Assessment of Left Ventricle Function in Aortic Stenosis
Assessment of Left Ventricle Function in Aortic Stenosis
In the present study, we show that 2D speckle tracking derived global longitudinal peak strain, mitral annular peak systolic excursion, as well as mitral annular peak systolic excursion index correlate inversely with the severity of AS. Moreover, there was a good correlation between GLPS and MAPSE and MAPSEI. All of these parameters quantify long-axis LV systolic function.
Although more than 50% of the stroke volume is generated by the longitudinal LV contractility, ejection fraction may remain preserved even when LV long- axis systolic function is impaired. This is possible due to the changes in LV geometry, with increased LV wall thickness and decreased LV radius as a compensatory mechanism minimizing the negative influence of the high afterload on the LV stroke volume. It was demonstrated that, impairment of the longitudinal contractility in AS precedes the deterioration of the radial and circumferential function of LV. Furthermore, Cramariuc et al. showed that average longitudinal strain depends on the LV geometry and as a marker of LV function is of the lowest value in concentric hypertrophy.
Speckle tracking echocardiography has been described as a method assessing LV multidirectional function. This technique enables to quantify global and regional LV contractility. Many studies reported decreased longitudinal strain measured in 2D-STE technique in patients with aortic stenosis in spite of normal EF. It has been also revealed that patients with lower GLPS before aortic valve replacement may have worse prognosis after surgery. However, the similar observation have been obtained previously with regard to MAPSE. Vinereanu et al. have shown that global LV function can be estimated by mitral annular excursion. They have found correlations between LV ejection fraction and mitral annular plane systolic motion, that were more pronounced in subjects without regional LV motion abnormalities caused by previous myocardial infarction. Similar relationships were noticed in patients with heart failure with preserved ejection fraction: Wenzelburger et al. have shown that MAPSE correlates with longitudinal strain at rest end during exercise.
Currently, in the era of the development of more advanced techniques, the measurement of the atrioventricular plane displacement may seem to be unnecessary. However, it may be of great value in many cases. MAPSE does not require good acoustic window, thus can by applied when visualization of the endocardial borders is not obtainable. Moreover, this old technique can be performed at the bedside. In the study of Bergenzaun et al., performed on critically ill patients with sepsis, MAPSE was obtainable in all the patients with low inter- and intra-observer variability (4.4% and 5.3%, respectively). The authors also showed that MAPSE was an independent predictor of a 28-day mortality. Another advantage of M-mode measurements is the possibility of assessing MAPSE during exercise test when the target heart rate (HR) is high, especially in young individuals who have predicted maximal values of HR close to 200 beats per minute. By contrast, images for 2D-STE are obtained with low frame rate, thus in higher heart rates the analysis may not be possible.
While there are no standards concerning the point where MAPSE should be measured, we decided to use the average value from septum and lateral wall.
The data concerning the relationship between 2D-STE derived global longitudinal peak strain and mitral annular plane excursion in aortic stenosis are limited. GLPS is a parameter calculated from all 17 LV segments while MAPSE in the present study was assessed in the LV lateral wall and interventricular septum only. Thus, the measurement of MAPSE is more simple and does not require good image quality of all LV segments- only the mitral annulus, being the highly accessible and sensitive method of early LV function impairment in aortic stenosis. Of note, in the current study, all LV function parameters (GLPS, MAPSE and MAPSEI) were decreased in symptomatic patients, while there was no difference in ejection fraction between these subgroups, what may have the prognostic clinical value.
Furthermore, both GLPS and MAPSE were characterized by having the AUC for symptoms prediction exceeding 0.7, and that could differentiate symptomatic from asymptomatic patients. Similar observation with regard to GLPS were obtain by Laffite et al. with the cut-off value for global longitudinal strain of −18% (with sensitivity 68% and specificity 75%, AUC = 0.77). The slightly higher threshold than that in the our study can be explained by the methodological differences: in their study symptoms were induced by the exercise test, while during taking the history patients denied symptoms. A cut-off value for MAPSE for predicting symptoms was previously not well established.
The main limitation of this study is heterogeneity of the study group. The concomitant diseases may impinge on the left ventricle longitudinal contractility. Nevertheless, we have decided to include patients with hypertension, diabetes and coronary artery disease because those diseases are common in the population of patients with aortic stenosis.
MAPSE may usually be normalized to the heart size. However, in this study, we indexed MAPSE to the body surface area, as we did with the other values: aortic valve area, left ventricle mass and volumes.
Discussion
In the present study, we show that 2D speckle tracking derived global longitudinal peak strain, mitral annular peak systolic excursion, as well as mitral annular peak systolic excursion index correlate inversely with the severity of AS. Moreover, there was a good correlation between GLPS and MAPSE and MAPSEI. All of these parameters quantify long-axis LV systolic function.
Although more than 50% of the stroke volume is generated by the longitudinal LV contractility, ejection fraction may remain preserved even when LV long- axis systolic function is impaired. This is possible due to the changes in LV geometry, with increased LV wall thickness and decreased LV radius as a compensatory mechanism minimizing the negative influence of the high afterload on the LV stroke volume. It was demonstrated that, impairment of the longitudinal contractility in AS precedes the deterioration of the radial and circumferential function of LV. Furthermore, Cramariuc et al. showed that average longitudinal strain depends on the LV geometry and as a marker of LV function is of the lowest value in concentric hypertrophy.
Speckle Tracking Echocardiography and Mitral Annular Plane Displacement
Speckle tracking echocardiography has been described as a method assessing LV multidirectional function. This technique enables to quantify global and regional LV contractility. Many studies reported decreased longitudinal strain measured in 2D-STE technique in patients with aortic stenosis in spite of normal EF. It has been also revealed that patients with lower GLPS before aortic valve replacement may have worse prognosis after surgery. However, the similar observation have been obtained previously with regard to MAPSE. Vinereanu et al. have shown that global LV function can be estimated by mitral annular excursion. They have found correlations between LV ejection fraction and mitral annular plane systolic motion, that were more pronounced in subjects without regional LV motion abnormalities caused by previous myocardial infarction. Similar relationships were noticed in patients with heart failure with preserved ejection fraction: Wenzelburger et al. have shown that MAPSE correlates with longitudinal strain at rest end during exercise.
Currently, in the era of the development of more advanced techniques, the measurement of the atrioventricular plane displacement may seem to be unnecessary. However, it may be of great value in many cases. MAPSE does not require good acoustic window, thus can by applied when visualization of the endocardial borders is not obtainable. Moreover, this old technique can be performed at the bedside. In the study of Bergenzaun et al., performed on critically ill patients with sepsis, MAPSE was obtainable in all the patients with low inter- and intra-observer variability (4.4% and 5.3%, respectively). The authors also showed that MAPSE was an independent predictor of a 28-day mortality. Another advantage of M-mode measurements is the possibility of assessing MAPSE during exercise test when the target heart rate (HR) is high, especially in young individuals who have predicted maximal values of HR close to 200 beats per minute. By contrast, images for 2D-STE are obtained with low frame rate, thus in higher heart rates the analysis may not be possible.
While there are no standards concerning the point where MAPSE should be measured, we decided to use the average value from septum and lateral wall.
The data concerning the relationship between 2D-STE derived global longitudinal peak strain and mitral annular plane excursion in aortic stenosis are limited. GLPS is a parameter calculated from all 17 LV segments while MAPSE in the present study was assessed in the LV lateral wall and interventricular septum only. Thus, the measurement of MAPSE is more simple and does not require good image quality of all LV segments- only the mitral annulus, being the highly accessible and sensitive method of early LV function impairment in aortic stenosis. Of note, in the current study, all LV function parameters (GLPS, MAPSE and MAPSEI) were decreased in symptomatic patients, while there was no difference in ejection fraction between these subgroups, what may have the prognostic clinical value.
Furthermore, both GLPS and MAPSE were characterized by having the AUC for symptoms prediction exceeding 0.7, and that could differentiate symptomatic from asymptomatic patients. Similar observation with regard to GLPS were obtain by Laffite et al. with the cut-off value for global longitudinal strain of −18% (with sensitivity 68% and specificity 75%, AUC = 0.77). The slightly higher threshold than that in the our study can be explained by the methodological differences: in their study symptoms were induced by the exercise test, while during taking the history patients denied symptoms. A cut-off value for MAPSE for predicting symptoms was previously not well established.
Limitations of the Study
The main limitation of this study is heterogeneity of the study group. The concomitant diseases may impinge on the left ventricle longitudinal contractility. Nevertheless, we have decided to include patients with hypertension, diabetes and coronary artery disease because those diseases are common in the population of patients with aortic stenosis.
MAPSE may usually be normalized to the heart size. However, in this study, we indexed MAPSE to the body surface area, as we did with the other values: aortic valve area, left ventricle mass and volumes.
Source...