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BACKGROUND: Myocardial bridge (MB) is described as an abnormal band of myocardium covering a variable portion of any coronary artery. METHODS: The current study explores the presence of MB throughout the coronary arterial system and provides a morphometric description through instrumented dissection of a sample of 100 human hearts. The study shows a higher prevalence of MB in the Mexican population than in previous reports. RESULTS: In the total sample (n=100), MB was identified in 96% of it. A total of 421 MBs were observed, with a mean of 4.38mm (±0.28) per dissected heart. The most frequently affected vessel is the anterior interventricular artery where a total of 52 MBs were found, of the total sample studied. DISCUSSION: The high prevalence of MB among Mexican patients could be the result of a genetic association for this population or the neoformation of MB after birth due to lifestyle-associated factors. Further studies are required to better understand the high prevalence of MB among Mexican subjects.

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Introducción. La arteria interventricular anterior se origina en la coronaria izquierda, irriga la cara anterior de los ventrículos, el ápex y el tabique interventricular; es la segunda arteria más relevante del corazón. Objetivo. Describir las características anatómicas y clínicas de la arteria interventricular anterior mediante angiografía. Materiales y métodos. Se realizó un estudio descriptivo con 200 reportes angiográficos de personas colombianas; se valoraron el origen, el trayecto y la permeabilidad de la arteria interventricular anterior, así como la dominancia coronaria. Se incluyeron datos relacionados con dolor precordial, infarto agudo de miocardio, dislipidemia y alteración electrocardiográfica. No fue posible hacer pruebas estadísticas, debido a la escasa prevalencia de variaciones anatómicas de dicha arteria. Resultados. Se encontró una arteria interventricular anterior con su origen en el seno aórtico izquierdo, sin puente miocárdico, sin alteración de la permeabilidad y con dominancia izquierda. La frecuencia de los puentes fue del 2 % y la dominancia más frecuente fue la derecha en el 86 %. Se presentaron alteraciones de permeabilidad en el 43 % de los casos, las cuales afectaron principalmente al S13. El 25 % de los pacientes presentó dolor precordial; el 40 %, alteraciones ecocardiográficas; el 5 %, cardiopatía isquémica, y el 59 %, alguna alteración electrocardiográfica. Conclusiones. Las variaciones en el origen de la arteria interventricular anterior son poco prevalentes, según reportes de Chile, Colombia y España. Los puentes miocárdicos de esta arteria fueron escasos respecto a otros estudios, lo cual sugiere mejor especificidad de los hallazgos de la angiotomografía o de la disección directa. La permeabilidad coronaria se valora con la escala TIMI (Thrombolysis in Myocardial Infarction); puntajes de 0 y 1 indican una lesión oclusiva asociada con cardiopatía isquémica. La dominancia coronaria más frecuente, según diversas técnicas, es la derecha, seguida de la izquierda en hombres y de una circulación balanceada en mujeres.

Introduction. The anterior interventricular artery originates from the left coronary artery and irrigates the anterior surface of the ventricles, apex, and interventricular septum, making it the second most relevant artery of the heart. Objective. To describe the anatomical and clinical aspects of the anterior interventricular artery through angiography. Materials and methods. A descriptive study was conducted using 200 angiographic reports of Colombian individuals. The anterior interventricular artery's origin, course, patency, and coronary dominance were evaluated. Data related to chest pain, acute myocardial infarction, dyslipidemia, and electrocardiographic abnormalities were included. Statistical tests could not be performed due to this artery's low prevalence of anatomical variations. Results. One anterior interventricular artery was found to have originated from the left coronary sinus without a myocardial bridge, with no alteration in permeability, and with left dominance. The frequency of bridges was 2%, and the most frequent dominance was right in 86; permeability alterations occurred in 43% mainly affecting S13. Twenty-five per cent presented chest pain; 40%, echocardiographic alterations; 5%, ischemic heart disease, and 59%, electrocardiographic alterations. Conclusions. Variations of origin of the anterior interventricular artery have a low prevalence according to reports from Chile, Colombia, and Spain. anterior interventricular artery myocardial bridges were scarce compared to other studies, suggesting better specificity of computed tomography angiography or direct dissection for these findings. The assessment of coronary permeability is graded with the thrombolysis in myocardial infarction scale; values 0 and 1 indicate occlusive lesion associated with ischemic heart disease. According to various techniques, the most frequent coronary dominance the right, followed by the left in men and balanced circulation in women.

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SUMMARY: Myocardial bridges are inborn anomalies frequently found in authopsies. Although tipically clinically silent, they are occasionally associated with severe clinical manifestations, e.g. myocardial ischemia or even sudden death. The pathophysiology and risk factors for these manifestations have not yet been completely elucidated. The connective tissue underneath the bridge has been considered as one of the factors the symptoms depend on. Thus, the aim of this research was to determine the histological characteristics of the connective tissue lying underneath the myocardial bridge and to contribute to a better understanding of the protective effects this passive compartment might have in prevention of severe clinical manifestations of myocardial bridging. The study was carried out on twenty hearts with myocardial bridges. Length of the bridge was determined using a precise electronic caliper. Sections of the myocardial bridges with the underlying connective tissue were obtained and prepared for qualitative and quantitative analysis. The connective tissue underneath the bridges was composed of adipose tissue and loose connective tissue in different ratios. The tissue underneath thin bridges was predominantly composed of adipose tissue, while loose connective tissue was the dominant component under thick bridges. The myocardial bridges had an average thickness of 0,98 ± 0.44 mm and an average length of 15,25±5,65 mm. We found a strong positive correlation between the myocardial bridge thickness and length (r = 0,860, p = 0,0001). The thickness of the passive connective tissue compartment under the myocardial bridges was 0,58±0,22 mm, and there was no correlation between this parameter and the myocardial bridge thickness (r = -0,011; p = 0,963). In the clinical evaluation of patients with these anomalies it is necessary to take into account independently the myocardial bridge thickness and length on one side and the thickness of the connective tissue lying underneath it on the other.

Los puentes miocárdicos son anomalías congénitas que se encuentran con frecuencia en las autopsias. Aunque típicamente éstos son clínicamente silenciosos, ocasionalmente se asocian con manifestaciones clínicas graves, como isquemia miocárdica o incluso muerte súbita. La fisiopatología y los factores de riesgo de estas manifestaciones aún no se han dilucidado por completo. El tejido conectivo debajo del puente se ha considerado como uno de los factores de los que dependen los síntomas. Por lo tanto, el objetivo de esta investigación fue determinar las características histológicas del tejido conectivo que se encuentra debajo del puente miocárdico y contribuir a una mejor comprensión de los efectos protectores que este compartimento pasivo podría tener en la prevención de manifestaciones clínicas graves de puente miocárdico. El estudio se llevó a cabo en veinte corazones con puentes miocárdicos. La longitud del puente se determinó utilizando un calibrador electrónico preciso. Se obtuvieron secciones de los puentes miocárdicos con el tejido conjuntivo subyacente y se prepararon para análisis cualitativo y cuantitativo. El tejido conectivo debajo de los puentes estaba compuesto de tejido adiposo y tejido conectivo laxo en diferentes proporciones. El tejido debajo de los puentes delgados estaba predominantemente compuesto de tejido adiposo, mientras que el tejido conectivo laxo era el componente dominante debajo de los puentes gruesos. Los puentes de miocardio tenían un espesor promedio de 0,98 ± 0,44 mm y una longitud promedio de 15,25 ± 5,65 mm. Encontramos una fuerte correlación positiva entre el grosor y la longitud del puente miocárdico (r = 0,860, p = 0,0001). El grosor del compartimiento de tejido conectivo pasivo debajo de los puentes miocárdicos era de 0,58±0,22 mm, y no hubo correlación entre este parámetro y el grosor del puente miocárdico (r = -0,011; p = 0,963). En la evaluación clínica de pacientes con estas anomalías es necesario tener en consideración de forma independiente el grosor y la longitud del puente de miocardio por un lado y el grosor del tejido conectivo que se encuentra debajo del mismo por el otro.

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Wellens' syndrome is an electrocardiographic harbinger of a critical left anterior descending (LAD) coronary artery stenosis in acute coronary syndromes (ACS), whereas pseudo-Wellens' syndrome typically has angiographically normal coronary arteries. Myocardial bridging (MB) occurs when an epicardial coronary artery segment takes a tunneled intramuscular course. We describe a rare case of MB-induced pseudo-Wellens' syndrome in a young patient presenting with unstable angina (USA).

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Mazama gouazoubira is a widely distributed deer in the South American continent. However, studies on its anatomical characteristics are still scarce. The objective of this study was to elucidate the coronary circulation of M. gouazoubira. With this aim, after collecting cadavers on highways, twenty-four hearts injected with latex and preserved in formaldehyde at 10% were dissected. The dissections revealed that all specimens presented left coronary dominance, characterized by the origin of the subsinuous interventricular branch from the circumflex branch of the left coronary artery. The number of ventricular branches originated from branches of the left coronary artery was approximately five times higher than that of the right coronary artery. The occurrence of myocardial bridges was registered in 91.7% of the individuals, with bridges predominating over the paraconal interventricular branch. The mean length of the paraconal interventricular sulcus was significantly higher in males (p = 0.02). The number of atrial branches and ventricular branches, length of myocardial bridges and length of subsinuous interventricular sulcus did not vary significantly between sex. Left coronary dominance and high frequency of myocardial bridges in M. gouazoubira are preponderant anatomical traits also present in different species of Ruminantia suborder. Coronary dominance studies in other South American deer species may confirm the correlation of this trait with the evolutionary history of these animals.(AU)

Mazama gouazoubira é um cervídeo com ampla distribuição no continente sul americano. Entretanto, estudos sobre suas características anatômicas, ainda, são escassos. Objetivou-se elucidar a circulação coronariana do M. gouazoubira. Para tal, foram dissecados 24 corações injetados com látex e conservados em formaldeído a 10%, obtidos de cadáveres recolhidos em rodovias. As dissecações revelaram que todos os espécimes apresentaram dominância coronariana esquerda, caracterizada pela origem do ramo interventricular subsinuoso, a partir do ramo circunflexo da artéria coronária esquerda. O número de ramos ventriculares originados, a partir de ramos da artéria coronária esquerda, foi aproximadamente cinco vezes maior do que aquele da artéria coronária direita. A ocorrência de pontes de miocárdio foi registrada em 91,7% dos indivíduos, predominando as pontes sobre o ramo interventricular paraconal. O comprimento médio do sulco interventricular paraconal foi significativa-mente maior em machos (p = 0,02). O número de ramos atriais e ramos ventriculares, comprimento das pontes de miocárdio e comprimento do sulco interventricular subsinuoso, não variaram, significativamente, entre os sexos. A dominância corona-riana esquerda e a elevada frequência de pontes de miocárdio no M. gouazoubira são traços anatômicos preponderantes, tam-bém, em diferentes espécies da subordem Ruminantia. Estudos sobre dominância coronariana em outras espécies de cervídeos sul americanos poderão sugerir a correlação desta característica com a história evolutiva destes animais.(AU)

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Mazama gouazoubira is a widely distributed deer in the South American continent. However, studies on its anatomical characteristics are still scarce. The objective of this study was to elucidate the coronary circulation of M. gouazoubira. With this aim, after collecting cadavers on highways, twenty-four hearts injected with latex and preserved in formaldehyde at 10% were dissected. The dissections revealed that all specimens presented left coronary dominance, characterized by the origin of the subsinuous interventricular branch from the circumflex branch of the left coronary artery. The number of ventricular branches originated from branches of the left coronary artery was approximately five times higher than that of the right coronary artery. The occurrence of myocardial bridges was registered in 91.7% of the individuals, with bridges predominating over the paraconal interventricular branch. The mean length of the paraconal interventricular sulcus was significantly higher in males (p = 0.02). The number of atrial branches and ventricular branches, length of myocardial bridges and length of subsinuous interventricular sulcus did not vary significantly between sex. Left coronary dominance and high frequency of myocardial bridges in M. gouazoubira are preponderant anatomical traits also present in different species of Ruminantia suborder. Coronary dominance studies in other South American deer species may confirm the correlation of this trait with the evolutionary history of these animals.

Mazama gouazoubira é um cervídeo com ampla distribuição no continente sul americano. Entretanto, estudos sobre suas características anatômicas, ainda, são escassos. Objetivou-se elucidar a circulação coronariana do M. gouazoubira. Para tal, foram dissecados 24 corações injetados com látex e conservados em formaldeído a 10%, obtidos de cadáveres recolhidos em rodovias. As dissecações revelaram que todos os espécimes apresentaram dominância coronariana esquerda, caracterizada pela origem do ramo interventricular subsinuoso, a partir do ramo circunflexo da artéria coronária esquerda. O número de ramos ventriculares originados, a partir de ramos da artéria coronária esquerda, foi aproximadamente cinco vezes maior do que aquele da artéria coronária direita. A ocorrência de pontes de miocárdio foi registrada em 91,7% dos indivíduos, predominando as pontes sobre o ramo interventricular paraconal. O comprimento médio do sulco interventricular paraconal foi significativa-mente maior em machos (p = 0,02). O número de ramos atriais e ramos ventriculares, comprimento das pontes de miocárdio e comprimento do sulco interventricular subsinuoso, não variaram, significativamente, entre os sexos. A dominância corona-riana esquerda e a elevada frequência de pontes de miocárdio no M. gouazoubira são traços anatômicos preponderantes, tam-bém, em diferentes espécies da subordem Ruminantia. Estudos sobre dominância coronariana em outras espécies de cervídeos sul americanos poderão sugerir a correlação desta característica com a história evolutiva destes animais.

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SUMMARY: Most histopathological studies have reported that the segment of the coronary artery below the myocardial bridge does not present atheromatous plaque, while the segment proximal to the myocardial bridge may have it. The aim of this study was to evaluate the microscopic environment of myocardial bridges. This descriptive study was carried out with 60 hearts of individuals who underwent autopsy at the National Institute of Legal Medicine and Forensic Sciences in Bucaramanga-Colombia. For each specimen, the coronary arteries and their branches were dissected, removing the subepicardial adipose tissue to identify the myocardial bridges and obtain histological sections of the compromised arterial branches. The presence of myocardial bridges was observed in 22 hearts (36.7%) with a length of 17.31 + 4.41 mm and a thickness of 904.57 + 312.27 mm. The coronary vessel caliber at the prepontine level was 246.57 + 49.33 mm and was significantly higher than in the pontine (188.92 + 60.55 mm) and postpontin (190.40 + 47 mm) segments (p=0.001 for both values). Atheromatous plaque was observed in the prepontine segment in 12 cases (46.15 %) and in 8 samples (30.76%) at the pontine level, but in this segment, there was slight damage to the vascular endothelium, or phase I level. The thickness of the tunica intima in the cases with atheromatous plaque was 15.68 + 13.39 mm and that of the plaque-free segments was 5.10 + 4.40 mm (p=0.005), and in the pontine segment the overlying periarterial adipose tissue had a thickness of 72.01 + 69.44 mm, which was higher than the other three locations (p=0.005). The morphometry of the perivascular fat pad and the presence of phase I atheromatous plaque are the main contributions of this study to the histology of myocardial bridges.

RESUMEN: La mayoría de los estudios histopatológicos han reportado que el segmento de la arteria coronaria debajo del puente miocárdico no presenta placa ateromatosa, mientras que el segmento proximal al puente miocárdico puede tenerla. El objetivo de este estudio fue evaluar el entorno microscópico de los puentes miocárdico. Este estudio descriptivo se realizó con 60 corazones de individuos a quienes se les práctico autopsia en el Instituto Nacional de Medicina Legal y Ciencias Forenses de Bucaramanga-Colombia. Para cada espécimen se realizó disección de las arterias coronarias y sus ramas, eliminando el tejido adiposo subepicárdico para identificar los puentes miocárdicos y obtener secciones histológicas de las ramas arteriales comprometidas. Se observó presencia de puentes miocárdicos en 22 corazones (36,7 %) con una longitud de 17.31 + 4.41 mm y un espesor de 904.57 + 312.27 mm. El calibre del vaso coronario a nivel prepontino fue 246.57 + 49.33 mm y fue significativamente mayor que en el segmento pontino (188.92 + 60.55 mm) y pospontino (190.40 + 47 mm) (p=0.001 para ambos valores). Se observó placa ateromatosa en el segmento prepontino en 12 casos (46.15 %) y en 8 muestras (30.76%) al nivel pontino, pero en este segmento, correspondieron a fase I, con ligero daño en el endotelio vascular. El espesor de la túnica íntima en los casos con placa ateromatosa fue de 15.68 + 13.39 mm y de los segmentos libres de placa fue 5.10 + 4.40 mm (p=0.005) y en el segmento pontino el tejido adiposo periarterial suprayacente presento un espesor de 72.01 + 69.44 mm, el cual fue mayor a las otras tres ubicaciones (p=0.005). La morfometría de la almohadilla adiposa perivascular y la presencia de placa ateromatosa en fase I son los principales aportes de este estudio a la histología de los puentes miocárdicos.

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Abstract Myocardial bypass (MB) is known to have scientific relevance and is present in several studies with great statistical significance regarding its clinical manifestations and complications. There are still questions about MB in its relationship with heart disease and repercussion in life-threatening conditions. We present a case report of a MB in the left anterior descending coronary artery, whose objective is to identify this rare congenital anomaly and to highlight the patient's clinical outcome in order to elicit greater contributions about the presence of this variant in the emergency room, its diagnosis by angiography and therapeutic management.

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RESUMEN Las arterias coronarias principales generalmente tienen un trayecto epicárdico. En algunos casos, pequeños segmentos de éstas se introducen en el interior del miocardio formando los denominados puentes miocárdicos. Esta particularidad anatómica puede producir un estrechamiento sistólico súbito del trayecto tunelizado (fenómeno de milking) y afectar el flujo coronario tanto en sístole como en diástole, con la consiguiente reducción de la reserva coronaria. Afecta principalmente a la arteria descendente anterior en sus segmentos medio y distal. Su presentación clínica puede ir desde un cuadro anginoso hasta la muerte súbita. Hasta el momento, parece ser, que el uso de betabloqueadores y anticálcicos es la opción terapéutica más efectiva en los casos sintomáticos. Se expone un caso en el que un síndrome coronario agudo fue la forma de presentación de esta variante anatómica y el oportuno diagnóstico angiográfico permitió realizar los reajustes terapéuticos necesarios para mejorar la sintomatología del paciente.

ABSTRACT Coronary arteries usually run along the outer surface of the heart. In some cases, small segments of them take a "tunneled" intramuscular course forming the so-called myocardial bridging. This anatomical feature may lead to a sudden systolic narrowing of the "tunneled" segment (milking effect), thereby impairing coronary blood flow in both systole and diastole; which further reduces coronary reserve. Myocardial bridging mainly affects the middle-distal segments of left anterior descending (LAD) artery and may cause anything from chest pain to sudden death. So far, it seems that the use of beta-blockers and anti-calcium agents is the most effective therapeutic option for symptomatic cases. We now report a case where the clinical presentation of this anatomical feature was an acute coronary syndrome. Timely, accurate angiographic diagnosis allowed for adequate therapeutic adjustments to improve the patient's symptomatology

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