Myocardial bridging as a cause of acute transient left heart dysfunction

Contemporary Review of Myocardial Bridging for Internists

Myocardial bridging is a congenital coronary condition in which an epicardial coronary artery courses within the myocardial muscle instead of running on its surface. Its prevalence varies depending upon the diagnostic modality used for its testing. It is reported to be 40%-80% in autopsy studies, 58% on coronary artery computed tomography, and 0.5%-16% on invasive coronary angiography. Historically, myocardial bridging was considered to be a benign entity. Recent data have shown that this entity not only can cause chronic angina in patients with non-obstructive coronary artery disease but is also associated with an increased risk of major adverse cardiovascular events. Indeed, this condition remains overlooked and not well understood among internal medicine physicians and even among many cardiologists. This review aimed to describe this disease entity and its clinical presentations, understand the anatomic and physiological mechanisms of angina related to this entity, and introduce a comprehensive algorithm for detailed evaluation and phenotype-guided treatment.

Impact of Clinical and Morphological Factors on Long-Term Mortality in Patients with Myocardial Bridge

Although myocardial bridging (MB) has been intensively investigated using different methods, the effect of bridge morphology on long-term outcome is still doubtful. We aimed at describing the anatomical differences in coronary angiography between symptomatic and non-symptomatic LAD myocardial bridges and to investigate the influence of clinical and morphological factors on long-term mortality. In our retrospective, long-term, single center study we found relevant MB on the left anterior descendent (LAD) coronary artery in 146 cases during a two-year period, when 11,385 patients underwent coronary angiography due to angina pectoris. Patients were divided into two groups: those with myocardial bridge only (LAD-MBneg, n = 78) and those with associated obstructive coronary artery disease (LAD-MBpos, n = 68). Clinical factors, morphology of bridge by quantitative coronary analysis and ten-year long mortality data were collected. The LAD-MBneg group was associated with younger age and decreased incidence of diabetes mellitus, as well as with increased minimal diameter to reference diameter ratio (LAD-MBneg 54.5 (13.1)% vs. LAD-MBpos 46.5 (16.4)%, p = 0.016), while there was a tendency towards longer lesions and higher vessel diameter values compared to the LAD-MBpos group. The LAD-MBpos group was associated with increased mortality compared to the LAD-MBneg group. The analysis of our data showed that morphological parameters of LAD bridge did not influence long-term mortality, either in the overall population or in the LAD-MBneg patients. Morphological parameters of LAD bridge did not influence long-term mortality outcomes; therefore, it suggests that anatomical differences might not predict long-term outcomes and should not influence therapy.

Myocardial bridges: A meta-analysis

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

What is the optimal treatment for symptomatic patients with isolated coronary myocardial bridge? A systematic review and pooled analysis

BACKGROUND

Myocardial bridging is a common coronary anomaly, with few severe adverse events but a relevant symptom burden. Myocardial bridging treatment, however, remains uncertain because of the lack of randomized trials.

MATERIAL

MEDLINE/PubMed was systematically screened for studies reporting on isolated myocardial bridging diagnosed at coronary angiography or with coronary computed tomography in patients admitted for suspected angina or with an acute coronary syndrome. Baseline, treatment and outcome data were appraised and pooled according to treatment (medical therapy, bypass surgery/myotomy or stenting).

RESULTS

A total of 899 patients in 18 studies were included with a low prevalence of traditional risk factors, especially diabetes (15.6%, interquartile range 2.5-21.5). After a median of 31.0 months (interquartile range 12.4-37.1), major cardiovascular events (composite of death, myocardial infarction or target vessel revascularization) occurred in only 3.4% of the study patients and 78.7% [70.5-86.9; 95% confidence intervals (CI)] were managed conservatively and free of symptoms. When an invasive strategy was planned, freedom from angina was higher in patients treated with surgery [84.5% (78.4-90.7; 95% CI)] than in those treated with stenting [54.7% (38.9-70.6; 95% CI)]. Patients in the stenting group experienced a high incidence of major cardiovascular events related to target vessel revascularization [40.07% (19.83-60.32; 95% CI)]. Meta-regression showed that patients treated with beta-blockers or with a history of hypertension were more likely to remain free from angina (B -0.6, P = 0.013; B -0.66, P = 0.006).

CONCLUSION

Patients with symptomatic isolated myocardial bridging generally have a good long-term prognosis. Pharmacological treatment alone, especially with beta-blockers, is able to improve angina in most cases. Surgical treatment appears to be more effective than stenting in nonresponders.

Myocardial bridging: contemporary understanding of pathophysiology with implications for diagnostic and therapeutic strategies

Patients with myocardial bridging are often asymptomatic, but this anomaly may be associated with exertional angina, acute coronary syndromes, cardiac arrhythmias, syncope, or even sudden cardiac death. This review presents our understanding of the pathophysiology of myocardial bridging and describes prevailing diagnostic modalities and therapeutic options for this challenging clinical entity.

Assessment of myocardial bridge and mural coronary artery using ECG-gated 256-slice CT angiography: a retrospective study

Recent clinical reports have indicated that myocardial bridge and mural coronary artery complex (MB-MCA) might cause major adverse cardiac events. 256-slice CT angiography (256-slice CTA) is a newly developed CT system with faster scanning and lower radiation dose compared with other CT systems. The objective of this study is to evaluate the morphological features of MB-MCA and determine its changes from diastole to systole phase using 256-slice CTA. The imaging data of 2462 patients were collected retrospectively. Two independent radiologists reviewed the collected images and the diagnosis of MB-MCA was confirmed when consistency was obtained. The length, diameter, and thickness of MB-MCA in diastole and systole phases were recorded, and changes of MB-MCA were calculated. Our results showed that among the 2462 patients examined, 336 have one or multiple MB-MCA (13.6%). Out of 389 MB-MCA segments, 235 sites were located in LAD2 (60.41%). The average diameter change of MCA in LAD2 from systole phase to diastole phase was 1.1 ± 0.4 mm, and 34.9% of MCA have more than 50% diameter stenosis in systole phase. This study suggested that 256-slice CTA multiple-phase reconstruction technique is a reliable method to determine the changes of MB-MCA from diastole to systole phase.

Myocardial bridging assessed by multidetector computed tomography: likely cause of chest pain in younger patients with low prevalence of dyslipidemia

INTRODUCTION AND OBJECTIVES

The relationship between myocardial bridging and symptoms is still unclear. The purpose of our study was to assess the relationship between myocardial bridging detected by multidetector computed tomography and symptoms in a patient population with chest pain syndrome.

METHODS

The study enrolled 393 consecutive patients without previous coronary artery disease studied for chest pain and referred to multidetector computed tomography between January 2007 and December 2010. Noninvasive coronary angiography was performed using multidetector computed tomography. Myocardial bridging was defined as part of a coronary artery completely surrounded by myocardium on axial and multiplanar reformatted images.

RESULTS

Mean age was 64.6 (12.4) years and 44.8% were male. Multidetector computed tomography detected 86 myocardial bridging images in 82 of the 393 patients (20.9%). Left anterior descending was the most frequent coronary artery involved (87.2%). The prevalence of myocardial bridging was significantly higher in patients without significant atherosclerotic coronary stenosis on multidetector computed tomography (24.9% vs 15.0%; P=.02). Patients with myocardial bridging were younger (60.3 [13.8] vs 65.8 [11.9]; P<.001), had less prevalence of hyperlipidemia (29.3% vs 41.8%; P=.03), and more prevalence of cardiomyopathy (6.1% vs 1.6%, P=.02) compared with patients without myocardial bridging on multidetector computed tomography.

CONCLUSIONS

Multidetector computed tomography is an easy and reliable tool for comprehensive in vivo diagnosis of myocardial bridging. The results of the present study suggest myocardial bridging is the cause of chest pain in a subgroup of younger aged patients with less prevalence of hyperlipidemia and more prevalence of cardiomyopathy than patients with significant atherosclerotic coronary artery disease on multidetector computed tomography. Full English text available from:www.revespcardiol.org.

Kounis Syndrome together with Myocardial Bridging Leading to Acute Myocardial Infarction at Young Age

Kounis syndrome, also named as "allergic angina syndrome," is a diagnosis in which exposure to an allergen causes mostly coronary spasm and rarely plaque rupture, resulting in ischemic myocardial events. Myocardial bridging is defined as an intramural segment of a coronary artery and its systolic compression by overlying fibers. Myocardial bridging generally has a benign prognosis and mostly affects the mid portion of left anterior descending coronary artery. However, some cases with myocardial ischemia, infarction, and sudden death have also been reported. A 17-year-old boy presented to the clinic with acute anterolateral myocardial infarction after having first dose of clindamycin and diagnosed as Kounis syndrome. Further diagnostic workup of the patient showed myocardial bridging at the mid left anterior descending artery. In this report, we present the combination of Kounis syndrome and myocardial bridging leading to myocardial infarction at young age.

Myocardial bridging in an adult patient with d-transposition of the great arteries

Myocardial bridging is characterized by intra-myocardial course of a segment of an epicardial coronary artery, leading to systolic compression. In most cases, it is considered a benign condition but rarely has been associated with serious cardiac events like myocardial infarction and sudden death. We describe a 25-year-old man with known d-transposition of the great arteries (d-TGA) status post-Mustard procedure who presented with palpitations and chest pain. Cardiac catheterization revealed complete systolic compression of a myocardial bridging segment of the left anterior descending artery and also complete compression of the first septal perforator during episodes of ectopic atrial tachycardia. No percutaneous or surgical interventions were performed. Symptoms improved after cautious use of beta-blockers. This appears to be the first report of symptomatic myocardial bridging in an adult patient with d-TGA.

Evaluation of myocardial bridge with multidetector computed tomography

BACKGROUND

The myocardial bridge (MB) is an intramural segment of coronary artery that is covered with myocardial tissue. The current diagnostic methods are coronary angiography, intravascular ultrasound and intracoronary Doppler, which are all invasive modalities. In this study, multidetector computed tomography (MDCT) was used to detect and evaluate the anatomical properties of the MB.

METHODS AND RESULTS

The 607 patients with suspected or known coronary artery disease underwent 64-slice MDCT. MB was diagnosed when an intramural segment of coronary artery was visualized on axial and multiplanar reconstruction images. The prevalence, length, myocardial thickness, and location were evaluated. Of the 607 patients, 39 (6.42%) had a MB. In 20 patients (52.6%), the MB was located in the mid left anterior descending artery. The length of tunneled artery was a mean 16.3 mm, from 6.9 mm to 30 mm, and the maximum thickness of the myocardial tissue was between 0.5 mm and 3.9 mm, with a mean of 1.8 mm. The length of the MB correlated significantly with thickness (P=0.049).

CONCLUSIONS

The incidence of MB and its anatomical properties can be evaluated with MDCT, which might be a useful and noninvasive method of detecting this variant. (Circ J 2010; 74: 137 - 141).

Systolic total narrowing of left anterior descending coronary artery and flow interruption secondary to myocardial bridge: a rare case report and review of literature

A 33-y-old man was admitted to the emergency department with sudden onset of severe substernal chest pain radiating to the left arm and neck. No pathological signs were recorded upon physical examination. The admission electrocardiogram (ECG) recorded during chest pain showed a large anterior wall myocardial infarction. Intravenous (IV) infusion of 1.5 million units of streptokinase over 1 h was initiated. Coronary angiography revealed total narrowing and flow interruption in the midsegment of the left anterior descending (LAD) coronary artery secondary to a myocardial bridge during systole and disappearance with diastole. He was discharged on aspirin (300 mg/d), metoprolol (100 mg/d), enalapril (10 mg twice daily), and atorvastatin (40 mg/d) treatment at the follow-up period.

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.

Myocardial bridging in absence of coronary artery disease: proposal of a new classification based on clinical-angiographic data and long-term follow-up

BACKGROUND

There is no widely accepted classification to guide therapy in patients with symptomatic myocardial bridging (MB).

METHODS

A retrospective analysis of 157 patients with chest pain, angiographic MB of the left anterior descending artery without obstructive coronary artery disease (CAD) was performed. Patients were evaluated for clinical symptoms, objective signs of ischemia by stress test, intracoronary Doppler flow measurement and coronary flow reserve. 100 patients without CAD or MB served as controls.

RESULTS

There was no difference in clinical symptoms and objective signs of ischemia between controls and patients with MB. The length of MB was 22.6 +/- 7.8 mm, maximal systolic luminal diameter reduction 71 +/- 16%, and maximal mid-diastolic luminal reduction 34.7 +/- 13% as demonstrated by quantitative coronary angiography (QCA). Intracoronary Doppler showed significantly increased average peak flow velocity (APV), average systolic peak velocity (ASPV), average diastolic peak flow velocity (ADPV), and maximal peak velocity (MPV) in MB versus proximal and distal segments at rest and after maximal vasodilatation (p < 0.001 for all parameters). Coronary flow reserve was significantly higher proximally (2.9 +/- 0.9) compared with segments distal to the MB (2.0 +/- 0.6, p < 0.01). We propose a new MB classification for symptomatic patients with MB:Type A:incidental finding on angiography, no objective signs of ischemia; Type B: objective signs of ischemia, and Type C: with or without objective signs of ischemia and altered intracoronary hemodynamics (by QCA/CFR/intracoronary Doppler). 5-Year follow-up data based on this classification showed that types B and C responded well to beta-blockers or calcium channel antagonists. Patients with type C refractory to medical therapy were treated with stenting of the MB.

CONCLUSION

Patients with MB without CAD did not have a higher prevalence of chest pain or abnormal non-invasive stress tests compared to patients without CAD or MB. Intracoronary hemodynamic measurement is a novel approach that may be valuable in defining the functional significance of MB. We propose a classification of symptomatic patients with MB without CAD using non-invasive and invasive parameters to guide therapeutic choices.

Myocardial bridging as evaluated by 16 row MDCT

PURPOSE

The purpose of this study is to find out the prevalence, appearance and clinical symptoms of myocardial bridging (MB) by MDCT coronary angiography (CTA).

MATERIALS AND METHODS

A total of 280 (50 females) consecutive patients followed with coronary artery disease or postoperative stent and bypass control, underwent CTA performed by 16-MDCT scanner between January 2006 and April 2006. Short axis multiplanar reformatted images were evaluated. MBs were classified as complete and incomplete bridges with respect to continuity of the myocardium over the tunneled segment of left anterior descending artery (LAD) in interventricular groove and the cut-off value is 1.3mm. Patients diagnosed with MB on CTA who had prior catheter angiography studies were re-evaluated for the presence of MB.

RESULTS

One hundred and twenty MBs [98 (81.6%) on LAD, 2 (1.6%) on diagonal branch, 11 (9.1%) on obtuse marginal, 4 (3.3%) on right coronary artery, 5 (4.1%) on ramus intermedius artery] were detected in 108 (38.5%) patients. Eighty-five (70.8%) of bridged segments in 79 (28.2%) patients were complete and the rest [35 (29.2%) in 34 (12.1%) patients] were incomplete. In 12 patients two MBs (either on different arteries or on the same artery) were detected. The length of bridged segments in patients with complete and incomplete MBs varied between 4-50.9mm (mean 18mm) and 4-37.3mm (mean 13.6mm), respectively, and the depth of myocardium over the artery ranged between 1-6.4mm (mean 2.3mm) and 1-1.2mm (mean 1mm), respectively. Thirty (27.7%) out of 108 patients, in whom MB was detected on CTA, were found to have correlative catheter angiography studies, retrospectively and MB was detected only in 4 (13.3%) out of 30 patients.

CONCLUSION

MDCT coronary angiography is a non-invasive, efficient method in the diagnosis of MB avoiding the procedural risks that catheter angiography carries. MDCT coronary angiography allows direct visualization of the bridge itself and may thus give the opportunity to differentiate between complete and incomplete myocardial bridges.

Myocardial bridge: evaluation on MDCT

OBJECTIVE

The correlation between myocardial bridge and atherosclerotic changes has been controversial. The aim of this study was to evaluate the relation between myocardial bridge and atheromatous coronary artery disease (CAD).

MATERIALS AND METHODS

Three hundred consecutive subjects who underwent coronary CT angiography (CTA) were included in this study. The prevalence, length, depth, precise location, and concomitant atheromatous changes were evaluated. The group of subjects with myocardial bridge was compared with another subgroup, the control group, which included subjects without myocardial bridge.

RESULTS

From a total of 300 subjects, 78 subjects (26%) were found to have one myocardial bridge each. The mid left anterior descending artery (LAD) was the most common coronary artery involved (48/78). A significant difference was found between the LAD myocardial bridge group and the control group regarding presence of atheromatous changes in a similar LAD segment proximal to the myocardial bridge (p < 0.0001) and in the severity of atheromatous changes in these segments (mild, p < 0.0001; moderate, p < 0.02; and severe, p < 0.0001). The presence of stenosis in the LAD proximal to the myocardial bridge correlated with the thickness and length of the bridge.

CONCLUSION

Myocardial bridge predisposes to the development of atherosclerosis in the coronary artery segment proximal to the bridge. This may indicate that myocardial bridge should be considered an anatomic risk factor in the evaluation of CAD.

Off-pump supraarterial decompression myotomy for myocardial bridging

BACKGROUND

Myocardial bridging of the left anterior descending (LAD) artery may result in clinical symptoms. Surgery with cardiopulmonary bypass (CPB) is a therapeutic option with considerable risk. We hypothesized that off-pump supraarterial myotomy could be an effective treatment modality.

METHODS

Between October 1998 and May 2000, 13 patients were referred for surgery. All were symptomatic despite medical therapy. Anteroseptal ischemia had been proven by thallium scintigraphy in all 13 patients, exercise testing was positive in 11. All patients were operated on with an off-pump approach after median sternotomy.

RESULTS

Mean patient age was 61 +/- 8 years (range, 43-71 years). Coronary artery disease mandating additional bypasses was present in 3 patients. The bypasses were done off pump in 2 patients. Conversion to on-pump surgery was necessary in 3 of 13 patients (23%) because of hemodynamic compromise (1 patient), opening of the right ventricle (1 patient), and injury to the LAD (1 patient). Supraarterial myotomy was performed in all patients. One patient who underwent surgery with CPB developed postoperative anteroseptal myocardial infarction. Postoperative exercise testing was performed in all patients and did not reveal any persistent ischemia. Mortality was 0%. All patients were free from symptoms and had not undergone repeat interventions after an average of 51 +/- 7 months of follow-up.

CONCLUSIONS

Off-pump supraarterial myotomy effectively relieves coronary obstruction but has a certain periprocedural risk as evidenced by 1 myocardial infarction, 1 right ventricular injury, and 1 LAD injury. Long-term freedom from symptoms and from reintervention favor further investigation of this surgical therapy.

Myocardial perfusion SPECT imaging in patients with myocardial bridging

BACKGROUND

Although myocardial perfusion single photon emission computed tomography (SPECT) imaging is widely used to assess myocardial ischemia in patients with known or suspected coronary artery disease, only a few patients with myocardial bridging have been evaluated with nuclear techniques. Furthermore, it has been suggested that dipyridamole stress images might underestimate perfusion defects compared with exercise stress images. This study was done to determine the concordance of exercise stress SPECT images with that obtained by dipyridamole stress SPECT images as a means of detecting ischemia in patients with myocardial bridging.

METHODS AND RESULTS

Sixteen consecutive patients with angina and normal arteries but myocardial bridging of the left anterior descending artery underwent rest-exercise stress SPECT imaging. Within 2 weeks after angiograms were obtained, only dipyridamole stress images were repeated. The mean angiographic systolic occlusion within the myocardial bridges was 73% +/- 10%. Overall, the prevalence of an abnormal scan was no different in patients who underwent exercise stress myocardial perfusion imaging (MPI) as compared with patients who underwent dipyridamole stress MPI (14/16 [88%] vs 13/16 [81%], respectively; P = .953). Exercise stress MPI showed a higher stress score than dipyridamole stress MPI, but the difference did not reach statistical significance (7.5 +/- 3.3 vs 6 +/- 2.7, P = .147). The strength of agreement among exercise stress MPI and dipyridamole stress MPI studies was good (kappa = 0.765; 95% CI, 0.318 to 1.211; P < .05).

CONCLUSIONS

Cardiac SPECT studies can be used effectively for assessing ischemia in patients with angina and myocardial bridging. The evaluation of myocardial perfusion with dipyridamole stress SPECT imaging showed a good agreement with exercise stress SPECT imaging for the detection of ischemia in this group of patients.

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.

PCR identification system for the genus Aspergillus and three major pathogenic species: Aspergillus fumigatus, Aspergillus flavus and Aspergillus niger

A PCR system was developed that allowed recognition of three major pathogenic Aspergillus species, namely A. fumigatus, A. niger and A. flavus, in isolates obtained from clinical specimens. The primer pair for PCR was designed from conserved sequences of internal transcribed spacer 1 (ITS1) ribosomal DNA and its flanking regions. Products 521 bp in size were successfully amplified by PCR from the seven Aspergillus species most frequently encountered as opportunistic pathogens, and the three most commonly significant species were identified by separate PCR reactions or nested PCR based on use of species-specific primers. To our knowledge, this is first report of identification of the second and third most frequent pathogenic Aspergillus species using specific PCR amplification. The PCR based identification system reported here will be a powerful tool to control difficult pulmonary fungal infections and to speed the application of effective treatment.