Importance of diastolic fractional flow reserve and dobutamine challenge in physiologic assessment of myocardial bridging

Myocardial Bridging as a Trigger in Angina With No Obstructive Coronary Artery Disease

We present 2 patients with angina with no obstructive coronary artery disease and concomitant myocardial bridging. Despite maximal tolerated pharmacotherapy, symptoms remained. Invasive anatomical and hemodynamic assessment identified myocardial bridging as a contributing cause of angina. Following heart team discussion, both patients underwent successful coronary artery unroofing of the left anterior descending artery.

Prevalence of Coronary Vasomotor Disorders in Patients With Angina and Nonobstructive Coronary Arteries: A Sydney Experience

BACKGROUND

Patients with angina and non-obstructive coronary arteries (ANOCA) frequently have coronary vasomotor disorders (CVaD), characterised by transient pathological vasoconstriction and/or impaired microvascular vasodilatation. Functional coronary angiography is the gold standard for diagnosing CVaD. Despite recommendations, testing is only available at a limited number of Australian and New Zealand centres. This study aimed to determine the prevalence of CVaDs in an Australian ANOCA population and identify predictive factors associated with specific endotypes.

METHOD

Functional coronary angiography was performed in patients with suspected ANOCA. Vasoreactivity testing was performed using intracoronary acetylcholine provocation. A pressure-temperature sensor guidewire was used for coronary physiology assessment. Comprehensive clinical data on patient characteristics, cardiac risk factors, and symptom profiles was collected before testing.

RESULTS

This prospective observational study at Royal Prince Alfred and Concord Repatriation General Hospital included 110 patients (58±13 years with 63.6% women), with 81.8% (90/110) having a CVaD. Regarding specific ANOCA endotypes, microvascular angina (MVA) occurred in 31.8% (35/110) of cases, vasospastic angina (VSA) in 25.5% (28/110) and a mixed presentation of MVA and VSA in 24.5% (27/110) of patients. Patients with CVaD were found to be older (59±11 vs 51±15, p=0.024), overweight (61.1% vs 15.0%, p<0.001) and had a worse quality of life (EuroQol 5 Dimensions-5 Levels; 0.61 vs 0.67, p=0.043). MVA was associated with being overweight (odds ratio [OR] 4.2 [95% confidence interval [CI] 1.9-9.3]; p=0.015) and ischaemia on stress testing (OR 2.4 [95% CI 1.1-4.3]; p=0.028), while VSA was associated with smoking (OR 9.1 [95% CI 2.21-39.3]; p=0.007).

CONCLUSIONS

Coronary vasomotor disorders are highly prevalent among ANOCA patients. This study highlights the importance of increasing national awareness and the use of functional coronary angiography to evaluate and manage this unique cohort.

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.

Anomalous Coronary Arteries: A State-of-the-Art Approach

Congenital coronary anomalies are not an infrequent occurrence and their clinical presentation typically occurs during early years, though may be manifested only in adulthood. In the setting of anomalous aortic origin of a coronary artery, this is particularly concerning as it inflicts sudden loss of healthy young lives. Risk stratification remains a challenge and so does the best management decision-making in these patients, particularly if asymptomatic. Standardized approach to evaluation and management, with careful data collection and collaboration among centers, will likely impact future outcomes in this patient population, thus allowing for exercise participation and healthier lives.

Role of Transesophageal Echocardiography in the Diagnosis of Coronary Ischemia in a Patient with History of Ross Procedure

•Multidisciplinary management is essential for complications post–Ross procedure. •Symptomatic coronary ischemia may occur late in Ross procedure patients. •Coronary ostium narrowing is a differential for ischemia post–Ross procedure. •TEE can aid in diagnosing coronary stenosis in a Ross procedure patient. •TTE may miss eccentric AR post–Ross surgery; high suspicion justifies TEE.

Myocardial bridges in a pediatric population: Outcomes following a standardized approach

OBJECTIVE

To describe clinical, functional, surgical, and outcomes data in pediatric patients with a myocardial bridge (MB) evaluated and managed following a standardized approach.

METHODS

Prospective observational study included patients evaluated in the Coronary Artery Anomalies Program. Anatomy was determined by computed tomography angiography, myocardial perfusion by stress perfusion imaging, and coronary hemodynamic assessment by cardiac catheterization.

RESULTS

In total, 39 of 42 patients with a complete evaluation for MB were included (December 2012 to June 2022) at a median age of 14.1 years (interquartile range, 12.2-16.4). Sudden cardiac arrest occurred in 3 of 39 (8%), exertional symptoms in 14 (36%), and no/nonspecific symptoms in 7 (18%) patients. Exercise stress test was abnormal in 3 of 34 (9%), stress perfusion imaging in 8 of 34 (24%), and resting instantaneous wave-free ratio ≤0.89 or diastolic dobutamine fractional flow reserve ≤0.80 in 11 of 21 (52%) patients. As a result, 15 of 39 (38%) patients were determined to have hemodynamically significant MB, 1 of 15 patients started beta-blocker, and 14 of 15 were referred for surgery. Myotomy (n = 11) and coronary bypass (n = 1) were performed successfully, resulting in improved symptoms and stress testing results. One patient required pericardiocentesis postoperatively, and all were discharged without other complications. At median follow-up time of 2.9 (1.8-5.8) years, all (except 2 pending surgery) were doing well without exercise restriction.

CONCLUSIONS

Pediatric patients with MB can present with myocardial ischemia and sudden cardiac arrest. Provocative stress test and intracoronary hemodynamic tests helped risk-stratify symptomatic patients with MB and concern for ischemia. Surgical repair was safe and effective in mitigating exertional symptoms and stress test results, allowing patients to return to exercise without restriction.

Anomalous Coronary Arteries: A State-of-the-Art Approach

Congenital coronary anomalies are not an infrequent occurrence and their clinical presentation typically occurs during early years, though may be manifested only in adulthood. In the setting of anomalous aortic origin of a coronary artery, this is particularly concerning as it inflicts sudden loss of healthy young lives. Risk stratification remains a challenge and so does the best management decision-making in these patients, particularly if asymptomatic. Standardized approach to evaluation and management, with careful data collection and collaboration among centers, will likely impact future outcomes in this patient population, thus allowing for exercise participation and healthier lives.

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.

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.

Contrast Stress Echocardiography Findings in Myocardial Bridging Compared to Normal Coronary Course, With and Without Coronary Artery Disease

BACKGROUND

Myocardial bridging (MB) correlation with ischemia remains a diagnostic challenge. There is a lack of studies that have assessed MB using contrast stress echo and compared the findings with those in patients demonstrating a normal coronary course, with or without obstructive coronary artery disease (CAD).

METHODS

We evaluated all consecutive patients who underwent contrast stress echocardiography and coronary computed tomography angiography (CCTA) due to suspected symptoms of CAD within 3 months in Parma Hospital. Coronary computed tomography angiography served as the reference standard for detecting MB and obstructive CAD. The patients were divided into 3 groups: (1) MB and no evidence of obstructive CAD (MB group, N = 64), (2) no evidence of obstructive CAD or MB (NoCAD group, N = 135), (3) obstructive CAD without MB (CAD group, N = 68).

RESULTS

The coronary flow velocity reserve in the LAD (CFVR-LAD) was reduced in the MB and CAD groups, measuring 1.91 ± 0.21 and 1.82 ± 0.28, respectively, whereas it was 2.27 ± 0.34 in the NoCAD group (P < .001). The MB and CAD groups exhibited a higher prevalence of reversible myocardial perfusion defects (rMPDs) compared to the NoCAD group (57.8% vs 64.7% vs 3.7%, P < .001). Reversible wall motion abnormalities were frequently observed in the CAD group and rarely found in the MB and NoCAD groups (47.1% vs 18.8% vs 4.4%, P < .001). In multivariable analyses, the presence of MB was independently associated with reduced CFVR-LAD (odds ratio = 14.55; 95% CI, 6.84-30.93; P < .001) and the presence of rMPD (odds ratio = 37.96; 95% CI, 13.49-106.84; P < .001). Patients with deep MB (>2 mm depth) and very deep MB (≥5 mm depth) exhibited significantly greater CFVR-LAD reduction and rMPD than those with superficial MB.

CONCLUSIONS

Myocardial bridging is capable of inducing rMPD and reducing CFVR-LAD similar to obstructive CAD. The depth of the MB correlates with the abnormalities found in the stress echo evaluation. Contrast stress echo may serve as a valuable noninvasive tool for evaluating patients with MB.

Comprehensive Management of ANOCA, Part 1-Definition, Patient Population, and Diagnosis: JACC State-of-the-Art Review

Angina with nonobstructive coronary arteries (ANOCA) is increasingly recognized and may affect nearly one-half of patients undergoing invasive coronary angiography for suspected ischemic heart disease. This working diagnosis encompasses coronary microvascular dysfunction, microvascular and epicardial spasm, myocardial bridging, and other occult coronary abnormalities. Patients with ANOCA often face a high burden of symptoms and may experience repeated presentations to multiple medical providers before receiving a diagnosis. Given the challenges of establishing a diagnosis, patients with ANOCA frequently experience invalidation and recidivism, possibly leading to anxiety and depression. Advances in scientific knowledge and diagnostic testing now allow for routine evaluation of ANOCA noninvasively and in the cardiac catheterization laboratory with coronary function testing (CFT). CFT includes diagnostic coronary angiography, assessment of coronary flow reserve and microcirculatory resistance, provocative testing for endothelial dysfunction and coronary vasospasm, and intravascular imaging for identification of myocardial bridging, with hemodynamic assessment as needed.

Application of Patient-Specific Computational Fluid Dynamics in Anomalous Aortic Origin of Coronary Artery: A Systematic Review

Anomalous aortic origin of a coronary artery (AAOCA) is a rare congenital heart condition with fixed and dynamic stenotic elements, potentially causing ischemia. Invasive coronary angiography under stress is the established method for assessing hemodynamics in AAOCA, yet it is costly, technically intricate, and uncomfortable. Computational fluid dynamics (CFD) simulations offer a noninvasive alternative for patient-specific hemodynamic analysis in AAOCA. This systematic review examines the role of CFD simulations in AAOCA, encompassing patient-specific modeling, noninvasive imaging-based boundary conditions, and flow characteristics. Screening articles using AAOCA and CFD-related terms prior to February 2023 yielded 19 publications, covering 370 patients. Over the past four years, 12 (63%) publications (259 patients) employed dedicated CFD models, whereas 7 (37%) publications (111 patients) used general-purpose CFD models. Dedicated CFD models were validated for fixed stenosis but lacked dynamic component representation. General-purpose CFD models exhibited variability and limitations, with fluid-solid interaction models showing promise. Interest in CFD modeling of AAOCA has surged recently, mainly utilizing dedicated models. However, these models inadequately replicate hemodynamics, necessitating novel CFD approaches to accurately simulate pathophysiological changes in AAOCA under stress conditions.

MINOCA Associated with a Myocardial Bridge: Pathogenesis, Diagnosis and Treatment

Myocardial bridging (MB) is the most frequent congenital coronary anomaly characterized by a segment of an epicardial coronary artery that passes through the myocardium. MB is an important cause of myocardial ischemia and is also emerging as a possible cause of myocardial infarction with non-obstructed coronary arteries (MINOCA). There are multiple mechanisms underlying MINOCA in patients with MB (i.e., MB-mediated increased risk of epicardial or microvascular coronary spasm, atherosclerotic plaque disruption and spontaneous coronary artery dissection). The identification of the exact pathogenetic mechanism is crucial in order to establish a patient-tailored therapy. This review provides the most up-to-date evidence regarding the pathophysiology of MINOCA in patients with MB. Moreover, it focuses on the available diagnostic tools that could be implemented at the time of coronary angiography to achieve a pathophysiologic diagnosis. Finally, it focuses on the therapeutic implications associated with the different pathogenetic mechanisms of MINOCA in patients with MB.

A spatiotemporal analysis of the left coronary artery biomechanics using fluid-structure interaction models

Biomechanics plays a critical role in coronary artery disease development. FSI simulation is commonly used to understand the hemodynamics and mechanical environment associated with atherosclerosis pathology. To provide a comprehensive characterization of patient-specific coronary biomechanics, an analysis of FSI simulation in the spatial and temporal domains was performed. In the current study, a three-dimensional FSI model of the LAD coronary artery was built based on a patient-specific geometry using COMSOL Multiphysics. The effect of myocardial bridging was simulated. Wall shear stress and its derivatives including time-averaged wall shear stress, wall shear stress gradient, and OSI were calculated across the cardiac cycle in multiple locations. Arterial wall strain (radial, circumferential, and longitudinal) and von Mises stress were calculated. To assess perfusion, vFFR was calculated. The results demonstrated the FSI model could identify regional and transient differences in biomechanical parameters within the coronary artery. The addition of myocardial bridging caused a notable change in von Mises stress and an increase in arterial strain during systole. The analysis performed in this manner takes greater advantage of the information provided in the space and time domains and can potentially assist clinical evaluation.

Going under the bridge: unmasking ischaemia and endothelial dysfunction of myocardial bridging: a case report

Background

Physiological assessment of myocardial bridging prevents unnecessary interventions. Non-invasive workup or visual coronary artery compression may underestimate the underlying ischaemia associated with myocardial bridging in symptomatic patients.

Case summary

A 74-year-old male presented to the outpatient clinic with chest pain and shortness of breath on exertion. He underwent coronary artery calcium scan showing an elevated calcium score of 404. On follow-up, he endorsed progressive worsening of symptoms with chest pain and decreased exercise tolerance. He was then referred for coronary angiography that revealed mid-left anterior descending myocardial bridging with initial normal resting full-cycle ratio of 0.92. Further workup after ruling out coronary microvascular disease demonstrated abnormal hyperaemic full-cycle ratio of 0.80 with a diffuse rise across the myocardial bridging segment on pullback. Our patient also had increased spastic response to hyperaemia on angiography, supporting the presence of underlying endothelial dysfunction and ischaemia, likely contributing to his exertional symptomology. The patient was started on beta-blocker therapy with improvement in symptoms and resolution of chest pain on follow-up.

Conclusion

Our case highlights the importance of thorough workup of myocardial bridging in symptomatic patients to better understand the underlying physiology and endothelial function after ruling out microvascular disease and consideration of hyperaemic testing if symptoms are suggestive of ischaemia.

Impact of coronary bifurcation angle on computed tomography derived fractional flow reserve in coronary vessels with no apparent coronary artery disease

OBJECTIVES

Computed tomography (CT) derived fractional flow reserve (FFR_CT) decreases from the proximal to the distal part due to a variety of factors. The energy loss due to the bifurcation angle may potentially contribute to a progressive decline in FFR_CT. However, the association of the bifurcation angle with FFR_CT is still not entirely understood. This study aimed to investigate the impact of various bifurcation angles on FFR_CT decline below the clinically crucial relevance of 0.80 in vessels with no apparent coronary artery disease (CAD).

METHODS

A total of 83 patients who underwent both CT angiography including FFR_CT and invasive coronary angiography, exhibiting no apparent CAD were evaluated. ΔFFR_CT was defined as the change in FFR_CT from the proximal to the distal in the left anterior descending artery (LAD) and left circumflex artery (LCX). The bifurcation angle was calculated from three-dimensional volume rendered images. Vessel morphology and plaque characteristics were also assessed.

RESULTS

ΔFFR_CT significantly correlated with the bifurcation angle (LAD angle, r = 0.35, p = 0.001; LCX angle, r = 0.26, p = 0.02) and vessel length (LAD angle, r = 0.30, p = 0.005; LCX angle, r = 0.49, p < 0.0001). In LAD, vessel length was the strongest predictor for distal FFR_CT of ≤ 0.80 (β-coefficient = 0.55, p = 0.0003), immediately followed by the bifurcation angle (β-coefficient = 0.24, p = 0.02). The bifurcation angle was a good predictor for a distal FFR_CT ≤ 0.80 (LAD angle, cut-off 31.0°, AUC 0.70, sensitivity 74%, specificity 68%; LCX angle, cut-off 52.6°, AUC 0.86, sensitivity 88%, specificity 85%).

CONCLUSIONS

In vessels with no apparent CAD, vessel length was the most influential factor on FFR_CT, directly followed by the bifurcation angle.

KEY POINTS

• Both LAD and LCX bifurcation angles are factors influencing FFR _CT. • Bifurcation angle is one of the predictors of a distal FFR_CT of ≤ 0.80 and an optimal cut-off value of 31.0° for the LAD and 52.6° for the LCX. • Bifurcation angle should be taken into consideration when interpreting numerical values of FFR_CT.

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.

Detection of myocardial bridge by optical coherence tomography

Myocardial bridge (MB) is less commonly documented by angiography than autopsy. Optical coherence tomography (OCT) may be useful to detect angiographically undetectable MB. To investigate OCT characteristics of MB, 86 LAD vessels were imaged by OCT. MB was defined as presence of intermediate optical intensity, "fine" layer surrounding coronary artery by OCT. Frequency and characteristics of the angio-detectable and angio-undetectable but OCT-detectable MB were investigated. In a subset of patients with angio-detectable MB, cyclic changes in coronary arterial dimensions were analyzed. OCT detected MB in 44 of 86 (51%). Arc of the MB was significantly larger (334.8 ± 58.5° vs. 268.4 ± 92.1°, P = 0.008) and length was significantly longer (22.6 ± 11.7 mm vs. 14.5 ± 8.1 mm, P = 0.014) in angio-detectable MB than OCT-detectable but angio-undetectable MB. Both vessel (6.8 ± 1.5 to 5.3 ± 1.0 mm2, P = 0.035) and lumen area (4.4 ± 1.5 to 3.1 ± 0.7 mm2, P = 0.040) decreased significantly from diastole to systole. Adventitial (0.08 ± 0.03 to 0.08 ± 0.02 mm, P = 0.828) and intima + plaque thickness (0.12 ± 0.05 to 0.10 ± 0.03 mm, P = 0.398) did not change significantly during cardiac cycle. On the other hand, medial thickness increased significantly from diastole to systole (0.08 ± 0.03 to 0.12 ± 0.03 mm, P = 0.022). In conclusion, MB is frequently detected as intermediate intensity, fine layer by OCT. During systole, vessel and lumen size decrease with increased medial thickness. Therefore, we should be careful for OCT interpretation of the coronary arteries with MB.

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.

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.

Fractional Flow Reserve: Patient Selection and Perspectives

The aim of this review was to discuss the current practice and patient selection for invasive FFR, new techniques to estimate invasive FFR and future of coronary physiology tests. We elaborate on the indication and application of FFR and on the contraindications and concerns in certain patient populations.

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.

CT-based fractional flow reserve: development and expanded application

Computations of fractional flow reserve, based on CT coronary angiography and computational fluid dynamics (CT-based FFR) to assess the severity of coronary artery stenosis, was introduced around a decade ago and is now one of the most successful applications of computational fluid dynamic modelling in clinical practice. Although the mathematical modelling framework behind this approach and the clinical operational model vary, its clinical efficacy has been demonstrated well in general. In this review, technical elements behind CT-based FFR computation are summarised with some key assumptions and challenges. Examples of these challenges include the complexity of the model (such as blood viscosity and vessel wall compliance modelling), whose impact has been debated in the research. Efforts made to address the practical challenge of processing time are also reviewed. Then, further application areas—myocardial bridge, renal stenosis and lower limb stenosis—are discussed along with specific challenges expected in these areas.

CT Fractional Flow Reserve for the Diagnosis of Myocardial Bridging-Related Ischemia: A Study Using Dynamic CT Myocardial Perfusion Imaging as a Reference Standard

Objective

To investigate the diagnostic performance of CT fractional flow reserve (CT-FFR) for myocardial bridging-related ischemia using dynamic CT myocardial perfusion imaging (CT-MPI) as a reference standard.

Materials and Methods

Dynamic CT-MPI and coronary CT angiography (CCTA) data obtained from 498 symptomatic patients were retrospectively reviewed. Seventy-five patients (mean age ± standard deviation, 62.7 ± 13.2 years; 48 males) who showed myocardial bridging in the left anterior descending artery without concomitant obstructive stenosis on the imaging were included. The change in CT-FFR across myocardial bridging (ΔCT-FFR, defined as the difference in CT-FFR values between the proximal and distal ends of the myocardial bridging) in different cardiac phases, as well as other anatomical parameters, were measured to evaluate their performance for diagnosing myocardial bridging-related myocardial ischemia using dynamic CT-MPI as the reference standard (myocardial blood flow < 100 mL/100 mL/min or myocardial blood flow ratio ≤ 0.8).

Results

ΔCT-FFR_systolic (ΔCT-FFR calculated in the best systolic phase) was higher in patients with vs. without myocardial bridging-related myocardial ischemia (median [interquartile range], 0.12 [0.08–0.17] vs. 0.04 [0.01–0.07], p < 0.001), while CT-FFR_systolic (CT-FFR distal to the myocardial bridging calculated in the best systolic phase) was lower (0.85 [0.81–0.89] vs. 0.91 [0.88–0.96], p = 0.043). In contrast, ΔCT-FFR_diastolic (ΔCT-FFR calculated in the best diastolic phase) and CT-FFR_diastolic (CT-FFR distal to the myocardial bridging calculated in the best diastolic phase) did not differ significantly. Receiver operating characteristic curve analysis showed that ΔCT-FFR_systolic had largest area under the curve (0.822; 95% confidence interval, 0.717–0.901) for identifying myocardial bridging-related ischemia. ΔCT-FFR_systolic had the highest sensitivity (91.7%) and negative predictive value (NPV) (97.8%). ΔCT-FFR_diastolic had the highest specificity (85.7%) for diagnosing myocardial bridging-related ischemia. The positive predictive values of all CT-related parameters were low.

Conclusion

ΔCT-FFR_systolic reliably excluded myocardial bridging-related ischemia with high sensitivity and NPV. Myocardial bridging showing positive CT-FFR results requires further evaluation.

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.

Diagnostic Accuracy of Diastolic Fractional Flow Reserve for Functional Evaluation of Coronary Stenosis

Background

In the resting conditions, narrowing the window of coronary pressure measurements from the whole cardiac cycle to diastole improves diagnostic performance of coronary pressure–derived physiological index. However, whether this also applies to the hyperemic conditions has not yet been thoroughly evaluated.

Objectives

The purpose of this study was to assess whether diastolic fractional flow reserve (diastolic FFR) has better diagnostic performance in identifying ischemia-causing coronary lesions than conventional FFR in a prospective, multicenter, and independent core laboratory–based environment.

Methods

In this prospective multicenter registry at 29 Japanese centers, we compared the diagnostic performance of FFR, diastolic FFR, resting distal to aortic coronary pressure (Pd/Pa), and diastolic pressure ratio (dPR) using myocardial perfusion scintigraphy (MPS) as the reference standard in 378 patients with single-vessel coronary disease.

Results

Inducible myocardial ischemia was found on MPS in the relevant myocardial territory of the target vessel in 85 patients (22%). In the receiver-operating curve analyses, diastolic FFR had comparable area under the curve (AUC) compared with FFR (AUC_{diastolic FFR}: 0.66; 95% confidence interval [CI]: 0.58-0.73, vs AUC_FFR: 0.66; 95% CI: 0.58-0.74, P = 0.624). FFR and diastolic FFR showed significantly larger AUCs than resting Pd/Pa (0.62; 95% CI: 0.54-0.70; P = 0.033 and P = 0.046) but did not show significantly larger AUCs than dPR (0.62; 95% CI: 0.55-0.70; P = 0.102 and P = 0.113).

Conclusions

Diastolic FFR showed a similar diagnostic performance to FFR as compared with MPS. This result reaffirms the use of FFR as the most accurate invasive physiological lesion assessment. (Diagnostic accuracy of diastolic fractional flow reserve (d-FFR) for functional evaluation of coronary stenosis; UMIN000015906)

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.

Interplay Between Myocardial Bridging and Coronary Spasm in Patients With Myocardial Ischemia and Non-Obstructive Coronary Arteries: Pathogenic and Prognostic Implications

Background Myocardial bridging (MB) may represent a cause of myocardial ischemia in patients with non-obstructive coronary artery disease (NOCAD). Herein, we assessed the interplay between MB and coronary vasomotor disorders, also evaluating their prognostic relevance in patients with myocardial infarction and non-obstructive coronary arteries (MINOCA) or stable NOCAD. Methods and Results We prospectively enrolled patients with NOCAD undergoing intracoronary acetylcholine provocative test. The incidence of major adverse cardiac events, defined as the composite of cardiac death, non-fatal myocardial infarction, and rehospitalization for unstable angina, was assessed at follow-up. We also assessed angina status using Seattle Angina Questionnaires summary score. We enrolled 310 patients (mean age, 60.6±11.9; 136 [43.9%] men; 169 [54.5%] stable NOCAD and 141 [45.5%] MINOCA). MB was found in 53 (17.1%) patients. MB and a positive acetylcholine test coexisted more frequently in patients with MINOCA versus stable NOCAD. MB was an independent predictor of positive acetylcholine test and MINOCA. At follow-up (median, 22 months; interquartile range, 13-32), patients with MB had a higher rate of major adverse cardiac events, mainly driven by a higher rate of hospitalization attributable to angina, and a lower Seattle Angina Questionnaires summary score (all P<0.001) compared with patients without MB. In particular, the group of patients with MB and a positive acetylcholine test had the worst prognosis. Conclusions Among patients with NOCAD, coronary spasm associated with MB may predict a worse clinical presentation with MINOCA and a higher rate of hospitalization attributable to angina at long-term follow-up with a low rate of hard events.

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.

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.

Echocardiographic changes and quality of life after surgical unroofing of myocardial bridges

OBJECTIVE

To examine the echocardiographic changes and quality of life (QoL) after surgical unroofing of myocardial bridges (MBs) involving the left anterior descending (LAD) coronary artery compared with optimal medical therapy (OMT).

METHODS

Twenty-two patients (median age, 24 years; interquartile range, 16-40 years) with MBs of the LAD artery and exertional angina from 2018 to 2019 were retrospectively analyzed. Twelve patients underwent OMT and 10 underwent surgery. Both groups underwent clinical and echocardiographic examinations during hospitalization and follow-up (mean, 1.0 ± 0.8 years). QoL was assessed with the Seattle Angina Questionnaire, short version (SAQ-7).

RESULTS

Surgery resulted in significantly better QoL than OMT, with a significant improvement in left ventricular global longitudinal strain (GLS) [mean (standard error): 19% (0.19) to 22% (0.34) and 19% (0.15) to 20% (0.24), respectively; delta-change (delta-GLS) of 0.15 vs. 0.067]. In the univariate and multivariable analyses, delta-GLS was positively correlated with the SAQ-7 score and MB length (rho = 0.64 and 0.71, respectively), with a significant interaction between MB length and surgical treatment (beta coefficient, 1.95; 95% confidence interval, 0.14-3.77).

CONCLUSIONS

MB unroofing surgery provided benefits in terms of QoL and left ventricular GLS improvement compared with 1 year of OMT.

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.

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.

Off-Pump Minithoracotomy Versus Sternotomy for Left Anterior Descending Myocardial Bridge Unroofing

BACKGROUND

Myocardial bridge (MB) of the left anterior descending (LAD) coronary artery occurs in approximately 25% of the population. When medical therapy fails in patients with a symptomatic, hemodynamically significant MB, MB unroofing represents the optimal surgical management. Here, we evaluated minimally invasive MB unroofing in selected patients compared with sternotomy.

METHODS

MB unroofing was performed in 141 adult patients by sternotomy on-pump (ST-on, n = 40), sternotomy off-pump (ST-off, n = 62), or minithoracotomy off-pump (MT, n = 39). Angina symptoms were assessed preoperatively and 6 months postoperatively using the Seattle Angina Questionnaire. Matching included all MT patients and 31 ST-off patients with similar MB characteristics, no previous cardiac operations or coronary interventions, and no concomitant procedures.

RESULTS

MT patients tended to have a shorter MB length than ST-on and ST-off patients (2.57 vs 2.93 vs 3.09 cm, P = .166). ST-on patients had a longer hospital stay than ST-off and MT patients (5.0 vs 4.0 vs 3.0 days, P < .001), and more blood transfusions (15.2% vs 0.0% vs 2.6%, P = .002). After matching, MT patients had a shorter hospital stay than ST-off patients (3.0 vs 4.0 days, P = .005). No deaths or major complications occurred in any group. In all groups, MB unroofing yielded significant symptomatic improvement regarding physical limitation, angina stability, angina frequency, treatment satisfaction, and quality of life.

CONCLUSIONS

We report our single-center experience of off-pump minimally invasive MB unroofing, which may be safely performed in carefully selected patients, yielding dramatic improvements in angina symptoms at 6 months after the operation.

Non-hyperaemic pressure ratios to guide percutaneous coronary intervention

The use of fractional flow reserve (FFR) in guiding revascularisation improves patient outcomes and has been well-established in clinical guidelines. Despite this, the uptake of FFR has been limited, likely attributable to the perceived increase in procedural time and use of hyperaemic agents that can cause patient discomfort. This has led to the development of instantaneous wave-free ratio (iFR), an alternative non-hyperaemic pressure ratio (NHPR). Since its inception, the use of iFR has been supported by an increasing body of evidence and is now guideline recommended. More recently, other commercially available NHPRs including diastolic hyperaemia-free ratio and resting full-cycle ratio have emerged. Studies have demonstrated that these indices, in addition to mean distal coronary artery pressure to mean aortic pressure ratio, are mathematically analogous (with specific nuances) to iFR. Additionally, there is increasing data demonstrating the equivalent diagnostic performance of alternative NHPRs in comparison with iFR and FFR. These NHPRs are now integral within most current pressure wire systems and are commonly available in the catheter laboratory. It is therefore key to understand the fundamental differences and evidence for NHPRs to guide appropriate clinical decision-making.

Assessment of Vascular Dysfunction in Patients Without Obstructive Coronary Artery Disease: Why, How, and When

Ischemic heart disease secondary to coronary vascular dysfunction causes angina and impairs quality of life and prognosis. About one-half of patients with symptoms and signs of ischemia turn out not to have obstructive coronary artery disease, and coronary vascular dysfunction may be relevant. Adjunctive tests of coronary vasomotion include guidewire-based techniques with adenosine and reactivity testing, typically by intracoronary infusion of acetylcholine. The CorMicA (Coronary Microvascular Angina) trial provided evidence that routine management guided by an interventional diagnostic procedure and stratified therapy improves angina and quality of life in patients with angina but no obstructive coronary artery disease. In this paper, the COVADIS study group provide a comprehensive review of why, how, and when coronary vascular dysfunction should be assessed invasively. They discuss the rationale through a shared understanding of vascular pathophysiology and clinical evidence. They propose a consensus approach to how an interventional diagnostic procedure is performed with focus on practical aspects. Finally, the authors discuss the clinical scenarios in patients with stable and acute coronary syndromes in which measurement of coronary vascular function may be helpful for patient care.

Unroofing of Myocardial Bridging After Septal Myectomy in a Child With Noonan Syndrome

Myocardial bridging is a controversial topic that remained with no well-defined management protocol. We present a ten-year-old child with Noonan syndrome and a myocardial bridge.

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.

Effect of QTU prolongation on hyperemic instantaneous wave-free ratio value: a prospective single-center study

We hypothesized that in patients with QT prolongation, resistance might not decrease in the wave-free period, because QTU prolongation cannot be detected by instantaneous wave-free ratio (iFR) analysis software. We investigated whether corrected QTU (QTUc) prolongation affects the hyperemic iFR value. Forty-two consecutive patients with intermediate stenosis (≥ 50%) in the left anterior descending coronary artery (LAD) were analyzed. Fractional flow reserve (FFR) and hyperemic iFR were simultaneously and continuously recorded with intravenous adenosine triphosphate (ATP) and papaverine infusions. In 17 patients with stenosis in the proximal LAD, coronary flow was measured. Patients were divided into two groups according to the median absolute deviation of the QTUc by ATP administration/QTUc by papaverine administration. FFR, hyperemic iFR, and flow data were compared between each stimulus and group. Moreover, influences of pressure and electrocardiogram parameters on differences in iFR values under ATP and papaverine administration were compared between the following two groups (group 1: the absolute difference of hyperemic iFR values between ATP and papaverine administration is ≤ 0.05; group 2: that is > 0.05). The paired t test and t test were used in analysis. Hyperemic iFR values of patients under the use of papaverine were lower than those of patients under the use of ATP when QTUc was more prolonged by papaverine administration than by ATP administration (ATP 0.74 ± 0.14, papaverine 0.71 ± 0.15, P = 0.025). No significant differences were observed in the FFR value and flow data between the groups. Regarding QTU, QTUc, and QTUc by ATP/QTUc by papaverine, significant differences were observed between group 1 and group 2. Pressure parameters did not induce significant differences. QTUc prolongation induced by papaverine was associated with lower hyperemic iFR values. An iFR-based assessment might lead to inappropriate treatment of patients with QTUc prolongation.

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.

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.