Clinical application in routine practice of the proximal flow convergence method to calculate the mitral surface area in mitral valve stenosis

Simplifying proximal isovelocity surface area as an assessment method of mitral valve area in patients with rheumatic mitral stenosis by fixing aliasing velocity and mitral valve angle

We aimed to test the ability of a simple equation using proximal isovelocity surface area method (PISA), created by fixing the angle to 100° and the aliasing velocity to 33 cm/s, to calculate mitral valve area (MVA) and assess severity in patients with rheumatic mitral stenosis (MS).

METHODS AND RESULTS

In a series of 51 consecutive patients with rheumatic MS, MVA was assessed by four methods, conventional PISA equation (PISAconventional), simple PISA equation (PISAsimple), pressure half time (PHT), and planimetry (PLN) which was taken as the reference method. All methods correlated significantly with PLN with the highest correlation found in case of PISAconventional and PISAsimple (r = 0.97, 0.96, p < 0.001), while the correlation in case PHT was relatively weaker (r = 0.69, p < 0.001). Bland-Altman analysis revealed that the level of agreement with PLN was better in case of both PISA methods than PHT and, moreover, were close to each other. The number of cases that showed agreement of severity grade with planinetry was better in case of PISAconventional (42 cases) and PISAsimple (44 cases) than that in case of PHT (34 cases, p = 0.037). Finally, the measure of agreement with Cohen's Kappa test was better in case of PISAconventional and PISAsimple than that in case of PHT.

CONCLUSION

Provided that aliasing velocity is fixed at 33 cm/s, PISA can effectively predict mitral valve area and severity of MS by a simple equation, with the advantage of easy and accurate calculation over other methods.

Comparison of mitral valve area by pressure half-time and proximal isovelocity surface area method in patients with mitral stenosis: effect of net atrioventricular compliance

AIMS

The aim of this study was to test the hypothesis that, unlike calculation of the mitral valve area (MVA) with the pressure half-time method (PHT), the proximal isovelocity surface area method (PISA) is not affected by changes in net atrioventricular compliance (C(n)).

METHODS AND RESULTS

We studied 51 patients with mitral stenosis (MS) from two centres. MVA was assessed with the PISA (MVA(PISA)), PHT (MVA(PHT)), and planimetry (MVA(PLN), serving as the gold standard) method. C(n) was calculated with a previously validated equation using 2D echocardiography. MVA(PISA) closely correlated with MVA(PLN) (r = 0.96, P < 0.0001), while MVA(PHT) and MVA(PLN) showed a weaker but still good correlation (r = 0.69, P < 0.0001). The correlation between MVA(PHT) and MVA(PLN) for patients with C(n) between 4 and 6 mL/mmHg (considered to be normal) was excellent (r = 0.93, P < 0.0001), but that for patients with C(n) of less than 4 or more than 6 mL/mmHg was not as good (r = 0.64, P < 0.0001). Importantly, a significant inverse correlation was detected between the percentage difference among MVA(PHT), MVA(PLN), and C(n) (r = -0.77, P < 0.0001), but the line of fit was nearly flat for the percentage difference among MVA(PISA), MVA(PLN), and C(n) (r = 0.1, P = 0.388).

CONCLUSION

MVA calculated with both the PISA and PHT methods correlated well with MVA calculated with the planimetry method. However, the PISA rather than PHT is recommended for patients with MS and extreme C(n) values because PISA, unlike PHT, is not affected by changes in C(n).

Serum N-terminal brain natriuretic peptide indicates exercise induced augmentation of pulmonary artery pressure in patients with mitral stenosis

INTRODUCTION

To determine whether elevated N-terminal pro-BNP (NT pro-BNP) predicts pulmonary artery systolic pressure increase on exercise stress echocardiography in asymptomatic or mildly symptomatic patients with moderate to severe mitral stenosis.

METHODS AND RESULTS

Forty-one asymptomatic or mildly symptomatic patients with moderate to severe mitral stenosis and 21 age- and sex-matched healthy subjects. Transthoracic echocardiography was performed in all patients to assess the severity of the valve disease and to measure pulmonary artery pressure before and immediately after treadmill exercise. Blood samples for NT pro-BNP were also collected before and immediately after treadmill exercise at the time of echocardiographic examination. The plasma concentrations of NT pro-BNP levels were significantly higher in patients with mitral stenosis than in control subjects before and after exercise (P < 0.001). Patients with atrial fibrillation had significantly higher NT pro-BNP levels compared to those with sinus rhythm (P < 0.001). Pre- and postexercise NT pro-BNP levels correlated statistically significantly with the left atrial (LA) dimension, right ventricle enddiastolic diameter, exercise duration, heart rate, rest, and exercise pulmonary artery systolic pressure, after exercise mitral valve mean gradient. Area under the receiver-operating characteristic curve for NT pro-BNP as an exercise induced augmentation of pulmonary artery pressure was 0.78. Using an optimized cutoff value of 251 pg/mL for NT pro-BNP, sensitivity was 89.47%. The independent determinants of higher pulmonary artery pressure were LA diameter and pretest NT pro-BNP levels in multivariante analysis.

CONCLUSION

NT pro-BNP levels correlate with functional class and echocardiographic findings in patients with mitral stenosis and indicate exercise induced augmentation of peak PAP > 60 mmHg. (Echocardiography 2011;28:8-14).

A nomogram for measurement of mitral valve area by proximal isovelocity surface area method

INTRODUCTION

Although its accuracy has been documented in many studies, the proximal isovelocity surface area (PISA) method is not used widely for mitral valve area (MVA) measurement. In this study, we prepared a new nomogram and tested its use in MVA assessment.

MATERIAL AND METHODS

The study included 23 patients (age: 27 +/- 5 years) with mitral stenosis, of whom 7 were in atrial fibrillation. The MVA was measured by four methods: planimetry (PL) (reference method), pressure-half time (PHT), conventional PISA (CP), and nomogram (Nomo) methods. The nomogram included two unknowns: (1) r; the radius of the first PISA section; (2) a; the length of the border opposite to the PISA angle in the triangle with both adjacent borders of 1 cm. The nomogram was also tested for its popularity potential by eight echocardiographers, none of whom were included in the author list.

RESULTS

Mean MVA(PL) was 1.85 +/- 0.53 cm(2) (range: 0.72-2.99), mean MVA(PHT) was 1.72 +/- 0.56 cm(2) (range: 0.91-3.30), mean MVA(CP) was 1.69 +/- 0.45 cm(2) (range: 0.97-2.54), and MVA(Nomo) was 1.70 +/- 0.44 cm(2) (0.96-2.49). The nomogram correlated with planimetry (r = 0.87; P < 0.001), pressure half-time (r = 0.71; P < 0.001) and conventional PISA (r = 0.99; P = 0.000) methods. The nomogram method also correlated with planimetry in patients with atrial fibrillation (r = 0.81; P = 0.026). The echocardiographers found that the nomogram is superior to the planimetry and conventional PISA methods but inferior to the pressure half-time method in terms of simplicity.

CONCLUSION

The new nomogram is potentially helpful in measurement of MVA. It may be used as an additional method in assessing severity of mitral stenosis.

The relationship between the level of plasma B-type natriuretic peptide and mitral stenosis

B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are both secreted primarily from the ventricle myocardium in response to the increase in volume and pressure. We aimed to investigate the relationship between the severity of mitral stenosis (MS) and the level of plasma BNP. A total of 56 patients (50 female, 6 male) were included in the study. Mitral stenosis and its related parameters were evaluated by echocardiographic methods. Patients were divided into three groups as with mild, moderate and severe MS according to their planimetric valvular area. Plasma BNP levels were measured using "Triage-B-type natriuretic peptide test" method (Biosite Diagnostics, San Diego). The relationship of BNP with mitral stenosis and other echocardiographic parameters were studied. The comparison of the 3 groups with one another revealed that the BNP level in the group with moderate MS was higher than that in the group with mild MS, however it was statistically insignificant (74.9 +/- 49.7 versus 49.9 +/- 40.5 pg/ml, p > 0.05). BNP level in the group with severe MS was significantly higher than that in the mild MS (144.3 +/- 83.9 versus 49.9 +/- 40.5 pg/ml, p < 0.001) and that in the moderate MS group (144.3 +/- 83.9 versus. 74.9 +/- 49.7 pg/ml, p < 0.05). When patients were taken together, as the area of the mitral valve decreased, the level of BNP underwent a corresponding increase (r:-0.48, p < 0.001). We have ascertained that the level of plasma BNP and the degree of MS are significantly correlated, and as MS becomes more serious, the plasma BNP level rises.

A simple different method to use proximal isovelocity surface area (PISA) for measuring mitral valve area

BACKGROUND

Angle-correction is an important limiting factor for using proximal isovelocity surface area (PISA) method in measuring mitral valve area (MVA). In this study, we derived a novel formula, which simplifies the angle-correction, and tested its use in patients with mitral stenosis (MS).

METHODS

The study included 30 MS patients without concomitant aortic or mitral regurgitation. We used mathematical equations and established a relation between the angle and its corresponding border, 'a', by using linear regression analysis. It was found that MVA is equal to [(1.11*a2 + 0.95)* r2 (Val/Vmax)]. We compared this formula with plain angle-corrected and solid angle-corrected PISA methods, planimetry (reference method) and pressure-half time method by linear regression analysis.

RESULTS

All methods were in significant relation with the reference method, two-dimensional planimetry. We found that there is a good relation between our method and planimetry (r = 0.79, p < 0.001), pressure half-time method (r = 0.85, p < 0.001), angle-corrected PISA method (r = 0.99, p < 0.001), and solid angle-corrected PISA method (r = 0.88, p < 0.001). The time duration of the new method was shorter (p < 0.001).

CONCLUSION

Our method is an easy way for applying angle-corrected PISA method to mitral valve area measurement in patients with mitral stenosis. Absence of the need for estimating the angle is the major advantage.