Images in cardiovascular medicine. Coronary thrombosis and myocardial bridging

Is myocardial bridge more frequently detected on radial access coronary angiography?

Background

Although the incidence of myocardial bridge (MB) has been defined in different femoral access conventional coronary angiography (FACCA) studies, the frequency of MB on radial access coronary angiography (RACA) is unknown. The aim of this study was to determine the difference in the incidence of MB between patients undergoing RACA and FACCA.

Method

A total of 2500 consecutive patients who underwent RACA and a total of 1455 consecutive patients who underwent FACCA were retrospectively investigated to detect the presence of MB. The incidences of the groups were calculated separately and compared. The clinical and angiographic features of the patients with MB were analyzed.

Results

MB was detected at an incidence of 10.2%, in 255/2500 patients who underwent RACA, and 1.8% in 27/1455 patients who underwent FACCA (p < 0.001). In both RACA and FACCA patients, the most involved coronary artery was the left anterior descending artery (LAD) (86.9% and 93.1%) and the mid-segment (84.9% and 88.9%) was the most affected section. Co-involvement of multiple coronary arteries by MB was 7.8% in patients who underwent RACA and 7.4% in patients who underwent FACCA. Coronary artery disease (CAD) was determined in 111 (35.7%) of the coronary arteries with MB, of which 81.9% were proximal to the MB. No significant CAD was detected in any of the vessels of 69.8% (178/255) of the patients who underwent RACA for different clinical indications.

Conclusion

These data demonstrated that the incidence of myocardial bridge able to be detected on RACA was much higher than FACCA.

The prevalence of myocardial bridging on multidetector computed tomography and its relation to coronary plaques

PURPOSE

To test the hypothesis that the prevalence of myocardial bridging varies between ethnic groups, and that the segment proximal to the myocardial bridge is more prone to plaque formation.

MATERIAL AND METHODS

A total of 4500 patients who had undergone computerised tomography (CT) coronary angiography at our institute were studied for myocardial bridging. Data on the clinical profile and indication for CT coronary angiography in myocardial bridging were collected. Patients with and without proximal disease were compared using the chi-square test for ordinal variables and Student's t-test for continuous variables. The length to depth ratio (RA-MA ratio) of the bridged segment was determined.

RESULTS

The prevalence of atherosclerotic plaques in the segment proximal to the bridged segment was 37.8%, which was lower than the prevalence of 48.7% for plaques in the corresponding segments among patients without myocardial bridging. The average length of the bridged segment was 15.5 ± 5 mm, and that for patients with and without proximal plaques was 13 ± 4 and 16 ± 6 mm (p = 0.1), respectively. Similarly, the average depth of the segments with and without proximal plaques was 1.8 ± 0.6 mm and 1.4 ± 0.5 mm (p = 0.06), respectively. Only the RA-MA ratio (8 ± 3 vs. 13 ± 6, p = 0.01) was significantly lower in patients with atherosclerotic plaques.

CONCLUSIONS

The prevalence in our study population was 10%, with mid left anterior descending artery (LAD) being the most common segment involved. Moreover, the prevalence and distribution of coronary plaques in LAD were similar in patients with and without myocardial bridging.

Assessment of the Relationship between Monocyte to High-Density Lipoprotein Ratio and Myocardial Bridge

BACKGROUND

Assessing the monocyte to high-density lipoprotein ratio (MHR) is a new tool for predicting inflamation, which plays a major role in atherosclerosis. Myocardial bridge (MB) is thought to be a benign condition with development of atherosclerosis, particularly at the proximal segment of the brigde.

OBJECTIVE

To evaluate the relationhip between MHR and the presence of MB.

METHODS

We consecutively scanned patients referred for coronary angiography between January 2013- December 2016, and a total of 160 patients who had a MB and normal coronary artery were enrolled in the study. The patients' angiographic, demographic and clinic characteristics of the patients were reviewed from medical records. Monocytes and HDL-cholesterols were measured via complete blood count. MHR was calculated as the ratio of the absolute monocyte count to the HDL-cholesterol value. MHR values were divided into three tertiles as follows: lower (8.25 ± 1.61), moderate (13.11 ± 1.46), and higher (21.21 ± 4.30) tertile. A p-value of < 0.05 was considered significant.

RESULTS

MHR was significantly higher in the MB group compared to the control group with normal coronary arteries. We found the frequency of MB (p = 0.002) to increase as the MHR tertiles rose. The Monocyte-HDL ratio with a cut-point of 13.35 had 59% sensitivity and 65.0% specificity (ROC area under curve: 0.687, 95% CI: 0.606-0.769, p < 0.001) in accurately predicting a MB diagnosis. In the multivariate analysis, MHR (p = 0.013) was found to be a significant independent predictor of the presence of MB, after adjusting for other risk factors.

CONCLUSION

The present study revealed a significant correlation between MHR and MB.

Nonsymptomatic myocardial bridge causing systolic total narrowing of circumflex artery

Myocardial bridge is defined as the narrowing of any coronary artery segment in systole but a normal diameter in diastole. It is most frequently seen on left anterior descending (LAD) artery. Left circumflex artery (LCx) is very rare. A 62 year-old male patient presented with severe, squeezing chest pain. The electrocardiogram showed T wave inversion in V1–V4 and ST depression in DII, DIII, aVF. Coronary angiography showed complicated lesion on after S2 branches of LAD and myocardial bridge causing 100% systolic narrowing of fourth obtus marginal branch of LCx. Bare metal stent was placed to LAD lesions with no residual occlusion. The patient was discharged with beta-blocker therapy. He had no recurrent chest pain during six months of follow-up.

Exercise Strain Echocardiography in Patients With a Hemodynamically Significant Myocardial Bridge Assessed by Physiological Study

BACKGROUND

Although a myocardial bridge (MB) is often regarded as a benign coronary variant, recent studies have associated MB with focal myocardial ischemia. The physiological consequences of MB on ventricular function during stress have not been well established.

METHODS AND RESULTS

We enrolled 58 patients with MB of the left anterior descending artery, diagnosed by intravascular ultrasound. Patients underwent invasive physiological evaluation of the MB by diastolic fractional flow reserve during dobutamine challenge and exercise echocardiography. Septal and lateral longitudinal strain (LS) were assessed at rest and immediately after exercise and compared with strain of matched controls. Absolute and relative changes in strain were also calculated. The mean age was 42.5±16.0 years. Fifty-five patients had a diastolic fractional flow reserve ≤0.76. At rest, there was no significant difference between the 2 groups in septal LS (19.0±1.8% for patients with MB versus 19.2±1.5% for control, P=0.53) and lateral LS (20.1±2.0% versus 20.0±1.6%, P=0.83). With stress, compared with controls, patients with MB had a lower peak septal LS (18.9±2.6% versus 21.7±1.6%, P<0.001) and lower absolute (-0.1±2.1% versus 2.5±1.3%, P<0.001) and relative change (-0.6±11.2% versus 13.1±7.8%, P<0.001) in septal LS, whereas there was no significant difference in lateral LS. In multivariate analysis, diastolic fractional flow reserve and length were independent determinants of lower changes in septal LS.

CONCLUSIONS

Patients with a hemodynamically significant MB, determined by invasive diastolic fractional flow reserve, have significantly lower change in septal LS on exercise echocardiography, suggesting that septal LS may be useful for noninvasively assessing the hemodynamic significance of an MB.

Coronary artery manifestations of fibromuscular dysplasia

Fibromuscular dysplasia (FMD) involving the coronary arteries is an uncommon but important condition that can present as acute coronary syndrome, left ventricular dysfunction, or potentially sudden cardiac death. Although the classic angiographic "string of beads" that may be observed in renal artery FMD does not occur in coronary arteries, potential manifestations include spontaneous coronary artery dissection, distal tapering or long, smooth narrowing that may represent dissection, intramural hematoma, spasm, or tortuosity. Importantly, FMD must be identified in at least one other noncoronary arterial territory to attribute any coronary findings to FMD. Although there is limited evidence to guide treatment, many lesions heal spontaneously; thus, a conservative approach is generally preferred. The etiology is poorly understood, but there are ongoing efforts to better characterize FMD and define its genetic and molecular basis. This report reviews the clinical course of FMD involving the coronary arteries and provides guidance for diagnosis and treatment strategies.

Myocardial bridge: The cause of angina in a young man

Myocardial bridging is basically the systolic narrowing of epicardial coronary arteries, secondary to their tunneled course in myocardium. Though it is a benign condition it can have the symptoms like acute coronary syndrome, arrhythmias and sudden cardiac death. We report a 32-year-old male, who presented with typical exertional angina, had positive exercise treadmill and thallium-201 test. Coronary angiography revealed myocardial bridge of distal left anterior descending coronary artery. He was put on β-blockers and was doing well at 8 years of follow-up.

Myocardial bridging: A 'forgotten' cause of acute coronary syndrome - a case report

During a stress test, an asymptomatic 40-year-old man showed an ST depression above 4 mm and a horizontal ST depression above 2 mm in the V3 to V6 precordial leads during the recovery phase, without symptoms related to myocardial ischemia. After several days, he experienced recurrent episodes of oppressive retrosternal pain with radiation to the interscapular region, associated with stress dyspnea. Stress myocardial scintigraphy using technetium sestamibi was performed, which showed a modest push-pull deficit of perfusion in the septal-anterior basal area associated with a small deficit of perfusion in the apical region.The patient was admitted to hospital with a diagnosis of unstable angina. Repeated episodes of chest pain appeared during this period, which were partially relieved with the administration of sublingual nitrate. There were no significant changes in the electrocardiogram or cardiac enzyme levels. Coronary angiography showed initial parietal hypertrophy with normal segmentary kinesis and global systolic function and, most importantly, the presence of a systolic narrowing (myocardial bridging) of the middle one-third of the left anterior descending artery from the likely intramyocardial route. There was no significant stenosis of the remaining coronary tracts.Myocardial bridges have traditionally been considered a benign condition, but recent studies have demonstrated that the clinical complications can be dangerous; these complications include acute coronary syndromes, arrhythmias (including supraventricular tachycardia and ventricular tachycardia), exercise-induced atrioventricular conduction blocks, transient ventricular dysfunction and sudden death.

Alteration of left ventricular function with dobutamine challenge in patients with myocardial bridge

BACKGROUND/AIMS

The aim of this study was to identify changes in left ventricular (LV) performance in patients with a myocardial bridge (MB) in the left anterior descending coronary artery during resting and in an inotropic state.

METHODS

Myocardial strain measurement by speckle-tracking echocardiography and conventional LV wall-motion scoring was performed in 18 patients with MB (mean age, 48.1 ± 1.7 years, eight female) during resting and intravenous dobutamine challenge (10 and 20 µg/kg/min).

RESULTS

Conventional LV wall-motion scoring was normal in all patients during resting and in an inotropic state. Peak regional circumferential strain increased dose dependently upon dobutamine challenge. Longitudinal strains of the anterior and anteroseptal segments were, however, reduced at 20 µg/kg/min and showed a dyssynchronous pattern at 20 µg/kg/min. Although there were no significant differences in radial strain and displacement of all segments at rest compared with under 10 µg/kg/min challenge, radial strain and displacement of anterior segments at 20 µg/kg/min were significantly reduced compared with posterior segments at the papillary muscle level (44.8 ± 14.9% vs. 78.4 ± 20.1% and 5.3 ± 2.3 mm vs. 8.5 ± 1.8 mm, respectively; all p < 0.001), and showed plateau (40%) or biphasic (62%) patterns.

CONCLUSIONS

Reduced LV strain of patients with MB after inotropic stimulation was identified. Speckle-tracking strain echocardiography identified a LV myocardial dyssynchrony that was not demonstrated by conventional echocardiography in patients with MB.

Thrombus in normal coronary arteries: retrospective study and review of case reports

BACKGROUND

Myocardial infarction is rarely caused by non-occlusive thrombus in angiographically normal coronary arteries. The cases reported in the literature are scarce and follow-up was usually short. The efficacy and tolerability of the exclusively medical treatment strategy used in most cases remain unknown.

AIMS

To evaluate efficacy of medical treatment and long-term prognosis in these patients.

METHODS

We retrospectively selected and analysed patients hospitalized in our centre between 1998 and 2008 for myocardial infarction caused by non-occlusive thrombus in angiographically normal coronary arteries (defined as stenosis<30%), who were exclusively medically treated. A long-term follow-up was performed. A review of the literature regarding such cases was carried out.

RESULTS

Sixteen patients were identified; apart from smoking, they had few conventional cardiovascular risk factors. Two patients died in hospital. The 14 survivors were followed up for an average of 4.9 years and only one death (non-cardiac cause) and one stroke (related to supraventricular arrhythmia) occurred in this period. Medical treatment included the use of glycoprotein IIb/IIIa inhibitors in 75% of cases. The literature review revealed 36 similar cases due to multiple aetiologies-particularly coronary artery spasm and prothrombotic coagulopathies.

CONCLUSION

Patients with myocardial infarction secondary to non-occlusive thrombus in angiographically normal coronary arteries seem to have a good long-term prognosis after the acute phase when treated with an exclusively medical strategy. However, initial clinical presentation was often severe, leading to early in-hospital death.

Anatomical characteristics of myocardial bridge in patients with myocardial infarction by multi-detector computed tomography

BACKGROUND

Recent development of multi-detector computed tomography (MDCT) has made the detection of myocardial bridge (MB) easier on the left anterior descending coronary artery (LAD). The LAD segment proximal to the MB is well known to be susceptible to atherosclerosis. Anatomical characteristics of MB on LAD in patients with myocardial infarction (MI) were examined by MDCT.

METHODS AND RESULTS

Subjects were 43 MI patients who had MB in the LAD and comprised 2 groups: 14 with culprit lesions in the LAD proximal to MB (culprit group) and 29 without culprit lesions in the LAD (non-culprit group). MB length, MB thickness, and the distance from the orifice of left main trunk (LMT) to MB entrance were compared. Age and coronary risk factors showed no significant difference between the 2 groups. MB length (P=0.011), MB thickness (P=0.035), and index of the length multiplied by thickness of MB (P=0.031) were significantly greater in the culprit group. The distance from the orifice of the LMT to MB entrance was significantly shorter in the culprit group (P=0.006).

CONCLUSIONS

Anatomical properties of MB, such as length and thickness of MB as well as MB location, are associated with the formation of culprit lesions of LAD proximal to MB in MI.

Myocardial bridges spared from atherosclerosis: overview of the underlying mechanisms

Myocardial bridging constitutes a congenital, usually benign, coronary abnormality defined as a segment of a major epicardial coronary artery that follows an intramural course through the myocardium. On the basis of clinical and histopathological data, myocardial bridges appear to be spared from atherosclerosis. Although the mechanisms involved are largely unknown, the surrounding myocardium appears to be a key factor by generating a unique atheroprotective hemodynamic microenvironment within bridges. The main components of this environment include low tensile stress and high shear stress. Reduced coronary wall motion due to external support of the surrounding myocardium may also play a role. Better investigation of these mechanisms in appropriate animal models is anticipated to advance our understanding of the pathophysiology of atherosclerosis, providing a framework for the development of new atheroprotective strategies.

Detection of myocardial bridging by 64-row computed tomography angiography of the coronaries

INTRODUCTION

Myocardial bridging is a congenital condition in which a section of coronary artery is surrounded by myocardium. Historically, myocardial bridging has been diagnosed by catheter angiography. This study investigates the effectiveness of electrocardiogram-gated 64-slice multidetector computed tomography in detecting myocardial bridging.

MATERIALS AND METHODS

We retrospectively reviewed 167 consecutive patients referred for coronary computed tomography angiography between January 4, 2005, and May 24, 2006. We recorded the number of coronary segments exhibiting myocardial bridging and described the location of each according to the American Heart Association classification system. Association of bridging with factors influencing image quality (body mass index and heart rate) was analyzed.

RESULTS

Of 152 eligible participants, 49 (32%) showed myocardial bridging. The mid-left anterior descending coronary artery (segment 7) was the most common location accounting for 69% of positive cases. Body mass index and heart rate did not affect detection rates.

CONCLUSION

Electrocardiogram-gated 64-slice multidetector computed tomography is a feasible, noninvasive method of detecting myocardial bridging which may offer higher sensitivity than catheter angiography for this diagnosis.

High-sensitivity C-reactive protein may be an indicator of the development of atherosclerosis in myocardial bridging

BACKGROUND

Inflammation is one of the key mechanism in the development and progression of coronary artery disease. Myocardial bridging (MB) increases the tendency for development of atherosclerosis. The role of inflammation on the development of atherosclerosis in the MB is not clear. In this study, we investigated the existence of inflammation in the patients who have atherosclerotic plaque in the bridged segment.

METHODS

This study included 40 patients (group I) presented with stable angina pectoris and detected MB in LAD on coronary angiography and 30 control subjects (group II) with normal coronary angiogram. Patients in group I were divided into two subgroups based on the findings on intravascular ultrasound (IVUS): group IA included 25 patients without atherosclerotic lesion in any coronary artery and group IB included 15 patients with atherosclerotic lesion in addition to MB in bridged segment of LAD. High-sensitivity C-reactive protein (hs-CRP) levels were compared between group I and II and group IA and IB.

RESULTS

IVUS showed an atherosclerotic involvement with the proximal segment of MB in 15 patients (=group IB). No plaques were seen in other coronary arteries, in distal of MB or in the bridged segment. With regards to the level of hs-CRP, while no difference was established between group I and group II (1.7+/-0.4 mg/L vs 1.9+/-0.6 mg/L, p>0.05), hs-CRP was significantly higher in group IB than in group IA (3.2+/-0.3 mg/L vs 1.5+/-0.2 mg/L, p=0.001) and control group (3.2+/-0.3 mg/L vs 1.9+/-0.6 mg/L, p=0.03). A significant positive correlation was detected between the hs-CRP and the percentage of atherosclerotic stenosis on IVUS in group IB (R=0.639, p=0.01).

CONCLUSIONS

These results indicate the presence of a low grade inflammation in patients with atherosclerotic lesion in bridged segment.

Extensive scar myocardium in hypertrophic cardiomyopathy with severe myocardial bridge

We present a patient with hypertrophic cardiomyopathy and a large scar in the apex demonstrated on 201Tl SPECT and 18F-FDG PET images. Subsequent coronary angiography revealed no significant coronary artery stenosis but a myocardial bridge with severe systolic milking in the middle segment of the left anterior descending artery.

Impaired endothelial function in patients with myocardial bridge

OBJECTIVE

The relationship between myocardial bridging (MB) and ischemic heart disease is still controversial. In this study, we aimed to evaluate the existing atherosclerosis and noninvasive endothelial function of brachial artery in patients with MB.

METHODS

The present study included 50 patients (group I) who had MB in left anterior descending (LAD) on coronary angiography. All of the coronary artery segments were evaluated by intravascular ultrasound (IVUS). Endothelial function was assessed with measurement of flow-mediated dilatation (FMD) and nitrate-dependent dilatation in the brachial artery. The study also included 30 healthy control subjects (group II). Patients in the group I were further subdivided into two subgroups based on the findings on IVUS: group IA included 20 patients without atherosclerotic lesions and group IB included 30 patients with atherosclerotic coronary artery disease in addition to MB.

RESULTS

FMD values were found to be significantly lower in the patients with MB (group I) than in the control (6.4 +/- 3% vs 11 +/- 4%, P <0.001). In regard to FMD values in subgroups, FMD was 7 +/- 2% in the group IA and 5.8 +/- 1% in the group IB (P = 0.023). On IVUS, atherosclerotic plaque was found proximal to the bridge in the same coronary artery segment in addition to MB in 75% of the patients in group I (group IB). No atherosclerotic plaque was found in within or distal segments of MB.

CONCLUSION

Endothelial function is impaired in patients with MB and there is an increased tendency for atherosclerosis proximal to the bridge in the patients with MB. Endothelial dysfunction is more severe in the patients with atherosclerosis proximal to the bridge.

Evaluation of coronary stents in vitro with CT angiography: effect of stent diameter, convolution kernel, and vessel orientation to the z-axis

BACKGROUND

The aims of the present study were to assess the effect of the stent diameter, convolution kernel, and vessel orientation to the z-axis on the evaluation of coronary stents, in vitro with computed tomography (CT) angiography.

METHODS AND RESULTS

Seven vascular models (2 models without stenosis, 2 with obstruction, and 3 with stenosis) with an approximate inner diameter of 3 or 4 mm, filled with contrast material (79 or 330 HU) were scanned with a 16-detector CT. The diameter measurement of the stent lumen and stenosis evaluation were both done in an orientation parallel to the z-axis of the scanner using 4 convolution kernels. The measured diameters of the stented lumen were 47-57% and 36-45% smaller than the actual inner diameter of the 3- and 4-mm diameter models, respectively. The diameter measurement of the stent lumen and visualization of the in-stent stenosis were improved by using convolution kernels with higher spatial resolution. The in-stent artifacts were evaluated in 4 orientations (0 degrees , 30 degrees , 60 degrees , 90 degrees ) to the z-axis. The artifact was the minimum in 0 degrees to the z-axis, and the maximum in 90 degrees .

CONCLUSION

Visualization of the lumen of a stent by CT is affected by its diameter, convolution kernel, and vessel orientation to the z-axis, and these factors should be taken into consideration in the stent evaluation.

Myocardial bridging

Myocardial bridging, a congenital coronary anomaly, is a clinical condition with several possible manifestations, and its clinical relevance is debated. This article reviews current knowledge about the anatomy, pathophysiology, clinical relevance, and treatment of myocardial bridging. Myocardial bridging is present when a segment of a major epicardial coronary artery, the 'tunnelled artery', runs intramurally through the myocardium. With each systole, the coronary artery is compressed. Myocardial bridging has been associated with angina, arrhythmia, depressed left ventricular function, myocardial stunning, early death after cardiac transplantation, and sudden death. Evidence indicates that the intima beneath the bridge is protected from atherosclerosis, and the proximal segment is more susceptible to development of atherosclerotic lesions because of haemodynamic disturbances. New techniques (e.g. intravascular ultrasonography and intracoronary Doppler studies) have revealed new characteristics and pathophysiologic processes such as diastolic flow abnormalities. Medical treatment generally includes beta-blockers. Nitrates should be avoided because symptoms may worsen. Intracoronary stents and surgery have been attempted in selected patients. Additional research is needed to define patients in whom myocardial bridging is potentially pathologic, and randomized multicentre long-term follow-up studies are needed to assess the natural history, patient selection, and therapeutic approaches.

Symptomatic myocardial bridges: overview of ischemic mechanisms and current diagnostic and treatment strategies

This review article focuses on the morphological and functional alterations that characterize patients with myocardial bridges (MB) as well as the currently available diagnostic and treatment strategies. Because of incomplete understanding of the pathophysiology of MB, their clinical significance has been the subject of debate for the last quarter century. Investigational tools now available in the cardiac catheterization laboratory have helped clarify why symptoms and signs of ischemia can occur in such patients, especially when the only angiographic finding appears to be systolic compression or milking effect of a coronary vessel. Quantitative coronary angiography and intravascular ultrasound (IVUS) clearly demonstrate that the phasic systolic vessel compression visualized on the angiogram is coupled with a persistent diastolic diameter reduction. Intracoronary Doppler reveals increased flow velocities, retrograde systolic flow, and reduced coronary flow reserve. The clinical diagnosis can be established by significant percent lumen diameter and area narrowing, increased flow velocity, and by characteristic patterns such as the "half moon" phenomenon on IVUS and the early diastolic "finger tip" phenomenon on intracoronary Doppler. Successful medical, interventional, or surgical therapy leads not only to marked improvement or normalization of these alterations but also relief of angina and ischemia.

Myocardial bridging as a cause of acute myocardial infarction: a case report

BACKGROUND

Systolic compression of a coronary artery by overlying myocardial tissue is termed myocardial bridging. Myocardial bridging usually has a benign prognosis, but some cases resulting in myocardial ischemia, infarction and sudden cardiac death have been reported. We are reporting a case of myocardial bridging which was complicated with acute myocardial infarction associated with inappropriate blood donation.

CASE PRESENTATION

A 33 year-old-man was admitted to our emergency with acute anteroseptal myocardial infarction after a blood donation. The electrocardiography showed sinus rhythm and was consistent with an acute anteroseptal myocardial infarction. We decided to perform primary percutanous intervention (PCI). Myocardial bridging was observed in the mid segment of the left anterior descending coronary artery on coronary angiogram. PCI was canceled and medical follow up was decided. Blood transfusion was made because he had a deep anemia. A normal hemoglobin level and clinical reperfusion was achieved after ten hours by blood transfusion. At the one year follow up visit, our patient was healthy and had no cardiac complaints.

CONCLUSIONS

Myocardial bridging may cause acute myocardial infarction in various clinical conditions. Although the condition in this case caused profound anemia related acute myocardial infarction, its treatment and management was unusual.