Effect of Valsalva Maneuver in Measuring Valve Area

Background: Echocardiographic measurement of the mitral valve in patients with mitral stenosis is important for treatment and follow-up. The aim of this study was to assess the effect on the valsalva maneuver mitral valve area measurement. Methods: 83 patients with mitral stenosis were included in the study. Valve area of the patients was measured by echocardiography before and after valsalva maneuver. Results: Mitral valve area of the patients were measured as the planimetric being 1.62 ± 0.41, cm. It was found out that valsalva maneuver had no effect on valve area measured by planimetry. It was observed that valve area measured by PHT decreased with valsalva maneuver while valve area measured by PISA method significantly increased with valsalva maneuver. It was understood from other echocardiographic findings that systolic pulmonary artery pressure, gradients on the cover and velocities decreased with the valsalva. Conclusion: The modes of measurement of mitral valve area are discretely influenced by valsalva maneuver. It is significant to keep in mind potential effects as patients may suffer involuntarily during echocardiography.

Patients with MS were decided on the premise of the following criteria: Fibrotic thickening of the mitral valve, doming of the anterior mitral valve along with diminished E to F slope during diastole, and upward movement of the posterior valve during early diastole [11]. MVA was decided by 2-dimensional planimetry, Doppler pressure halftime (PHT) and proximal isovelocity surface area method (PISA). Planimetry estimation was obtained through direct tracing of the mitral orifice including opened commissures on a parasternal short-axis view [11]. Mitral valve orrifice by PHT strategy was estimated by using the formula [11]: MVA= 220/T ½. T ½ was obtained by tracing the deceleration slope of the E-wave on doppler spectral display of transmitral flow (longest flow in those with atrial fibrillation) and valve area is automatically calculated by the echo-machine. The hemispherical shape of the convergence of diastolic mitral flow on the atrial side of mitral valve is the basis of the proximal isovelocity method.
MVA was determined by dividing mitral volume flow by the maximum velocity of diastolic mitral flow by using the formula: MVA= π(r²)(V aliasing)/peak V mitral .θ/180, hwere r is radius of the convergence hemisphere (in cm), V aliasing is the aliasing velocity (in cm/sec), peak V mitral is the peak diastolic continuous wave Doppler velocity of mitral inflow (in cm/sec), and θ is the opening angle of mital leaflets relative to flow direction [12].
The modified Bernolli equation at rest [13] was used to calculate the transmitral gradient including the mitral peak pressure gradient and mitral mean pressure gradient and it was repeated subsequently during the strain phase of Valsalva maneuver. The mitral valve Wilkins echocardiographic score was calculated between 4 and 16 for each patient [14]. Systolic pulmonary artery pressure (PAP) was derived from the tricuspid regurgitation jet velocity through modified Bernolli equation (4v² ) and estimating a right atrial pressure form inferior vena cava collapsibility [15]. Masuyama method was used for the calculation of mean pulmonary artery pressure (MPAP) [16]. Before and during echocardiography, all patients were carefully instructed about Valsalva maneuver. The Valsalva maneuver, which is expiratory strain, performed against a closed glottis, is a part of dynamic auscultation in cardiovascular practice. Whole population was inquired to start and keep up the strain 15 to 20 seconds after normal inspiration by forcefully blowing into a smallcaliber tube, connected to an aneroid manometer to maintain a constant expiratory effort equivalent to an intraoral pressure of 40 mmHg during a certain period of time. All tests were repeated during strain phase of Valsalva maneuver.

Results
Mean age of the subjects was 47.2 ± 12.9 years (65 females, 18 males). The fundamental rhythm in 35 patients (42.2%) was atrial fibrillation. Forty three patients (51.8%) had mild mitral stenosis, characterized as mitral valve area by planimetry >1.5 cm 2 at baseline. Median NYHA was class II. Mean body surface area was 1.76 ± 0.18 m 2 .
Mitral valve area (MVA) before and after valsalva maneuver was measured and then recorrected according to body surface area. Mean MVA at baseline was 1.62 ± 0.41cm 2 by planimetry, ranging between 1.36-2.31 cm 2 . Corrected MVA per body surface area (cm 2 /m 2 ) by each method was presented in Table 1.   Valvular calcification did not seem to influence the effect of valsalva onto different methods (Table 4).

Discussion
This study invesitaged the effect of Valsalva maneuver on different methods of measuring the valve area and hemodynamics in MS patients and results indicate that measurement of the mitral valve area by different methods was influenced by Valsalva maneuver when different subgroups were examined, and each method was affected differently in different subgroups. Although when the whole groups were examined, the planimetric method was not affected by Valsalva maneuver, and the valve areas measured by PHT and PISA methods before valsalva were not significantly correlated with the valve areas measured after the maneuver; in the subgroups of patients with mild and moderate to severe MS, PHT method seemed to be more reliable with no influence of Valsalva maneuver. We think physicians should take care of bidirectional valsalva influence onto planimetric method. However, planimetric method was found out to be the most reliable one in patients who had significant mitral regurgitation accompanying mitral stenosis,. Although, in patients with none to mild valvular calcification, Valsalva maneuver had no effect on the other methods, in patients with moderate to severe valvular calcification PISA method could overestimate valve area following valsalva maneuver. Additionally, there was an important change in all measures except for MPAB in response to valsalva.
All echocardiographic methods of MVA measurement in MS have potential intrinsic limitations, although measuring mitral valve area (MVA) in determining the severity seems a more reliable method [3,4]. Two dimensional echocardiographic planimetry is not always feasible [17,18], and is dependent on locating the true mitral orifice in the short axis view and on the use of the proper gain settings [19]. The accuracy of PHT may be influenced by tachycardia, atrial fibrillation, associated regurgitations, changes in the left ventricular end-diastolic pressure and acute chamber compliance after post-valvotomy [20][21][22]. Because of the fact that the proximal convergence region can be easily visualized [23], The PISA method is attractive for MVA determination in MS, however the accuracy of the 2D-PISA method [24] may sometimes be reduced by the low frame rate and temporal resolution of the 2D-colour imaging. It is not always possible to use each method in every patient for the mitral valve area evaluation in patients with mitral stenosis because of these limitations. Besides, we showed that Valsalva maneuver could affect the measurements obtained by different methods, and physicians should take into account that during echocardiographic examination some patients may strain involuntarily mimicking the effects of Valsalva maneuver. Hence, it may be important to remember that each method has its own limitation in different subgroups.
Valsalva maneuver is a complex hemodynamic process that involving 4 phases. Alteration of loading conditions during the Valsalva maneuver is a helpful ancillary method in the noninvasive assesment of diastolic filling of the heart by Doppler echocardiography [5][6][7] is also well-known. The clinicians use the period at the end of phase II (the strain phase) in order to enhance the accuracy of physical diagnosis. The hemodynamic manifestation of the Valsalva maneuver are in part the result of changes in the venous return accompanying changes in the intrathoracic pressure [5][6][7][8]. Valsalva maneuver may result in decrease in LA pressure and subsequent transmitral gradient in MS [9]. Hence, in this study we showed that Valsalva maneuver influenced the results of different methods to measure mitral valve area.

Conclusion
In conlusion, we suggest that clinicians should measure the mitral valve area by using different methods, and also should be alerted to relax patients during each measurement to minimize the effects of Valsalva maneuver especially for making a clinical decision. Because, Valsalva maneuver can affect both hemodynamics and measurements of mitral valve area by different methods, and during echocardiographic examination some patients may strain involuntarily mimicking the effects of Valsalva maneuver.