Mitral valve analysis adding a virtual semi-transparent annulus plane for detection of prolapsing segments

Abstract

Background: We hypothesized that a novel three-dimensional virtual semi-transparent annulus plane (3D VSAP) presented on a holographic screen can be used to visualize the prolapsing tissue in degenerative mitral valve disease and furthermore, provide us with geometrical data of the mitral valve apparatus. Phantom and patient studies were designed to demonstrate the feasibility of creating a semi-automatic, semi-transparent mitral annulus plane visualized on a holographic display.

Methods: Ten pipe cleaners mimicking the mitral annulus with different shapes and three types of annuloplasty rings served as phantoms. We obtained 3D transoesophageal examination of the phantoms in a special designed box filled with water. Recordings were converted to the holographic display and a 3D VSAP was created. The ratio of the major and minor axes as well as the non-planar angles were calculated and compared with direct measures of the phantoms. Forty patients with degenerative mitral valve disease were then analyzed with 3D transthoracic echocardiography (TTE) and a 3D VSAP was created on the holographic display. A total of 240 segments were analyzed by two independent observers, one echo expert (observer I), and the other novice with limited echo experience (observer II). The two observers created the 3D VSAP in each patient before suggesting the valve pathology.

Results: The major/minor axes ratio and non-planar angles by 3D VSAP correlated with direct measurements by r = 0.65, p < 0.02 and r = 0.99, p < 0.0001, respectively. The sensitivity and specificity of the 3D VSAP method in patients was 81 and 97%, respectively (observer I) and for observer II 77 and 96%, respectively. The accuracy and precisions were 93.9 and 89.4%, respectively (observer I), 92.3 and 85.1% (observer II). Mitral valve analysis adding a 3D VSAP was feasible with high accuracy and precision, providing a quick and less subjective method for diagnosing mitral valve prolapse. This novel method may improve preoperative diagnostics and may relieve a better understanding of the pathophysiology of mitral valve disease. Thus, based on the specific findings in each patient, a tailored surgical repair can be planned and hopefully enhance long-term repair patency in the future.

Fig. 1

Pipe cleaner number 2 mimicking mitral annulus seen from front (a) and profile view (b). c Profile of the same pipe cleaner with 3D VSAP as presented on the holographic screen. AL-PM anterolateral-posteromedial. AP anteroposterior

Fig. 2

Shematic illustration of a phantom mimicking the mitral valve (Surgeon view) after labeling the circumference by mouse clicking (circular blue points) in a cropping plane perpendicular to the virtual plane. A line was drawn by clicking out points from “commissure to commissure“ (PMC to ALC) along the curvature of the phantoms to ensure the saddle shape of the annulus plane. A series of small triangles (Delaunay Triangulation) between the points generated the 3D surface that was made semitransparent (blue) to better appreciate the prolapsing tissue crossing the blue surface. ALC: Anterolateral commissure PMC: Posteromedial commissure

Fig. 3

Mitral valve and its corresponding measurements front view (a) and profile (b). AL-PM anterolateral-posteromedial. AP anteroposterior. Ao aorta

Fig. 4

Correlation between non-planar angle in pipe cleaners and annuloplasty rings determined by 3D VSAP and direct measurements. y = 0.97x + 5.5265, r = 0.99, p < 0.0001

Fig. 5

Correlation between AL-PM/AP ratio in pipe cleaners and annuloplasty rings determined by 3D VSAP and direct measurements. y = 0.7776x + 0.2944, r = 0.65, p < 0.02

Fig. 6

Agreement between non-planar angle by 3D VSAP and direct measurements. Mean difference between methods and ± 2 SD are indicated

Fig. 7

Agreement between AL-PM/AP ratio by 3D VSAP and direct measurements. Mean difference between methods and ± 2 SD are indicated

Fig. 8

Surgeon view of the mitral valve from a patient with P2 prolapse as presented on the holographic screen. 3D VSAP is visible as a semi-transparent blue plane showing clearly the prolapsing segment that crosses the surface (a). b The same patient without 3D VSAP. Ao aorta, RV right ventricle, P2 indicating prolapse of mid segment posterior leaflet

Fig. 9

Surgeon view of the mitral valve from a patient with A3/P3 prolapse as presented on the holographic screen. 3D VSAP is visible as a semi-transparent blue plane showing clearly the prolapsing segments that crosses the surface (a). b The same patient without 3D VSAP. Ao aorta, RV right ventricle, A3 and P3 indicating prolapse of the posteromedial segments of the mitral leaflets