Settlement of Stenotic Site and Enhancement of Risk Factor Load for Atherosclerosis in Left Anterior Descending Coronary Artery by Myocardial Bridge

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.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Methodology of generation of CFD meshes and 4D shape reconstruction of coronary arteries from patient-specific dynamic CT

Due to the difficulties in retrieving both the time-dependent shapes of the vessels and the generation of numerical meshes for such cases, most of the simulations of blood flow in the cardiac arteries use static geometry. The article describes a methodology for generating a sequence of time-dependent 3D shapes based on images of different resolutions and qualities acquired from ECG-gated coronary artery CT angiography. The precision of the shape restoration method has been validated using an independent technique. The original proposed approach also generates for each of the retrieved vessel shapes a numerical mesh of the same topology (connectivity matrix), greatly simplifying the CFD blood flow simulations. This feature is of significant importance in practical CFD simulations, as it gives the possibility of using the mesh-morphing utility, minimizing the computation time and the need of interpolation between boundary meshes at subsequent time instants. The developed technique can be applied to generate numerical meshes in arteries and other organs whose shapes change over time. It is applicable to medical images produced by other than angio-CT modalities.

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.

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.

Incidence and Morphological Study of Myocardial Bridge in the State of Ceará: A Cadaveric Study

BACKGROUND

Myocardial bridges (MB) are anatomical anomalies with possible clinical repercussions; hence, their understanding deserves attention.

OBJECTIVE

To determinate the prevalence and characterize MB in human hearts from the state of Ceará. Methods: Fifty hearts of adult human cadavers from the Medicine School of Federal University of Ceará, Brazil. The hearts were dissected to identify MBs that pass over part of the coronary artery. The segment of the artery (proximal, middle, and distal) with a bridge was identified. The external diameter of the artery at the proximal and distal points of the MB was measured. The length and thickness of the MB were also measured with an electronic caliper. The muscle index (MMI) of the MB was calculated as the product of length and thickness expressed in millimeters. The significance level adopted in the statistical analysis was 5%.

RESULTS

MB was confirmed in 40% of sample. Approximately one third of the sample had only 1 MB. MB was most frequently found over the anterior interventricular branch of the left coronary artery (59.25%, p=0.02), and its prevalence in other branches was much lower (22.23%). The most affected segments of arteries were the superior (44.44%) and medium (40.74%). The mean diameter of arteries proximal to the MB was 2.38±0.97mm (range=0.78-5.15mm), and the diameter distal to the MB was 1.71±0.75mm (range=0.42-3.58mm). The length was measured as mean=8.55±5.27mm, while the mean thickness was 0.89±0.33mm.

CONCLUSION

A high prevalence of MB is more likely to affect the left coronary artery system with larger MMI than other affected branches.

Assessment of myocardial bridging and the pericoronary fat attenuation index on coronary computed tomography angiography: predicting coronary artery disease risk

BACKGROUND

The fat attenuation index (FAI) is a radiological parameter that represents pericoronary adipose tissue (PCAT) inflammation, along with myocardial bridging (MB), which leads to pathological shear stress in the coronary vessels; both are associated with coronary atherosclerosis. In the present study, we assessed the predictive value of FAI values and MB parameters through coronary computed tomography angiography (CCTA) for predicting the risk of coronary atherosclerosis and vulnerable plaque in patients with MB.

METHODS

We included 428 patients who underwent CCTA and were diagnosed with MB. FAI values, MB parameters, and high-risk coronary plaque (HRP) characteristics were recorded. The subjects were classified into two groups (A and B) according to the absence or presence of coronary plaque in the segment proximal to the MB. Group B was further divided into Groups B₁ (HRP-positive) and B₂ (HRP-negative) according to the HRP characteristic classification method. The differences among the groups were analysed. Multiple logistic regression analysis was performed to determine the independent correlation between FAI values and MB parameters and coronary atherosclerosis and vulnerable plaque risk.

RESULTS

Compared to the subjects in Group A, those in Group B presented greater MB lengths, MB depths and muscle index values, more severe MB systolic stenosis and higher FAI_lesion values (all P < 0.05). In multivariate logistic analysis, age (OR 1.076, P < 0.001), MB systolic stenosis (OR 1.102, P < 0.001) and FAI_lesion values (OR 1.502, P < 0.001) were independent risk factors for the occurrence of coronary atherosclerosis. Compared to subjects in Group B₂, those in Group B₁ presented greater MB lengths and higher FAI values (both P < 0.05). However, only the FAI_lesion value was an independent factor for predicting HRP (OR 1.641, P < 0.001).

CONCLUSION

In patients with MB, MB systolic stenosis was associated with coronary plaque occurrence in the segment proximal to the MB. The FAI value was not only closely related to coronary atherosclerosis occurrence but also associated with plaque vulnerability. FAI values may provide more significant value in the prediction of coronary atherosclerosis than MB parameters in CCTA.

Colocalization of Coronary Plaque with Wall Shear Stress in Myocardial Bridge Patients

PURPOSE

Patients with myocardial bridges (MBs) have a higher prevalence of atherosclerosis. Wall shear stress (WSS) has previously been correlated with plaque in coronary artery disease patients, but such correlations have not been investigated in symptomatic MB patients. The aim of this paper was to use a multi-scale computational fluid dynamics (CFD) framework to simulate hemodynamics in MB patient, and investigate the co-localization of WSS and plaque.

METHODS

We identified N = 10 patients from a previously reported cohort of 50 symptomatic MB patients, all of whom had plaque in the proximal vessel. Dynamic 3D models were reconstructed from coronary computed tomography angiography (CCTA), intravascular ultrasound (IVUS) and catheter angiograms. CFD simulations were performed to compute WSS proximal to, within and distal to the MB. Plaque was quantified from IVUS images in 2 mm segments and registered to CFD model. Plaque area was compared to absolute and patient-normalized WSS.

RESULTS

WSS was lower in the proximal segment compared to the bridge segment (6.1 ± 2.9 vs. 16.0 ± 7.1 dynes/cm², p value < 0.01). Plaque area and plaque burden measured from IVUS peaked at 1-3 cm proximal to the MB entrance, coinciding with the first diagonal branch. Normalized WSS showed a statistically significant moderate correlation with plaque area (r = 0.41, p < 0.01).

CONCLUSION

WSS may be obtained non-invasively in MB patients and provides a surrogate marker of plaque area. Using CFD, it may be possible to non-invasively assess the extent of plaque area, and identify patients who could benefit from frequent monitoring or medical management.

Comparison of Framingham risk score and atherogenic indices as a predictor of atherosclerosis in patients with myocardial bridge in left anterior descending artery

BACKGROUND

Myocardial bridge (MB) is generally considered as a benign condition, but it may trigger atherosclerosis, especially in the adjacent proximal coronary artery segment. In this study, we aimed to investigate whether the Framingham risk score (FRS) or atherogenic indices are risk factors for coronary atherosclerosis in patients with MB in the left anterior descending coronary artery (LAD).

METHODS

We performed a retrospective study evaluating 155 patients who have MB in LAD. The patients were evaluated in two groups according to the presence of atherosclerosis (74 patients in atherosclerotic group vs. 81 patients in non-atherosclerotic group). Baseline characteristics, FRS and atherogenic indices were reviewed between groups. Significant independent risk factors for coronary atherosclerosis were investigated by logistic regression analysis.

RESULTS

Patients in atherosclerotic group were significantly older (58.15 ± 10.04 vs. 50.22 ± 9.27 years, p < .001) and 74.3% of the patients were male. While the mean FRS in the atherosclerotic group was 21.20 ± 8.81, it was 12.79 ± 8.61 in the non-atherosclerotic group (p < .001). Among the atherogenic indices, only LDL-c/HDL-c ratio was significantly higher in the atherosclerotic group (3.49 ± 1.2 vs. 3.11 ± 0.98, p:.033). Multivariable analysis showed that age (OR: 1.08, 95% CI 1.03-1.13, p < .001) and FRS (OR: 1.06, 95% CI 1.01-1.11, p:.012) were independently associated with the presence of atherosclerotic lesion.

CONCLUSIONS

FRS is an easily applicable predictor in clinical practice that indicates the presence of coronary atherosclerosis in patients with MB in LAD.

Influence of myocardial bridge on atherosclerotic plaque distribution and characteristics evaluated by near-infrared spectroscopy intravascular ultrasound

BACKGROUND

This study aims to clarify whether myocardial bridge (MB) could influence atherosclerotic plaque characteristics assessed using near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) imaging.

METHODS

One hundred and sixteen patients who underwent percutaneous coronary intervention (PCI) using NIRS-IVUS imaging were included. MB was defined as an echo-lucent band surrounding left anterior descending artery (LAD). In MB patients, LAD was divided into three segments: proximal, MB, and distal segments. In non-MB patients, corresponding three segments were defined based on the average length of the above segments. Segmental maximum plaque burden and lipid content derived from NIRS-IVUS imaging in the section of maximum plaque burden were evaluated in each segment. Lipid content of atherosclerotic plaque was evaluated as lipid core burden index (LCBI) and maxLCBI_4mm. LCBI is the fraction of pixels indicating lipid within a region multiplied by 1000, and the maximum LCBI in any 4-mm region was defined as maxLCBI_4mm.

RESULTS

MB was identified in 42 patients. MB was not associated with maximum plaque burden in proximal segment. LCBI and maxLCBI_4mm were significantly lower in patients with MB than those without in proximal segment. Multivariable analysis demonstrated both MB and maximum plaque burden in proximal segment to be independent predictors of LCBI in proximal segment.

CONCLUSIONS

Lipid content of atherosclerotic plaque assessed by NIRS-IVUS imaging was significantly smaller in patients with MB than those without. MB could be considered as a predictor of lipid content of atherosclerotic plaque when assessed by NIRS-IVUS imaging.

Myocardial bridges: A meta-analysis

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

Coronary Plaque Characteristics and Cut-Off Stenosis for Developing Spasm in Patients with Vasospastic Angina

Coronary plaque distribution, frequency and cut-off value of percent stenosis for developing vasospasm are uncertain in patients with vasospastic angina (VA). We enrolled 2960 patients who received coronary angiography (CAG) and ergonovine provocation test prospectively in 11 university hospitals in Korea. A total of 1836 patients with VA and 867 without VA were included. Plaque and % stenosis were defined as ≥1% luminal narrowing and mean of each segmental stenosis. Overall frequency of plaque and % diameter stenosis was compared among VA-patients with index coronary spasm positive, those with index arterial spasm negative/other arterial spasm positive (INOP) and non-VA patients. Diameter stenosis associated with the spasm positivity was investigated. Overall plaque frequency and % stenosis were higher in VA patients than non-VA patients. Plaque frequency was 27.6% (243/881) in spasm positive at LAD, 16.4% (157/955) in LAD INOP and 12.6% (109/867) in non-VA with statistic difference (P < 0.001). Same trend for higher rate was observed in LCx and RCA. For % stenosis, 36.6 vs 32.4% (p = 0.010) in LAD, 36.1 vs. 28% (p < 0.001) in LCx and 35.3 vs.30.0% (p = 0.047) in RCA, respectively. Diameter stenosis of LAD with spasm positive vs. LAD INOP vs. non-VA were 38.3%, 34.0%, 32% (P = 0.002) with similar pattern in LCx and RCA. By multivariate logistic regression analysis, coronary stenosis of LAD ≥ 35% or LCx ≥35% or RCA ≥ 40% were independent predictor of developing spasm (OR 2.019, 95% CI 1.315–3.100, P = 0.001). In conclusions, spastic coronary artery had more plaque frequency, higher % stenosis than in non-spastic coronary in VA patients. The spasm related and unrelated coronary in VA patients had more plaque than in matched and unmatched coronary arteries in non-VA patients. Coronary stenosis ≥35% in LAD and LCx was an independent predictor of developing spasm.

Impact of myocardial bridge on late lumen enlargement in distal reference segments after recanalization of coronary chronic total occlusion

Successful recanalization of coronary chronic total occlusion (CTO) can induce subsequent positive vascular remodeling. Although myocardial bridge (MB) is known to alter endothelial function and wall shear stress, the impact of MB on late lumen enlargement in the distal segment is unclear. A total of 59 patients who underwent successful percutaneous coronary intervention (PCI) for CTO in the left anterior descending artery (LAD) under intravascular ultrasound (IVUS) guidance and follow-up angiography at 8-12 months were included. Gray-scale IVUS images were analyzed and MB was detected. Lumen diameter (LD) at distal reference at post-PCI was quantitatively compared with corresponding LD at follow-up coronary angiography to assess late lumen enlargement. MB on IVUS was detected in 17 patients (29%). The length from LAD ostium to the entry of CTO was shorter (11.7 ± 13.9 vs. 22.8 ± 13.4 mm, p = 0.006) and LD at distal reference at post-PCI was smaller (1.65 ± 0.54 vs. 1.97 ± 0.56 mm, p = 0.049) in patients with MB than those without. At the mean follow-up of 10.4 ± 2.4 months, LD at distal reference was significantly increased by 25% from baseline to follow-up in the overall population (1.88 ± 0.57 vs. 2.21 ± 0.41 mm, p < 0.001), with a greater increase in patients with MB compared to those without (46 ± 31% vs. 17 ± 29%, p < 0.001). Multivariable analysis indicated MB as an independent predictor of late lumen enlargement. In patients with MB on IVUS, CTO was located in more proximal segment of LAD than those without. Late lumen enlargement at follow-up was greater in patients with MB compared to the counterpart.

Clinical characteristics and factors associated with coronary stenosis proximal to a myocardial bridge: a retrospective study

BACKGROUND

The association of myocardial bridge (MB) with cardiovascular risk and the possible cardiovascular risk factors remain unclear. This study aimed to explore the clinical characteristics and related factors of coronary stenosis proximal to an MB.

METHODS

This was a retrospective study of patients with symptoms of coronary atherosclerotic heart disease admitted between 10/2011 and 12/2014 to the Emergency and Cardiology Department of Bayannur Hospital, who underwent selective coronary angiography (SCAG). The patients were assigned to the non-stenosis and stenosis groups according to whether coronary stenosis was proximal to the MB.

RESULTS

Among 244 patients with MB and cardiovascular symptoms, 91 (37.3%) had stenosis proximal to the MB. Compared with the non-stenosis group, there were more males (80.2% vs. 55.6%, P < 0.001) and smokers (including those who had quit smoking) (P < 0.001) in the stenosis group. There were no significant differences in blood lipid-related indexes (TG, TC, HDL-C, LDL-C, and VLDL-C) between the two groups. Multivariable analysis suggested that MB location in the middle distal or distal segment of the left anterior descending artery (LAD) increased the odds of coronary stenosis proximal to the MB (OR = 0.439, 95% CI: 1.57-7.532, P = 0.002), which was then considered an independent factor associated with coronary stenosis proximal to the MB.

CONCLUSIONS

In patients diagnosed with an MB by SCAG, only MB located in the middle distal or distal segment of the LAD is independently associated with coronary stenosis proximal to the MB.