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European Journal of Echocardiography 2004 5(6):422-429; doi:10.1016/j.euje.2004.03.007
© 2004 by European Society of Cardiology
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Copyright © 2004, The European Society of Cardiology

Localization and quantification of mitral valve prolapse using three-dimensional echocardiography

A. Delabays*, X. Jeanrenaud, P.-G. Chassot, L.K. Von Segesser and L. Kappenberger

Division of Cardiology, the Department of Cardiothoracic Surgery and the Department of Anesthesiology, University Hospital Lausanne, BH 16, 1011 Lausanne-CHUV, Switzerland

Received 15 September 2003; received in revised form 10 March 2004; accepted after revision 12 March 2004.

* Corresponding author. Tel.: +41-21-3140103; fax: +41-21-3140055. alain.delabays{at}chuv.hospvd.ch


   Abstract
Top
 Abstract
1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
Aims: Mitral valve prolapse is a common source of severe mitral regurgitation in Western countries. Three-dimensional echocardiography can provide views of the entire valve, allowing a complete assessment of the valve leaflets and commissures. It has the potential to precisely locate and quantify mitral valve prolapse.

Methods and results: Between January 1997 and December 2000, 91 patients with severe mitral regurgitation due to mitral valve prolapse underwent a transesophageal echocardiography with three-dimensional reconstruction of the mitral valve as part of their pre-operative work-up. The location and extent of the prolapse by echo was compared to the surgical status. The volume of prolapsing leaflet was calculated and compared to the volume of resected tissue whenever a repair was attempted. There was an excellent correspondence between the echographic localization of the prolapse and surgical inspection, and between the volume of prolapsing and surgically resected tissue (r = 0.94, p<0.0001).

Conclusions: In patients with severe mitral regurgitation due to mitral valve prolapse, 3D echo allowed a precise localization and an accurate quantification of the prolapsing portion of the leaflets. This technique can provide refinements in the surgical planning of mitral valve repair and in the selection of candidates for this intervention.

Keywords: Mitral valve; Regurgitation; Echocardiography; Surgery


   1. Introduction
Top
 Abstract
 1. Introduction
2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 
Mitral valve prolapse is the most frequent etiology of mitral regurgitation in industrialized countries. Recent work has underlined the importance of early surgical intervention, particularly valve repair, to preserve long term left ventricular function in severe mitral regurgitation.1,2

Echocardiography has been traditionally involved in the diagnosis of mitral valve prolapse from the early beginning of this technique. The characteristic billowing of the leaflets was first recognized with M-mode than with two-dimensional imaging. But it is only when we were able to reconstruct the mitral annulus in three dimensions that the saddle shape of this structure was recognized and the criteria for the diagnosis of mitral valve prolapse widely accepted.3 If diagnosis is no more a problem, the precise location and the extent of the prolapse is still difficult to assess using two-dimensional echocardiography. Three-dimensional echocardiography (3DE) is a new imaging modality that allows recording of volumetric echographic data.4 It has the potential for a better visualization and a more precise quantification of cardiac structures with a complex geometry like the mitral valve.5 It has also been of great value in the study of the different mechanisms of mitral regurgitation6–8 as well as the understanding of the spatial geometry of intracardiac blood flow jets.9,10 The aim of this study was to assess prospectively the role of this technique in the exact localization of mitral prolapse and its potential in quantifying the diseased portion of the valve.


   2. Methods
Top
 Abstract
 1. Introduction
 2. Methods
3. Results
 4. Discussion
 5. Conclusion
 References
 
2.1 Study protocol
We prospectively studied patients referred to our hospital between January 1997 and December 2000 for severe mitral regurgitation due to mitral valve prolapse. 3DE was performed using a transesophageal approach, as part of the pre-operative work-up. A reconstruction of the mitral valve viewed from the left atrium was obtained. The prolapse was localized according to the diseased leaflet and the various scallops prolapsing. We applied the accepted surgical classification proposed by Duran, dividing each mitral leaflet into 3 scallops (anterior, middle and posterior).11 These findings were then compared to the operative status. To evaluate the potential of the technique in the quantification of mitral valve prolapse, the volume of prolapsing tissue was also calculated in the three-dimensional data set and compared to the volume of the resected leaflet by the surgeon whenever a repair of the valve was attempted. This protocol was approved by our institution ethical review committee and all patients gave their informed consent.

2.2 Three-dimensional echocardiography
3DE was done via a transesophageal route using a rotational mode of data acquisition.12 A modified multiplane probe (3.7–5 MHz) equipped with an external stepper motor was attached to a conventional echographic scanner (Hewlet Packard 2500, model 77020, Andover, MA, USA). The stepper motor was driven by a dedicated three-dimensional workstation (Echoscan, TomTec Imaging System, Unterschleissheim, Germany). Acquisition was gated to ECG and respiration. Sixty comparable cardiac cycles over a span of 180 degrees were recorded during the expiratory phase and digitally stored for off-line processing. Computer generated 3D reconstruction included positioning of the various cycles according to their spatial location and geometric interpolation to produce a conical volume containing the portion of the heart scanned. From this 3D data set, a view of the mitral valve from above was obtained by positioning a view plane horizontally through the left atrium and applying different shading techniques. The location of the prolapse was compared to the status in the operating room.

From the same data set, the volume of prolapsing leaflet was calculated using the incorporated software. The frame exhibiting the most pronounced prolapse was selected. Parallel and equidistant long axis cut-planes through the prolapse were positioned every 2 mm. On each cut-plane, the prolapsing portion of the leaflets was traced, including ruptured chordae when present, its area computed, and its volume obtained by multiplying the area by the slice thickness. The total volume of the prolapse was calculated by adding the individual volumes traced on each cut-plane.

2.3 Surgical validation
When the mitral valve was exposed, each scallop of both the anterior and posterior leaflets was individually tested for prolapse and the result compared to the data obtained from the pre-operative 3D reconstruction of the valve. Whenever a repair was undertaken, the portion of the leaflet resected by the surgeon was collected in the operating room and its volume measured by water displacement. This volume was compared to the volume of the prolapse measured pre-operatively in the 3D data set.

2.4 Statistical analysis
The volumes of prolapsing leaflets obtained by 3DE and actual measurements in the operating room were compared by a paired t-test and a simple regression line. A p value <0.05 was considered as significant. The standard error of the estimate was calculated according to the method described by Bland and Altman.13


   3. Results
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
4. Discussion
 5. Conclusion
 References
 
Between January 1997 and December 2000, 116 patients were screened and 91 (21 females) were enrolled in the study. Mean age was 61.2 ± 11.1 years (34–83 years old).

3.1 Three-dimensional echocardiography
A 3D data set of adequate quality was obtained in all patients. For each patient, 1–3 acquisitions were realized and the best one chosen for imaging and quantification. Acquisition time varied between 40 s and 2 min 30 s, depending on the basal heart rate and rhythm disturbances. Mean processing time was 3 min 27 s. Reconstruction time varied between 2 and 7 min for the best quality images, according to the number of views and the size of the data set.

3.2 Localization of mitral valve prolapse
According to the surgical inspection during the intervention, 66 patients had an isolated prolapse of the posterior mitral leaflet, 11 a prolapse localized to the anterior mitral leaflet and 14 a prolapse extending to both valve leaflets. The prolapsing portion of the mitral valve was identified in all patients on the 3D reconstruction of the valve viewed from the left atrium (Figs. 1–4GoGoGo). In patients with diffuse prolapse of both leaflets, the classical billowing appearance of the valve was well appreciated on the "surgical" view (Fig. 1). In patients with localized prolapse, the exact location and extent of the diseased portion of the valve was clearly delineated on the 3D reconstruction (Figs. 2–4GoGo). In every patient, the prolapse was confirmed in a long axis view that allowed a better appreciation of the relations between valve tissue and the plane of the mitral annulus. This view generally allowed depiction of the regurgitant orifice, its shape and variations during systole (Fig. 2). The 3D reconstruction of the valve corresponded well with the gross anatomical appearance of the mitral leaflets at surgery (Fig. 5). The findings at surgery and by 3D echocardiography in all the patients are summarized in Fig. 6. There was an excellent correspondence between the two.


Figure 1
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  		Figure 1 Three-dimensional reconstruction of a myxoid mitral valve viewed from the roof of the left atrium ("surgical view") in diastole (left) and systole (right). The anatomical landmarks are well depicted: LAA = left atrial appendage, AO = aorta, RA = right atrium. In systole, both the anterior (AML) and the posterior mitral leaflet (PML) are redundant with excess of tissue. The coaptation line is visible as well as the anterior (AC) and the posterior commissure (PC).

 


Figure 2
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  		Figure 2 Three-dimensional reconstruction of a flail mitral valve from above (a) and in a long axis view through the left atrial appendage (LAA) looking "en face" to the posterior mitral leaflet (b). The flail portion of the valve is limited to the middle scallop of the posterior leaflet (thin arrow) with a ruptured chord (thick arrow). In the long axis view, the regurgitant orifice is nicely delineated. LV = left ventricle.

 


Figure 3
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  		Figure 3 "Surgical views" of the mitral valve in a patient with a prolapse of the mitral valve limited to the posterior scallop of the posterior leaflet (a) and in another patient with a prolapse of the anterior scallop of the posterior leaflet (b). The flail portions are indicated by the arrows. LAA = left atrial appendage, AO = aorta, RA = right atrium.

 


Figure 4
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  		Figure 4 Three-dimensional reconstructions of the mitral valve from above with slightly different angulations in a patient with a prolapse of the anterior scallop of the anterior leaflet (a). In a slightly angulated view (b), the regurgitant orifice is well depicted (arrow). LAA = left atrial appendage, AO = aorta, RA = right atrium.

 


Figure 5
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  		Figure 5 Anatomical specimen of the entire anterior mitral leaflet excised in the patient from Fig. 4. The prolapse of the anterior portion of the leaflet is well recognizable, with thickening of the valve tissue and a ruptured chord. The middle and posterior scallops are normal.

 


Figure 6
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  		Figure 6 Localization of the mitral valve prolapse according to the surgeon exploration (anatomy) and three-dimensional echocardiography (3D echo). There is an excellent correspondence between the two. The majority of the prolapses were localized to the middle scallop of the posterior leaflet.

 
3.3 Quantification of the prolapsing portion of the valve
Among the 91 patients enrolled in the study, 67 had mitral valve repair and 24 mitral valve replacement. Comparison between the volume of the surgically resected portion of the valve and the volume of the prolapse calculated by 3DE was available in 61 patients. In the remaining 6, 3 had folding of a small prolapse without tissue resection and the anatomical specimen was not obtained in the other 3.

The mean volume of the prolapsing tissue calculated pre-operatively by 3DE and the mean volume of mitral valve leaflet resected during surgery were similar: 1.13 ± 0.55 ml vs 1.12 ± 0.59 ml (p = ns). The individual values for each patient are presented in Fig. 7. There was an excellent correspondence between the two with a correlation coefficient of 0.94 (p = 0.0001). An analysis according to Bland and Altman revealed no systematic under- or over-estimation by 3DE (Fig. 8).


Figure 7
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  		Figure 7 Correlation between the volume of resected tissue during mitral valve repair (anatomy) and the volume of mitral valve prolapse calculated by three-dimensional echocardiography (3D echo) in 61 patients. The correspondence is excellent with a correlation coefficient of 0.94 (p<0.0001).

 


Figure 8
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  		Figure 8 Correlation between the true volume of mitral valve prolapse (anatomy) and the difference between three-dimensionally calculated and the true volume of the prolapse (3D echo—anatomy) according to the method described by Bland and Altman. There is no systematic over- or under-estimation by 3D echo.

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
5. Conclusion
 References
 
The present study showed that 3DE using a transesophageal approach is feasible and provides a realistic portrayal of the mitral valve. It allowed visualization of diffusely diseased valves of the myxomatous type as well as valves with localized prolapse. In the latter, the diseased portions could be precisely located and their extension nicely delineated in 3D reconstructions from the roof of the left atrium. The localization and extension of the prolapse corresponded well with the surgical status. A long axis view of the valve looking at the prolapse "en face" allowed a better appreciation of the vertical extension of the prolapse above the plane of the annulus and generally offered a nice view of the regurgitant orifice. This approach could be of value in the quantification of mitral regurgitation severity by direct planimetry of the regurgitant orifice.14

The potential of 3DE for imaging the mitral valve was recognized early in the development of the method. A study of 30 patients with various pathologies showed that it was superior to conventional 2D echocardiography for the evaluation of the commissures, the orifice and the relation of the valve to the adjacent structures.15 Its specific value in mitral valve prolapse was further explored by 2 studies using also a transesophageal approach.16,17 These works demonstrated its unique ability to precisely locate and appreciate the extension of a flail portion of the valve. These findings were largely confirmed in the present study including a much larger number of patients. But none of these works used the potential of three-dimensional echocardiography to quantify the extent of the prolapse.

So far, only one study18 used 3DE from a transesophageal approach to measure the posterior part of mitral annulus circumference and the width of implantation of the prolapse. These 2 parameters corresponded well to the actual measurements done intraoperatively in the same patients. In our approach we chose to measure the volume of prolapsing tissue in flail valves because this parameter is simple and easy to compute in the acquired data set. It also offered an elegant way to validate the measurements against the volume of surgically resected tissue during valve repair. Indeed, these two volumes corresponded well to no systematic over- or under-estimation. So in our study 3D echocardiography was able to accurately predict the volume of prolapsing tissue that the surgeon will need to resect during correction of the valvular leak.

This parameter may prove to be interesting in the pre-operative assessment of patients with severe mitral insufficiency due to flail leaflets. Early intervention is now proposed even in asymptomatic patients, provided a repair is feasible.2,19 Knowing the exact extent of the prolapsing portions of the valve could refine the pre-operative assessment of such patients. Further studies including prospectively 3DE in the initial work-up are needed to clarify this potential.

4.1 Study limitations
There were some limitations to the use of 3DE in patients with mitral valve prolapse. First, the technique still requires a transesophageal approach to obtain images of sufficient quality for a detailed anatomic depiction of the valve and an accurate quantification of its diseased portions.20 Another limitation was inherent to the use of a sequential mode of acquisition. Careful ECG and respiratory gating was mandatory to obtain good quality reconstructions. The problem was particularly evident in patients with atrial fibrillation and very irregular ventricular responses. Finally, validation of the volume of prolapsing tissue was obtained for methodological reasons only in valves with localized prolapse. These results cannot be extended to diffusely diseased valves of the myxoid type without further evaluation.


   5. Conclusion
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
References
 
In conclusion, this study showed that three-dimensional echocardiography using a transesophageal approach is feasible and provides a detailed anatomic depiction of the mitral valve. In patients with severe mitral regurgitation due to mitral valve prolapse, it allowed to precisely locate the diseased portion of the leaflets, visualize its extension and appreciate its relations to important anatomic landmarks like the valve commissures. Moreover, in patients with mitral valve repair, the technique allowed measurements of the volume of prolapsing tissue that corresponded well to the volume of resected tissue by the surgeon. This approach should be of value in the pre-operative assessment of patients with severe mitral insufficiency due to mitral valve prolapse, providing a complete visualization of the valve before the intervention and possibly a better prediction of the feasibility of valve repair.


   Acknowledgements
 
This study was supported by a grant from the Teo Rossi di Montelera Foundation. The authors thank all the staff of the Cardiology Division, the Cardiovascular Surgery Department and the Anesthesiology Department for their active support.


   References
Top
 Abstract
 1. Introduction
 2. Methods
 3. Results
 4. Discussion
 5. Conclusion
 References
 

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