Basic Clinical Characteristics
Patient demographics are illustrated in Table 1. There were no statistically significant differences in age, sex, body mass index, diabetes mellitus, hypertension, hyperlipidemia, or current smoking status between the two groups (all P > 0.05; Table 1).
Table 1. Demographic characteristics of participants
|
Control group (n = 27)
|
MB group (n = 52)
|
P-value
|
Age, years
|
55.56 ± 9.78
|
57.10 ± 9.23
|
0.514
|
Sex (male), n (%)
|
23 (85.2)
|
46 (88.5)
|
0.953
|
Body mass index
|
25.56 ± 4.27
|
25.84 ± 2.23
|
0.606
|
Diabetes mellitus, n (%)
|
5 (18.5)
|
11 (21.2)
|
0.782
|
Hypertension, n (%)
|
16 (59.3)
|
32 (61.5)
|
0.844
|
Hyperlipidemia, n (%)
|
14 (51.9)
|
19 (36.5)
|
0.191
|
Current smoking status, n (%)
|
11 (40.7)
|
18 (34.6)
|
0.592
|
MB, myocardial bridge |
Data are expressed as the mean ± standard deviation or as the frequency (%)
Anatomical and CT-FFR Features of MBs
The anatomical and CT-FFR features of MBs in the patients are shown in Table 2. During systole, the median CT-FFRsystole in the MB and control groups was 0.73 [0.55–0.80] and 0.82 [0.72–0.86], respectively (P = 0.005). The median ΔCT-FFRsystole in the MB group was 0.26 [0.13–0.38], and the mean ΔCT-FFRsystole in the control group was 0.18 ± 0.10 (P = 0.022), which was significantly different. During diastole, the median CT-FFRdiastole in the MB and control groups was 0.77 [0.65–0.85] and 0.79 [0.71–0.87], respectively (P = 0.355), which was not significantly different. The median ΔCT-FFRdiastole in the MB group was 0.20 [0.0–0.29], and the mean ΔCT-FFRdiastole in the control group was 0.19 ± 0.12 (P = 0.710), which was not significantly different.
During systole, the mean CT-FFRsystole in the deep MB group was 0.64 ± 0.19, and the median CT-FFRsystole in the superficial MB group was 0.76 [0.57–0.86] (P = 0.178), with no significant difference. In addition, the mean ΔCT-FFRsystole in the deep MB group was 0.33 ± 0.18, and the median ΔCT-FFRsystole in the superficial MB group was 0.18 [0.11–0.37] (P = 0.055), which was not significantly different. During systole, the degrees of stenosis in the deep and superficial MB groups were 43.2 ± 15.7% and 33.8 ± 13.8%, respectively (P = 0.026), which was significantly different. However, during diastole, the degree of stenosis in the deep and superficial MB groups was 29.2 ± 13.7% and 23.2 ± 11.5%, respectively (P = 0.094), which was not significantly different.
In 52 patients with MBs, the median CT-FFRsystole was 0.73 [0.55–0.80], and the median CT-FFRdiastole was 0.77 [0.65–0.85]. The median of the difference was 0.03, and the Wilcoxon signed-rank test showed Z = -2.541 and P = 0.011, indicating that the CT-FFRsystole was significantly lower than the CT-FFRdiastole in patients with MBs. The median ΔCT-FFRsystole was 0.26 [0.13–0.38], and the median ΔCT-FFRdiastole was 0.20 [0.09–0.29]. The median of the difference was 0.04, and the Wilcoxon signed-rank test showed Z = -2.701 and P = 0.007, indicating that ΔCT-FFRsystole was significantly higher than ΔCT-FFRdiastole in patients with MBs (Table 3).
In terms of grouping according to the degree of systolic and diastolic compression (systolic compression with luminal stenosis ≥ 30% and systolic compression with luminal stenosis < 30%), there were no significant differences in the position and length of the MBs between the high and low compression groups. However, the mean MB depth in the high compression group was 3.27 ± 1.58, while the median MB depth in the low compression group was 1.60 [0.65–2.88] (P = 0.018), which was significantly different (Table 4).
Table 2. Anatomical and CT-FFR features of myocardial bridges
Anatomical features
|
Control group (n = 27)
|
MB group (n = 52)
|
P-value
|
MB Group
|
|
Deep MB group
|
Superficial MB group (n = 26)
|
P-value
|
Depth, mm
|
|
2.00 (1.00–3.28)
|
|
3.25 (2.38–3.95)
|
1.00 (0.00–1.33)
|
|
Length, mm
|
|
24.11 ± 11.55
|
|
28.55 (19.80–37.48)
|
18.82 ± 8.71
|
0.001
|
Position, mm
|
|
31.43 ± 9.05
|
|
27.36 ± 7.83
|
35.50 ± 8.45
|
0.001
|
CT-FFRsystole
|
0.82 (0.72–0.86)
|
0.73 (0.55–0.80)
|
0.005
|
0.64 ± 0.19
|
0.76 (0.57–0.86)
|
0.178
|
CT-FFRdiastole
|
0.79 (0.71–0.87)
|
0.77 (0.65–0.85)
|
0.355
|
0.76 (0.61–0.86)
|
0.75 ± 0.14
|
0.763
|
ΔCT-FFRsystole
|
0.18 ± 0.10
|
0.26 (0.13–0.38)
|
0.022
|
0.33 ± 0.18
|
0.18 (0.11–0.37)
|
0.055
|
ΔCT-FFRdiastole
|
0.19 ± 0.12
|
0.20 (0.09–0.29)
|
0.710
|
0.20 (0.11–0.29)
|
0.19 ± 0.12
|
0.510
|
Systolic stenosis, %
|
|
38.50 ± 15.36
|
|
43.19 ± 13.72
|
33.81 ± 13.75
|
0.026
|
Diastolic stenosis, %
|
|
26.19 ± 12.91
|
|
29.19 ± 13.72
|
23.19 ± 11.52
|
0.094
|
MBF (mL/g/min)
|
149.74 ± 28.11
|
143.08 (118.21–168.03)
|
0.301
|
150.04 ± 25.20
|
140.53 ± 28.36
|
0.212
|
CT-FFR, computed tomography-fractional flow reserve; MB, myocardial bridge; MBF, myocardial blood flow
Data are expressed as the mean ± standard deviation or as the median (interquartile range)
Table 3
Comparison of systolic and diastolic parameters in patients with myocardial bridges
Parameters
|
MB group (n = 52)
|
P-value
|
|
|
CT-FFRsystole
|
0.73 (0.55–0.80)
|
0.011
|
CT-FFRdiastole
|
0.77 (0.65–0.85)
|
ΔCT-FFRsystole
|
0.26 (0.13–0.38)
|
0.007
|
ΔCT-FFRdiastole
|
0.20 (0.09–0.29)
|
Systolic stenosis, %
|
38.50 ± 15.36
|
< 0.001
|
Diastolic stenosis, %
|
26.19 ± 12.91
|
CT-FFR, computed tomography-fractional flow reserve; MB, myocardial bridge
Data are expressed as the mean ± standard deviation or as the median (interquartile range)
MBF Features on MPI of Patients with MBs
The median MBF in the MB group was 143.08 [118.21–168.03] mL/g/min, and the mean MBF in the control group was 149.74 ± 28.11 mL/g/min (P = 0.301), with no significant difference.
In 52 patients with MBs, MBFs in the deep and superficial MB groups were 150.04 ± 25.20 mL/g/min and 140.53 ± 28.36 mL/g/min, respectively (P = 0.212), with no significant difference. In terms of the degree of compression, the mean MBF in the high compression group was 140.09 ± 28.41 mL/g/min, and the median MBF in the low compression group was 146.42 [117.53–169.39] mL/g/min (P = 0.609), which was significantly different (Tables 2 and 4). Representative cases (Figs. 3 and 4) .
Table 4
Parameters of patients in the MB high and low compression subgroups
|
Systolic compression ≥ 30% (n = 10)
|
Systolic compression < 30% (n = 42)
|
P-value
|
Position, mm
|
32.63 ± 8.74
|
31.14 ± 9.20
|
0.645
|
Length, mm
|
25.27 ± 8.27
|
22.45 (14.80–30.60)
|
0.554
|
Depth, mm
|
3.27 ± 1.58
|
1.60 (0.65–2.88)
|
0.018
|
MBF (mL/g/min)
|
140.09 ± 28.41
|
146.42 (117.53–169.39)
|
0.609
|
MB, myocardial bridge; MBF, myocardial blood flow
Data are expressed as the mean ± standard deviation or as the median (interquartile range)