Myocardial bridges spared from atherosclerosis: overview of the underlying mechanisms

Myocardial Bridge and Atherosclerosis, an Intimal Relationship

PURPOSE OF REVIEW

This review investigates the relationship between myocardial bridges (MBs), intimal thickening in coronary arteries, and Atherosclerotic cardiovascular disease. It focuses on the role of mechanical forces, such as circumferential strain, in arterial wall remodeling and aims to clarify how MBs affect coronary artery pathology.

REVIEW FINDINGS

MBs have been identified as influential in modulating coronary artery intimal thickness, demonstrating a protective effect against thickening within the MB segment and an increase in thickness proximal to the MB. This is attributed to changes in mechanical stress and hemodynamics. Research involving arterial hypertension models and vein graft disease has underscored the importance of circumferential strain in vascular remodeling and intimal hyperplasia. Understanding the complex dynamics between MBs, mechanical strain, and vascular remodeling is crucial for advancing our knowledge of coronary artery disease mechanisms. This could lead to improved management strategies for cardiovascular diseases, highlighting the need for further research into MB-related vascular changes.

A bibliometric analysis of myocardial bridge combined with myocardial infarction

BACKGROUND

The aim of this study is to analyze the process and frontiers of research in myocardial bridges (MB) to identify future research directions in the last 3 decades.

METHODS

Relevant literature on MB combined with myocardial infarction (MI) was searched from 1991 to 2023 in the Web of Science database, and was analyzed by bibliometric analysis using VOSviewer, CiteSpace, and the R package "bibliometrix."

RESULTS

A total of 1233 English articles were included in this study. The number of published articles showed an increasing trend yearly. From 2017 to 2022, the annual publication volume rose rapidly, and in 2021 the publication volume even reached 95 articles, which was the highest in all years. These publications were from 68 countries and 1854 institutions, with the leading country being the U.S. and the leading institution being Columbia University. Myoho Clinical International has a close collaborative relationship with Columbia University, while in recent years, the Harvard Medical School has explored the study of MB combined with MI. Annals of Thoracic Surgery was the journal with the highest number of publications, and Takayama Hiroo and Naka Yoshifumi were the authors with the highest number of publications. The most common keywords were MI, cardiogenic shock, and MB.

CONCLUSIONS

Our findings can help researchers explore the current status of MB combined with MI research and choose new survey routes for upcoming studies. Prevalence and prognosis, mechanism of MB combined with MI and molecular mechanism may become the focus of future research. In addition, more research and cooperation are needed worldwide.

Myocardial Bridging-Induced Acute Coronary Syndrome: A Bridge Too Far

Recent studies suggest a potential association between myocardial bridging (MB) and accelerated atherosclerotic plaque formation. We describe the case report of a 37-year-old South Asian male with no established risk factors for coronary artery disease (CAD) who presented with a non-ST-segment-elevation acute coronary syndrome (NSTE-ACS) with a coincident widowmaker lesion and severe MB. He was successfully managed with comprehensive guideline-directed medical therapy (GDMT) and urgent percutaneous coronary intervention (PCI) of the culprit lesion, sparing the MB segment. The clinician should be cognizant of MB implicating ACS as a major adverse cardiovascular event (MACE) and its key management strategies.

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.

Atheroprotective effect of myocardial bridge sustains in aging: Autopsy study on subjects with dual left anterior descending coronary artery type 3

BACKGROUND

The atheroprotective role of the myocardial bridge (MB) on a tunneled segment is already demonstrated in subjects with dual left anterior descending coronary artery (dual LAD) type 3 anomaly, but the dynamics of changes and whether this protective effect sustains during aging is unknown.

METHODS

The retrospective autopsy study included cases of dual LAD type 3 anomaly identified over 18 years. The severity grade of atherosclerosis in branches of dual LAD was estimated by microscopy. The Spearman's correlation test and Receiver operator characteristics (ROC) curve analyses were performed to determine the relation of subjects' age with a degree of the protective role of the myocardial bridge.

RESULTS

A total of 32 dual LAD type 3 cases were identified. The systematic heart examination revealed an anomaly prevalence of 2.1%. The age significantly positively correlated with the severity of atherosclerosis in the subepicardial dual LAD branch but not with the severity of atherosclerosis in the intramyocardial dual LAD branch. Subjects aged ≥38 years were likely to have a more severe degree of atherosclerosis in subepicardial than in intramyocardial LAD arteries (AUC 0.81 95% CI 0.59-1; sensitivity 100%, specificity 66.7%). In subjects aged ≥58 years, this difference was likely to be more pronounced (≥2 degree difference; AUC 0.75 95% CI 0.58-0.93; sensitivity 92.9%, specificity 66.7%).

CONCLUSION

The atheroprotective effect of the myocardial bridge on tunneled segments usually becomes evident throughout the second half of the fourth decade of life and is most pronounced after about 60 years and ceases only in some.

Systematic Review and Meta-Analysis of Cardiovascular Consequences of Myocardial Bridging in Hypertrophic Cardiomyopathy

Myocardial bridging (MB) is a congenital variant in which a segment of a coronary artery follows an atypical intramural course under a "bridge" of myocardium and is notably common in hypertrophic cardiomyopathy (HCM). This systematic review and meta-analysis explored the clinical consequences of MB in patients with HCM. A total of 3 outcome domains were investigated: cardiovascular mortality, nonfatal adverse cardiac events, and investigative indicators of myocardial ischemia. A meta-analysis was performed on 10 observational studies comparing outcomes in patients with HCM with and without MB. Studies were identified through a systematic search of 4 databases (PubMed, Scopus, Medline Complete, and Web of Science). The quality of the studies was assessed using a modified version of the Downs and Black tool, from which studies could score a maximum of 23 points. The mean score was 17.5 ± 1.3 (good). The meta-analysis showed that MB was not associated with cardiovascular mortality (odds ratio [OR] 1.70, 95% confidence interval [CI] 0.56 to 5.15, p = 0.35) or nonfatal adverse cardiac events (OR 1.80, 95% CI 0.98 to 3.28, p = 0.06) but was associated with myocardial ischemia (OR 1.89, 95% CI 1.03 to 3.44, p = 0.04). In conclusion, the potential prognostic implications of MB in HCM, especially in those with hemodynamically significant bridges and/or severe underlying disease, should not be ignored. The focus of future studies should be to establish functional and morphologic thresholds, by which MB may adversely influence prognosis by corroborating imaging findings with clinical outcome data.

Comprehensive functional and anatomic assessment of myocardial bridging: Unlocking the Gordian Knot

Myocardial bridging (MB) is the most frequent congenital coronary anomaly in which a segment of an epicardial coronary artery takes a tunneled course under a bridge of the myocardium. This segment is compressed during systole, resulting in the so-called "milking effect" at coronary angiography. As coronary blood flow occurs primarily during diastole, the clinical relevance of MB is heterogeneous, being usually considered an asymptomatic bystander. However, many studies have suggested its association with myocardial ischemia, anginal symptoms, and adverse cardiac events. The advent of contemporary non-invasive and invasive imaging modalities and the standardization of intracoronary functional assessment tools have remarkably improved our understanding of MB-related ischemia, suggesting the role of atherosclerotic lesions proximal to MB, vasomotor disorders and microvascular dysfunction as possible pathophysiological substrates. The aim of this review is to provide a contemporary overview of the pathophysiology and of the non-invasive and invasive assessment of MB, in the attempt to implement a case-by-case therapeutic approach according to the specific endotype of MB-related ischemia.

Perivascular mechanical environment: A narrative review of the role of externally applied mechanical force in the pathogenesis of atherosclerosis

Atherosclerosis is promoted by systemic factors, such as dyslipidemia, hypertension, diabetes, and smoking, which cause atherosclerosis in blood vessels throughout the body. However, atherosclerotic lesions are characterized by their frequent occurrence in specific vessels and sites. Blood vessels are exposed to various mechanical forces related to blood pressure and flow. Although shear stress promotes the initiation and progression of atherosclerotic lesions, the pathogenesis of site specificity of atherosclerosis is not sufficiently explained by shear stress. We propose the concept of a perivascular mechanical environment (PVME). Compelling evidence suggests that site specificity in atherosclerotic lesions depends on a distinct local PVME. Atheroprone arteries, such as the coronary artery, are markedly affected by externally applied mechanical force (EMF), whereas atheroprotective arteries, such as the internal thoracic artery, are less affected. Recent studies have shown that the coronary artery is affected by cardiac muscle contraction, the carotid artery by the hyoid bone and the thyroid cartilage, and the abdominal aorta and lower extremity arteries by musculoskeletal motion. We speculate that the thoracic cage protects the internal thoracic artery from EMF owing to a favorable PVME. Furthermore, evidence suggests that plaque eccentricity is provided by EMF; plaques are frequently observed on an external force-applied side. In each vascular tree, site-specific characteristics of the PVME differ substantially, inducing individual atherogenicity. From the perspective of the mechanical environment, hemodynamic stress occurs in an inside-out manner, whereas EMF occurs in an outside-in manner. These inward and outward forces apply mechanical load individually, but interact synergistically. The concept of a PVME is a novel pathogenesis of atherosclerosis and also might be a pathogenesis of other arterial diseases.

Abnormal shear stress and residence time are associated with proximal coronary atheroma in the presence of myocardial bridging

BACKGROUND

Atheromatous plaques tend to form in the coronary segments proximal to a myocardial bridge (MB), but the mechanism of this occurrence remains unclear. This study evaluates the relationship between blood flow perturbations and plaque formation in patients with an MB.

METHODS AND RESULTS

A total of 92 patients with an MB in the mid left anterior descending artery (LAD) and 20 patients without an MB were included. Coronary angiography, intravascular ultrasound, and coronary physiology measurements were performed. A moving-boundary computational fluid dynamics algorithm was used to derive wall shear stress (WSS) and peak residence time (PRT). Patients with an MB had lower WSS (0.46 ± 0.21 vs. 0.96 ± 0.33 Pa, p < 0.001) and higher maximal plaque burden (33.6 ± 15.0 vs. 14.2 ± 5.8%, p < 0.001) within the proximal LAD compared to those without. Plaque burden in the proximal LAD correlated significantly with proximal WSS (r = -0.51, p < 0.001) and PRT (r = 0.60, p < 0.001). In patients with an MB, the site of maximal plaque burden occurred 23.4 ± 13.3 mm proximal to the entrance of the MB, corresponding to the site of PRT.

CONCLUSIONS

Regions of low WSS and high PRT occur in arterial segments proximal to an MB, and this is associated with the degree and location of coronary atheroma formation.

A Hemodynamic Comparison of Myocardial Bridging and Coronary Atherosclerotic Stenosis: A Computational Model With Experimental Evaluation

Myocardial bridging (MB) and coronary atherosclerotic stenosis can impair coronary blood flow and may cause myocardial ischemia or even heart attack. It remains unclear how MB and stenosis are similar or different regarding their impacts on coronary hemodynamics. The purpose of this study was to compare the hemodynamic effects of coronary stenosis and MB using experimental and computational fluid dynamics (CFD) approaches. For CFD modeling, three MB patients with different levels of lumen obstruction, mild, moderate, and severe were selected. Patient-specific left anterior descending (LAD) coronary artery models were reconstructed from biplane angiograms. For each MB patient, the virtually healthy and stenotic models were also simulated for comparison. In addition, an in vitro flow-loop was developed, and the pressure drop was measured for comparison. The CFD simulations results demonstrated that the difference between MB and stenosis increased with increasing MB/stenosis severity and flowrate. Experimental results showed that increasing the MB length (by 140%) only had significant impact on the pressure drop in the severe MB (39% increase at the exercise), but increasing the stenosis length dramatically increased the pressure drop in both moderate and severe stenoses at all flow rates (31% and 93% increase at the exercise, respectively). Both CFD and experimental results confirmed that the MB had a higher maximum and a lower mean pressure drop in comparison with the stenosis, regardless of the degree of lumen obstruction. A better understanding of MB and atherosclerotic stenosis may improve the therapeutic strategies in coronary disease patients and prevent acute coronary syndromes.

Diagnostic Performance of Machine Learning Based CT-FFR in Detecting Ischemia in Myocardial Bridging and Concomitant Proximal Atherosclerotic Disease

BACKGROUND

The diagnostic performance of coronary computed tomography angiography-derived fractional flow reserve (CT-FFR) in detecting ischemia in myocardial bridging (MB) has not been investigated to date.

METHODS

This retrospective multicentre study included 104 patients with left anterior descending MBs. MB was classified as either superficial or deep, short, or long, whereas all MB vessels were further divided into <50%, 50% to 69%, and ≥70% groups, according to proximal lumen stenosis on invasive coronary angiography. Diagnostic performance and receiver operating characteristics (ROC) of CT-FFR to detect lesion-specific ischemia was assessed on a per-vessel level, using invasive FFR as reference standard. Intraclass correlation coefficient (ICC) and Bland-Altman plots were used for agreement measurement.

RESULTS

Forty-eight MB vessels (46.2%) showed ischemia by invasive FFR (≤0.80). Sensitivity, specificity, and accuracy of CT-FFR to detect functional ischemia were 0.96 (0.85 to 0.99), 0.84 (0.71 to 0.92), and 0.89 (0.81 to 0.94), respectively, in all MB vessels. There were no differences in diagnostic performance between superficial and deep MB or between short and long MB (all P > 0.05). The accuracy of CT-FFR was 0.96 (0.85 to 0.99) in ≥70% stenosis, 0.82 (0.67 to 0.91) in 50% to 69% stenosis, and 0.89 (0.51 to 0.99) in <50% stenosis (P = 0.081). Bland-Altman analysis showed a slight mean difference between CT-FFR and invasive FFR of 0.014 (95% limit of agreement, -0.117 to 0.145). The ICC was 0.775 (95% confidence interval, 0.685-0.842, P < 0.001).

CONCLUSIONS

CT-FFR demonstrated high diagnostic performance for identifying functional ischemia in vessels with MB and concomitant proximal atherosclerotic disease when compared with invasive FFR. However, the clinical use of CT-FFR in patients with MB needs further study for stronger and more robust results.

Haemodynamic impacts of myocardial bridge length: A congenital heart disease

OBJECTIVES

There is an association between long and thick myocardial bridging (MB), haemodynamic perturbations and increased risk of myocardial infarction. This study aims to investigate the alteration in coronary haemodynamics with increasing the length of MB.

METHODS

Angiography and intravascular ultrasound were performed in 10 patients with varying length of MB in the left anterior descending (LAD) artery. In silico models of MB were developed based on the reconstructed three-dimensional model of the LAD. The entire LAD was divided into 3 segments, proximal (pre-bridge), bridge and distal (post-bridge). Transient computational fluid dynamics simulations were performed to derive distribution of blood residence time and wall shear stress (WSS) over entire vessel including proximal, bridge and distal segments.

RESULTS

With increasing the length of MB, a decreasing trend was observed in the WSS over proximal segment whereas an increasing trend was found in the WSS over bridge segment. When patients were divided into 2 groups based on the average length of MB in the whole cohort (L_ave = 23.92 mm), patients with bridges longer than L_ave had smaller WSS and higher residence time in the proximal segment compared to those with bridges shorter than L_ave (0.59 ± 0.31 vs 0.21 ± 0.14 Pa and 0.0021 ± 0.0015 vs 0.0045 ± 0.0021 s). In contrast, patients with bridges longer than L_ave had greater WSS in the bridge segment compared to those with bridges shorter than L_ave (1.37 ± 1.66 vs 2.53 ± 3.14 Pa). No significant difference was found in the distal WSS of patients with short and long bridges.

CONCLUSION

Our findings revealed a direct relationship between the length of MB and haemodynamic perturbations in the proximal segment such that the increased length of MB is associated with decreased WSS and increased residence time.

Intracavitary Coronary Artery: An Unusual Coronary Anomaly

PURPOSE

A few case reports of intracavitary coronary arteries (ICCA) have been reported and only a single case series on the coronary computed tomography angiography (CCTA) prevalence rate of ICCA of the right coronary artery (RCA). We describe several cases of ICCA that were noted incidentally and also determine the overall prevalence rate of anomalous ICCA.

MATERIALS AND METHODS

A retrospective analysis of ICCA was performed consisting of consecutive CCTA cases as well as a group of ICCA from teaching files. To establish a prevalence rate, we reviewed 464 consecutive CCTA referred to our center for transcatheter aortic valve replacement. The presence of ICCA and several imaging features were evaluated.

RESULTS

Our cohort comprises a total of 12 patients with ICCA, with 1 patient containing 2 anomalous ICCA. 83.3% of affected patients were adult males, with an average age of 69.8 years. The RCA was the most commonly affected vessel (53.8%). The mean length of the intracavitary segment was 33.4 mm for the RCA and 27 mm for the LAD. No cases involved the left circumflex coronary artery. Six of the cases were identified routinely as part of clinical practice and therefore not included in the prevalence analysis. On review of our transcatheter aortic valve replacement database, there was a 1.3% prevalence rate of ICCA. RCA had a prevalence of 0.4%, whereas LAD had a prevalence of 0.9%.

CONCLUSIONS

Although rare, our study suggests that ICCA may be more common than previously described. Its presence is important to communicate to clinicians prior to invasive cardiac procedures to prevent potentially catastrophic outcomes.

Expression of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 in Human Epicardial and Intramyocardial Coronary Arteries of Male Patients Undergoing Coronary Artery Bypass Grafting

OBJECTIVES

Atherosclerosis is almost absent in intramyocardial coronary arteries, while epicardial coronary arteries may show extensive occlusive disease. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) expression has been implicated in atherogenesis. We aimed to investigate differences in arterial wall LOX-1 expression between human epicardial and intramyocardial coronary arteries.

METHODS

Epicardial and intramyocardial total artery wall specimens were obtained from 13 male patients (aged 61.9 ± 10.3 years) undergoing coronary artery bypass graft surgery due to 3-vessel coronary artery disease. LOX-1 expression was examined by reverse transcription-polymerase chain reaction.

RESULTS

LOX-1 expression was significantly higher in the arterial wall of epicardial coronary arteries compared to intramyocardial coronary arteries. The LOX-1/GAPDH ratio was 0.48 ± 0.07 vs. 0.35 ± 0.03 (p < 0.001).

CONCLUSIONS

Our findings may partially explain the atheroprotective effect of the intramyocardial course since arterial wall LOX-1 expression was lower in intramyocardial arteries and higher in epicardial coronary arteries.

Predominant location of coronary artery atherosclerosis in the left anterior descending artery. The impact of septal perforators and the myocardial bridging effect

Introduction

Coronary artery atherosclerosis presents characteristic patterns of plaque distribution despite systemic exposure to risk factors. We hypothesized that local hemodynamic forces induced by the systolic compression of intramuscular septal perforators could be involved in atherosclerotic processes in the left anterior descending artery (LAD) adjacent to the septal perforators’ origin. Therefore we studied the spatial distribution of atherosclerosis in coronary arteries, especially in relation to the septal perforators’ origin.

Material and methods

64-slice computed tomography angiography was performed in 309 consecutive patients (92 male and 217 female) with a mean age of 59.9 years. Spatial plaque distribution in the LAD was analyzed in relation to the septal perforators’ origin. Additionally, plaque distribution throughout the coronary artery tree is discussed.

Results

The coronary calcium score (CCS) was positive in 164 patients (53.1%). In subjects with a CCS > 0, calcifications were more frequent in the LAD (n = 150, 91.5%) compared with the right coronary artery (RCA) (n = 94, 57.3%), circumflex branch (CX) (n = 76, 46.3%) or the left main stem (n = 42, 25.6%) (p < 0.001). Total CCS was higher in the LAD at 46.1 (IQR: 104.2) and RCA at 34.1 (IQR: 90.7) than in the CX at 16.8 (IQR: 61.3) (p = 0.007). In patients with calcifications restricted to a single vessel (n = 54), the most frequently affected artery was the LAD (n = 42, 77.8%). In patients with lesions limited to the LAD, the plaque was located mostly (n = 37, 88.1%) adjacent to the septal perforators’ origin.

Conclusions

We demonstrated that coronary calcifications are most frequently located in the LAD in proximity to the septal branch origin. A possible explanation for this phenomenon could be the dynamic compression of the tunneled septal branches, which may result in disturbed blood flow in the adjacent LAD segment (milking effect).

The role of septal perforators and "myocardial bridging effect" in atherosclerotic plaque distribution in the coronary artery disease

The distribution of atherosclerotic plaque burden in the human coronary arteries is not uniform. Plaques are located mostly in the left anterior descending artery (LAD), then in the right coronary artery (RCA), circumflex branch (LCx) and the left main coronary artery (LM) in a decreasing order of frequency. In the LAD and LCx, plaques tend to cluster within the proximal segment, while in the RCA their distribution is more uniform. Several factors have been involved in this phenomenon, particularly flow patterns in the left and right coronary artery. Nevertheless, it does not explain the difference in lesion frequency between the LAD and the LCx as these are both parts of the left coronary artery. Branching points are considered to be the risk points of atherosclerosis. In the LCx, the number of side branches is lower than in the LAD or RCA and there are no septal perforators with intramuscular courses like in the proximal third of the LAD and the posterior descending artery (PDA). We hypothesized that septal branches generate disturbed flow in the LAD and PDA in a similar fashion to the myocardial bridge (myocardial bridging effect). This coronary architecture determines the non-uniform plaque distribution in coronary arteries and LAD predisposition to plaque formation.

Prediction of coronary plaque location on arteries having myocardial bridge, using finite element models

This study was performed to evaluate the influences of the myocardial bridges on the plaque initializations and progression in the coronary arteries. The wall structure is changed due to the plaque presence, which could be the reason for multiple heart malfunctions. Using simplified parametric finite element model (FE model) of the coronary artery having myocardial bridge and analyzing different mechanical parameters from blood circulation through the artery (wall shear stress, oscillatory shear index, residence time), we investigated the prediction of "the best" position for plaque progression. We chose six patients from the angiography records and used data from DICOM images to generate FE models with our software tools for FE preprocessing, solving and post-processing. We found a good correlation between real positions of the plaque and the ones that we predicted to develop at the proximal part of the myocardial bridges with wall shear stress, oscillatory shear index and residence time. This computer model could be additional predictive tool for everyday clinical examination of the patient with myocardial bridge.

Hypercholesterolemia is Accounted for Atherosclerosis at the Proximal Arterial Segments of Myocardial Bridging

Arterial shear stress was generally implicated in the development of atherosclerotic plaque (AP). Atherosclerotic plaque may be associated with myocardial bridging (MB). We evaluated the metabolic abnormalities which could determine the localization of AP at the proximal coronary segment of MB. We analyzed the patients with MB, AP&MB, and AP on left anterior descending (LAD) artery who were diagnosed by multislice computed tomography coronary angiography. Serum levels of metabolic parameters were compared among study groups. Patients with MB&AP and AP were significantly older than those in the MB group. Patients with MB&AP had AP and MB at the proximal and middle segments of LAD artery, respectively. Total cholesterol, low-density lipoprotein (LDL) cholesterol and very LDL, and triglyceride levels were significantly higher in patients with MB&AP and AP compared to only MB. Low-density lipoprotein cholesterol was significantly correlated with the type of coronary artery disease in multiple regression analysis. Myocardial bridging may be an anatomical determinant for the localization of AP proximal to itself in the presence of hypercholesterolemia.

Fluid-structure interaction analysis of the left coronary artery with variable angulation

The aim of this study is to elucidate the correlation between coronary artery branch angulation, local mechanical and haemodynamic forces at the vicinity of bifurcation. Using a coupled fluid-structure interaction (FSI) modelling approach, five idealized left coronary artery models with various angles ranging from 70° to 110° were developed to investigate the influence of branch angulations. In addition, one CT image-based model was reconstructed to further demonstrate the medical application potential of the proposed FSI coupling method. The results show that the angulation strongly alters its mechanical stress distribution, and the instantaneous wall shear stress distributions are substantially moderated by the arterial wall compliance. As high tensile stress is hypothesized to cause stenosis, the left circumflex side bifurcation shoulder is indicated to induce atherosclerotic changes with a high tendency for wide-angled models.

Myocardial bridging: what have we learned in the past and will new diagnostic modalities provide new insights?

The clinical significance of myocardial bridging has been a subject of discussion and controversy since the introduction of coronary arteriography (CAG) in the early 1960s. More recently computed tomography coronary angiography (CTCA) has made it possible to visualise the overlying muscular bands and appears to have a higher sensitivity for detecting myocardial bridging than CAG. Combining CTCA with invasive techniques such as CAG should make it possible to improve our understanding of the pathophysiology of myocardial bridging and to provide answers to hitherto unresolved questions. This paper critically reviews the outcomes of previous studies and defines remaining questions that should be answered to optimise the management of the presumably fast growing number of patients in whom a diagnosis of myocardial bridging has been made.

Left ventricular systolic dyssynchrony in patients with isolated symptomatic myocardial bridge

OBJECTIVES

The impact of myocardial bridge (MB) on left ventricular (LV) systolic synchrony is insufficiently understood.

DESIGN

Thirty-five subjects with isolated mid-left, anterior, descending artery (LAD) MB, preserved LV ejection fraction (LVEF > 50%), and otherwise, normal coronary angiogram were identified from 3607 patients who underwent diagnostic coronary angiography and were evaluated by tissue Doppler imaging and real-time three-dimensional echocardiography (RT3DE). Control subjects consisted of 26 age and sex-matched coronary angiographically "normal" subjects.

RESULTS

MB patients were characterized by reduced, early, diastolic strain rate in LAD-supplied apical segments (lateral and anterior), with prevalence of LV systolic dyssynchrony of 25.7% (9/35). MB patients were further classified by the medians of MB stenosis and length. For MB stenosis < 52.5%, Class I: length < 17 mm (n = 7), Class II: length ≥ 17 mm (n = 10); for stenosis ≥ 52.5%, Class III: length < 17 mm (n = 10), Class IV: length ≥ 17 mm (n = 8). Binary Logistic regression model revealed that higher MB lesion classification (odds ratio: 4.944, 95%CI 1.174-20.82, P < 0.05) and hypertension (odds ratio: 15.32, 95%CI: 1.252-187.6, P < 0.05) are statistically associated with LV systolic dyssynchrony, which was independent of LV mass.

CONCLUSIONS

MB in the mid LAD is associated with myocardial dyssynchrony. Hypertensive individuals and those with more severe bridging (determined by length and stenosis) tend to have an increased incidence of dyssynchrony.

Physiologic evaluation of myocardial bridging: a new analysis for an old disease

BACKGROUND

Myocardial bridging (MB) is the most common congenital coronary anomaly. However, the functional relevance of MB is not well understood.

METHODS

Eighteen patients with lone MB were consecutively enrolled. Fractional flow reserve (FFR) was measured before and after dobutamine infusion. Diastolic FFR was calculated by offline analysis. Cutoff values for functional significance of FFR and diastolic FFR were 0.75 and 0.76, respectively.

RESULTS

Baseline systolic percent diameter stenosis and lesion length of MB were 70 ± 16% and 24 ± 7 mm. FFR and diastolic FFR were 0.92 ± 0.05 and 0.89 ± 0.07 at maximal hyperemia induced by adenosine, respectively (P = 0.006). Despite the angiographic stenosis, only 1 lesion was functionally significant. After dobutamine infusion, percent diameter stenosis (84 ± 11%, P = 0.002) and lesion length (26 ± 6 mm, P = 0.019) were aggravated and diastolic FFR was lowered (0.84 ± 0.10, P = 0.006). Two additional lesions became functionally significant after dobutamine infusion. Angiographic percent diameter stenosis at diastole was correlated with dobutamine diastolic FFR (R = -0.58, P = 0.04), but stenosis at systole was not. During median follow-up of 54 months, 2 patients underwent target-lesion revascularization.

CONCLUSIONS

Dobutamine increased the morphologic and functional severity of MB. Dobutamine-FFR seems to be helpful in the functional assessment of MB.

Coronary CTA assessment of coronary anomalies

Coronary anomalies occur in <1% of the general population and can range from a benign incidental finding to the cause of sudden cardiac death. The coronary anomalies are classified here according to the traditional grouping into those of origin and course, intrinsic arterial anatomy, and termination. Classic coronary anomalies of origin and course include those in which a coronary artery originates from the contralateral aortic sinus or the pulmonary artery with anomalous course. Single coronary artery anomalies, in which single coronary artery branches to supply the entire coronary tree, are also included in this category. Anomalies of intrinsic arterial anatomy are a broad class that includes myocardial bridges, coronary ectasia and aneurysms, subendocardial coursing arteries, and coronary artery duplication. Coronary anomalies of termination are those in which a coronary artery terminates in a fistulous connection to a great vessel or cardiac chamber. In the case of those anomalies associated with a risk of sudden cardiac death, the relevant imaging features on CT angiography (CTA) associated with poorer prognosis are reviewed. Recent guidelines and appropriateness criteria favor the use of coronary CTA for the evaluation of coronary anomalies. Although invasive angiography has historically been used to diagnose coronary anomalies, multidetector CT imaging techniques have now become an accurate noninvasive alternative. Cardiac CTA provides excellent spatial and temporal resolution, allowing accurate anatomical assessment of these anomalies.

Triple coronary pathologies complicated by acute cholecystitis

Coronary atherosclerosis, myocardial bridge, and coronary aneurysm are different causes of myocardial ischemia. Patients with cardiac ischemia can be complicated by acute cholecystitis. A 39-year-old man referred with chest pain and cold sweating and scheduled for coronary artery bypass grafting (CABG) because of severe stenosis in right coronary artery, aneurysm of left circumflex artery, and long-segment muscle bridge in the middle part of left anterior descending artery. He developed acute cholecystitis before operation. Concomitant cholecystectomy and CABG was done. He is the first patient with three different coronary pathologies and simultaneous cholecystitis in the English-language literature who was operated on in a single session.