Doppler echocardiographic estimation of mitral valve area during changing hemodynamic conditions

A Novel Assessment Using Projected Transmitral Gradient Improves Diagnostic Yield of Doppler Hemodynamics in Rheumatic and Calcific Mitral Stenosis

OBJECTIVES

The aims of this study were to: 1) develop a formula for projected transmitral gradient (TMG), expected gradient under normal heart rate (HR), and stroke volume (SV); and 2) assess the prognostic value of projected TMG.

BACKGROUND

In mitral stenosis (MS), TMG is highly dependent on hemodynamics, often leading to discordance between TMG and mitral valve area.

METHODS

All patients with suspected MS based on echocardiography from 2001 to 2017 were analyzed. Data were randomly split (2:1); projected TMG was modeled in the derivation cohort, then tested in the validation cohort. The composite endpoint was death or mitral valve intervention.

RESULTS

Of 4,973 patients with suspected MS, severe and moderate MS, defined as mitral valve area ≤1.5 and >1.5 to 2.0 cm², were present in 437 (9%) and 936 (19%), respectively. In the derivation cohort (n = 3,315; age 73 ± 12 years; 34% male), corresponding gradients were TMG ≥6 and 4 to <6 mm Hg, respectively, under normal hemodynamics. Based on the impact of hemodynamics on TMG, the formula was projected TMG = TMG - 0.07 (HR - 70) - 0.03 (SV - 97) in men and projected TMG = TMG - 0.08 (HR - 72) - 0.04 (SV - 84) in women. In the validation cohort (n = 1,658), projected TMG had better agreement with MS severity than TMG (kappa 0.61 vs. 0.28). Among 281 patients with TMG ≥6 mm Hg, projected TMG ≥6 mm Hg, present in 171 patients (61%), was associated with higher probability of the endpoint versus projected TMG <6 mm Hg (adjusted hazard ratio: 1.8; 95% confidence interval: 1.2 to 2.6; p < 0.01).

CONCLUSIONS

The novel concept of projected TMG, constructed using the observed impact of HR and SV on TMG, significantly improved the concordance of gradient and valve area in MS and provided better risk stratification than TMG.

Hemodynamics and Prognostic Impact of Concomitant Mitral Stenosis in Patients Undergoing Surgical or Transcatheter Aortic Valve Replacement for Aortic Stenosis

BACKGROUND

Mitral stenosis frequently coexists in patients with severe aortic stenosis. Mitral stenosis severity evaluation is challenging in the setting of combined aortic stenosis and mitral stenosis because of hemodynamic interactions between the 2 valve lesions. The impact of aortic valve replacement (AVR) for severe aortic stenosis on mitral stenosis is unknown. This study aimed to assess the effect of AVR on mitral stenosis hemodynamics and the clinical outcomes of patients with severe aortic stenosis with and without mitral stenosis.

METHODS

We retrospectively investigated patients who underwent surgical AVR or transcatheter AVR for severe aortic stenosis from 2008 to 2015. Mean transmitral gradient by Doppler echocardiography ≥4 mm Hg was identified as mitral stenosis; patients were then stratified according to mitral valve area (MVA, by continuity equation) as >2.0 cm² or ≤2.0 cm². MVA before and after AVR in patients with mitral stenosis were evaluated. Clinical outcomes of patients with and without mitral stenosis were compared using 1:2 matching for age, sex, left ventricular ejection fraction, method of AVR (surgical AVR versus transcatheter AVR) and year of AVR.

RESULTS

Of 190 patients with severe aortic stenosis and mitral stenosis (age 76±9 years, 42% men), 184 were matched with 362 with severe aortic stenosis without mitral stenosis. Among all mitral stenosis patients, the mean MVA increased after AVR by 0.26±0.59 cm² (from 2.00±0.50 to 2.26±0.62 cm², P<0.01). MVA increased in 105 (55%) and remained unchanged in 34 (18%). Indexed stroke volume ≤45 mL/m² (odds ratio [OR] 2.40; 95% CI, 1.15-5.01; P=0.020) and transcatheter AVR (OR, 2.36; 95% CI, 1.17-4.77; P=0.017) were independently associated with increase in MVA. Of 107 with significant mitral stenosis (MVA ≤2.0 cm²), MVA increased to >2.0 cm² after AVR in 52 (49%, pseudo mitral stenosis) and remained ≤2.0 cm² in 55 (51%, true mitral stenosis). During follow-up of median 2.9 (0.7-4.9) years, true mitral stenosis was an independent predictor of all-cause mortality (adjusted hazard ratio, 1.88; 95% CI, 1.20-2.94; P<0.01).

CONCLUSIONS

MVA improved after AVR in nearly half of patients with severe aortic stenosis and mitral stenosis. MVA remained ≤2.0 cm² (true mitral stenosis) in nearly half of patients with severe aortic stenosis and significant mitral stenosis; this was associated with worse survival among patients undergoing AVR for severe aortic stenosis.

Echocardiographic Evaluation of Hemodynamic Changes in Left-Sided Heart Valves in Pregnant Women With Valvular Heart Disease

Physiologic changes during pregnancy can deteriorate or improve patients' hemodynamic status in the setting of valvular heart disease. There are sparse data regarding the effect of pregnancy on valve hemodynamics in normal pregnant women with known valvular heart disease. In a prospective study from July 2014 to January 2016, a total of 52 normal pregnant women who had mitral stenosis, aortic stenosis, or a history of mitral valve or aortic valve replacements were assessed. All patients underwent echocardiographic examinations and hemodynamic parameters were measured for both the mitral valve and aortic valve at first, second, and third trimesters. The parameters included mean gradient, peak gradient, mean gradient/heart rate, peak gradient/heart rate, pressure halftime, dimensionless velocity index, and valve area. Although most hemodynamic parameters (i.e., mean gradient, peak gradient, mean gradient/heart rate, and peak gradient/heart rate) increased approximately 50% from first to second trimester and first to third trimester (p <0.05) but those remained stable at third compared with second trimester (p >0.05). The ratio of changes between trimesters for valve area and dimensionless velocity index were comparable. No clinical decompensations were observed except for 3 and 7 cases of deterioration to functional class II at second and third trimesters, respectively. In conclusion, during a full-term and uncomplicated pregnancy, mitral and aortic valve gradients increase without significant changes in valve area that are more marked between the second and first trimester than between the third and second trimester.

Mitral valve area during exercise after restrictive mitral valve annuloplasty: importance of diastolic anterior leaflet tethering

BACKGROUND

Restrictive mitral valve annuloplasty (RMA) for secondary mitral regurgitation might cause functional mitral stenosis, yet its clinical impact and underlying pathophysiological mechanisms remain debated.

OBJECTIVES

The purpose of our study was to assess the hemodynamic and clinical impact of effective orifice area (EOA) after RMA and its relationship with diastolic anterior leaflet (AL) tethering at rest and during exercise.

METHODS

Consecutive RMA patients (n = 39) underwent a symptom-limited supine bicycle exercise test with Doppler echocardiography and respiratory gas analysis. EOA, transmitral flow rate, mean transmitral gradient, and systolic pulmonary arterial pressure were assessed at different stages of exercise. AL opening angles were measured at rest and peak exercise. Mortality and heart failure readmission data were collected for at least 20 months after surgery.

RESULTS

EOA and AL opening angle were 1.5 ± 0.4 cm(2) and 68 ± 10°, respectively, at rest (r = 0.4; p = 0.014). EOA increased significantly to 2.0 ± 0.5 cm(2) at peak exercise (p < 0.001), showing an improved correlation with AL opening angle (r = 0.6; p < 0.001). Indexed EOA (EOAi) at peak exercise was an independent predictor of exercise capacity (maximal oxygen uptake, p = 0.004) and was independently associated with freedom from all-cause mortality or hospital admission for heart failure (p = 0.034). Patients with exercise EOAi <0.9 cm(2)/m(2) (n = 14) compared with ≥0.9 cm(2)/m(2) (n = 25) had a significantly worse outcome (p = 0.048). In multivariate analysis, AL opening angle at peak exercise (p = 0.037) was the strongest predictor of exercise EOAi.

CONCLUSIONS

In RMA patients, EOA increases during exercise despite fixed annular size. Diastolic AL tethering plays a key role in this dynamic process, with increasing AL opening during exercise being associated with higher exercise EOA. EOAi at peak exercise is a strong and independent predictor of exercise capacity and is associated with clinical outcome. Our findings stress the importance of maximizing AL opening by targeting the subvalvular apparatus in future repair algorithms for secondary mitral regurgitation.

Stress echocardiographic assessment of mitral valve function repaired using rough-zone trimming

Background

We invented novel mitral valve repair technique; rough-zone trimming procedure (RZT) for anterior mitral valve prolapse. Prolapse site was resected in obtuse triangle shape and sutured edges to creates deep coaptation and improves regurgitation. Though it is simple and reproducible technique, functional mitral stenosis is a risk. Valve function and hemodynamics were investigated using dobutamine stress echocardiography (DSE) in patients after mitral valve repair using RZT.

Methods

Patients underwent RZT for the anterior mitral valve (AML, n = 10), quadrangular resection (QR) of the posterior mitral valve (PML; n = 4), RZT + QR of bileaflet valves (bileaflet; n = 4) and healthy individuals (control; n = 10) and were assessed by DSE (doses up to 20 μg/Kg/min). Echocardiographic data including mitral valve area (MVA), mitral valve mean pressure gradient (MVmeanPG), and systolic pulmonary artery pressure (sPAP) were measured at rest and at peak stress.

Results

Rest/stress MVA (cm²), MVmeanPG (mmHg) and sPAP (mmHg) were 2.8 ± 0.4 and 3.4 ± 0.3, 3.3 ± 1.1 and 7.4 ± 4.1, and 25.7 ± 4.7and 49.1 ± 4.1, respectively, in the AML group. Dobutamine stress increased all parameters but not to pathological levels. The results were similar to those of the other groups after mitral valve repair, whereas MVA was larger and MVmeanPG was lower in the control than in the AML group.

Conclusions

Valve repair using RZT does not pathologically obstruct the mitral valve, either at baseline or during dobutamine stress, and does not affect valve hemodynamics and reserve.

The role of exercise echocardiography in the management of mitral valve disease

PURPOSE

Exercise echocardiography can assess the dynamic component of mitral valve (MV) disease and may therefore be helpful for the clinical decision-making by the heart team. The purpose of this study is to determine the role of exercise echocardiography in the management of disproportionately symptomatic or otherwise atypical patients with mitral regurgitation (MR) and stenosis (MS) in clinical practice.

METHODS

Data of 14 MR and 14 MS patients, including echocardiograms at rest, were presented retrospectively to an experienced heart team to determine treatment strategy. Subsequently, exercise echo data were provided whereupon once again the treatment strategy was determined. This resulted in: value of exercise echo by means of 1) alteration or 2) confirmation of treatment strategy or 3) no additional value.

RESULTS

During exercise the echocardiographic severity of MV disease increased in 9 (64 %) MR and 8 (57 %) MS patients. Based upon alteration or confirmation of the treatment strategy, the value of exercise echocardiography in the management of MR and MS was 86 % and 57 %, respectively.

CONCLUSION

This study showed that physical exercise echo can have an important role in the clinical decision-making of challenging patients with MV disease. Exercise echocardiography had additional value to the treatment strategy in 71 % of these patients.

A computational procedure for prediction of structural effects of edge-to-edge repair on mitral valve

Edge-to-edge technique is a surgical procedure for the correction of mitral valve leaflets prolapse by suturing the edge of the prolapsed leaflet to the free edge of the opposing one. Suture presence modifies valve mechanical behavior and orifice flow area in the diastolic phase, when the valve opens and blood flows into the ventricle. In the present work, in order to support identification of potentially critical conditions, a computational procedure is described to evaluate the effects of changing suture length and position in combination with valve size and shape. The procedure is based on finite element method analyses applied to a range of different mitral valves, investigating for each configuration the influence of repair on functional parameters, such as mitral valve orifice area and transvalvular pressure gradient, and on structural parameters, such as stress in the leaflets and stitch tension. This kind of prediction would ideally require a coupled fluid-structural analysis, where the interactions between blood flows and mitral apparatus deformation are simultaneously considered. In the present study, however, an alternative approach is proposed, in which results obtained by purely structural finite element analyses are elaborated and interpreted taking into account the Bernoulli type equations available in literature to describe blood flow through mitral orifice. In this way, the effects of each parameter in terms of orifice flow area, suture loads, and leaflets stresses can be expressed as functions of atrioventricular pressure gradient and then correlated to blood flow rate. Results obtained by using this procedure for different configurations are finally discussed.

Mitral Valve Resistance as a Determinant of Resting and Stress Pulmonary Artery Pressure in Patients with Mitral Stenosis: A Dobutamine Stress Study

BACKGROUND

Severity of mitral stenosis (MS) is assessed by means of mitral valve area and mean transmitral gradient. However, these conventional stenosis indexes poorly reflect the major hemodynamic consequence of MS, which is increase in pulmonary artery pressure (PAP). Valve resistance (VR) is a physiologic expression of stenosis because it incorporates both the pressure gradient and flow data. Previously, in patients with aortic stenosis, hemodynamic burden on the left ventricle has been shown to be closely related to aortic VR but not to aortic valve area. Accordingly, we hypothesized that mitral VR may also better reflect the hemodynamic burden of MS and, hence, be an important determinant of PAP in patients with MS. This study sought to evaluate the relation between several echocardiographic parameters of MS severity, in particular mitral VR and the resting and stress PAP in patients with MS. Determinants of exercise capacity were also assessed.

METHODS

Twenty patients with pure MS were studied by Doppler echocardiography. Mitral valve area, mean transmitral gradient, mitral VR, net atrioventricular compliance, and left atrial diameter were derived from resting Doppler echocardiographic examination as possible determinants of resting and stress PAP. PAP was measured by Doppler echocardiography at rest and during dobutamine-induced stress. Patients completed a symptom-limited exercise test to determine exercise capacity. Determinants of resting and stress PAP and exercise capacity were analyzed.

RESULTS

Systolic PAP increased significantly from 39.2 +/- 9.4 mm Hg at rest to 59.5 +/- 18.4 mm Hg during dobutamine-induced stress. Mitral VR was the most closely correlated stenosis index with the resting and stress PAP (r = 0.80, P < .001 and r = 0.93, P < .001, respectively) and it was an independent predictor for both with multivariate analysis. Exercise capacity was mostly and equally correlated with stress PAP (r = -0.62, P = .004) and mitral VR (r = -0.62, P = .004). Multivariate analysis revealed stress PAP as the only significant independent predictor of exercise capacity.

CONCLUSION

Mitral VR is the strongest and the independent predictor of both resting and stress PAP in patients with MS and by this aspect it is superior to mitral valve area and mean transmitral gradient in the expression of stenosis severity. These results underline the importance of mitral VR as a severity index in patients with MS.

Normal mitral and aortic valve areas assessed by three- and two-dimensional echocardiography in 168 children and young adults

Our purpose was to investigate the effects of body size on the sizes of mitral (MV) and aortic valve (AV) areas by three-dimensional (3-D) and two-dimensional (2-D) echocardiography and to create the normal values for 3-D echocardiography. A total of 168 healthy subjects aged 2-27 years were studied by digitized 3-DE, 2-DE, and Doppler echocardiography.3-D echocardiography was performed by using rotational acquisition of planes at 18 degrees intervals from a parasternal view with electrocardiogram gating and without respiratory gating. The annular levels of MV and AV were identified from short-axis cut planes and their areas were measured by planimetry. The diameters of mitral annulus, left ventricular outflow tract (LVOT), and aortic annulus were measured by 2-DE from the apical and parasternal long-axis views. Flow indices were measured by Doppler from MV inflow and the flow in LVOT and in the ascending aorta. Both MV and AV annular areas increased linearly in relation to body size. In the total study group the estimated areas for MV were 5.2 +/- 0.9 cm2/m2 by 3-DE, 3.7 +/- 0.5 cm2/m2 by 2-DE, and 2.0 +/- 0.4 cm2/m2 by continuity equation. The respective values for AV were 2.7 +/- 0.5, 2.1 +/- 0.3, and 1.8 +/- 0.4 cm2/m2. MV velocity time integral (VTI)/ascending aorta VTI increased from 0.80 (0.26) to 0.95 (0.23) with increased body surface area (BSA), whereas MV VTI/LVOT VTI was 1.2 (0.2) in all BSA groups. MV and AV annulus areas increase linearly in relation to body size. 3-DE gives greater estimates for the areas than 2-DE and Doppler equation methods. The data obtained from 168 healthy subjects may serve as a reference for clinical use in patients with various cardiac abnormalities.

Does chronic mitral regurgitation influence Doppler pressure half-time-derived calculation of the mitral valve area in patients with mitral stenosis?

BACKGROUND

In patients with mitral stenosis (MS), Doppler pressure half-time (PHT) may be influenced by hemodynamic variables other than the anatomic mitral valve orifice narrowing. This study was undertaken to assess whether the presence of concomitant mitral regurgitation (MR) affects mitral valve area (MVA) estimation by PHT.

METHODS

Consecutive patients (n = 166) with noncalcific MS, in sinus rhythm, were studied. Group 1 (n = 106) had no or mild MR, and group 2 (n = 60) had moderate or severe MR. MVA was assessed by using the PHT method and planimetry.

RESULTS

There was a strong correlation between planimetry and PHT MVA in both groups (group 1: r = 0.86, P <.001; group 2: r = 0.73, P <.001). However, compared with planimetry MVA, PHT underestimated MVA by > or =20% in 18 patients (17%) in group 1 and 21 patients (35%) in group 2 (P <.01). Overestimation by > or =20% occurred in 12 patients (11%) in group 1 and in 7 (12%) in group 2. Group 2 subanalysis (group 2A: moderate MR, n = 16; group 2B: severe MR, n = 44) revealed that linear regression weakened with increasing severity of MR (group 2A: r = 0.824, P <.001, group 2B: r = 0.70, P <.001). PHT underestimation of MVA occurred in 31% and 36% of patients in Groups IIA and IIB, respectively (P = NS).

CONCLUSIONS

PHT appears to be reliable for estimating MVA in most patients with MS, even in the presence of MR. However, the presence of significant MR reduces the reliability of PHT-derived MVA, with underestimation of MVA in a significant number of subjects. The severity of MR has a direct impact on PHT-derived MVA.

The Use of Stress Echocardiography in the Assessment of Mitral Valvular Disease

Stress echocardiography plays an important role in evaluating asymptomatic patients with significant mitral stenosis and symptomatic patients with only mild disease at rest, as it correlates the exercise-induced symptoms with changes in transmitral gradients, pulmonary pressures, and mitral valve area. In patients with mitral regurgitation (MR), exercise or dobutamine protocols assess for the change in the degree of regurgitation and the pulmonary artery pressure (PAP) in response to high flow states, and detect underlying left ventricular (LV) dysfunction prior to valvular surgery. Exercise echocardiography also helps in the prognostic assessment of patients with mitral valve prolapse as new MR, or latent LV dysfunction may be provoked to identify a group of high risk individuals with normal resting echocardiographic parameters. Finally, it evaluates the proper functioning of prosthetic mitral valves and helps on the monitoring of transmitral gradients and PAPs after mitral valve surgery.

Is the mitral valve area flow-dependent in mitral stenosis? A dobutamine stress echocardiographic study

OBJECTIVES

The purpose of this study was to compare the effect of changes in flow rate on the mitral valve area (MVA) derived from two-dimensional echocardiographic planimetry and Doppler pressure half-time (PHT) methods in patients with mitral stenosis (MS).

BACKGROUND

Dobutamine stress echocardiography has been proposed as a means of assessing the severity of MS. However, data regarding the effect of an increase in flow rate on MVA are limited. If MVA is indeed flow-dependent, this has important implications for the assessment of the severity of MS, particularly in the setting of reduced cardiac output (CO).

METHODS

Dobutamine echocardiography was performed in 57 patients with isolated MS who were in sinus rhythm. The MVA was determined by planimetry and Doppler PHT methods.

RESULTS

Cardiac output increased by > or =50% in 27 patients (group I) and by <50% in 30 patients (group II). In group I, the MVA by planimetry increased by only 10.6 +/- 2% and the MVA by PHT increased by 21.9 +/- 4.8%. These changes were similar to those observed in group II (10.7 +/- 3% and 14.8 +/- 4%, respectively; p = NS), despite a much smaller increase in CO. A clinically important change (from the severe to mild category) occurred in only one patient when using the PHT method and in none by planimetry.

CONCLUSIONS

Changes in flow rate result in small but clinically insignificant changes in echocardiographic MVA measurement. These methods provide an accurate assessment of MS severity in a majority of patients, independent of changes in flow rate.

Overview of stress echocardiography: uses, advantages, and limitations

Responses of the heart to changes in our environment are probably even more important than how the heart functions at rest. Accordingly, stress testing with noninvasive imaging has become important for diagnosis, prognosis, and monitoring the effects of therapy. Echocardiography at rest and with stress permits characterization of global and segmental left ventricular function as well as valvular structure and function. Moreover, echocardiography can be performed during or after a number of different physical or even mental stressors. Advantages of stress echocardiography include its ready availability, relatively low capital cost, and incremental value in that it allows characterization of cardiac anatomy as well as the myocardial response to a potentially ischemic stimulus. Moreover, echocardiography has the potential to image myocardial perfusion along with wall motion and wall thickening. Substantial literature has now been accumulated on the value of stress echocardiography for the diagnosis of ischemic disease, preoperative risk assessment, and assessment of myocardial viability. Echocardiography has compared generally well with nuclear imaging techniques for the detection of angiographic coronary artery disease. Overall sensitivity, however, has been slightly less, particularly for the detection of single-vessel coronary disease, although specificity has been on average somewhat higher than nuclear cardiology techniques. Because of the potential for variability in study acquisition as well as interpretation, careful safeguards need to be employed. Specifically, meticulous technique needs to be applied to obtain high-quality images and to assure that those images are obtained promptly after treadmill exercise stress. Only readers with specific interest and expertise should interpret stress echocardiography studies. Continuing efforts need to be made to assess and minimize variability and to assure continuing quality improvement. Advances in instrumentation, including evolving technology for real-time 3-dimensional imaging, and echocardiography contrast assessment of myocardial perfusion will likely improve the sensitivity of echocardiography and further extend its usefulness.

Impact of atrioventricular compliance on pulmonary artery pressure in mitral stenosis: an exercise echocardiographic study

BACKGROUND

The decay of the pressure gradient across a stenotic mitral valve is determined by the size of the orifice and net AV compliance (C(n)). We have observed a group of symptomatic patients, usually in sinus rhythm, characterized by pulmonary hypertension (particularly during exercise) despite a relatively large mitral valve area by pressure half-time. We speculated that this discrepancy was due to low atrial compliance causing both pulmonary hypertension and a steep decay of the transmitral pressure gradient despite significant stenosis. We therefore tested the hypothesis that C(n) is an important physiological determinant of pulmonary artery pressure at rest and during exercise in mitral stenosis.

METHODS AND RESULTS

Twenty patients with mitral stenosis were examined by Doppler echocardiography. C(n), calculated from the ratio of effective mitral valve area (continuity equation) and the E-wave downslope, ranged from 1.7 to 8.1 mL/mm Hg. Systolic pulmonary artery pressure (PAP) increased from 43+/-12 mm Hg at rest to 71+/-23 mm Hg (range, 40 to 110 mm Hg) during exercise. There was a particularly close correlation between C(n) and exercise PAP (r=-0.85). Patients with a low compliance were more symptomatic (P<0.025). Catheter- and Doppler-derived values for C(n), determined in 10 cases, correlated well (r=0.79).

CONCLUSIONS

C(n), which can be noninvasively assessed, is an important physiological determinant of PAP in mitral stenosis. Patients with low C(n) represent an important clinical entity, with symptoms corresponding to severe increases in PAP during stress echocardiography.

[The effect of the duration of the cardiac cycles on determining mitral valve area by means of pressure half-time]

INTRODUCTION AND AIMS

To analyze the influence of variations in the length of cardiac cycle length of calculating mitral valve area by means of the pressure half time in patients with mitral valve stenosis and atrial fibrillation.

METHODS

Fifty-nine patients with pure mitral valve stenosis and atrial fibrillation were subjected to transmitral flow measurements by continuous Doppler monitoring from the apical window. In each patient the pressure half time was quantified, corresponding to a minimum of 30 consecutive cycles.

RESULTS

Considering all the measurements made in each patient, the correlation between pressure half time and cardiac cycle was significant in 20 cases (34%). The pressure half time variation coefficients were significantly greater when including the values corresponding to the shortest cycles. Thus, for cycle duration of > or = 800, 700, 600, 500 and 400 ms, the mean values were 0.096 +/- 0.041, 0.106 +/- 0.042 (NS), 0.128 +/- 0.032 (p < 0.05), 0.167 +/- 0.048 (p < 0.001) and 0.231 +/- 0.057 (p < 0.0001), respectively. Upon analyzing the relation between pressure half time and cardiac cycle with progressive exclusion of the longer cycles > or = 800, 700 and 600 ms the number of patients with significant correlation coefficients increased to 19/37 (51%), 12/23 (52%) and 4/6 (67%) on respectively excluding.

CONCLUSIONS

Patients with mitral valve stenosis and atrial fibrillation show a variation in pressure half time that may complicate calculation of the mitral valve area. Variability is inherent to the measurement method, and is furthermore dependent upon cardiac cycle duration. This may be resolved by limiting determinations to cycles longer than 800 ms.

Stress echocardiography in valvular heart disease

Stress echocardiography has been widely accepted as an important diagnostic and prognostic tool in the assessment of known or suspected coronary artery disease. Its use in valvular heart disease, to date, has been more limited, but is continuing to grow as the technology and the understanding of valvular disorders progress. In this article, we will review the current literature regarding the use of both exercise and pharmacological stress testing in conjunction with echocardiography in the settings of native and prosthetic mitral and aortic valve disease. We will also discuss the limitations of this modality and touch upon possible future areas of investigation.

Valve Resistance in Mitral Stenosis: Its Determinants and its Role in the Evaluation of the Disease

To evaluate the value and the determinants of valve resistance in mitral stenosis, 95 patients with pure mitral stenosis were examined by Doppler echocardiography during their clinical follow-up, measuring cavity dimensions, left ventricular function, mitral area (by planimetry and pressure half time), mean transmitral pressure gradient, aortic flow, and pulmonary artery systolic pressure. The mitral resistance was calculated as mean transmitral pressure gradient/aortic flow ratio. To graduate the severity of the morphological abnormalities in valvular structure, we used a point score system with evaluation of leaflet and subvalvular thickness, calcification, and valvular mobility. The functional class was determined according to NYHA classification. In this study, both mitral area (r = -0.79, P < 0.001 and r(p) = -0.60, P < 0.001) and mitral score (r = 0.68, P < 0.001 and r(p) = 0.25, P = 0.013) were independent determinants of mitral resistance. In multivariate analysis, mitral resistance and female gender were selected by multiple linear regression analysis as determinants of pulmonary artery systolic pressure, and mitral area and pulmonary artery systolic pressure were selected by logistic linear regression analysis as determinants of NYHA functional class. In patients with moderate or severe mitral stenosis, the estimated probability for III and IV NYHA functional class considering mitral area 1 cm(2) or below went from 51.1-86.4% when mitral resistance below or above 130 dynes.sec.cm(-5), respectively, was considered together. Thus, mitral valve resistance should be used as a complement to the mitral area method in assessment of mitral stenosis, adding the effects of the reduction in mitral area and the damage in mitral valve apparatus.

Comparison of exercise and dobutamine stress echocardiography in assessing mitral stenosis

Dobutamine elicited similar hemodynamic response to exercise in 20 consecutive patients with mitral stenosis, and significantly altered management in 6 of them (30%). Dobutamine stress echocardiography is a safe and feasible alternative to exercise in patients with mitral stenosis of mild-to-moderate severity and ambiguous symptoms.

[Usefulness of exercise Doppler in the diagnosis of severe mitral stenosis]

BACKGROUND

Exercise in mitral stenosis produces an increase in cardiac output and heart rate which determines the increment in the transmitral gradient. However, it has not yet been established what level is reached by the gradients on exercise in severe mitral stenosis nor whether the rise in the gradient during such exercise is different to that occurring in non-severe stenosis.

OBJECTIVE

To evaluate the effect of exercise in patients with severe mitral stenosis on the mitral valve gradients in absolute values and on the increment with respect to base values.

METHODS

Forty-eight mitral stenosis patients (mean age: 48.8 +/- 11 years) underwent 50 exercise Doppler echocardiographic studies using supine bicycle ergometry in two stages with increases of 25 W every 3 minutes; from each of these we obtained the peak and mean mitral gradient using a non-imaging continuous-wave Doppler probe. We also conducted this procedure on 14 patients with a mean age of 50 +/- 6 who had Bjork mitral prostheses which were functioning normally.

RESULTS

We defined a hemodynamic profile of severity based on the data from 18 patients whose basal mitral valve areas was < 1.2 cm2 (group I), and compared them with the data from the 32 studies of mitral stenosis patients with an area > 1.1 cm2 (group II) and with the patients with mitral prostheses (group III). The mean mitral gradient (mmHg) in group I was greater than in group II at rest (9.3 +/- 3.2 and 6.6 +/- 2.7; p < 0.001), at 25 W (20.6 +/- 4.8 and 14.1 +/- 5; p < 0.001) and at 50 W (25.9 +/- 5.4 and 17.3 +/- 5.8; p < 0.001). The increase in mean mitral gradient from the baseline to 50 watts was 16.7 +/- 4.5 mmHg in group I, which was greater than in group II and III (11.1 +/- 4.1 and 6.8 +/- 2.6 mmHg; p < 0.001).

CONCLUSIONS

Exercise Doppler echocardiography enabled us to define a differential hemodynamic profile in patients with severe mitral stenosis which can be used in isolation as an indicator of severity in this condition.

Determination of mitral valve area in patients with mitral stenosis by the flow-convergence-region method during changing hemodynamic conditions

Twenty-eight patients with mitral stenosis underwent Doppler echocardiography at rest and during exercise to determine the accuracy of mitral valve area determination by the flow-convergence-region method during exercise-induced changing hemodynamic conditions. The mitral valve area calculated by using the flow-convergence-region method correlated strongly with that measured by the Gorlin formula both at rest (r = 0.85) and during exercise (r = 0.92) for all 28 patients studied. Although mitral valve area obtained by the flow-convergence-region method did not change (p = 0.1) in 16 patients with echocardiographic mitral scores > or = 12, it increased significantly during exercise (p = 0.0001) in 12 patients with echocardiographic mitral scores < 12. This study suggests that in mitral stenosis, the mitral valve area can be accurately estimated by the flow-convergence-region method both at rest and during changing hemodynamic conditions induced by supine bicycle exercise.

Transesophageal echocardiographic evaluation of native valvular disease and repair

Surgery for valvular heart disease corrects systolic or diastolic dysfunction of the mitral, aortic, or tricuspid valves. 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.

Comparison of valvular resistance, stroke work loss, and Gorlin valve area for quantification of aortic stenosis. An in vitro study in a pulsatile aortic flow model

BACKGROUND

Valvular resistance and stroke work loss have been proposed as alternative measures of stenotic valvular lesions that may be less flow dependent and, thus, superior over valve area calculations for the quantification of aortic stenosis. The present in vitro study was designed to compare the impacts of valvular resistance, stroke work loss, and Gorlin valve area as hemodynamic indexes of aortic stenosis.

METHODS AND RESULTS

In a pulsatile aortic flow model, rigid stenotic orifices in varying sizes (0.5, 1.0, 1.5 and 2.0 cm2) and geometry were studied under different hemodynamic conditions. Ventricular and aortic pressures were measured to determine the mean systolic ventricular pressure (LVSPm) and the transstenotic pressure gradient (delta Pm). Transvalvular flow (Fm) was assessed with an electromagnetic flowmeter. Valvular resistance [VR = 1333.(delta Pm/Fm)] and stroke work loss [SWL = 100.(delta Pm/LVSPm)] were calculated and compared with aortic valve area [AVA = Fm/(50 square root of delta Pm)]. The measurements were performed for a large range of transvalvular flows. At low-flow states, flow augmentation (100-->200 mL/s) increased calculated valvular resistance between 21% (2.0 cm2 orifice) and 66% (0.5-cm2 orifice). Stroke work loss demonstrated an increase from 43% (2.0 cm2) to 100% (1.0 cm2). In contrast, Gorlin valve area revealed only a moderate change from 29% (2.0 cm2) to 5% (0.5 cm2). At physiological flow rates, increase in transvalvular flow (200-->300 mL/s) did not alter calculated Gorlin valve area, whereas valvular resistance and stroke work loss demonstrated a continuing increase. Our experimental results were adopted to interpret the results of three clinical studies in aortic stenosis. The flow-dependent increase of Gorlin valve area, which was found in the cited clinical studies, can be elucidated as true further opening of the stenotic valve but not as a calculation error due to the Gorlin formula.

CONCLUSIONS

Within the physiological range of flow, calculated aortic valve area was less dependent on hemodynamic conditions than were valvular resistance and stroke work loss, which varied as a function of flow. Thus, for the assessment of the severity of aortic stenosis, the Gorlin valve area is superior over valvular resistance and stroke work loss, which must be indexed for flow to adequately quantify the hemodynamic severity of the obstruction.

Observations suggesting a high incidence of exercise-induced severe mitral regurgitation in patients with mild rheumatic mitral valve disease at rest

OBJECTIVES

The aim of this study was to determine the hemodynamic effects of upright bicycle ergometry in symptomatic patients with mild, mixed mitral stenosis and regurgitation.

BACKGROUND

Patients with seemingly mild rheumatic mitral valve disease often complain of exertional dyspnea or fatigue. These symptoms are usually ascribed to flow-dependent increases in the gradient across the stenotic mitral valve. Although catheterization studies in these patients may demonstrate an increase in mitral valve gradient proportional to an increase in cardiac output, this approach does not specifically address the underlying mechanism of any observed increases in mitral gradient or left atrial (i.e., pulmonary capillary wedge) pressure. Exercise echocardiography is uniquely suited to the dynamic assessment of exercise-induced hemodynamic changes.

METHODS

Fourteen symptomatic patients with exertional dyspnea and mild mitral stenosis and regurgitation at rest performed symptom-limited upright bicycle ergometry with quantitative two-dimensional, Doppler and color Doppler echocardiographic analysis.

RESULTS

Average pulmonary artery systolic pressure in the 13 patients with adequate spectral signals of tricuspid regurgitation increased from 36 +/- 5 mm Hg (mean +/- SD) at rest to 63 +/- 14 mm Hg at peak exercise (p < 0.001). The mean transmitral pressure gradient in all patients increased from 4.5 +/- 1.4 mm Hg at rest to 12.7 +/- 2.7 mm Hg at peak exercise (p < 0.001). Five patients developed severe mitral regurgitation during exercise.

CONCLUSIONS

Patients with exertional dyspnea and mild mitral stenosis and regurgitation at rest demonstrate a marked increase in pulmonary artery systolic pressure and mean transmitral pressure gradient during dynamic exercise. In a subset of these patients, marked worsening of mitral regurgitation appears to be the underlying mechanism of this hemodynamic deterioration. Because of the small sample size, this novel observation must be considered preliminary with respect to the true prevalence of exercise-related development of severe mitral regurgitation. If additional studies confirm the importance of this phenomenon, it has important implications for the management of patients with rheumatic mitral valve disease.

Value of exercise Doppler-echocardiography in patients with mitral stenosis

The value of exercise Doppler-echocardiography was studied in 60 patients with mitral valve stenosis. Patients were divided in three groups. In patients with a mitral valve area of more than 1.4 cm2, maximal and mean diastolic gradient over the mitral valve increased from 13.2 +/- 3.6 to 18.4 +/- 5.4 and from 5.2 +/- 1.9 to 8.8 +/- 3.0 mmHg, respectively. In patients with a mitral valve area in between 1.0 and 1.4 cm2, maximal and mean gradient increased from 19.0 +/- 8.0 to 28.1 +/- 8.9 and from 8.8 +/- 4.9 to 14.8 +/- 6.4 mmHg, respectively. In patients with a mitral valve area of less than 1 cm2, the maximal gradient increased from 21.5 +/- 5.8 to 34.2 +/- 8.7 and mean gradient increased from 11.8 +/- 4.1 to 20.3 +/- 5.8 mmHg. Mean tricuspid regurgitation velocity increased from 2.9 +/- 0.5 m/s to 3.6 +/- 0.5 m/s, indicating increase in right ventricular to right atrial pressure difference from 34 mmHg to 52 mmHg. We conclude that exercise during the Doppler-echocardiographic evaluation provides additional information about the hemodynamic significance of mitral stenosis and can therefore be of value in decision making.

Contribution of mitral valve reserve capacity to sustained symptomatic improvement after balloon valvulotomy in mitral stenosis: implications for restenosis

OBJECTIVES

To explain the discrepancy between the symptomatic status of patients and the hemodynamically calculated mitral valve area during long-term follow-up after mitral balloon valvulotomy, mitral valve orifice variability after dobutamine infusion was investigated in two groups of patients.

BACKGROUND

A significant increase in aortic valve area with increased aortic transvalvular flow has been reported in patients with calcific aortic stenosis after aortic balloon valvulotomy. A similar phenomenon with regard to the mitral valve has not been studied in detail.

METHODS

Group 1 comprised 10 patients (mean age 33 +/- 9 years) with untreated mitral stenosis. Group 2 comprised 29 consecutive patients (mean age 32 +/- 7 years) who underwent successful percutaneous mitral balloon valvulotomy 13 +/- 2 months before the study.

RESULTS

After dobutamine infusion, heart rate and cardiac index increased significantly in both groups. The mean pulmonary artery pressure, mitral valve gradient and pulmonary capillary pressure remained unchanged in Group 2 but increased significantly in Group 1. The mean mitral valve area was significantly larger in Group 2 after dobutamine infusion than at baseline (1.9 +/- 0.5 vs. 2.4 +/- 0.6 cm2, p < 0.0001) but was unchanged in Group 1 (1.2 +/- 0.2 vs. 1.3 +/- 0.3 cm2, p = NS). The mean mitral valve area in seven patients in Group 2 (24%) was < or = 1.5 cm2 before dobutamine infusion (1.3 +/- 0.4 cm2), which was defined as restenosis. In five of these seven patients who had minimal or no symptoms, the mitral valve area increased significantly after dobutamine infusion (1.3 +/- 0.1 vs. 1.9 +/- 0.1 cm2). In the other two patients who were symptomatic, the mitral valve area did not change after dobutamine infusion. These two patients were identified as having "true" restenosis, and redilation of the mitral valve was performed in both.

CONCLUSIONS

In patients who underwent mitral balloon valvulotomy, increased mitral valve reserve capacity contributed to symptomatic improvement on long-term follow-up. Dobutamine infusion may be helpful in detecting clinically significant restenosis.

Exercise echocardiography in combined mild mitral valve stenosis and regurgitation

Dynamic mitral regurgitation (MR) is typically associated with either severe systolic left ventricular dysfunction or episodes of acute myocardial ischemia. We report three patients with mild combined mitral stenosis and regurgitation and normal global left ventricular systolic function who presented with severe exertional dyspnea. Upright bicycle exercise echocardiography revealed development of severe dynamic MR in all three cases with Doppler evidence of severe pulmonary hypertension. There was no echocardiographic or electrocardiographic evidence of ischemia. Exercise echocardiography is an established tool for assessing dynamic changes in transvalvar pressure gradients. These results suggest that exercise echocardiography may also be useful for evaluating changes in severity of MR and for the assessment of dynamic changes in pulmonary artery systolic pressures.

Effect of exercise on valvular resistance in patients with mitral stenosis

OBJECTIVES

This exercise study assessed the relation between valvular resistance and flow in patients with mitral stenosis.

BACKGROUND

Valvular resistance has been proposed as an alternative measure of stenotic valvular lesions, which is speculated to remain stable under changing hemodynamic conditions.

METHODS

In 35 of 40 patients with pure or predominant mitral stenosis, continuous wave Doppler measurements of the mitral stenotic jet were possible at rest and during supine bicycle ergometry. Simultaneously, transvalvular flow was assessed by thermodilution technique. For calculation of valvular resistance, the mean mitral valve pressure gradient was determined according to the simplified Bernoulli equation and divided by transvalvular flow. Additionally, effective mitral valve area was calculated according to the continuity equation method, dividing flow by the mean diastolic flow velocity.

RESULTS

Valvular resistance was 65 +/- 32 dynes.s.cm-5 at rest and increased to 82 +/- 43 dynes.s.cm-5 at 25 W (p < 0.001). The most prominent increase in valvular resistance (rest to 25 W 63 +/- 28 to 95 +/- 48 dynes.s.cm-5, p < 0.001) was found in those patients who had no or only a moderate (< 20%) change in effective mitral valve area. In contrast, valvular resistance remained constant (67 +/- 36 vs. 70 +/- 32 dynes.s.cm-5) in patients with a significant (> or = 20%) increase in mitral valve area with exercise.

CONCLUSIONS

In patients with mitral stenosis, the exercise-induced changes in valvular resistance are heterogeneous. This is the result of the variable response of mitral valve area to an increase in flow. In the individual patient, mitral valve area can significantly increase, a factor that has to be taken into account when interpreting the hemodynamic relevance of the obstruction. Calculated valvular resistance is flow dependent and has no advantage over valve area calculations for quantifying mitral stenosis.

Determinants of stroke volume response to exercise in patients with mitral stenosis: a Doppler echocardiographic study

OBJECTIVES

The aim of this study was to assess exercise-induced changes in stroke volume and their main determinants in mitral stenosis.

BACKGROUND

The mechanisms of the stroke volume response to exercise in mitral stenosis are not clearly established.

METHODS

Twenty-seven patients with mitral stenosis, aged 47 +/- 13 years, and 10 healthy control subjects, aged 46 +/- 11 years, were examined by Doppler echocardiography to obtain stroke volume, mitral velocity-time integral and calculated mitral valve area (by continuity equation) at rest and during submaximal supine bicycle exercise. Measured mitral valve area at rest and total mitral score were also obtained.

RESULTS

During exercise, stroke volume increased significantly (p < 0.001) in the control subjects (+25 +/- 6%) but remained unchanged in the patients. In 10 patients (Group I), stroke volume increased by > or = 14% (+23 +/- 10%, p < 0.001); in the other 17 (Group II), it decreased or increased by < 14% (-5 +/- 14%, p = NS). Mitral velocity-time integral did not change in the three groups, whereas calculated mitral valve area increased significantly (p < 0.001) and similarly in Group I and the control group but remained unchanged in Group II. The exercise change in calculated mitral valve area correlated significantly with both measured mitral valve area at rest (r = 0.46, p < 0.05) and total mitral score (r - 0.53, p < 0.005). However, at constant mitral score, exercise change in calculated mitral valve area no longer correlated significantly with measured mitral valve area at rest.

CONCLUSIONS

In mitral stenosis, the change in stroke volume during exercise depends on the change in mitral valve area, which itself depends on the degree of mitral valve damage.

Value and limitations of Doppler echocardiographic determination of mitral valve area in Lutembacher syndrome

OBJECTIVES

Our objective was to compare the Doppler pressure half-time, Doppler continuity equation and two-dimensional echocardiographic planimetric methods of estimating mitral valve area in Lutembacher syndrome.

BACKGROUND

Fluid dynamics theory predicts that mitral pressure half-time varies inversely with mitral valve area and directly with net chamber compliance and the peak early diastolic transmitral gradient in pure mitral stenosis. The effects of an atrial shunt on these interrelations have not been investigated.

METHODS

Correlation and agreement between mitral valve area estimates obtained by the three methods and that obtained by cardiac catheterization was ascertained in 11 patients with Lutembacher syndrome.

RESULTS

Valve areas determined by planimetry and the continuity equation method correlated and agreed well with catheterization measurements (r = 0.83 and 0.81, respectively). The pressure half-time method consistently overestimated mitral valve area; the extent of overestimation was greater in patients with larger atrial shunts. The hemodynamic pressure half-time was independent of the mitral valve area, chamber compliance and the peak transmitral gradient. It was dependent on the magnitude of the atrial shunt, although the correlation obtained was only fair (r = 0.61).

CONCLUSIONS

These findings suggest that the Doppler pressure half-time method is an inaccurate measure of mitral valve area whenever an atrial shunt coexists with mitral stenosis. Planimetry and the Doppler continuity equation methods yield accurate estimates of mitral valve area in Lutembacher syndrome.