New signs characteristic of myocardial bridging demonstrated by intracoronary ultrasound and Doppler

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.

Association of Coronary Computed Tomography-Defined Myocardial Bridge With Pre- and Post-Procedural Fractional Flow Reserve in Patients Undergoing Elective Percutaneous Coronary Intervention

BACKGROUND

Myocardial bridge (MB) is a common coronary anomaly characterized by a tunneled course through the myocardium. Coronary computed tomography angiography (CCTA) can identify MB. The impact of MB detected by CCTA on coronary physiological parameters before and after percutaneous coronary intervention (PCI) is unknown.Methods and Results: We investigated 141 consecutive patients who underwent pre-PCI CCTA and fractional flow reserve (FFR)-guided elective PCI for de novo single proximal lesions in the left anterior descending artery (LAD). We compared clinical demographics and physiological parameters between patients with and without CCTA-defined MB. MB was identified in 46 (32.6%) patients using pre-PCI CCTA. The prevalence of diabetes was higher among patients with MB. Median post-PCI FFR values were significantly lower among patients with than without MB (0.82 [interquartile range 0.79-0.85] vs. 0.85 [interquartile range 0.82-0.89]; P=0.003), whereas pre-PCI FFR values were similar between the 2 groups. Multivariable linear regression analysis revealed that the presence of MB and greater left ventricular mass volume in the LAD territory were independently associated with lower post-PCI FFR values. Multivariable logistic regression analysis also revealed that the presence of MB and lower pre-PCI FFR values were independent predictors of post-PCI FFR values ≤0.80.

CONCLUSIONS

CCTA-defined MB independently predicted both lower post-PCI FFR as a continuous variable and ischemic FFR as a categorical variable in patients undergoing elective PCI for LAD.

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.

Clinically significant myocardial bridging

Myocardial bridging is a common anatomical variant in which a major epicardial coronary artery takes an intramyocardial course, leading to dynamic systolic compression. Because coronary perfusion occurs primarily during diastole, most patients with this anatomical variant have no associated perfusion abnormalities or symptoms. Despite this, there is a subset of patients with myocardial bridging who experience ischaemic symptoms. Determining which anatomical variants are benign and which are clinically relevant remains a challenge. Further complicating the picture, functional factors such as diastolic dysfunction and coronary vasospasm may exacerbate myocardial bridging-related ischaemia. In patients with ischaemic symptoms in the absence of alternative explanations, a detailed assessment of myocardial bridging with invasive physiology should be performed to define the significance of the lesion and guide tailored medical therapy. Patients with refractory symptoms despite maximally tolerated medical therapy should be considered for surgical coronary unroofing.

Myocardial bridge in a child with cardiac arrest and ventricular fibrillation: a bridge over troubled water?

Resuscitated cardiac arrest in a child triggers a comprehensive workup to identify an aetiology and direct management. The presence of a myocardial bridge does not automatically imply causation. Careful determination of the haemodynamic significance of the myocardial bridge is critical to avoid an unnecessary sternotomy and to provide appropriate treatment.

Use of Intravascular Ultrasound and Coronary Angiography to Measure the Prevalence of Myocardial Bridge in Heart Transplant Patients

Myocardial bridge (MB) detection rates vary across methods and most studies that have assessed MB include symptomatic patients. Intravascular ultrasound (IVUS) is a sensitive tool for MB detection and donor hearts may serve as a surrogate measure of asymptomatic patients. We used IVUS and coronary angiography to measure MB prevalence in heart transplant patients during routine follow-up invasive coronary assessments. This was a retrospective, single-center study of heart transplant patients who received follow-up coronary assessments at the University of Chicago Heart and Vascular Center between December 2014 and December 2021. A single experienced interventional cardiologist assessed incidental findings of MB in IVUS and coronary angiography. Detection rates were compared with meta-analysis-reported prevalence. Of 129 patients, IVUS-detected MB in 87 patients (67.4%), whereas coronary angiography detected 41 (31.8%). All MB found by coronary angiography were detected by IVUS. Some level of cardiac allograft vasculopathy was found in 92 patients (71.3%). Our IVUS-detected MB prevalence was greater than meta-analysis-reported pooled prevalence across all methods: autopsy, computed tomography angiography, and coronary angiography (67.4% [95% confidence interval [CI] 59.4 to 75.5] vs 42% [95% CI 30 to 55]; 22% [95% CI 18 to 25]; 6% [95% CI 5 to 8], p ≤0.005). The difference between our observed IVUS-detected MB prevalence and meta-analysis autopsy reported MB prevalence was 1.25 (95% CI 1.11 to 1.40). In conclusion, the high prevalence of MB recorded in donor hearts emphasizes the need to further investigate the causes of chest pain in patients who are found to have MB.

Dynamic perfusion SPECT for functional evaluation in symptomatic patients with myocardial bridging

BACKGROUND

The aim of this study was to investigate the feasibility and diagnostic value of myocardial flow reserve (MFR) assessed by rest/stress myocardial perfusion imaging with dynamic single-photon emission computed tomography (SPECT) in the functional evaluation of myocardial bridge (MB).

METHODS

From May 2017 to July 2021, patients with angiographically confirmed isolated MB on the left anterior descending artery (LAD) who underwent dynamic SPECT myocardial perfusion imaging were retrospectively included. The assessment of semiquantitative indices of myocardial perfusion (summed stress scores, SSS) and quantitative parameters (MFR) was performed.

RESULTS

A total of 49 patients were enrolled. The mean age of the subjects was 61.0 ± 9.0 years. All of the patients were symptomatic, and 16 cases (32.7%) presented with typical angina. SPECT-derived MFR showed a borderline significantly negative correlation with SSS (r = 0.261, P = .070). There was a trend of higher prevalence of impaired myocardial perfusion defined as MFR < 2 than as SSS ≥ 4 (42.9% vs 26.5%; P = .090).

CONCLUSION

Our data support that SPECT MFR may be a useful parameter for the functional assessment of MB. In patients with MB, the use of dynamic SPECT could be a potential method for hemodynamic assessment.

Plaque morphology and distribution in patients with and without myocardial bridge - an intravascular ultrasound study

BACKGROUND

Myocardial bridging (MB) is a common congenital cardiovascular anomaly. There are reported associations of MB with different clinical presentations like effort angina, acute coronary syndromes (ACS) and sudden cardiac death. Acceleration of atherosclerosis in proximal vessel is reported in patients with MB, while bridged segments are reported to be free of atherosclerosis.

METHODS

We assessed patients who underwent intravascular ultrasound (IVUS) guided percutaneous intervention (PCI) of left anterior descending (LAD) artery. Plaque characteristics derived from IVUS analysis were compared between those who displayed myocardial bridge versus those who did not harbour the anomaly.

RESULTS

One hundred and forty-seven (147) patients underwent IVUS guided PCI. Incidence of MB was 44/147 (29.9%). Mean age of patients who had MB {+} was higher (62.1 ± 10.3 vs. 57.8 ± 11.2 (p = .03). 142/147 (96.6%) patients presented with ACS. ST elevation myocardial infarction (STEMI) was the most common presenting diagnosis (110/147 to 74.8%). There were no differences in qualitative plaque characteristics - attenuated plaque, calcification or calcium score between two groups. Plaque burden and length of the lesion in the proximal vessel were not different. Among patients with MB {+}, atheromatous extension to segments underlying the bridge was seen in 31/44 (70.5%) cases.

CONCLUSIONS

In a series of patients who presented with advanced clinical atherosclerosis, plaque characteristics were not different in patients who harboured myocardial bridge vs. those who did not have the anomaly. Atheromatous involvement was seen extending into bridged segment contrary to previous reports.

Myocardial Bridging: Review on the Role of Coronary Computed Tomography Angiography

Myocardial bridging (MB) is a congenital coronary anomaly in which a segment of a coronary artery, most frequently the left anterior descending artery, deviates from its epicardial route by passing through the myocardium. The advent of cardiac computed tomography angiography (CCTA), equipped with its multiplane and three-dimensional functionalities, has notably enhanced the ability to identify MBs. Furthermore, novel post-processing methods have recently emerged to extract functional insights from anatomical evaluations. MB is generally considered a benign entity with very good survival rates; however, there is an increasing volume of evidence that certain MB characteristics may be associated with cardiovascular morbidity. This review is intended to depict the diagnostic and prognostic role of CCTA in the MB context.

A Comprehensive Review of Myocardial Bridging: Exploring Diagnostic and Treatment Modalities

Myocardial bridging (MB) is a congenital coronary artery anomaly involving an overlying myocardium's partial or complete encasement of a coronary artery segment. The obstruction can lead to significant cardiac symptoms, resulting in myocardial ischemia, arrhythmia, and sudden cardiac death. Several approaches, including invasive and non-invasive methods, have been proposed to diagnose and manage MB. Invasive modalities, such as intravascular ultrasound (IVUS) and coronary angiography, offer high specificity and sensitivity. In contrast, non-invasive methods like Doppler ultrasound, multislice computed tomography (MSCT), and magnetic resonance imaging (MRI) are advantageous due to their non-invasive nature, high sensitivity and specificity, and cost-effectiveness. Treatment options for MB mainly focus on relieving symptoms and preventing adverse outcomes. The use of pharmacological agents and surgical and percutaneous interventions has been documented in numerous studies. Studies conclude that MB is a treatable cardiac anomaly, and a combined approach of diagnosis, treatment, and follow-up is necessary to reduce the morbidity and mortality associated with this condition.

Clinical Implication and Optimal Management of Myocardial Bridging: Role of Cardiovascular Imaging

Myocardial bridging (MB) was historically considered a benign structure as most people with MB are clinically asymptomatic. Recently, however, mounting evidence indicates that MB can cause adverse cardiac events owing to arterial systolic compression/diastolic restriction, atherosclerotic plaque progression upstream from MB, and/or vasospastic angina. In MB patients with refractory angina, the optimal treatment strategy should be determined individually based on versatile anatomic and hemodynamical assessments that often require multidisciplinary diagnostic approaches. The present review summarizes the clinical implication and management of MB, highlighting the role of imaging modalities currently available in this arena.

Prognostic impact of nitrate therapy in patients with myocardial bridge and coexisting coronary artery spasm

The aim of this study was to investigate the prognostic impact of nitrate therapy in patients with myocardial bridge (MB) and coexisting coronary artery spasm (CAS). MB often accompanies CAS. Nitrates have been widely used as anti-ischemic drugs in CAS patients, while it is not recommended in MB patients. Thus, we investigated the long-term impact of nitrate on clinical outcomes in patients with both CAS and MB. A retrospective observational study was performed using propensity score matching (PSM) in a total of 757 consecutive MB patients with positive acetylcholine (Ach) provocation test. Patients were divided into two groups according to the regular administration of nitrates (nitrate group: n = 504, No nitrate group; n = 253). The PSM was used to adjust for selection bias and potential confounding factors, and major clinical outcomes were compared between the two groups up to 5 years. Baseline characteristics were well-matched between the two groups following PSM (n = 211 for both groups). There was no significant difference in the incidence of death, myocardial infarction, and major adverse cardiovascular events (MACEs) between the two groups. However, the nitrate group showed a significantly higher rate of recurrent angina which subsequently needed re-evaluation of coronary arteries by follow-up angiography (15.7 vs. 5.7%, Log-rank p = 0.012) compared to the non-nitrate group. Long-term nitrate administration in patients with MB and coexisting CAS did not show benefit in reducing MACE, rather it was associated with a higher incidence of recurrent angina requiring follow-up angiography.

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.

The Impact of Myocardial Bridging on the Coronary Functional Test in Patients with Ischaemia with Non-Obstructive Coronary Artery Disease

Background: The possibility of myocardial bridging (MB) causing chest pain has been widely reported; however, the effect of MB on coronary microvessels has not been thoroughly investigated. Therefore, this study evaluated the effects of MB on epicardial coronary artery and coronary microvascular function during coronary angiography (CAG) and coronary function test (CFT) in patients with ischaemia with non-obstructive coronary artery disease (INOCA). Methods: This study included 62 patients with INOCA who underwent CAG and CFT for the left anterior descending coronary artery (LAD) to evaluate chest pain. In the CFT, acetylcholine was first administered intracoronarily in a stepwise manner, followed by chest symptoms, electrocardiographic ST-T changes and CAG. Positive coronary spasm was defined as coronary vasoconstriction of >90% on CAG accompanied by chest symptoms or electrocardiographic ST-T changes. After nitroglycerin administration, CAG was performed to assess MB, which was defined as systolic narrowing of the coronary artery diameter by >20% compared with that in diastole. Coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) were subsequently obtained via transvenous adenosine triphosphate infusion using a pressure wire. Coronary microvascular vasodilatory dysfunction (CMD) was defined as a CFR of <2.0 or an IMR of ≥25 units. Results: Of the 62 patients, 15 (24%) had MB. The patients’ characteristics did not differ between the two groups. Regarding the CAG and CFT results, the presence of coronary spasm in the LAD was higher in the MB (+) group (87%) than in the MB (−) group (53%, p = 0.02), whereas the values of CFR (MB (+): 2.7 ± 1.4, MB (−): 2.8 ± 1.1) and IMR (MB (+): 26.9 ± 1.0, MB (−): 30.0 ± 17.3) and the presence of CMD (MB (+): 53%, MB (−): 60%) were similar in the two groups. Conclusions: The findings suggest that MB predisposes patients with INOCA to coronary spasms. Conversely, MBs may have a limited effect on microvessels, particularly in such patients.

Rebound sign: a case report and review of literature

We reviewed previously reported imaging features of coronary air embolism. We also reported an unusual image 'rebound sign' of proximal coronary artery air embolism for the first time, that is, with the regular contraction and relaxation of the heart, the contrast medium near the embolus rebounds regularly, and the smooth gas-liquid boundary is alternately clear and blurred. We conclude that myocardial bridge plays a role in the formation of 'rebound sign.'Abbreviations: CAE: Coronary Air Embolism; CAG: Coronary Angiography; RCA: Right Coronary Artery; LCA: Left Coronary Artery; LAD: Left Anterior Descending Coronary Artery; LCX: Left Circumflex Artery; MB: Myocardial Bridge; STEMI: ST Segment Elevation Myocardial Infarction; TOE: Transesophageal Echocardiography.

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.

Implications of Myocardial Bridge on Coronary Atherosclerosis and Survival

Background: In this study, we aimed to describe the impact of MBs on atherosclerosis and survival, in patients with coronary artery disease (CAD). Methods: We retrospectively studied 1920 consecutive patients who underwent conventional coronary angiography for suspected CAD. Atherosclerotic load (AL), defined as the sum of degrees of stenosis, and general atherosclerotic load (GAL), representing the sum of AL, were compared between patients with MB and a control group without MB; patients in these groups were similar in age and sex. We assessed survival at 10 years after the last enrolled patient. Results: Prevalence of MB was 3.96%, predominantly in the mid-segment of left anterior descendent artery (LAD). In the presence of MB, GAL was lower (158.1 ± 93.7 vs. 205.3 ± 117.9, p = 0.004) with a lesser AL in the proximal (30.3 ± 39.9 vs. 42.9 ± 41.1, p = 0.038) and mid-segments (8.1 ± 20.0 vs. 25.3 ± 35.9, p < 0.001) of LAD. Based on a Multinominal Logistic Regression, we found that the presence of MB on LAD (regardless of its location on this artery) is a protective factor against atherosclerotic lesions, decreasing the probability of significant stenosis, especially of those ≥70%, on the entire artery (B −1.539, OR 4660; 95% CI = 1.873−11.595, p = 0.001) and on each of its segments as well: proximal LAD (B −1.275, OR 0.280; 95% CI = 0.015−5.073; p = 0.038), mid-LAD (B −1.879, OR 6.545; 95% CI = 1.492−28.712; p = 0.013) and distal LAD (B −0.900, OR 2.459, 95% CI = 2.459−2.459, p = 0.032). However, 10-year survival was similar between groups (76.70% vs. 74.30%, p = 0.740). Conclusion: The presence of MB on LAD proved to be a protective factor against atherosclerosis for the entire artery and for each of its segments, but it does not influence long-term survival in patients with CAD.

Coronary Flow Velocity Reserve Using Dobutamine Test for Noninvasive Functional Assessment of Myocardial Bridging

Background: It has been shown that coronary flow velocity reserve (CFVR) measurement by transthoracic Doppler echocardiography (TTDE) during dobutamine (DOB) provocation provides a more accurate functional evaluation of myocardial bridging (MB) compared to adenosine. However; the cut-off value of CFVR during DOB for identification of MB associated with myocardial ischemia has not been fully clarified. Purpose: This prospective study aimed to determine the cut-off value of TTDE-CFVR during DOB in patients with isolated-MB, as compared with stress-induced wall motion abnormalities (VMA) during exercise stress-echocardiography (SE) as reference. Methods: Eighty-one symptomatic patients (55 males [68%], mean age 56 ± 10 years; range: 27–74 years) with the existence of isolated-MB on the left anterior descending artery (LAD) and systolic MB-compression ≥50% diameter stenosis (DS) were eligible to participate in the study. Each patient underwent treadmill exercise-SE, invasive coronary angiography, and TTDE-CFVR measurements in the distal segment of LAD during DOB infusion (DOB: 10–40 μg/kg/min). Using quantitative coronary angiography, both minimal luminal diameter (MLD) and percent DS at MB-site at end-systole and end-diastole were determined. Results: Stress-induced myocardial ischemia with the occurrence of WMA was found in 23 patients (28%). CFVR during peak DOB was significantly lower in the SE-positive group compared with the SE-negative group (1.94 ± 0.16 vs. 2.78 ± 0.53; p < 0.001). ROC analyses identified the optimal CFVR cut-off value ≤ 2.1 obtained during high-dose dobutamine (>20 µg/kg/min) for the identification of MB associated with stress-induced WMA, with a sensitivity, specificity, positive and negative predictive value of 96%, 95%, 88%, and 98%, respectively (AUC 0.986; 95% CI: 0.967–1.000; p < 0.001). Multivariate logistic regression analysis revealed that MLD and percent DS, both at end-diastole, were the only independent predictors of ischemic CFVR values ≤2.1 (OR: 0.023; 95% CI: 0.001–0.534; p = 0.019; OR: 1.147; 95% CI: 1.042–1.263; p = 0.005; respectively). Conclusions: Noninvasive CFVR during dobutamine provocation appears to be an additional and important noninvasive tool to determine the functional severity of isolated-MB. A transthoracic CFVR cut-off ≤2.1 measured at a high-dobutamine dose may be adequate for detecting myocardial ischemia in patients with isolated-MB.

The fundamental role of stress echo in evaluating coronary artery disease in specific patient populations

Stress echocardiography (SE) was initially used for assessing patients with known or suspected coronary heart disease by detecting and evaluating myocardial ischemia and viability. The implementation of SE has gradually been extended to several cardiovascular diseases beyond coronary artery disease, and SE protocols have been modified and adapted for the detection of coronary artery disease (CAD) or other cardiovascular diseases in specific patient populations. This review attempts to summarize current data concerning SE implementation and clinical value in these specific and diverse populations: patients with an intramural course of a coronary artery - known as a myocardial bridge, chronic severe or end-stage hepatic disease, chronic severe or end-stage kidney disease, cardiac allograft vasculopathy, patients scheduled for solid-organ transplantation and other intermediate and high-risk surgery and, finally, patients treated with anticancer drugs or radiotherapy.

Myocardial Bridging: Diagnosis, Functional Assessment, and Management: JACC State-of-the-Art Review

Myocardial bridging (MB) is a congenital coronary anomaly in which a segment of the epicardial coronary artery traverses through the myocardium for a portion of its length. The muscle overlying the artery is termed a myocardial bridge, and the intramyocardial segment is referred to as a tunneled artery. MB can occur in any coronary artery, although is most commonly seen in the left anterior descending artery. Although traditionally considered benign in nature, increasing attention is being given to specific subsets of MB associated with ischemic symptomatology. The advent of contemporary functional and anatomic imaging modalities, both invasive and noninvasive, have dramatically improved our understanding of dynamic pathophysiology associated with MBs. This review provides a contemporary overview of epidemiology, pathobiology, diagnosis, functional assessment, and management of MBs.

Relationship Between Coronary Atheroma, Epicardial Adipose Tissue Inflammation, and Adipocyte Differentiation Across the Human Myocardial Bridge

Background Inflammation in epicardial adipose tissue (EAT) may contribute to coronary atherosclerosis. Myocardial bridge is a congenital anomaly in which the left anterior descending coronary artery takes a "tunneled" course under a bridge of myocardium: while atherosclerosis develops in the proximal left anterior descending coronary artery, the bridged portion is spared, highlighting the possibility that geographic separation from inflamed EAT is protective. We tested the hypothesis that inflammation in EAT was related to atherosclerosis by comparing EAT from proximal and bridge depots in individuals with myocardial bridge and varying degrees of atherosclerotic plaque. Methods and Results Maximal plaque burden was quantified by intravascular ultrasound, and inflammation was quantified by pericoronary EAT signal attenuation (pericoronary adipose tissue attenuation) from cardiac computed tomography scans. EAT overlying the proximal left anterior descending coronary artery and myocardial bridge was harvested for measurement of mRNA and microRNA (miRNA) using custom chips by Nanostring; inflammatory cytokines were measured in tissue culture supernatants. Pericoronary adipose tissue attenuation was increased, indicating inflammation, in proximal versus bridge EAT, in proportion to atherosclerotic plaque. Individuals with moderate-high versus low plaque burden exhibited greater expression of inflammation and hypoxia genes, and lower expression of adipogenesis genes. Comparison of gene expression in proximal versus bridge depots revealed differences only in participants with moderate-high plaque: inflammation was higher in proximal and adipogenesis lower in bridge EAT. Secreted inflammatory cytokines tended to be higher in proximal EAT. Hypoxia-inducible factor 1a was highly associated with inflammatory gene expression. Seven miRNAs were differentially expressed by depot: 3192-5P, 518D-3P, and 532-5P were upregulated in proximal EAT, whereas miR 630, 575, 16-5P, and 320E were upregulated in bridge EAT. miR 630 correlated directly with plaque burden and inversely with adipogenesis genes. miR 3192-5P, 518D-3P, and 532-5P correlated inversely with hypoxia/oxidative stress, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PCG1a), adipogenesis, and angiogenesis genes. Conclusions Inflammation is specifically elevated in EAT overlying atherosclerotic plaque, suggesting that EAT inflammation is caused by atherogenic molecular signals, including hypoxia-inducible factor 1a and/or miRNAs in an "inside-to-out" relationship. Adipogenesis was suppressed in the bridge EAT, but only in the presence of atherosclerotic plaque, supporting cross talk between the vasculature and EAT. miR 630 in EAT, expressed differentially according to burden of atherosclerotic plaque, and 3 other miRNAs appear to inhibit key genes related to adipogenesis, angiogenesis, hypoxia/oxidative stress, and thermogenesis in EAT, highlighting a role for miRNA in mediating cross talk between the coronary vasculature and EAT.

Complications associated with myocardial bridging in four children without underlying cardiac disease: a case series

BACKGROUND

Myocardial bridging is largely considered to be a benign, symptomless congenital anomaly of the coronary arteries in which the intramyocardial coronary course is partially 'tunnelled' and leads to vessel compression during ventricular systole. There are few data regarding children.

OBJECTIVE

To report on myocardial bridging observed in children seeking medical help in the paediatric emergency room.

CASE PRESENTATION

A series of four children aged 6-13 years with symptomatic myocardial bridging but no other underlying cardiac abnormalities is reported. They were admitted to the paediatric emergency department during 2013-2016, three with chest pain after physical activity and one with septic shock.

RESULTS

Heart computed tomography scan in the first three demonstrated myocardial bridging of the left anterior descendent coronary artery's branches; their 2-year follow-up was uneventful. The fourth patient presented with ventricular fibrillation 24 hours after admission and at autopsy there was an intramyocardial tract 4 cm long on the left anterior descendent coronary artery.

CONCLUSIONS

This case series demonstrates that myocardial bridging can be symptomatic in children with no underlying cardiac disorders and should be included in the differential diagnosis of exertional chest pain and/or arrhythmias.Abbreviations: CRP, C-reactive protein; CT, computed tomography; D1, diagonal 1 artery; ECG, electrocardiogram; ED, emergency department; KD, Kawasaki disease; LAD, left anterior descending coronary artery; MB, myocardial bridging; RI, ramus intermedius artery; TN, troponin.

Impact of Diastolic Vessel Restriction on Quality of Life in Symptomatic Myocardial Bridging Patients Treated With Surgical Unroofing: Preoperative Assessments With Intravascular Ultrasound and Coronary Computed Tomography Angiography

[Figure: see text].

Left anterior descending artery myocardial bridge manifesting as episodic, symptomatic exertional non-sustained ventricular tachycardia

A 48-year-old man presented to the emergency department (ED) with exertional chest pressure associated with palpitations and lightheadedness. He was found to have non-sustained ventricular tachycardia (NSVT) in the ED, which resolved spontaneously. Given his history of hyperlipidaemia, unknown family history due to being adopted and episode of NSVT in the ED, he underwent cardiac catheterisation, which showed non-obstructive coronary artery disease and distal left anterior descending artery myocardial bridge (MB). The patient subsequently underwent ECG treadmill stress test with reproduction of chest pressure and NSVT. The patient was referred to cardiac surgery for definitive management of symptomatic MB and underwent resection of MB.

Acute coronary syndrome caused by myocardial bridging

Myocardial bridging (MB) is a phenomenon that occurs when coronary arteries course through myocardial tissue rather than, as is normal, on the surface of the myocardium. Although often asymptomatic, contraction of the myocardium in the presence of a myocardial bridge can sometimes occlude the lumen of coronary arteries that penetrate the myocardium, resulting in symptoms, signs, and electrocardiographic changes indistinguishable from those associated with acute coronary syndromes (ACS) caused by intraluminal narrowing of coronary arteries or coronary artery plaque rupture. In this monograph, we present the case of a 45-year-old man who presented to the emergency department with typical chest pain accompanied by electrocardiographic changes consistent with acute occlusion of the left anterior descending artery. During percutaneous coronary intervention, fluoroscopically-obtained cine image loops revealed evidence of dynamic coronary artery narrowing due to myocardial bridging. There was no evidence of static coronary artery occlusion. Myocardial bridging is typically managed medically when symptomatic, although refractory cases may ultimately require invasive or surgical intervention. Given that emergency physicians are frequently the first providers to evaluate patients with acute coronary syndromes, myocardial bridging as an etiology for ACS is a clinical entity of which emergency physicians should be aware.

Surgical intervention and outcome for treatment of myocardial bridging refractory to medication

INTRODUCTION

Myocardial bridging (MB) is a common and usually benign inborn coronary abnormality that may lead to anginal symptoms, acute coronary syndrome, arrhythmias, and rarely sudden cardiac death. MB are most commonly localized in the middle segment of the left anterior descending coronary artery (LAD). The treatment of LAD-MB is still challenging. Our objective was to assess the short- and long-term results of surgical procedures in patients with LAD-MB who had chest pain refractory to medical therapy.

METHODS

Between March 2005 and January 2020, 26 patients (19 males and 7 females; mean 55.8 ± 12.4 years) with MB underwent surgery. All MB was located in the mid-segment of the LAD with a mean length of 4.2 ± 1.7 cm. Coronary angiography before surgery demonstrated LAD-MB with systolic compression more than or equal to 70% in all patients.

RESULTS

Twenty-five patients underwent myotomy and one patient underwent coronary artery bypass grafting (CABG). All patients survived and recovered uneventfully. Neither hospital or late death nor major complications occurred. Follow-up time was 3-173 months (mean 55.7 months). Follow-up of coronary angiography or computed tomography scan performed in 16 patients demonstrated restoration of coronary blood flow and myocardial perfusion without significant residual compression of the artery. All patients were symptom-free and are currently in NYHA Class I.

CONCLUSION

The symptomatic LAD-MB patients who are refractory to medication should actively undergo the surgical intervention such as myotomy and CABG to eliminate the clinical symptoms and achieve satisfactory results by follow-up findings. Myotomy is a preferred procedure because of its safety and satisfactory results.

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.

Evaluation of the morphological and clinical features of left anterior descending myocardial bridging with multi-detector computed tomography

Aim

The aim of the study was to assess the incidence, localization, depth, length of myocardial bridging (MB) with left anterior descending (LAD), systolic compression ratio, atherosclerotic plaque localization and degree of stenosis by 256-slice multi-detector computed tomography (MDCT).

Material and methods

Computed tomography (CT) scans from a total of 3947 patients who underwent MDCT were reviewed retrospectively for LAD MB. A diastolic and systolic dataset with the best image quality was selected. Myocardial bridge was defined as a coronary artery with an intra-myocardial course. Myocardial bridging was divided into “deep” or “superficial”. The length and depth of the bridging segment were calculated. For each bridging segment, the presence of atherosclerosis was saved in a 2-cm-long segment proximal to the entry of the bridging segment. The degree of stenosis made by atherosclerotic plaques was determined.

Results

LAD myocardial bridging was detected in 410 (10.4%) patients. Among these, 97 (23.7%) patients had a deep and 313 (76.3%) patients had a superficial course. The mean LAD MB length was 20.28 ±9.63 mm and the depth was 1.72 ±1.11 mm. The systolic and diastolic mean diameter difference was 0.193 mm and the average compression ratio was 9.44%. Atherosclerotic plaques were found in 167 (40.7%) of 410 LAD MB. Atherosclerotic plaques were found in 50.5% of deep MB and 37.7% of superficial MB.

Conclusions

256-slice MDCT coronary angiography has a high sensitivity to show myocardial bridging in LAD localization, to determine length, depth, compression ratio, atherosclerotic plaque localization and degree of stenosis.

Anomalous Coronary Arteries: When to Follow-up, Risk Stratify, and Plan Intervention

PURPOSE OF REVIEW

Coronary artery anomalies are a diverse group of entities, ranging from benign variations of normal anatomy to life-threatening conditions. There is, however, no universal consensus in their classification, risk stratification, and management. The aim of this review is to develop a straightforward clinical approach for the assessment and care of patients with anomalous coronary arteries.

RECENT FINDINGS

Autopsy series and population screening studies have recently provided useful clinical data on the prevalence and outcomes of coronary anomalies. Also, findings on coronary computed tomography angiography, magnetic resonance imaging, and invasive angiography, enriched with fractional flow reserve and intravascular ultrasound, have allowed identification of several high-risk features associated with specific coronary anomalies. Management of patients with anomalous coronary arteries requires an individualized approach based on clinical, physiological, and anatomic features. High-quality studies are paramount for further development of this fascinating field.

Left anterior descending myocardial bridge: Angiographic prevalence and its association to atherosclerosis

OBJECTIVE

Left anterior descending Myocardial Bridge (LADMB) is considered a benign condition and actually becomes a forgotten cause of serious cardiac events. This study was conducted to estimate the prevalence of LADMB and its association to atherosclerosis.

METHODS

An observational retrospective study was conducted on patients referred for coronary angiography between June 2012 and June 2020. Coronary angiography database was revisedand studied population was divided into 2 groups: LADMB group versus Non-LADMB group.

RESULTS

LADMB was detected in 510 patients out of 35813 included in the study resulting in a prevalence at 1.42%. The mean age was 66.5 years. Male gender was more common than female (70vs30%). The prevalence of significant atherosclerotic LAD disease was more than two times higher in the non-LADMB group compared to the LADMB group. Statistical analysis revealed a significant negative association between LADMB and atherosclerosis (p < 0.001). A significant greater rate of MINOCA cases was observed in acute coronary syndrome LADMB patients.

CONCLUSIONS

LADMB is an inborn anatomic variation associated to atherosclerotic risk reduction in LAD. Physicians must be aware about the potential complications and pay attention to those classified at high risk for cardiovascular events.

Functional Assessment of Myocardial Bridging With Conventional and Diastolic Fractional Flow Reserve: Vasodilator Versus Inotropic Provocation

Background

Functional assessment of myocardial bridging (MB) remains clinically challenging because of the dynamic nature of the extravascular coronary compression with a certain degree of intraluminal coronary reduction. The aim of our study was to assess performance and diagnostic value of diastolic‐fractional flow reserve (d‐FFR) during dobutamine provocation versus conventional‐FFR during adenosine provocation with exercise‐induced myocardial ischemia as reference.

Methods and Results

This prospective study includes 60 symptomatic patients (45 men, mean age 57±9 years) with MB on the left anterior descending artery and systolic compression ≥50% diameter stenosis. Patients were evaluated by exercise stress‐echocardiography test, and both conventional‐FFR and d‐FFR in the distal segment of left anterior descending artery during intravenous infusion of adenosine (140 μg/kg per minute) and dobutamine (10–50 μg/kg per minute), separately. Exercise–stress‐echocardiography test was positive for myocardial ischemia in 19/60 patients (32%). Conventional‐FFR during adenosine and peak dobutamine had similar values (0.84±0.04 versus 0.84±0.06, P=0.852), but d‐FFR during peak dobutamine was significantly lower than d‐FFR during adenosine (0.76±0.08 versus 0.79±0.08, P=0.018). Diastolic‐FFR during peak dobutamine was significantly lower in the exercise‐stress‐echocardiography test –positive group compared with the exercise‐ stress‐echocardiography test –negative group (0.70±0.07 versus 0.79±0.06, P<0.001), but not during adenosine (0.79±0.07 versus 0.78±0.09, P=0.613). Among physiological indices, d‐FFR during peak dobutamine was the only independent predictor of functionally significant MB (odds ratio, 0.870; 95% CI, 0.767–0.986, P=0.03). Receiver‐operating characteristics curve analysis identifies the optimal d‐FFR during peak dobutamine cut‐off ≤0.76 (area under curve, 0.927; 95% CI, 0.833–1.000; P<0.001) with a sensitivity, specificity, and positive and negative predictive value of 95%, 95%, 90%, and 98%, respectively, for identifying MB associated with stress‐induced ischemia.

Conclusions

Diastolic‐FFR, but not conventional‐FFR, during inotropic stimulation with high‐dose dobutamine, in comparison to vasodilatation with adenosine, provides more reliable functional significance of MB in relation to stress‐induced myocardial ischemia.

Myocardial Bridging, the Hidden Risk Factor for Ischemia

Myocardial bridging is an uncommon cause of a quite common emergency department complaint for chest pain and is often associated with left ventricular hypertrophy. We present a case of an otherwise healthy middle-aged U.S. military service member who presented with acute coronary syndrome which was ultimately determined to be the result of myocardial bridging.

Challenges in Evaluation and Management of Children with Myocardial Bridging

Myocardial bridging (MB) is a congenital anomaly where a coronary artery branch or group of branches extends inside a tunnel consisting of myocardium. Although it is mostly considered "benign," it is reported that MB may lead to significant cardiac problems and sudden cardiac deaths. While it is a congenital anomaly, its symptoms usually arise at further ages rather than childhood. The literature on MB in children is in the form of case reports or small case series. This is why pediatric cases are assessed in the light of information obtained from adults. This review compiled the literature on MB in adults and children and compared it, as well as discussing questions arising regarding the clinic, diagnosis, and treatment of MB.

Bridging the Gap in a Rare Cause of Angina

Myocardial bridging occurs when coronary arteries run intramurally. Episodes of tachycardia can cause a dynamic obstruction that extends into diastole, compromising coronary filling time, and subsequently leading to ischaemia. Myocardial ischaemia, acute coronary syndrome, coronary spasm, myocardial stunning, arrhythmia, takotsubo cardiomyopathy, and sudden cardiac death have all been reported with bridging. Atherosclerotic plaques develop proximally in the bridge due to low shear stress and high oscillatory wall-flow. Factors affecting atherosclerotic build-up include disrupted flow patterns (particularly flow recirculation, which exacerbates LDL internalisation), cell adhesion and monocyte adhesion to the endothelium. Endothelial health depends on arterial flow patterns, given that the vessel reacts differently to various flow types, as confirmed in 3D simulations. Medication is the first-line therapy, while surgical de-roofing and coronary bypass are reserved for severe stenosis. Distinguishing physiological arterial compression from pathological stenosis is essential. Deeper bridges correlating with recurrent angina with an instantaneous wave-free ratio ≤0.89 or fractional flow reserve ≤0.80 are treated.

Invasive assessment of myocardial bridging in patients with angina and no obstructive coronary artery disease

AIMS

Angina and no obstructive coronary artery disease (ANOCA) is common. A potential cause of angina in this patient population is a myocardial bridge (MB). We aimed to study the anatomical and haemodynamic characteristics of an MB in patients with ANOCA.

METHODS AND RESULTS

Using intravascular ultrasound (IVUS), we identified 184 MBs in 154 patients. We evaluated MB length, arterial compression, and halo thickness. MB muscle index (MMI) was defined as MB length×halo thickness. Haemodynamic testing of the MB was performed using an intracoronary pressure/Doppler flow wire at rest and during dobutamine stress. We defined an abnormal diastolic fractional flow reserve (dFFR) as ≤0.76 during stress. The median MB length was 22.9 mm, arterial compression 30.9%, and halo thickness 0.5 mm. The median MMI was 12.1. Endothelial and microvascular dysfunction were present in 85.4% and 22.1%, respectively. At peak dobutamine stress, 94.2% of patients had a dFFR ≤0.76 within and/or distal to the MB. MMI was associated with an abnormal dFFR.

CONCLUSIONS

In select patients with ANOCA who have an MB by IVUS, the majority have evidence of a haemodynamically significant dFFR during dobutamine stress, suggesting the MB as being a cause of their angina. A comprehensive invasive assessment of such patients during coronary angiography provides important diagnostic information that can guide management.

A case report of a coronary myocardial bridge with impaired full-cycle ratio during dobutamine challenge

Background

A myocardial bridge (MB) is a coronary variant in which an epicardial coronary artery tunnels through the myocardial band. Although MBs have been reported to cause ischaemia, physiological assessment of an MB has not been fully established.

Case summary

We encountered a case with exertional chest pain who underwent coronary angiography showing an MB at the mid-left anterior descending artery with systolic compression. Optical coherence tomography showed an MB defined as a homogeneous intermediate intensity surrounding the epicardial artery. The full-cycle ratio, defined as the lowest ratio of distal coronary pressure (P_d) to aortic pressure (P_a) during the entire cardiac cycle, measured 0.89 at rest and 0.73 with intravenous dobutamine of 20 µg/kg/min with a distinctive waveform pattern (early diastolic P_d drop) during a dobutamine challenge. Metoprolol succinate dosage was increased. The patient has been free from chest pain for 7 months after the discharge.

Discussion

Optical coherence tomography may contribute to anatomical detections of MBs. Because a systolic compression of the MB and release of the vascular lumen during early diastole leads to an early steep pressure loss, early diastolic P_d drop should be one of the specific haemodynamic characteristics of MBs. On the other hand, in a severe atherosclerotic stenosis, P_d drop is typically observed in late diastole, which could be differentiated from that of MBs. Because full-cycle ratio reflects the whole cardiac cycle including early diastole, this might be more useful than other physiological indices for detection of MB-related ischaemia induced by a dobutamine challenge.

Acute Myocardial Infarction Due to Fixed Coronary Artery Stenosis From Myocardial Bridging

Myocardial bridging is a common coronary abnormality often associated with left ventricular hypertrophy. It can be noted incidentally on coronary angiography by findings of systolic narrowing of the involved coronary artery. We present the case of a 59-year-old woman that presented with a non-ST elevation myocardial infarction. She had a history of angina and workup 9-months prior with CT coronary angiography that revealed an intra-myocardial course of the left anterior descending coronary artery (LAD) with minimal stenosis and no concomitant coronary artery disease. Invasive coronary angiography now demonstrated apparent myocardial bridging associated with a severe fixed stenosis of the LAD without change in diameter with nitroglycerin injection. Due to persistent symptoms, surgical myotomy was attempted and then aborted because of difficulty unroofing the LAD due to surrounding fibrosis. Coronary artery bypass grafting (CABG) was then successfully performed using a left internal mammary artery graft. The patient had complete resolution of her chest pain and was without functional limitation at 3-month follow-up. This case highlights possible sequelae of myocardial bridging and suggests that, in rare cases, fixed obstruction of the involved coronary artery may occur in the setting of fibrosis of the bridged segment. In such cases, surgical myotomy may not be feasible and CABG may be required.

Dose-Response Relationship Between Intracoronary Acetylcholine and Minimal Lumen Diameter in Coronary Endothelial Function Testing of Women and Men With Angina and No Obstructive Coronary Artery Disease

BACKGROUND

Intracoronary acetylcholine (Ach) provocation testing is the gold standard for assessing coronary endothelial function. However, dosing regimens of Ach are quite varied in the literature, and there are limited data evaluating the optimal dose. We evaluated the dose-response relationship between Ach and minimal lumen diameter (MLD) by sex and studied whether incremental intracoronary Ach doses given during endothelial function testing improve its diagnostic utility.

METHODS

We evaluated 65 men and 212 women with angina and no obstructive coronary artery disease who underwent endothelial function testing using the highest tolerable dose of intracoronary Ach, up to 200 μg. Epicardial endothelial dysfunction was defined as a decrease in MLD >20% after intracoronary Ach by quantitative coronary angiography. We used a linear mixed effects model to evaluate the dose-response relationship. Deming regression analysis was done to compare the %MLD constriction after incremental doses of intracoronary Ach.

RESULTS

The mean age was 53.5 years. Endothelial dysfunction was present in 186 (68.1%). Among men with endothelial dysfunction, there was a significant decrease in MLD/10 µg of Ach at doses above 50 μg and 100 µg, while this decrease in MLD was not observed in women (P<0.001). The %MLD constriction at 20 μg versus 50 μg and 50 μg versus 100 μg were not equivalent while the %MLD constriction at 100 μg versus 200 μg were equivalent.

CONCLUSIONS

Women and men appear to have different responses to Ach during endothelial function testing. In addition to having a greater response to intracoronary Ach at all doses, men also demonstrate an Ach-MLD dose-response relationship with doses up to 200 μg, while women have minimal change in MLD with doses above 50 µg. An incremental dosing regimen during endothelial function testing appears to improve the diagnostic utility of the test and should be adjusted based on the sex of the patient.

Associations of myocardial bridging with adverse cardiac events: a meta-analysis of published observational cohort studies involving 4,556 individuals

Background

Data derived from small series have demonstrated an association of myocardial bridge (MB) with adverse cardiac events, while MB has been traditionally considered as a benign condition. Hence, the precise clinical implications of MB on prognosis remains inconsistent. Our purpose is to perform a meta-analysis to assess the clinical implications of MB on prognosis.

Methods

We performed an extensive search of PubMed and reference lists of relevant articles. Studies which compared prognosis between subjects with and without MB were identified from 1960 to 31 March 2018. Studies selection was limited to human data and restricted to English language.

Results

Six eligible studies were included in current meta-analysis. Of 4,556 subjects, 1,389 (30.5%) presented MB. MB was associated with an increased risk of adverse cardiac events [odds ratio (OR), 1.71; 95% confidence interval (CI): 1.29 to 2.26; P=0.0002], non-fatal myocardial infarction (OR: 3.17; 95% CI: 1.21 to 8.31; P=0.02), and angina requiring hospitalization (OR: 2.31; 95% CI: 1.55 to 3.45; P<0.0001), respectively, compared with subjects without MB.

Conclusions

This meta-analysis of currently available observational cohort studies suggests that MB has an association with adverse cardiac events. Further prospective multicenter studies with large sample size are needed to confirm current findings. Moreover, studies refining the impact of different types of MB on cardiac events, myocardial ischemia, and symptoms requiring therapy, may provide more insights to this issue.

An Updated Review on Myocardial Bridging

Myocardial bridging is a congenital coronary anomaly with normal epicardial coronary artery taking an intra-myocardial course also described as tunneled artery. The majority of patients with this coronary anomaly are asymptomatic and generally it is a benign condition. However, it is an important cause of myocardial ischemia, which may lead to anginal symptoms, acute coronary syndrome, cardiac arrhythmias and rarely sudden cardiac death. There are numerous studies published in the recent past on understanding the pathophysiology, diagnostic and management strategies of myocardial bridging. This review highlights some of the recent updates in the diagnosis and management of patients with myocardial bridging. We discuss the role of various non-invasive and invasive diagnostic methods to evaluate functional significance of bridging. In addition, role of medical therapy such as beta-blockers, percutaneous coronary intervention with stents/bioresorbable scaffolds and surgical unroofing in patients unresponsive to medical therapy is highlighted as well.

Accuracy of a novel stress echocardiography pattern for myocardial bridging in patients with angina and no obstructive coronary artery disease - A retrospective and prospective cohort study

BACKGROUND

Myocardial bridge (MB) may cause angina in patients with no obstructive coronary artery disease (CAD). We previously reported a novel stress echocardiography (SE) pattern of focal septal buckling with apical sparing in the end-systolic to early-diastolic phase that is associated with the presence of an MB. We evaluated the diagnostic accuracy of this pattern, and prospectively validated our results.

METHODS

The retrospective cohort included 158 patients with angina who underwent both SE and coronary CT angiography (CCTA). The validation cohort included 37 patients who underwent CCTA in the emergency department for angina, and prospectively underwent SE. CCTA was used as a reference standard for the presence/absence of an MB, and also confirmed no obstructive CAD.

RESULTS

In the retrospective cohort, an MB was present in 107 (67.7%). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 91.6%, 70.6%, 86.7% and 80%, respectively. On logistic regression, focal septal buckling and Duke treadmill score were associated with an MB. In the validation cohort, an MB was present in 31 (84%). The sensitivity, specificity PPV and NPV were 90.3%, 83.3%, 96.5% and 62.5%, respectively. On logistic regression, focal septal buckling was associated with an MB.

CONCLUSION

Presence of focal septal buckling with apical sparing on SE is an accurate predictor of an MB in patients with angina and no obstructive CAD. This pattern can reliably be used to screen patients who may benefit from advanced non-invasive/invasive testing for an MB as a cause of their angina.

Ischemia and No Obstructive Coronary Artery Disease: Prevalence and Correlates of Coronary Vasomotion Disorders

BACKGROUND

Determine the prevalence and correlates of microvascular and vasospastic angina in patients with symptoms and signs of ischemia but no obstructive coronary artery disease (INOCA).

METHODS

Three hundred ninety-one patients with angina were enrolled at 2 regional centers over 12 months from November 2016 (NCT03193294). INOCA subjects (n=185; 47%) had more limiting dyspnea (New York Heart Association classification III/IV 54% versus 37%; odds ratio [OR], 2.0 [1.3-3.0]; P=0.001) and were more likely to be female (68% INOCA versus 38% in coronary artery disease; OR, 1.9 [1.5 to 2.5]; P<0.001) but with lower cardiovascular risk scores (ASSIGN score median 20% versus 24%; P=0.003). INOCA subjects had similar burden of angina (Seattle Angina Questionnaire) but reduced quality of life compared with coronary artery disease; subjects (EQ5D-5 L index 0.60 versus 0.65 units; P=0.041).

RESULTS

An interventional diagnostic procedure with reference invasive tests including coronary flow reserve, microvascular resistance, and vasomotor responses to intracoronary acetylcholine (vasospasm provocation) was performed in 151 INOCA subjects. Overall, 78 (52%) had isolated microvascular angina, 25 (17%) had isolated vasospastic angina, 31 (20%) had both, and 17 (11%) had noncardiac chest pain. Regression analysis showed inducible ischemia on treadmill testing (OR, 7.5 [95% CI, 1.7-33.0]; P=0.008) and typical angina (OR, 2.7 [1.1-6.6]; P=0.032) were independently associated with microvascular angina. Female sex tended to associate with a diagnosis of microvascular angina although this was not significant (OR, 2.7 [0.9-7.9]; P=0.063). Vasospastic angina was associated with smoking (OR, 9.5 [2.8-32.7]; P<0.001) and age (OR, 1.1 per year, [1.0-1.2]; P=0.032].

CONCLUSIONS

Over three quarters of patients with INOCA have identifiable disorders of coronary vasomotion including microvascular and vasospastic angina. These patients have comparable angina burden but reduced quality of life compared to patients with obstructive coronary artery disease. Microvascular angina and vasospastic angina are distinct disorders that may coexist but differ in associated clinical characteristics, symptoms, and angina severity.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT03193294.

Comparison of detection percentage and morphology of myocardial bridge between conventional coronary angiography and coronary CT angiography

Introduction: Myocardial bridge (MB) is a congenital anomaly in which a segment of a coronary artery is surrounded by myocardium. In our study, we want to use conventional coronary angiography (CCA) to describe morphologic characteristics of MB (unidentified or identified) in the patients with documented evidence of MB in coronary computed tomography angiography (CCTA). Methods: The present study was designed as cross-sectional and was conducted on 47 patients with documented evidence of MB in CCTA, who were referred to Nemazee and Faghihi hospitals for performing coronary angiography during a one year period. We compared the morphologic characteristics of tunneled segments, which were missed at CCA (unidentified), and the tunneled segments which were identified with CCA. Results: In sum, MB was found in 16 (34%) patients at CCA (identified), and it was not found in 31 (66%) patients (unidentified) based on compression sign. No significant correlation was found between the percentage of systolic compression and the length and depth of the tunneled segment in identified group (r=0.73, P = 0.18; r=1.09, P = 0.15; respectively). Degree of atherosclerotic plaque formation (diameter stenosis, percentage) (mean, 0.25 (25%) ±0.29; range, 0-0.98) of the tunneled segments in unidentified group was significantly more than the same degree (mean, 0.07 (7%) ±0.13; range, 0-0.41) of the identified group (P = 0.03). The measurement of the trapezoid area under the tunneled segment with this formula [(MB length+ intramyocardial segment) ×depth/2] had significant relation with systolic compression (r=0.304, P = 0.03) and defined the cut-off value of 250 mm² as the value of significant difference in detecting myocardial bridging with CCA. Conclusion: Our results showed that in most of identified MBs in CCA the tunneled segment area was equal and more than 250 mm². In addition, the degree of atherosclerotic plaque of the tunneled segments at CCA was significantly more in unidentified group.

Asymmetric dimethylarginine predicts impaired epicardial coronary vasomotion in patients with angina in the absence of obstructive coronary artery disease

BACKGROUND

Impaired epicardial coronary vasomotion is a potential mechanism of angina and a predictor of adverse cardiovascular outcomes in patients without angiographic evidence of obstructive coronary artery disease (CAD). We sought to evaluate the association of asymmetric dimethylarginine (ADMA)-a marker of nitric oxide-mediated vascular dysfunction-with epicardial coronary vasomotor dysfunction in this select population.

METHODS

Invasive testing for epicardial vasomotor dysfunction was performed using intracoronary acetylcholine in the left anterior descending coronary artery. Impaired vasomotor response was defined as a luminal constriction of >20% on quantitative coronary angiography. Plasma ADMA levels were measured using high performance liquid chromatography. A robust multivariate linear mixed-effect model approach and Akaike information criterion were used to determine predictors of vasomotor dysfunction.

RESULTS

In 191 patients with angina in the absence of obstructive CAD, abnormal epicardial vasomotion was observed in 137 (71.7%) patients. Median ADMA rose as the extent of impairment progressed: none (0.48 [0.44-0.59] μM), any (0.51 [0.46-0.60] μM, p = 0.12), focal (0.54 [0.49,0.61] μM, p = 0.17), and diffuse (0.55 [0.49,0.63] μM, p = 0.02). In unadjusted analysis, ADMA was highly predictive of vasomotor dysfunction (χ²=15.1, p = 0.002). Notably, ADMA remained a significant predictor even after adjusting for other factors in the best fit model (χ²=10.0, p = 0.02).

CONCLUSIONS

ADMA is an independent predictor of epicardial coronary vasomotor dysfunction in patients with angina in the absence of obstructive CAD. These data support a very early mechanistic role of ADMA in the continuum of atherosclerotic heart disease.

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.

Longitudinal strain measured by two-dimensional speckle tracking echocardiography to evaluate left ventricular function in patients with myocardial bridging of the left anterior descending coronary artery

OBJECTIVES

Myocardial bridging (MB) can cause myocardial ischemia, myocardial infarction, or even sudden cardiac death. We aimed to evaluate the left ventricular function in patients with MB of the left anterior descending coronary artery (LAD) using longitudinal strain (LS) measured by two-dimensional speckle tracking echocardiography.

METHODS

We enrolled 46 subjects with MB in the LAD diagnosed by coronary angiography. Patients were categorized into two groups according to the severity of tunneled artery stenosis: <50% as group I (23 patients) and ≥50% as group II (23 patients). Twenty-five gender- and age-matched subjects without MB confirmed by coronary angiography or with normal results on treadmill exercise test were included as controls. Two-dimensional strain software was applied to measure the territories systolic average peak LS of the LAD coronary artery (LAD-TPLS), right coronary artery (RCA-TPLS), and left circumflex coronary artery (LCX-TPLS) and to measure the global systolic peak LS of left ventricle (LV-GPLS).

RESULTS

The ratio of mitral peak early (E) and late (A) filling velocity (E/A) and the average mitral annular velocity (e') were lower, and the mitral E/e' ratio was higher in group II than in group I and controls (P < 0.05). LV-GPLS and LAD-TPLS were significantly less negative in group II than in group I and controls (LV-GPLS: -19.77 ± 1.60% vs -21.10 ± 1.91% and -21.76 ± 1.23%; LAD-TPLS: -19.24 ± 2.22% vs -22.00 ± 2.22% and -22.74 ± 1.82%, P < 0.001). The systolic compression severity of the tunneled artery was significantly correlated with LAD-TPLS (r = -0.56, P < 0.001), but less strongly correlated with LV-GPLS (r = -0.40, P < 0.05). The area under the curves of LAD-TPLS was larger than that of LV-GPLS; a cutoff value for LAD-TPLS of -21.68% had 91.3% sensitivity and 73.9% specificity for detection of ≥50% of the tunneled artery stenosis.

CONCLUSIONS

In patients with ≥50% systolic narrowing of the tunneled artery, left ventricular systolic function and diastolic function were impaired, and the LAD-TPLS is an excellent predictor of ≥50% systolic narrowing of the tunneled artery in patients with MB of the LAD.

The Myocardial Bridge: Potential Influences on the Coronary Artery Vasculature

A myocardial bridge (MB) is an anatomical abnormality of the coronary artery and is characterized by the systolic narrowing of the epicardial coronary artery caused by myocardial compression during systole. An MB is frequently observed on cardiac computed tomography or coronary angiography and generally appears to be harmless in the majority of patients. However, the presence of MB is reportedly associated with abnormalities of the cardiovascular system, including coronary artery diseases, arrhythmia, certain types of cardiomyopathy, and cardiac death, indicating that MB serves a pivotal role in the occurrence and/or development of such cardiovascular events. Recently, there has been an increasing interest in the coexistence of MB and coronary spasm in research due to opposing aspects regarding their treatments. For example, monotherapy using β-blockers, which are effective in patients with MB, may worsen symptoms in patients with coronary spasm. By contrast, nitroglycerin, which is an effective treatment option for coronary spasm, may worsen symptoms in patients with MB. This review focuses on the pathophysiology and diagnosis of MB and MB-related cardiovascular diseases, including coronary spasm, and on the treatment strategies for MB.