Online Appendix for the following JACC: Cardiovascular Imaging article
TITLE: Mechanism of Asymmetric Leaflet Tethering in Patients With Ischemic Mitral
Regurgitation: Three-Dimensional Analysis With Multislice Computed Tomography
AUTHORS: Kitae Kim, MD, Shuichiro Kaji, MD, Yoshimori An, MD, Hidetoshi
Yoshitani, MD, Masaaki Takeuchi, MD, Robert A. Levine, MD, Yutaka Otsuji, MD,
Yutaka Furukawa, MD
APPENDIX
MSCT Protocols and 3D Measurements
All of the patients underwent scanning on a 64-slice MSCT scanner (VCT, GE Medical
Systems, WI) using the following protocol: 120 kV, 300 mA, rotation time of 350 to 400
ms (depending on the heart rate), and collimation of 64  0.625 mm. To study the
anatomy and geometry of the mitral valve and LV, the data set was reconstructed with a
slice thickness of 0.625 mm and reconstruction interval of 0.35 mm at 30% to 40% of
the RR interval for the end-systolic phase.
First, a cross-sectional plane of the mitral valve that clearly visualized both
mitral commissures was obtained using multiplanar reformation in end-systole.
According to this plane, 9 equally spaced anteroposterior (AP) slice lines, which were
perpendicular to commissure-commissure line and both sides of which pass through
medial and lateral commissures, were drawn for cropping the plane, as shown in
Supplementary Figure 2A. After excluding planes at both sides, a total of 7 AP planes
including the central plane (yellow lines in Supplementary Fig. 2A), which pass through
the mid-anterior annulus (saddle horn) and the middle of posterior annulus (yellow
points in Supplementary Fig. 2A), and 3 transverse plane including the central plane
(red lines in Supplementary Fig. 2A), which pass through medial and lateral
commissures, were cropped from the 3D data set (Supplementary Fig. 2A). We
manually marked the 2 points of the mitral annulus and 4 leaflet points in each cropped
plane (Supplementary Fig. 2B and 2C). As a result, 20 annulus and 40 leaflet points
were marked for the assessment of mitral annulus and leaflet geometry. Besides, the
positions of lateral and medial PM tips closest to the base of the heart were determined
in the reconstructed images in additional planes by dynamic MPR, which allows one to
move and rotate cut planes (Supplementary Fig. 2D to 2F). If PM heads were equally
separated, each PM head was assessed separately and the mean position was used for
the analysis. The positions of PM bases were also determined as the center of the PM
base attached to the LV wall (Supplementary Fig. 2E and 2F). A total of 3 to 6
additional planes were used for the analysis of PM positions.
We determined the least-squares fitting plane to annulus as annular plane. The
leaflet tethering distances were measured as the distances between the both PM tips and
the saddle horn. In addition, 3D coordinates of these points were determined on these
images using a reference system with the origin of the centroid of the annular markers,
positive anterior axis in annular plane passing from the middle of posterior annulus to
the mid-anterior annulus marker, and positive apical axis perpendicular to annular plane.
With the 3D coordinates system, positions of PM tips were resolved into their posterior,
medial, or lateral and apical components.
We created anatomical 3D images of the mitral annulus, leaflets, and PMs, and
measured maximum tenting height and tenting volume. The maximum tenting height
was defined as a distance from the level of the annular plane to the most tethered leaflet
site. The tenting volume was calculated as a volume enclosed between the annulus and
mitral leaflets. We also calculated medial tenting volume as a volume of medial half of
the annular plane, divided by the line between the mid-anterior annulus point and the
middle of posterior annulus, and lateral tenting volume as a lateral half of the annular
plane. This central line between the mid-anterior annulus point and the middle of
posterior annulus must be equidistant from the both commissures.
Statistics
Categorical variables are compared with the chi-square test or Fisher’s exact test as
appropriate. Normally distributed continuous variables are described as mean ± SD.
Group comparison of these variables was performed by one-way ANOVA with the
Tukey post hoc test. A part of LV volume, PM positions, PM distance, and regional
(medial and lateral) or global tenting volume were not normally distributed and
summarized with the median and 25th and 75th percentiles. These variables were
compared by the Kruskal-Wallis test. For group comparisons, the Mann-Whitney test
was used for each pair of groups, and the Bonferroni correction was applied for the
adjustment of significance level. Data analyses were performed with SPSS software
(version 17.0, SPSS Inc, Chicago, Illinois).
Supplementary Figure 1. Flow Chart of Patient Selection
During the study period, 2,665 patients were diagnosed as having ischemic
cardiomyopathy (ICM) or dilated cardiomyopathy (DCM) by echocardiography. Of
these, 417 patients had significant functional mitral regurgitation (FMR [moderate or
greater]) and 74 patients underwent additional CT scan.
Supplementary Figure 2. Reconstructed Images From End-Systolic MSCT Data
Showing How to Obtain the 3D Points With Multiplanar Reformation
(A) Cross-sectional images of mitral valve. Note: yellow points indicate mid-anterior
annulus (left) and the middle of posterior annulus (right) (B) Example of AP plane. (C)
Example of transverse plane. (D) Short-axis image to obtain proper planes, which
visualize both lateral (red line) and medial (yellow line) PMs. (E, F) Double oblique
plane, which shows lateral PM (E) and medial PM (F).
Supplementary Table 1. Patient Characteristics and Geometry of Mitral
Apparatus
Controls (n = 20)
ICM-MR (n = 28)
DCM-MR (n = 13)
Age, yrs
65 ± 12
68 ± 11
62 ± 14
Male/female
9/11
17/7
9/3
LVEDVI, ml/m2
44 (36, 51)*
76 (63, 117)*§
115 (83, 136)*§
LVESVI, ml/m2
16 (12, 17)*
48 (35, 72)*§
78 (54, 102)*§
EF, %
64 ± 4
38 ± 10†
29 ± 12†‡
MR severity (vena contracta width, mm )
1.0 (0.0, 1.7)*
4.7 (4.2, 5.8)*§
5.2 (4.3, 5.9)*§
Lateral PM tethering distance, mm
28 ± 6
30 ± 4
34 ± 5†
Medial PM tethering distance, mm
31 ± 5
35 ± 5†
36 ± 6†
Posterior component, mm
3 (1, 6)*
3 (-1, 7)*
6 (1, 8)*
Lateral component, mm
6±4
12 ± 3†
13 ± 6†
Apical component, mm
20 ± 5
22 ± 4
22 ± 5
Posterior component, mm
6±3
10 ± 6†
11 ± 4†
Medial component, mm
7±3
9±4
12 ± 6†
Apical component, mm
22 ± 4
24 ± 3
22 ± 5
Total tenting volume, ml
1.4 (1.2, 1.8) *
3.0 (1.9, 3.6) *§
3.2 (2.2, 4.4) *§
Lateral tenting volume, ml
0.7 (0.6, 0.9) *
1.4 (0.9, 1.8) *§
1.5 (1.1, 2.3) *§
Medial tenting volume, ml
0.8 (0.6, 1.0) *
1.6 (1.0, 1.9) *§
1.7 (1.1, 2.1) *§
Medial dominant leaflet tethering
-
9 (32)
0 (0)
Balanced dominant leaflet tethering
-
19 (68)
12 (92)
Lateral dominant leaflet tethering
-
0 (0)
1 (8)
Positions of lateral PM tip
Positions of medial PM tip
Leaflet tethering pattern
*Data are expressed as the median (25%, 75% percentiles). †p < 0.05 vs controls; ‡p < 0.05 vs ICM-MR.
§Bonferroni-corrected p < 0.05 vs controls.
LVEDVI = left ventricular end-diastolic volume index; LVESVI = left ventricular end-systolic volume
index; EF = ejection fraction.
Supplementary Figure 1
Supplementary Figure 2