SEE

Echocardiography Estimates Mitral Valve Gradient Less Than Catheterization

Under-sampling of MS jet (alignment, poor signal intensity, poor planimetry)

Catheterization Estimates Transmitral Gradient Higher Than Does Echocardiography

Use of PCWP (not direct LAP) is the most likely cause of overestimation of MVG by catheterization. Use of PCWP tracing overestimates LAP–LVP by 3.3 ± 3.5 mm Hg (53%).²²

Use of phase-“corrected” PCWP improves correlation, but still leads to overestimation: 2.5 ± 2.9 mm Hg (43%) in one study ²² and a lesser mean difference in another study (1.7 mm Hg), as well as lesser difference in area.²³

Use of direct LAP results in a negligible mean difference between Doppler and catheterization gradient: only 0.2 ± 1.2 mm Hg.²²

Mitral Valve Catheter Balloon Valvuloplasty

Indications for Percutaneous Mitral Balloon Valvotomy

The indications for this procedure are presented in Boxes 5-1 and 5-2.

Summary

For MS, echocardiography is able to determine the following:

Suitability for catheter valvuloplasty

Assessment of severity should combine the calculation of gradient and suitable techniques for the determination of the stenotic orifice area.

Knowledge of the many details of echocardiography and catheterization determinations of MVA and gradient is essential to navigate cases of discordance. Echocardiographic calculations of mitral valve gradient correlate better with catheter LA–LV gradient than with LV pulmonary capillary wedge pressure–LV gradient.

BOX 5-1 Indications for Percutaneous Mitral Balloon Valvotomy: ACC/AHA 2006 Recommendations

Class I

Percutaneous mitral balloon valvotomy is effective for symptomatic patients (New York Heart Association [NYHA] functional class II, III, or IV), with moderate or severe mitral stenosis (MS) and valve morphology favorable for percutaneous mitral balloon valvotomy in the absence of left atrial thrombus or moderate to severe mitral regurgitation (MR). (Level of evidence: A)

Percutaneous mitral balloon valvotomy is effective for asymptomatic patients with moderate or severe MS and valve morphology that is favorable for percutaneous mitral balloon valvotomy who have pulmonary hypertension (pulmonary artery systolic pressure > 50 mm Hg at rest or > 60 mm Hg with exercise) in the absence of left atrial thrombus or moderate to severe MR. (Level of evidence: C)

Class IIa

Percutaneous mitral balloon valvotomy is reasonable for patients with moderate or severe MS who have a nonpliable calcified valve, are in NYHA functional class III–IV, and are either not candidates for surgery or are at high risk for surgery. (Level of evidence: C)

Class IIb

Percutaneous mitral balloon valvotomy may be considered for asymptomatic patients with moderate or severe MS and valve morphology favorable for percutaneous mitral balloon valvotomy who have new onset of atrial fibrillation in the absence of left atrial thrombus or moderate to severe MR. (Level of evidence: C)

Percutaneous mitral balloon valvotomy may be considered for symptomatic patients (NYHA functional class II, III, or IV) with mitral valve area >1.5 cm² if there is evidence of hemodynamically significant MS based on pulmonary artery systolic pressure >60 mm Hg, pulmonary artery wedge pressure ≥25 mm Hg, or mean MV gradient >15 mm Hg during exercise. (Level of evidence: C)

Percutaneous mitral balloon valvotomy may be considered as an alternative to surgery for patients with moderate or severe MS who have a nonpliable calcified valve and are in NYHA class III–IV. (Level of evidence: C)

Class III

Percutaneous mitral balloon valvotomy is not indicated for patients with mild MS. (Level of evidence: C)

Percutaneous mitral balloon valvotomy should not be performed in patients with moderate to severe MR or left atrial thrombus. (Level of evidence: C)

From ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol. 2006;48(3):e1–e148.

BOX 5-2 Indications for Surgery for Mitral Stenosis: ACC/AHA 2006 Recommendations

Class I

Mitral valve (MV) surgery (repair, if possible) is indicated in patients with symptomatic (NYHA functional class III–IV) moderate or severe MS when

• Percutaneous mitral balloon valvotomy is unavailable.

• Percutaneous mitral balloon valvotomy is contraindicated because of left atrial thrombus, despite anticoagulation or because concomitant moderate to severe MR is present.

• The valve morphology is not favorable for percutaneous mitral balloon valvotomy in a patient with acceptable operative risk. (Level of evidence: B)

Symptomatic patients with moderate to severe MS who also have moderate to severe MR should receive MV replacement, unless valve repair is possible at the time of surgery. (Level of evidence: C)

Class IIa

MV replacement is reasonable for patients with severe MS and severe pulmonary hypertension (i.e., pulmonary artery systolic pressure >60 mm Hg) with NYHA functional class I–II symptoms who are not considered candidates for percutaneous mitral balloon valvotomy or surgical MV repair. (Level of evidence: C)

Class IIb

MV repair may be considered for asymptomatic patients with moderate or severe MS who have had recurrent embolic events while receiving adequate anticoagulation and who have valve morphology favorable for repair. (Level of evidence: C)

Class III

MV repair for MS is not indicated for patients with mild MS. (Level of evidence: C)

Closed commissurotomy should not be performed in patients undergoing MV repair; open commissurotomy is the preferred approach. (Level of evidence: C)

From ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol. 2006;48(3):e1–e148.

BOX 5-3 Valvular Disease: Focused Update on Endocarditis: ACC/AHA 2008 Guidelines

Class IIa indication: Antibiotic prophylaxis is no longer indicated in patients with mitral stenosis for prevention of infective endocarditis.

From ACC/AHA 2006 guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol. 2006;48(3):e1–e148.

BOX 5-4 Appropriateness Criteria and Indications for Cardiac Imaging Modalities and Cardiac Catheterization for the Assessment of Mitral Stenosis

Transthoracic Echocardiography

ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 Appropriate Use Criteria for Echocardiography ²⁵

ACC/AHA 2003 Guideline Update for the Clinical Application of Echocardiography ²⁶

No update specific to MS

ACC/AHA 2006 Guidelines for the Management of Patients with Valvular Heart Disease ²⁸

Recommendations and Indications for Echocardiography in Mitral Stenosis

Class I

• Echocardiography should be performed in patients for the diagnosis of MS, assessment of hemodynamic severity (mean gradient, MV area, and pulmonary artery pressure), assessment of concomitant valvular lesions, and assessment of valve morphology (to determine suitability for percutaneous mitral balloon valvotomy). (Level of evidence: B)

• Echocardiography should be performed for re-evaluation in patients with known MS and changing symptoms or signs. (Level of evidence: B)

• Echocardiography should be performed for assessment of the hemodynamic response of the mean gradient and pulmonary artery pressure by exercise Doppler echocardiography in patients with MS when there is a discrepancy between resting Doppler echocardiographic findings, clinical findings, symptoms, and signs. (Level of evidence: C)

Class IIa

• Echocardiography is reasonable in the re-evaluation of asymptomatic patients with MS and stable clinical findings to assess pulmonary artery pressure (for those with severe MS, every year; moderate MS, every 1–2 yr; and mild MS, every 3–5 yr). (Level of evidence: C)

Transesophageal Echocardiography

ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 Appropriate Use Criteria for Echocardiography ²⁵

TEE as Initial or Supplemental Test—Valvular Disease

Evaluation of valvular structure and function to assess suitability for, and assist in planning of, an interventionAppropriateness criteria: A; median score: 9

ACC/AHA 2003 Guideline Update for the Clinical Application of Echocardiography ²⁶

Class I

• Use of echocardiography (especially TEE) in guiding the performance of interventional techniques and surgery (e.g., balloon valvuloplasty and valve repair for valvular diseases)

Cardiac Catheterization

ACC/AHA 2006 Guidelines for the Management of Patients with Valvular Heart Disease ²⁸

Indications for Invasive Hemodynamic Evaluation

Class I

• Cardiac catheterization for hemodynamic evaluation should be performed for assessment of severity of MS when noninvasive tests are inconclusive or when there is discrepancy between noninvasive tests and clinical findings regarding severity of MS. (Level of evidence: C)

• Catheterization for hemodynamic evaluation including left ventriculography (to evaluate severity of MR) for patients with MS is indicated when there is a discrepancy between the Doppler-derived mean gradient and valve area. (Level of evidence: C)

Class IIa

• Cardiac catheterization is reasonable to assess the hemodynamic response of pulmonary artery and left atrial pressures to exercise when clinical symptoms and resting hemodynamics are discordant. (Level of evidence: C)

• Cardiac catheterization is reasonable in patients with MS to assess the cause of severe pulmonary arterial hypertension when out of proportion to severity of MS as determined by noninvasive testing. (Level of evidence: C)

Class III

• Diagnostic cardiac catheterization is not recommended to assess the MV hemodynamics when 2D and Doppler echocardiographic data are concordant with clinical findings. (Level of evidence: C)

Cardiac Computed Tomography

ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac CT ³⁰

Evaluation of Intra- and Extracardiac Structures

Characterization of native cardiac valves

Suspected clinically significant valvular dysfunction

Inadequate images from other noninvasive methodsAppropriateness criteria: A; median score: 8

Nuclear

ACCF/ASNC/AHA/ASE/SCCT/SCMR/SNM 2009 Appropriate Use Criteria for Cardiac Radionuclide Imaging ³³

Evaluation of LV Function

Assessment of LV function with radionuclide angiography (ERNA or FP RNA)

In absence of recent reliable diagnostic information regarding ventricular function obtained with another imaging modalityAppropriateness criteria: A; median score: 8

TABLE 5-1 Mass Score (total of 16)

TABLE 5-2 Echocardiographic Prediction of Outcome of Percutaneous Mitral Balloon Valvotomy

TABLE 5-3 Utility of Different Imaging Modalities and Cardiac Catheterization in the Assessment of Mitral Stenosis

MODALITY	PROS	CONS/CAVEATS
Transthoracic Echocardiography	2D echocardiography • Short-axis planimetry of the MVA is a valuable and accurate means of directly determining MVA. • “Scoring” of the valve is predictive of success of balloon valvuloplasty, and is better performed by TTE than by TEE. • Commissural calcification predicts risk of balloon valvuloplasty.

• Accurate planimetry is technically demanding.

• More severe stenosis may exist at the subvalvar level, which is difficult to recognize by short-axis imaging.

Color Doppler echocardiography

• PISA determination of MVA, if feasible, is accurate.

• Color Doppler is able to recognize associated MI.

Spectral Doppler echocardiography

• CW Doppler determinations of mitral valve gradients are nearly equivalent to those determined by LA (trans-septal) to LV catheterization.

• CW Doppler determinations of MVA by the PHT method are accurate within the range of 1–1.5 cm², in the absence of variables that influence LV and LA compliance. The PHT relation is not confounded by the all-too-common presence of mitral insufficiency. The method is validated between 1 and 1.5 cm².

• Many non–mitral valve factors influence the transmitral gradient. (E.g., tachycardia, fever, anemia, pregnancy, and large dialysis fistula increase the gradient, and bradycardia and severe pulmonary hypertension reduce the gradient.)

• Many factors reduce the accuracy of the PHT method: e.g., valvuloplasty within three months, LVH, AS, AI, and prior MI.

Transesophageal Echocardiography

• Offers the best means to identify LA and LA appendage thrombi that are relevant to balloon valvuloplasty procedures

• Can guide catheter balloon valvuloplasty procedures (confirms safety of trans-septal punctures, and identifies significant increments in MI with successive balloon inflations)

• MS hemodynamics by TEE are similar to those of TTE, as long as Doppler alignment remains favorable.

• MS determination of PISA estimates of orifice area are generally better than those of TTE because PISAs are better depicted by TEE.

Cardiac CT

Cardiac CT is able to provide some measure, by planimetry, of the mitral valve orifice.

• Irregular heart rhythms (atrial fibrillation, common in mitral valve disease) are a significant technical problem for cardiac CT.

• Valvular (and annular) calcification confer the problem of spatial “blooming.”

Cardiac MRI

SSFP sequences:

Grossly, the mitral orifice can be planimetered.

• Irregular heart rhythms (atrial fibrillation) and valvular calcification conspire to limit the accuracy of CMR in assessing MS hemodynamics.

LGE sequences:NA

• Afford little to the assessment of MS

VEPC sequences:

Are able to approximate the gradient across, but only roughly

• VEPC sequences are often unruly.

• Irregular heart rhythms (atrial fibrillation) decrease the accuracy.

• CMR currently tends to underestimate the severity of MS when compared to echocardiography and catheterization estimates.^36,³⁷

Nuclear NA

• Afford little to the assessment of MS

Chest Radiography

Useful to depict pulmonary vasculature and the presence of left-sided heart failure, and other findings such as pulmonary hemorrhage and pulmonary hemosiderosis.

NA Cardiac Catheterization

• The traditional test to assess gradient and area, and the traditional reference standard to which other tests to compare their determinations of transmitral gradient and of valve area

• The most reliable means by which to determine the pulmonary artery pressures, and the only means by which to determine the pulmonary vascular resistence

• The platform from which to provide catheter balloon valvuloplasty

• LV to pulmonary capillary wedge gradients are less accurate (tend to overestimate) than are LV to LA gradient determinations or TTE Doppler determinations of mean gradient.

2D, two-dimensional; AI, aortic insufficiency; AS, aortic stenosis; CMR, cardiac magnetic resonance; CW, continuous wave; LA, left atrium; LGE, late gadolinium enhancement; LV, left ventricle; LVH, left ventricular hypertrophy; MI, mitrial insufficiency; MS, mitral stenosis; MVA, mitral valve area; NA, not applicable; PHT, pressure half time; PISA, proximal isovelocity surface area; SSFP, steady-state free precession; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography; VEPC, velocity-enhanced phase contrast.

Figure 5-1 Angle correction. Upper image: The top proximal isovelocity surface area (PISA) is a full hemisphere, because the orifice is planar; no angle correction is necessary. Middle image: The PISA is less than a full hemisphere, because the orifice is not planar. Angle correction is advised. Lower image: The PISA is not a full hemisphere, because the orifice is not clearly planar; it is not clear how to determine the optimal angle for correction.

Figure 5-2 Hemodynamic variables at baseline, 1 week, 6 months, and 3 years after balloon mitral valvuloplasty or open surgical commissuortomy. The bars indicate the standard errors. ^*All panels: P < 0.001 for the comparison with the baseline value. ^†Upper left panel: P < 0.001 for the comparison with the values at baseline, one week, and 6 months. ^‡Upper right panel: P = 0.002 for the comparison with the balloon valvuloplasty group and P = 0.16 (not significant) for the comparison with the baseline value. §Lower right panel: P < 0.001 for the comparison with the surgery group.

(From Reyes VP, Raju BS, Wynne J, et al. Percutaneous balloon valvuloplasty compared with open surgical commissurotomy for mitral stenosis. N Engl J Med. 1994;331[15]:961–967.)