Left ventricular systolic dyssynchrony in patients with isolated symptomatic myocardial bridge

Figures & data

Table I. General characteristics of participants.

	No MB (n = 26)	MB (n = 35)	P value
Gender (female/total)	12/26	17/35	1
Mean age, yr	51.5 ± 6.9	52.0 ± 8.0	0.8
Body weight (Kg)	64.5 ± 8.4	64.1 ± 8.8	0.85
Body mass index (Kg/m^2)	24.3 ± 2.8	23.8 ± 3.2	0.539
Smoking	6/26	13/35	0.276
Hypertension	10/26	15/35	0.796
Diabetes	0/26	2/35	0.503
TG (mmol/L)	1.28 ± 0.30	1.34 ± 0.25	0.397
TC (mmol/L)	3.64 ± 1.24	3.62 ± 1.30	0.972
HDL-C (mmol/L)	1.14 ± 0.28	1.10 ± 0.23	0.629
LDL-C (mmol/L)	2.58 ± 0.48	2.45 ± 0.49	0.311
Medication
β-Blockers	4/26	8/35	0.503
Calcium antagonists	1/26	4/35	0.382
Nitrates	2/26	7/35	0.278
Aspirin/clopidogrel	4/26	11/35	0.739
ACEI/ARB	3/26	8/35	0.325
Statins	2/26	7/35	0.278
2D Echocardiography
E peak velocity (cm/s)	79.7 ± 22.8	75.8 ± 16.6	0.436
A peak velocity (cm/s)	68.2 ± 18.3	78.0 ± 14.0	0.021
E/A ratio	1.25 ± 0.52	0.99 ± 0.25	0.008
LA diameter (mm)	35.0 ± 3.21	34.1 ± 4.02	0.353
LV mass (g)	177 ± 43.6	170 ± 44.0	0.59
LV mass index (g/m^2)	105 ± 29.2	101 ± 27.4	0.555
3-D Echocardiography
3D-EDV (mL)	73.8 ± 12.6	79.5 ± 16.7	0.149
3D-ESV (mL)	28.7 ± 6.43	30.5 ± 9.74	0.403
3D-LVEF (%)	61.9 ± 7.37	62.0 ± 6.21	0.981
3D-SV (mL)	46.0 ± 11.2	49.1 ± 12.1	0.316
3D-HR (bpm)	70.7 ± 11.3	71.0 ± 10.3	0.904
Tmsv-16SD (ms)	8.5 (6.75–12.0)	13.0 (9.0–17.0)	0.007
Tmsv-12SD (ms)	8.0 (5.75–11.0)	8.0 (5.0–10.0)	0.872
Tmsv-6SD (ms)	8.0 (5.0–12.5)	8.0 (6.0–12.0)	0.924
R-R interval (ms)	888 ± 148	870 ± 134	0.616
Tmsv-16SD/RR (%)	0.98 (0.85–1.34)	1.33 (1.06–2.05)	0.006
Tmsv-12SD/RR (%)	0.99 (0.60–1.10)	0.95 (0.65–1.11)	0.965
Tmsv-6SD/RR (%)	0.88 (0.61–1.30)	0.96 (0.70–1.31)	0.994

ACEI, angiotensin converting enzyme inhibitors; ARB, angiotensin II receptor blocker; MB, myocardial bridge; TC, total cholesterol; TG, triglyceride; LA, left atrial diameter; LV mass, left ventricular mass; EDV, end diastolic volume; ESV, end systolic volume; LVEF, left ventricular ejection fraction; SV, stroke volume; HR, heart rate; Tmsv-16SD, standard deviation of time to minimal systolic volume of 16 left ventricular segments; Tmsv-16SD/RR, Tmsv-16SD normalized by R-R interval (also known as systolic dyssynchrony index, SDI).

Figure 1. Tissue Doppler Imaging of left anterior descending artery (LAD) supplied left ventricular segments (17 segments model) in patients with and without mid-LAD myocardial bridge. The bar above each column indicates standard error of mean. A to C shows tissue velocity of 7 LAD-specific segments, and D to F show the corresponding strain rate values. MB, myocardial bridge; Apical-L, apical lateral; Basal-A, basal anterior; Mid-A, mid anterior; Apical-A, apical anterior; Basal-AS, basal anteroseptal; Mid-AS, mid anteroseptal; Apical-S, apical septal. *P < 0.05.

Figure 2. Relationships between myocardial bridge angiographic features [stenosis (A) and length (B)], their interactions (C) and left ventricular systolic synchrony. The dash line started from Y axis indicates the cutoff value of 1.91% derived from control group to define the presence of LV systolic dyssynchrony. Solid line in each scatter plot indicating the median. Tmsv-16SD/RR, the time-to-minimum systolic volume corrected by RR interval. SDI, systolic dyssynchrony index. *P < 0.05, **P < 0.01, ***P < 0.001.

Figure 3. Interaction of myocardial bridge percent stenosis and length on trans-mitral E wave peak velocity (A) and E/A ratio (B). Solid line in each scatter plot indicating the median. MB, myocardial bridge. *P < 0.05.

Figure 4. Receiver operator characteristic curve analysis of trans-mitral E wave peak velocity (A), E/A ratio (B) and myocardial bridge stenosis (C) for the diagnostic value of left ventricular dyssynchrony detected by real-time three dimensional echocardiography. AUC, area under curve; CI, confidence interval; MB, myocardial bridge.

Table II. Univariate logistic regression analyses.

	OR (95% CI)	P value
Gender (female/male)	1.458 (0.318–6.696)	0.628
Age, years	0.998 (0.907–1.098)	0.961
Smoking	0.800 (0.162–3.944)	0.784
Hypertension	21.71 (2.284–206.5)	0.007
Diabetes	3.125 (0.175–55.89)	0.439
Long MB length (≥ 17 mm)	1.250 (0.273–5.733)	0.774
MB stenosis (Nobel Grading)	3.567 (1.158–10.99)	0.027
MB lesion score	6.493 (1.715–24.58)	0.006
Echocardiography
Trans-mitral E peak velocity (m/s)	0.903 (0.830–0.982)	0.017
Trans-mitral A peak velocity (cm/s)	0.983 (0.930–1.040)	0.555
E/A ratio (1 SD change)	0.256 (0.080–0.822)	0.022
LA diameter (mm)	1.102 (0.899–1.351)	0.348
LVEF (%)	0.998 (0.844–1.181)	0.982
LV mass (g)	0.993 (0.976–1.011)	0.470
LV mass index (g/m^2)	0.988 (0.960–1.017)	0.420

LA, left atrium; LVEF, Left ventricular ejection fraction; MB, myocardial bridge.

Table III. Multivariate logistic regression analyses.

	OR (95% CI)	P value
Hypertension	15.32 (1.252–187.6)	0.033
MB lesion score	4.944 (1.174–20.82)	0.029
Trans-mitral E peak velocity (m/s)	0.903 (0.770–1.060)	0.113
E/A ratio (1 SD change)	0.879 (0.161–4.790)	0.332