Myocardial bridging on dual-source computed tomography: degree of systolic compression of mural coronary artery correlating with length and depth of the myocardial bridge

The effects of myocardial bridging on two-dimensional myocardial strain during dobutamine stress echocardiography

Myocardial bridging (MB) is a common anatomic variant in coronary arteries with unclear functional significance. We evaluated regional myocardial strain by speckle tracking during dobutamine stress echocardiography (DSE) in patients with MB in the left anterior descending coronary artery (LAD). We studied 11 patients with MB in the LAD and no obstructive coronary artery disease (CAD), 7 patients without MB, but obstructive CAD in the LAD, and 12 controls without MB or obstructive CAD. MB was defined as either > 1 mm (superficial) or > 2 mm (deep) intramyocardial course of the LAD in coronary CT angiography. Regional longitudinal, radial and circumferential strains and strain rates as well as post-systolic strain index (PSI) were measured at rest, peak stress, and early recovery (1 min after stress). Strain parameters during DSE were similar in the myocardium distal to MB and other myocardial regions of the same patients as well as the LAD territory in controls. However, patients with obstructive CAD showed impaired LS and strain rate as well as increased PSI at peak stress. None of the MB was associated with systolic compression in invasive coronary angiography and strain parameters were similar between superficial and deep MB. Stress myocardial blood flow by positron emission tomography correlated with LS and RS at peak stress in the myocardium distal to MB (r = - 0.73, p = 0.03, and r = 0.64, p = 0.04, respectively). Myocardial strain is not reduced during DSE in patients with MB in the LAD and no significant systolic compression.

Quantitative computed tomography angiography evaluation of the coronary fractional flow reserve in patients with left anterior descending artery myocardial bridging

PURPOSE

To quantitatively investigate the effect of myocardial bridge (MB) in the left anterior descending artery (LAD) on the fractional flow reserve (FFR).

MATERIALS AND METHODS

Three-hundred patients with LAD MB who had undergone coronary artery CT angiography (CCTA) were retrospectively enroled, and 104 normal patients were enroled as the control. The CCTA-derived fractional flow reserve (FFRCT) was measured at the LAD 10 mm proximal (FFR1) and 20-40 mm distal (FFR3) to the MB and at the MB location (FFR2).

RESULTS

FFR2 and FFR3 of the MB (with BM only) and MBLA (with both MB and atherosclerosis) groups were significantly (p < 0.01) lower than those of the control. The FFR3 distal to the MB was significantly lower (p < 0.01) than that of the control. The FFRCT of the whole LAD in the MBLA group was significantly (p < 0.05) lower than that of the MB and control group (p < 0.05). MB length (OR 1.061) and MB muscle index (odds ratio or OR 1.007) were two risk factors for abnormal FFRCT, and MB length was a significant independent risk factor for abnormal FFRCT (OR = 1.077). LAD stenosis degree was a risk factor for abnormal FFRCT values (OR 3.301, 95% confidence interval [CI] 1.441-7.562, p = 0.005) and was also a significant independent risk factor (OR = 3.369, 95% CI: 1.392-8.152; p = 0.007) for abnormal FFRCT.

CONCLUSION

MB significantly affects the FFRCT of distal coronary artery. For patients with MB without atherosclerosis, the MB length is a risk factor significantly affecting FFRCT, and for patients with MB accompanied by atherosclerosis, LAD stenotic severity is an independent risk factor for FFRCT.

Non-Invasive Assessment of Endothelial Shear Stress in Myocardial Bridges Using Coronary Computed Tomography Angiography

Myocardial bridging (MB) is a segment of coronary arteries with an intramural course, typically spared from atherosclerosis, while the adjacent proximal segment is reported to be atherosclerosis-prone, a phenomenon contributed to local endothelial shear stress (ESS). We aimed to describe the ESS milieu in coronaries with MBs combining coronary computed tomography angiography with computational fluid dynamics and to investigate the association of atherosclerosis presence proximal to MBs with hemorheological characteristics. Patients (n = 36) were identified and 36 arteries with MBs (11 deep and 25 superficial) were analyzed. ESS did not fluctuate 5 mm proximally to MBs vs 5 mm within MBs (0.94 vs 1.06 Pa, p = .56). There was no difference when comparing ESS in the proximal versus mid versus distal MB segments (1.48 vs 1.37 vs 1.9 Pa, p = ns). In arteries with plaques (n = 12), no significant ESS variances were observed around the MB entrance, when analyzing all arteries (p = .81) and irrespective of morphological features of the bridged segment (deep MBs; p = .65, superficial MBs; p = .84). MBs are characterized by homogeneous, atheroprotective ESS, possibly explaining the absence of atherosclerosis within bridged segments. The interplay between ESS and atherosclerosis is potentially not different in arteries with MB compared with arteries without bridges.

Quantitative analysis of the relationship between the myocardial bridge and the FAI of pericoronal fat on computed tomography

We performed this cohort study to investigate whether the myocardial bridge (MB) affects the fat attenuation index (FAI) and to determine the optimal cardiac phase to measure the volume and the FAI of pericoronary adipose tissue (PCAT). The data of 300 patients who were diagnosed with MB of the left anterior descending (LAD) coronary artery were retrospectively analyzed. All of patients were divided into the MB group and the MB with atherosclerosis group. In addition, 104 patients with negative CCTA results were enrolled as the control group. There was no significant difference between FAI values measured in systole and diastole (P > 0.05). There was no significant difference in FAI among the MB group, the MB with atherosclerosis group, and the control group (P > 0.05). In MB with atherosclerosis group, LAD stenosis degree (< 50%) (OR = 0.186, 95% CI 0.036-0.960; P = 0.045) and MB located in the distal part of LAD opening (OR = 0.880, 95% CI 0.789-0.980; P = 0.020) were protective factors of FAI value. A distance (from the LAD opening to the proximal point of the MB) of 29.85 mm had the highest predictive value for abnormal FAI [area under the curve (AUC), 0.798], with a sensitivity of 81.1% and a specificity of 74.6%.

Presence and Relevance of Myocardial Bridge in LAD-PCI of CTO and Non-CTO Lesions

BACKGROUND

Intravascular ultrasound (IVUS) studies show that one-quarter of left anterior descending (LAD) arteries have a myocardial bridge. An MB may be associated with stent failure when the stent extends into the MB.

OBJECTIVES

The aim of this study was to investigate: 1) the association between an MB and chronic total occlusion (CTO) in any LAD lesions; and 2) the association between an MB and subsequent clinical outcomes after percutaneous coronary intervention in LAD CTOs.

METHODS

A total of 3,342 LAD lesions with IVUS-guided percutaneous coronary intervention (280 CTO and 3,062 non-CTO lesions) were included. The primary outcome was target lesion failure (cardiac death, target vessel myocardial infarction, definite stent thrombosis, and ischemic-driven target lesion revascularization).

RESULTS

An MB by IVUS was significantly more prevalent in LAD CTOs than LAD non-CTOs (40.4% [113/280] vs 25.8% [789/3,062]; P < 0.0001). The discrepancy in CTO length between angiography and IVUS was greater in 113 LAD CTOs with an MB than 167 LAD CTOs without an MB (6.0 [Q1, Q3: 0.1, 12.2] mm vs 0.2 [Q1, Q3: -1.4, 8.4] mm; P < 0.0001). Overall, 48.7% (55/113) of LAD CTOs had a stent that extended into an MB after which target lesion failure was significantly higher compared to a stent that did not extend into an MB (26.3% vs 0%; P = 0.0004) or compared to an LAD CTO without an MB (26.3% vs 9.6%; P = 0.02).

CONCLUSIONS

An MB was more common in LAD CTO than non-CTO LAD lesions. If present, approximately one-half of LAD CTOs had a stent extending into an MB that, in turn, was associated with worse outcomes.

Nomogram to predict recurrent chest pain in patients with myocardial bridging

OBJECTIVE

Patients with myocardial bridging (MB) frequently experience recurrent chest pain, even in those without coronary heart disease. This study aims to predict the risk of recurrent chest pain in patients with MB by using a novel predictive nomogram.

METHODS

This retrospective study enrolled 250 patients with acute chest pain who underwent coronary computed tomography angiography (CCTA) between January and December 2018, including 111 patients with MB and 139 control patients. Least absolute shrinkage and selection operator (LASSO) and multivariable Cox regression analyses were used to screen for significant parameters that were included to develop a novel predictive nomogram model. Receiver operating characteristic curve, calibration curve, and decision curve analyses were used to evaluate the performance and clinical utility of the nomogram.

RESULTS

A predictive nomogram was constructed in 111 patients with MB, 34 of whom (30.9%) had recurrent chest pain. The significant predictors screened out by the LASSO regression included age, sex, branch type MB, and systolic compression index. The area under the curves (AUCs) for recurrent chest pain at 12, 24, and 36 months were 0.688, 0.742, and 0.729, respectively, indicating remarkable accuracy of the nomogram. The calibration curve and decision curve analyses indicated a good agreement with the observations and utility of the nomogram.

CONCLUSIONS

This study presents a high-accuracy nomogram to predict recurrent chest pain in patients with MB. This model incorporates clinical risk factors and CT imaging features and can be conveniently used to facilitate the individualised prediction.

KEY POINTS

• Symptomatic patients with myocardial bridging often present with recurrent chest pain. • The potential predictors of recurrent chest pain in patients with myocardial bridging were age, sex, branch type MB, and systolic compression index. • Nomogram based on clinical CT imaging features is valuable to predict recurrent chest pain in patients with myocardial bridging.

Impact of Clinical and Morphological Factors on Long-Term Mortality in Patients with Myocardial Bridge

Although myocardial bridging (MB) has been intensively investigated using different methods, the effect of bridge morphology on long-term outcome is still doubtful. We aimed at describing the anatomical differences in coronary angiography between symptomatic and non-symptomatic LAD myocardial bridges and to investigate the influence of clinical and morphological factors on long-term mortality. In our retrospective, long-term, single center study we found relevant MB on the left anterior descendent (LAD) coronary artery in 146 cases during a two-year period, when 11,385 patients underwent coronary angiography due to angina pectoris. Patients were divided into two groups: those with myocardial bridge only (LAD-MBneg, n = 78) and those with associated obstructive coronary artery disease (LAD-MBpos, n = 68). Clinical factors, morphology of bridge by quantitative coronary analysis and ten-year long mortality data were collected. The LAD-MBneg group was associated with younger age and decreased incidence of diabetes mellitus, as well as with increased minimal diameter to reference diameter ratio (LAD-MBneg 54.5 (13.1)% vs. LAD-MBpos 46.5 (16.4)%, p = 0.016), while there was a tendency towards longer lesions and higher vessel diameter values compared to the LAD-MBpos group. The LAD-MBpos group was associated with increased mortality compared to the LAD-MBneg group. The analysis of our data showed that morphological parameters of LAD bridge did not influence long-term mortality, either in the overall population or in the LAD-MBneg patients. Morphological parameters of LAD bridge did not influence long-term mortality outcomes; therefore, it suggests that anatomical differences might not predict long-term outcomes and should not influence therapy.

Myocardial bridges: A meta-analysis

Myocardial bridges are anatomical entities characterized by myocardium covering segments of coronary arteries. In some patients, the presence of a myocardial bridge is benign and is only incidentally found on autopsy. In other patients, however, myocardial bridges can lead to compression of the coronary artery during systolic contraction and delayed diastolic relaxation, resulting in myocardial ischemia. This ischemia in turn can lead to myocardial infarction, ventricular arrhythmias and sudden cardiac death. Myocardial bridges have also been linked to an increased incidence of atherosclerosis, which has been attributed to increased shear stress and the presence of vasoactive factors. Other studies however, demonstrated the protective roles of myocardial bridges. In this study, using systematic review and a meta-analytical approach we investigate the prevalence and morphology of myocardial bridges in both clinical imaging and cadaveric dissections. We also discuss the pathophysiology, clinical significance, and management of these anatomical entities.

Computed Tomography Angiographic Features of Anomalous Origination of the Coronary Arteries in Adult Patients: A Literature Review and Coronary Computed Tomography Angiographic Illustrations

Computed tomography angiography not only detects atherosclerotic coronary artery disease but also helps delineate the anomalous coronary arterial anatomy that may be more than just an incidental finding and could contribute to patients' symptomatology. Additionally, identification of coronary artery anomalies is clinically significant for preoperative planning and optimizing the approach for coronary catheterizations or surgical treatments. In this work, we review rare origination anomalies of coronary arteries and illustrate their characteristics through computed tomography images.

A case report of intramyocardial bridge on right coronary artery

Intramyocardial bridges are a coronary circulation anomaly. They usually occur on the path of the anterior descending artery and are classified as superficial or deep. During a routine autopsy, we found—and report—an intramyocardial bridge in large part of the right coronary artery pathway, including the sinoatrial and posterior descending branch. The patient did not show signs of coronary insufficiency, and died from an acute respiratory failure caused by aspiration pneumonia. Due to the infrequency of cases of intramyocardial bridges of the right coronary artery without concomitant clinical symptoms or signs, we conducted a literature review in this regard.

Myocardial Bridging: A Meta-Analysis of Prevalence

The main objective of this article was to analyze prevalence data about myocardial bridging (MB) in published studies. To this purpose, we performed a meta-analysis of studies published in English literature that contained data about the prevalence of MB and its anatomical characteristics. The overall prevalence was 19% (CI: 17-21%); autopsy studies revealed an overall prevalence of 42% (CI: 30-55%), CT studies 22% (CI: 18-25%), and coronary angiography 6% (CI: 5-8%). Most bridges were located on the left anterior descending artery (82% overall, 63% on autopsy studies), had a mean thickness of 2.47 mm and a mean length of 19.3 mm. In conclusion, autopsy studies should be the gold standard in evaluating the actual prevalence of myocardial bridges, while in vivo high-resolution CT scanning should be preferred to coronary angiography studies.

Measurements of myocardial bridges on computed tomography predict presence of clinical symptoms and outcomes of adverse heart events: a retrospective study in a large population from China

Background Clinical-radiological correlation of myocardial bridge (MB) remains unclear. Purpose To correlate clinical symptoms and outcomes of MBs with computed tomography (CT) coronary angiography findings. Material and Methods A total of 2092 patients with CT coronary angiography were collected. Patients were divided into symptomatic and asymptomatic groups, adverse heart events (AHE) and non-AHE groups, MB and non-MB groups, as well as left anterior descending (LAD)-MB and non-LAD-MB groups. Statistical analyses were performed to identify inter-group differences, and clinical-radiological correlations of MBs or mural coronary arteries (MCAs). Results The prevalence of MB, the MCA stenosis either in systole or in diastole, and the ratio of LAD-MB were significantly higher in the symptomatic group than in the asymptomatic group, and higher in the AHE group than in the non-AHE group ( P all <0.05). MB thickness, systolic MCA stenosis, and diastolic MCA stenosis were independent variables predicting clinical symptoms ( P < 0.05), with diastolic MCA stenosis having the highest diagnostic performance, when cutting at 24.6%. The corresponding sensitivity and specificity were 87.8% and 90.6%, respectively. Diastolic MCA stenosis independently indicated outcome of AHE (odds ratio, 1.047; P < 0.001). Conclusion Measurements of MB-MCA by CT predict the presence of clinical symptoms and outcomes of AHE, with diastolic MCA stenosis possessing the greatest performance.

Myocardial Bridges on Coronary Computed Tomography Angiography - Correlation With Intravascular Ultrasound and Fractional Flow Reserve

BACKGROUND

Myocardial bridges (MB) are commonly seen on coronary CT angiography (CCTA) in asymptomatic individuals, but in patients with recurrent typical angina symptoms, yet no obstructive coronary artery disease (CAD), evaluation of their potential hemodynamic significance is clinically relevant. The aim of this study was to compare CCTA to invasive coronary angiography (ICA), including intravascular ultrasound (IVUS), to confirm MB morphology and estimate their functional significance in symptomatic patients.Methods and Results:We retrospectively identified 59 patients from our clinical databases between 2009 and 2014 in whom the suspicion for MB was raised by symptoms of recurrent typical angina in the absence of significant obstructive CAD on ICA. All patients underwent CCTA, ICA and IVUS. MB length and depth by CCTA agreed well with length (0.6±23.7 mm) and depth (CT coverage) as seen on IVUS. The product of CT length and depth (CT coverage), (MB muscle index (MMI)), ≥31 predicted an abnormal diastolic fractional flow reserve (dFFR) ≤0.76 with a sensitivity and specificity of 74% and 62% respectively (area under the curve=0.722).

CONCLUSIONS

In patients with recurrent symptoms of typical angina yet no obstructive CAD, clinicians should consider dynamic ischemia from an MB in the differential diagnosis. The product of length and depth (i.e., MMI) by CCTA may provide some non-invasive insight into the hemodynamic significance of a myocardial bridge, as compared with invasive assessment with dFFR.

Systolic Compression of a Myocardial Bridged Coronary Artery and its Morphologic Characteristics: A Combination Study of Computed Tomography Angiography and Invasive Angiography

Background

Myocardial bridging (MB) is a congenital anomaly in which a segment of a major epicardial coronary artery courses through the myocardium. This anomaly can lead to myocardial ischemia, arrhythmia, and even death. The effectiveness of coronary computed tomographic angiography (CCTA) in the detection of MB and its morphological features, and the accuracy of invasive coronary angiography (ICA) in the evaluation of systolic compression have been shown in some prior studies.

Objectives

The present study aimed to evaluate the correlation between the depth and the length of MB as determined using CCTA, and the degree of luminal narrowing of the involved tunneled segment as calculated using the ICA.

Patients and Methods

For this study, 109 consecutive patients diagnosed with myocardial bridging using CCTA, and who had already undergone ICA, were studied. The depth and length of the MB was determined in the CCTA, while the degree of systolic compression was calculated in the ICA. The correlation between the depth and length of the MB and the systolic compression were then evaluated.

Results

The degree of systolic compression was found to be correlated with the depth of the MB. However, there was no correlation between the length of the MB and the degree of systolic compression.

Conclusion

The systolic compression of the MB was influenced by the depth of the tunneled segment, not by its length.

Multimodality Imaging in the Assessment of the Physiological Significance of Myocardial Bridging

In myocardial bridging (MB) a segment of the coronary artery is covered by the myocardium. MB can be seen as a systolic compression by invasive coronary angiography (ICA) or as an intramural course by computed tomography angiography (CTA). Intramural course is a common incidental finding in CTA studies. Only minority of the bridging segments are associated with systolic compression causing a possible impairment of myocardial perfusion. The relationship between myocardial blood flow and MB is complex and poorly evaluated by anatomic imaging. Furthermore, provocation tests are frequently needed to uncover systolic compression. Fractional flow reserve can be used to assess the hemodynamic significance of MB. Nuclear perfusion imaging can demonstrate flow abnormalities associated with MB. Stress echocardiography can demonstrate ischemic wall motion abnormalities. They can be complemented by hybrid imaging with CTA to distinguish epicardial coronary artery disease and MB. This article will review different imaging modalities for the evaluation of the physiologic significance of MB.

Evaluation of left ventricular function by three-dimensional speckle-tracking echocardiography in patients with myocardial bridging of the left anterior descending coronary artery

BACKGROUND

To understand the influence of myocardial bridging (MB) on left ventricular (LV) function, myocardial function was studied in patients with MB of the left anterior descending coronary artery (LAD) using three-dimensional speckle-tracking echocardiography (STE).

METHODS

Left anterior descending coronary artery MB was diagnosed by coronary angiography in 82 subjects. Patients were divided into three groups according to the percentage of systolic narrowing of the compressed segment: 30% to 49% was defined as group I (24 patients), 50% to 74% as group II (28 patients), and ≥75% as group III (30 patients). Thirty gender- and age-matched normal subjects were included as controls. Left ventricular myocardial deformation was estimated by three-dimensional STE.

RESULTS

Left ventricular ejection fractions were normal in all patients, but diastolic function was impaired in groups II and III (E/E' ratio, 9 ± 3 and 10 ± 3, respectively). The amplitudes of longitudinal strain (LS) and area strain (AS) of the LAD territory was significantly reduced in groups II and III compared with controls and group I (LS, -15 ± 2% and -12 ± 1% vs -19 ± 2% and -18 ± 2%; AS, -22 ± 2% and -13 ± 2% vs -33 ± 4% and -33 ± 3%; P < .0001), but the amplitudes of circumferential and radial strain showed no intergroup differences. Longitudinal strain and AS were significantly lower in patients with fractional flow reserve < 0.75 than in those with fractional flow reserve ≥ 0.75 (P < .0001), with relative preservation of circumferential and radial strain. The severity of LAD compression was significantly associated with AS and LS of the LAD territory (r = -0.92 and r = -0.84, respectively, P < .0001), but the correlations with circumferential and radial strain were modest (r = -0.36 and r = -0.32, respectively, P < .05).

CONCLUSIONS

With the increasing severity of systolic compression of the mural coronary artery, LV diastolic function and regional systolic deformation (AS and LS) of the MB perfusion territory were reduced. Three-dimensional STE can detect subtle myocardial dysfunction in patients with MB.

Clinical value of the correlations of mural coronary artery compression extent with myocardial bridge length and thickness evaluated by 128-slice CT

This study aimed to investigate the correlations between the detection rate of mural coronary artery (MCA) by 128-slice CT and the MCA compression extent in systole with myocardial bridge (MB) length and thickness. A retrospective analysis was conducted for 580 patients receiving multislicespiral CT coronary angiography (MSCTCA). In addition, the MCA incidence rate and position were detected, and the MB length and thickness in the left anterior descending branch (LAD) and MCA compression extent in systole were measured to compare the differences between MB-MCA length and thickness among the mild, moderate and severe groups. A total of 140 cases of MB-MCA (24.14%) were involved in the study. Among them, 104 cases occurred in the middle segment of the LAD (74.3%), 16 cases (11.4%) occurred in the distal segment of the LAD, 8 cases (5.7%) occurred in the left circumflex-obtuse marginal branch (LCX-OM), 7 cases (5.0%) occurred in the first diagonal branch (1st D), 3 cases (2.1%) in the intermediate branch (M) and 2 cases (1.5%) occurred in the posterior descending branch of the right coronary artery (RCA-PD). The mean length of the MB in the LAD was 21.80±5.98 mm, the mean thickness was 2.15±0.74 mm and the mean compression extent was 38.5±19.6%. Among the different groups, there were no significant difference in MB length (P>0.05) but there were significant differences in MB thickness (P<0.05). In addition, the extent of MCA compression in systole was linearly and positively correlated with MB thickness (r=0.408, P<0.05) but was not correlated with MB length (r=0.076, P>0.05). 128-slice CT coronary angiography (SCTCA) is able to accurately detect MB-MCA and evaluate the correlations of MCA compression extent in systole with MB length and thickness which provides a basis for its clinical use.

Association of variance in anatomical elements of myocardial bridge with coronary atherosclerosis

OBJECTIVES

The myocardial bridge (MB) is an anatomical structure consisting of myocardium covering a part of the left anterior descending coronary artery (LAD). The extent and spatial distribution of atherosclerosis in the LAD with an MB is influenced by the anatomical properties of the MB. In this study, the relationship between the overall anatomical framework of the MB including the periarterial adipose tissue as well as fibrosis of the MB itself and coronary atherosclerosis was histomorphometrically examined.

METHODS

Full-length LADs with an MB from 180 autopsied hearts were cross-sectioned at 5-mm intervals. Together with measurements of MB - length, thickness, and location, proportional decrease of the atherosclerosis ratio of LAD segments beneath MB for that of LAD segments proximal to MB was defined as the atherosclerosis suppression ratio. The area ratio of adipose tissue in the periarterial area beneath MB and area ratio of fibrosis in the MB muscle were also measured.

RESULTS

The atherosclerosis suppression ratio was significantly proportional to MB length and thickness. Periarterial adipose tissue beneath MB was detected in all cases (100%), and fibrosis within MB muscle for 136 cases (75.6%). The amount of adipose tissue beneath MB and MB fibrosis did not statistically affect the atherosclerosis suppression ratio. Multivariate analysis revealed MB length and thickness were the independent factors affecting the atherosclerosis suppression ratio.

CONCLUSIONS

The anatomical properties of an MB, especially of its length and thickness, play decisive roles as regulators of atherosclerosis in the LAD regardless of the amount of adipose tissue around LAD and MB fibrosis.

Histopathologic profiles of coronary atherosclerosis by myocardial bridge underlying myocardial infarction

OBJECTIVE

Anatomic properties of myocardial bridge (MB) are sometimes responsible for myocardial infarction (MI) through the changes in the atherosclerosis distribution in the left ascending coronary artery (LAD). The purpose of this study was to investigate histopathologic profiles of atherosclerotic lesions resulting from the MB presence in the LAD in the MI cases.

METHODS

In 150 consecutive autopsied MI hearts either with MBs [MI(+)MB(+); n = 67] or without MBs [MI(+)MB(-); n = 83] and 100 normal hearts with MBs [MI(-)MB(+)], LADs were consecutively cross-sectioned at 5-mm intervals. The most advanced intimal lesion and unstable plaque-related lesion characteristics (UPLCs) in each section were histopathologically evaluated in conjunction with the anatomic properties of the MB, such as its thickness, length, location, and MB muscle volume burden (MMV: the total volume of MB thickness multiplied by MB length).

RESULTS

The MB showed a significantly greater thickness (P = 0.0090), length (P = 0.0300), and MMV (P = 0.0019) in MI(+)MB(+) than in MI(-)MB(+). Mean age of acute MI cases was significantly younger (P = 0.0227) in MI(+)MB(+) than in MI(+)MB(-). Frequency of plaque fissure/rupture in the proximal LAD was significantly higher in acute MI cases of MI(+)MB(+) than in MI(+)MB(-). UPLCs tended to be located proximally in MI(+)MB(+) and frequent 2.0 cm or more proximal to the MB entrance in MI(+)MB(+).

CONCLUSION

In MI(+)MB(+), UPLCs tend to be located more proximally, and a plaque in the LAD proximal to the MB is prone to rupture, resulting in MI at younger age.

Myocardial bridging on coronary CTA: an innocent bystander or a culprit in myocardial infarction?

Myocardial bridging describes the clinical entity whereby a segment of coronary artery is either partially or completely covered by surrounding myocardium. It represents the most frequent congenital coronary anomaly and has an estimated prevalence of ≤13% on angiographic series. With the emergence of cardiac computed tomography and its ability to simultaneously image the coronary arteries and also the myocardium, there has been an apparent increase in the detection rates of myocardial bridges (prevalence as high as 44%). It has now become important to evaluate their clinical significance. Myocardial bridging is generally considered a benign entity with survival rates of 97% at 5 years; however, there is now emerging evidence that certain myocardial bridge characteristics may be associated with cardiovascular morbidity. The length and depth of myocardial bridges have been associated with increased atherosclerosis, whereas the degree of systolic compression has been associated with ischemia on myocardial perfusion single-photon emission tomography. On the basis of current evidence, it appears that limiting further testing for ischemia to symptomatic patients with long and/or deep myocardial brides would be appropriate.