Characteristics of infectious endocarditis patients from a town in Boyacá. A cross-sectional study / Caracterización de los pacientes con endocarditis infecciosa en población de Boyacá. Estudio transversal

Abstract Infectious endocarditis (IE) is a multisystemic disease caused by an infection, generally bacterial, of the endocardial surface. Its incidence is three to nine cases per 100,000 persons. Objective: to characterize the patients with a diagnosis of infectious endocarditis seen at the Hospital Universitario San Rafael de Tunja. Materials and methods: a descriptive observational study. Patients seen at the Hospital Uni versitario San Rafael de Tunja between January 1, 2010 and January 1, 2019. Sociodemographic, clinical, paraclinical, imaging, treatment and outcome variables were gathered. Results: a total of 87 persons with a confirmed diagnosis of infectious endocarditis were seen. The average age was 38.77 years, with an SD ± 13.32 years. Leukocytosis was seen in 90%, neutrophilia in 85%, lymphocytosis in 3%, thrombocytopenia in 4%, elevated serum CRP in 85%, transaminitis in 45%, hyponatremia in 2% and hypernatremia in 4%. All patients received antibiotic treatment; only 23% required surgery. Conclusions: this case series found similar clinical and microbiological characteristics to those reported in other national and international studies. Males were affected more often than females, with the main etiological agent being Staphylococcus aureus. Fever and infectious vasculitis signs were the main clinical manifestations, most often affecting the mitral valve.

Resumen La endocarditis infecciosa (EI) es una enfermedad multisistémica que resulta de una infección, generalmente bacteriana, de la superficie endocárdica. Su incidencia es de tres a nueve casos por cada 100 000 personas. Objetivo: realizar una caracterización de los pacientes atendidos en el Hospital Universitario San Rafael de Tunja con diagnóstico de endocarditis infecciosa. Material y métodos: estudio observacional descriptivo. Pacientes atendidos en el Hospital Universitario San Rafael de Tunja entre el 1°. de enero del 2010 a 1°. de enero del 2019. Se tomaron variables sociodemográficas, clínicas, paraclínicas, imagenológicos, terapéuticas y de desenlaces. Resultados: en total se atendieron 87 personas que presentaron diagnóstico confirmado de endocarditis infecciosa. La edad promedio fue 38.77 años con una DE ± 13.32 años. Se observó leucocitosis en 90%, neutrofilia en 85%, linfocitosis en 3%, trombocitopenia en 4%, aumento de los valores séricos de PCR en 85%, transaminitis en 45%, hiponatremia en 2% e hipernatremia en 4%. Todos los pacientes recibieron manejo antibiótico, tan solo 23% requi rieron manejo quirúrgico. Conclusiones: en esta serie de casos se encontraron características clínicas y microbiológicas similares a lo reportado en otras investigaciones nacionales e internacionales. Afectando con mayor frecuencia a personas del sexo masculino, siendo el principal agente causal el Staphylococcus aureus, el agente causal. La fiebre y los signos de vasculitis infecciosa fueron las principales manifestacio nes clínicas, afectado con mayor frecuencia la válvula mitral.

Tumorectomy to Avoid Sudden Death by Pulmonary Embolism in a Patient with a Cardiac Tumor Originating from the Esophagus / 日本心臓血管外科学会雑誌

Tumor metastasis to the endocardium is rare. The patient was 58-year-old man who was given a diagnosis of a metastatic tumor to the right atrium and right ventricle. The tumor originated from the esophagus, and the patient was at risk of sudden death caused by acute pulmonary embolism. We performed tumorectomy to reduce the risk of sudden death. The postoperative course was satisfactory, and the tumorectomy was followed by chemotherapy. The 5-year survival rate in such cases has been reported to be only approximately 11%. However, resection of tumor mass may be useful for improving postoperative QOL and reducing the risk of sudden death.

Characterization of Cardiopulmonary Exercise Testing Variables in Patients with Endomyocardial Fibrosis after Endocardial Resection / Caracterização das Variáveis do Teste de Esforço Cardiopulmonar em Pacientes com Endomiocardiofibrose após Cirurgia de Ressecção Endocárdica

Abstract Background: Endomyocardial fibrosis (EMF) is a rare disease, characterized by diastolic dysfunction which leads to reduced peak oxygen consumption (VO2). Cardiopulmonary exercise testing (CPET) has been proved to be a fundamental tool to identify central and peripheral alterations. However, most studies prioritize peak VO2 as the main variable, leaving aside other important CPET variables that can specify the severity of the disease and guide the clinical treatment. Objective: The aim of this study was to evaluate central and peripheral limitations in symptomatic patients with EMF by different CPET variables. Methods: Twenty-six EMF patients (functional class III, NYHA) were compared with 15 healthy subjects (HS). Functional capacity was evaluated using CPET and diastolic and systolic functions were evaluated by echocardiography. Results: Age and gender were similar between EMF patients and HS. Left ventricular ejection fraction was normal in EMF patients, but decreased compared to HS. Peak heart rate, peak workload, peak VO2, peak oxygen (O2) pulse and peak pulmonary ventilation (VE) were decreased in EMF compared to HS. Also, EMF patients showed increased Δ heart rate /Δ oxygen uptake and Δ oxygen uptake /Δ work rate compared to HS. Conclusion: Determination of the aerobic capacity by noninvasive respiratory gas exchange during incremental exercise provides additional information about the exercise tolerance in patients with EMF. The analysis of different CPET variables is necessary to help us understand more about the central and peripheral alterations cause by both diastolic dysfunction and restrictive pattern.

Resumo Fundamento: A endomiocardiofibrose (EMF) é uma doença rara, caracterizada por disfunção diastólica que leva à redução consumo de oxigênio (VO2) pico. O teste de esforço cardiopulmonar (TECP) tem se mostrado uma ferramenta fundamental na identificação de alterações centrais e periféricas. No entanto, a maioria dos estudos prioriza o VO2 pico como a variável principal, em detrimento de outras importantes variáveis do TECP que poderiam identificar a gravidade da doença e direcionar o tratamento clínico. Objetivo: O objetivo deste estudo foi avaliar limitações centrais e periféricas em pacientes com EMF sintomáticos por meio de variáveis do TECP. Métodos: Vinte e seis pacientes com EMF (classe funcional III, NYHA) foram comparados com 15 indivíduos controle saudáveis (CS). A capacidade funcional foi avaliada por TECP e funções sistólicas e diastólicas por ecocardiografia. Resultados: A idade e o gênero foram similares entre pacientes com EMF e CS. A fração de ejeção do ventrículo esquerdo foi normal em pacientes com EMF, porém diminuída em comparação aos CS. Os picos de frequência cardíaca, carga de trabalho, VO2, pulso de oxigênio (O2) e da ventilação pulmonar (VE) estavam diminuídos em pacientes com EMF em comparação aos CS. Ainda, os pacientes com EMF apresentaram Δ frequência cardíaca /Δ consumo de oxigênio e Δ consumo de oxigênio /Δ taxa de trabalho aumentados em comparação aos CS. Conclusão: A determinação da capacidade aeróbica por troca respiratória não invasiva durante exercício progressivo fornece informações sobre a tolerância ao exercício em pacientes com EMF. É necessária uma análise das diferentes variáveis do TECP para nos ajudar a compreender mais acerca das alterações centrais e periféricas causadas tanto pela disfunção diastólica como pelo padrão restritivo.

Fibrosis endomiocárdica / Endomyocardial fibrosis

Resumen La fibrosis endomiocárdica o endocarditis de Löffler es una patología de causa todavía desconocida, esta puede presentarse durante la evolución de diversas enfermedades de causa infecciosa, tumoral, autoinmune, medicamentos, etc. En muchos casos el presentar eosinofilia moderada (más de 1500 eosinófilos/microlitro) por largos períodos de tiempo puede producir toxicidad en diferentes órganos, entre ellos el corazón, produciendo disfunción del mismo por infiltración directa lo cual daña el tejido y también por las proteínas encontradas en los gránulos, principalmente la proteína catiónica eosinofílica y la proteína básica mayor que tienen predilección por el tejido endocárdico, llevando a su destrucción celular, lo que se traducirá en engrosamiento y fibrosis del subendocardio. Estas alteraciones conllevan a la cardiomiopatía restrictiva, siendo la fibrosis endomiocárdica su principal causa. Se presenta el caso de un paciente masculino de 30 a˜nos de edad, que ingresa al hospital por un cuadro de falla cardiaca aguda con evidencia en el ecocardiograma de ingreso de un componente restrictivo biventricular, el cual en diferentes series se presenta hasta en el 51% de los casos. El paciente presentaba una enfermedad hematológica de base, donde la eosinofilia era persistente durante más de 6 meses.

Abstract Endomyocardial fibrosis or Löffler endocarditis is a condition whose cause still remains unknown. It can develop during the progress of multiple infectious or tumour diseases, medication, etc. In many cases, showing moderate eosinophilia (more than 1500 eosinophils/ microliter) for long periods of time can cause organ toxicity, among them the heart. This produces a dysfunction of the heart due to direct infiltration, which damages the tissue, and also due to the proteins found in the granules, mostly eosinophil cationic protein and major basic protein, which have a predilection for endocardial tissue, leading to their cell destruction, which will translate into a subcardial enlargement and fibrosis. These alterations result in restrictive cardiomyopathy, endomyocardial fibrosis being their main cause. We present the case of a 30 year-old male patient who is admitted at the hospital due to acute heart failure with an admission echocardiogram that evidenced a restrictive biventricular component, present in up to 51% of the cases in different series. The patient had a base hematological disorder, where eosinophilia had been persistent for more than 6 months.

Safety and Efficacy of Left Atrial Endocardial Vagal Denervation Catheter Ablation for Treating the Patients With Refractory Vasovagal Syncope / 中国循环杂志

Objective: To explore the safety and efficacy of left atrial (LA) endocardial vagal denervation catheter ablation for treating the patients with refractory vasovagal syncope (VVS). Methods: A total of 57 consecutive refractory VVS patients with severe symptom and positive response to head-up tilt test (HUT) were enrolled. There were 22 male at the mean age of (43 ± 13) years. The patients had no response or couldn’t tolerate routine treatment. LA model was re-established by three-dimensional mapping system, 10 patients received high-frequency stimulation technique for ganglionated plexi (GP) ablation and 47 received regional catheter ablation at 5 anatomic sites of GP for LA endocardial vagal denervation treatment. In-operative vagal response including hypotension, sinus bradycardia or asystole were observed, the endpoint of ablation was abolition of evoked vagal relfexes. Periodical follow-up was conducted to record the syncope recurrence and to re-examine ECG and HUT in all patients. Results: There were 52/57(91.2%) patients had positive vagal response by radiofrequency application and reached the endpoint of ablation; 4 patients couldn’t receive obvious evoked vagal relfexes. During (36 ± 22) months follow-up period, there were 52 (91.2%) cases without syncope recurrence, 11 cases still having palpitation, amaurosis and dizziness as the precursors of syncope while the symptoms were much better then they were before. No complication occurred. Conclusion: LA endocardial vagal denervation catheter ablation is a safe and effective method for treating the patients with refractory VVS, it may also effectively prevent VVS recurrence.

Adaptação de um sistema de ensaio biológico para detecção de fatores relaxantes endoteliais derivados do endocárdio atrial canino / Adaptation of bioassay to detect endothelium-derived relaxing factors from the canine atrial endocardium

OBJETIVO: Estudar a liberação de fatores relaxantes derivados do endotélio (EDRF) pelo endocárdio de aurículas de corações caninos. MÉTODOS: Aurículas atriais caninas foram suturadas em forma de tubos e o efluente desses tubos foram submetidos a ensaios biológicos (sistema de perfusão isolada em câmaras de órgãos) utilizando artéria coronária canina, para a detecção de EDRFs. RESULTADOS: O efluente da aurícula direita promoveu relaxamento de 58,4 + 10,1 por cento e da aurícula esquerda 74,9 + 8,5 por cento da contração inicial obtida pela ação da prostagladina F2α em artéria coronária. Não houve diferença estatística no relaxamento da artéria coronária induzido pelos efluentes das aurículas direita e esquerda. O relaxamento induzido pelos efluentes das aurículas direita e esquerda foi abolido pelo tratamento das mesmas com Triton X-100. O tratamento das aurículas com L-NMMA, um inibidor competitivo da síntese de óxido nítrico, e com indometacina, um inibidor da via da ciclooxigenase, promoveu redução no relaxamento da artéria coronária induzido pelo efluente auricular, indicando que o endotélio endocárdico libera óxido nítrico e prostanóides. CONCLUSÕES: Esse estudo demonstra, pela primeira vez, a liberação luminal in vitro de EDRF e prostaciclina pelo átrio de coração canino. A habilidade do endotélio endocárdico em produzir esses fatores pode ter um papel importante na prevenção da formação de trombos nas câmaras cardíacas.

OBJECTIVE: The aim of this study was to assess the release of endothelium-derived relaxing factors from the endocardium of canine atrial appendage. METHODS: To study the release of endothelium-derived relaxing factor (EDRF) from intact atrial endocardial endothelium, tube-shaped sutures of canine atrial appendages were performed and effluents from these tubes were bioassayed (isolated perfused organ chamber system) for detection of EDRF in canine coronary artery. RESULTS: Effluent from the right atrial appendage caused a relaxation of 58.4 + 10.1 percent and the left atrial appendage 74.9 + 8.5 percent from the initial prostagladin F2α contraction in coronary artery. No significant statistical difference was detected in effluent from the right and left atrial appendages. This relaxation was abolished by treating the heart tubes with Triton X-100 and reduced by treatment with LNMMA, a competitive inhibitor of nitric oxide and with indomethacin, an inhibitor of the cyclo-oxygenase pathway, also indicating the release of vasodilatory prostanoids from the endocardial endothelium. CONCLUSION: This study showed for the first time, in vitro luminal release of EDRF and prostacyclin from the canine heart atrium. The ability of the endocardial endothelium to produce these factors could play an important role in preventing thrombus formation in the cardiac chambers.

Endomyocardial Biopsy: One Center's Report About Its Role

BACKGROUND AND OBJECTIVES: Cardiomyopathy is a common cause of heart failure, yet it is sometimes difficult to determine its exact etiology. Endomyocardial biopsy (EMBx) has been considered to be one of the important diagnostic modalities for unexplained cardiomyopathy. The aim of this study was to analyze the diagnostic value of EMBx. SUBJECTS AND METHODS: 30 patients (M : F=26 : 4, mean age: 41+/-11 yrs) who underwent EMBx since 1992 at St. Mary's hospital were enrolled. The patients were classified into 4 groups by their clinical manifestations as follows: Group I: 11 patients with left ventricular hypertrophy (LVH) of an unknown etiology and suspicious of having infiltrative disease on their non-invasive tests, Group II: 15 patients with heart failure of an unknown etiology and rapid progression, Group III: 2 patients with heart failure and peripheral eosinophilia, Group IV: 2 patients with suspicious arrhythmogenic right ventricular dysplasia and cardiac mass. RESULTS: EMBx confirmed the diagnosis in 8 of 30 cases (26.7%). In Group I, 3 patients were confirmed to have amyloidosis (27.3%). In Group II, 2 patients were diagnosed as having lymphocytic myocarditis (13.3%). In Group III, all of 2 patients (100%) were diagnosed as eosinophilic myocarditis. In Group IV, 1 patient was confirmed to have cardiac metastasis from esophageal cancer. The diagnostic rate was higher for Group III than for Group II (p=0.007). There were no complications related with EMBx. CONCLUSION: EMBx may be a useful tool to confirm the causes of cardiomyopathy in selected patients.

A queda da pressão de perfusão coronariana implica em dano subendocárdico da região do miocárdio remota ao infarto e em disfunção do ventrículo esquerdo / Low coronary driving pressure early in the course of myocardial infarction determines subendocardial remodeling and left ventricular dysfunction

No infarto, o remodelamento da região ventricular remota tem sido pouco examinado. Previamente, observamos que a redução da pressão de perfusão coronariana (PPC) associa-se ao aparecimento de fibrose subendocárdica. O objetivo do presente estudo foi investigar o papel da PPC no remodelamento e na função ventricular esquerda após o infarto. Medidas hemodinâmicas foram determinadas em ratos Wistar imediatamente após o infarto (IM) ou cirurgia fictícia (SH) e ao final dos seguimentos de 1, 3, 7, e 28 dias. Cortes teciduais do coração foram submetidos a coloração com HE, Sirius red, e a imunohistoquímica para a-actina. Duas regiões distintas do ventrículo esquerdo remotas ao infarto foram examinadas: subendocárdio (SE) e interstício (INT). A necrose de miócitos, a infiltração leucocitária e de miofibroblastos, e a fração de volume do colágeno foram determinadas. Comparados com SH, os grupos IM apresentaram menor PPC e disfunção sistólica e diastólica do ventrículo esquerdo. A necrose foi evidente em SE no dia 1. A inflamação e a fibroplasia ocorreram predominantemente em SE até o dia 7. A fibrose foi restrita a SE e evidente desde o dia 3. Em INT, a inflamação ocorreu predominantemente nos dias 1 e 3, mas em menor grau comparada a SE. A queda da PPC associou-se à dilatação progressiva do ventrículo esquerdo. Em SE, a PPC relacionou-se inversamente com a necrose (r =- 0,65, p = 0,003, no dia 1), com a inflamação (r = -0,76, p < 0,001, no dia 1), com a fibroplasia (r = -0,47, p = 0,04, no dia 7) e com a fibrose (r = -0,83, p < 0,001, no dia 28). A necrose no dia 1, a inflamação nos dias 3 e 7 e a fibroplasia no dia 7 relacionaram-se inversamente com a função do ventrículo esquerdo. A PPC é um fator determinante da integridade de SE e interfere com o remodelamento e a função do ventrículo esquerdo.

Left ventricular (LV) subendocardial remodeling has been poorly investigated after myocardial infarction. Previously, we have demonstrated that low coronary driving pressure (CDP) early in the course of infarction was associated with the subsequent development of subendocardial fibrosis. The present study aimed at the investigation of the role of CDP in LV remodeling and function following infarction. Hemodynamics were determined in Wistar rats immediately after infarct surgery (MI group) or sham (SH group) and at days 1, 3, 7, and 28. Heart tissue sections were stained with HE, Sirius red and immunostained for a- actin. Two distinct LV regions remote to MI were examined: subendocardium (SE) and interstitium (INT). Myocyte necrosis, leukocyte and myofibroblast infiltration, and collagen volume fraction were determined. Compared with SH, MI groups showed lower CDP and LV systolic and diastolic dysfunction. Necrosis was evident in SE at day 1. Inflammation and fibroplasia occurred predominantly in SE as far as day 7. Fibrosis was restricted to SE and was evident beginning from day 3. Inflammation occurred predominantly at days 1 and 3 in INT, but at a lower extent than in SE. CDP fall was associated with progressive LV dilatation. In SE, CDP correlated inversely with necrosis (r = -0.65, p=0.003, at day 1), inflammation (r = -0.76, p < 0.001, at day 1), fibroplasia (r = -0.47, p = 0.04, at day 7) and fibrosis (r = -0.83, p < 0.001, at day 28). Necrosis at day 1, inflammation at days 3 and 7, and fibroplasia at day 7 correlated inversely with LV function. CDP is a key factor to SE integrity following infarction and interferes with LV remodeling and function.

Complications of 2-D Echocardiography Guided Transfemoral Right Ventricular Endomyocardial Biopsy

Endomyocardial biopsy (EMBx) is a useful tool for diagnosing various cardiac pathologies. However, the routine use of EMBx has not gained widespread acceptance due to the possible complications related to the EMBx. Thus, not much information is available on the complications related to the EMBx. We prospectively evaluated 90 consecutive patients who underwent 2-D echocardiography guided transfemoral right ventricular EMBx at Kyungpook National University Hospital between March 2002 and November 2005 to determine the incidence, nature and subsequent management of complications related to EMBx. The clinical diagnoses before the EMBx were arrhythmogenic right ventricular dysplasia in 54, dilated cardiomyopathy in 19, Brugada syndrome in 9, myocarditis in 6 and miscellaneous in 2 patients. The overall major complication rate was 5.6% and no procedure-related mortality occurred. Myocardial perforation (n=3), which was the most frequent complication, did not progress to cardiac tamponade requiring pericardiocentesis in any patient. Hemodynamically unstable ventricular tachycardia occurred in 1 patient. New and persistent right bundle branch block occurred in another. Our findings suggest that 2-D echocardiography guided transfemoral right ventricular EMBx is a relatively safe procedure.

Complications of 2-D Echocardiography Guided Transfemoral Right Ventricular Endomyocardial Biopsy

Endomyocardial biopsy (EMBx) is a useful tool for diagnosing various cardiac pathologies. However, the routine use of EMBx has not gained widespread acceptance due to the possible complications related to the EMBx. Thus, not much information is available on the complications related to the EMBx. We prospectively evaluated 90 consecutive patients who underwent 2-D echocardiography guided transfemoral right ventricular EMBx at Kyungpook National University Hospital between March 2002 and November 2005 to determine the incidence, nature and subsequent management of complications related to EMBx. The clinical diagnoses before the EMBx were arrhythmogenic right ventricular dysplasia in 54, dilated cardiomyopathy in 19, Brugada syndrome in 9, myocarditis in 6 and miscellaneous in 2 patients. The overall major complication rate was 5.6% and no procedure-related mortality occurred. Myocardial perforation (n=3), which was the most frequent complication, did not progress to cardiac tamponade requiring pericardiocentesis in any patient. Hemodynamically unstable ventricular tachycardia occurred in 1 patient. New and persistent right bundle branch block occurred in another. Our findings suggest that 2-D echocardiography guided transfemoral right ventricular EMBx is a relatively safe procedure.

Changes in action potential and the conduction time of ventricular cells in subendocardium and subepicardium during ischemia and early reperfusion / 中国病理生理杂志

AIM: To investigate the electrophysiological characteristics of ventricular myocyte both in subendocardium and in subepicardium during ischemia. METHODS: Using modified Ferrier's method of ischemic and reperfusion injury in isolated guinea pig right ventricular wall. RESULTS: The transmembranal electric activities in subendocardium and in subepicardium were all significantly abnormal, and it was more significant in subendocardium. CONCLUSION: The alteration degree of ventricular myocyte in subendocardium and in subepicardium during ischemia and early reperfusion was different, and this might be the electrophysiological basis of the vulnerability of the subendocardium.

The effect of running training on regional cardiac myosin isozyme composition in rats / 体力科学

We examined the effect of running training on regional cardiac myosin isozyme composition in rats. Male Sprague-Dawley strain rats (4 weeks old) were used, and divided into two groups: sedentary control (C) and trained (T) groups. The T group was trained by treadmill running (40 m/min, 1h/day, 5 days/week, for 12 weeks) . At 16 weeks old, their hearts were excised. The left ventricle was separated into the subendocardium (Endo) and subepicardium (Epi) by dissecting the ventricle at the mid-wall. The ventricular myosin isozymes were examined by electrophoresis on pyrophosphate gel under non-dissociating conditions. The results showed the following: 1) The relative heart weight of the T group was significantly higher than the C group. 2) Left ventricular myosin isozyme composition showed a region-specific distribution in the C rats, and the proportion of V3 myosin or β-myosin heavy chain in the Endo was significantly higher than that of the Epi. However, the training had no effect on the cardiac myosin isozyme in either portion. 3) The activity of citrate synthase did not show transmural gradient in the ventricle of C animals. Training had no effect on the activities of either portion. 4) The activity of lactate dehydrogenase (LDH) showed transmural gradient in the ventricle of C rats. Training-induced changes in the activity of LDH were found in both portions, therefore, training abolished the transmural gradient in the activity of LDH, suggesting a corresponding redistribution of the myocardial work load.<BR>These results indicate that running training might induce the redistribution of the myocardial work load, whereas the stimulation apparently has no effect on the regional distribution of cardiac myosin isozyme composition.

Atrial Morphology Related to Secretory Function and Transport of Metabolites : I. Fenestrations of Basal Lamina in Rat Atrial Endocardium / 대한해부학회지

It was well known that atrial myocytes systhesize atrial natriuretic peptide[ANP], and secrete it into the atrial lumen through the atrial endocardium. But the mechanism for regulation of ANP secretion has not been clearly elucidated, because there was little information of the atrial morphology concerning basal lamina. Basal lamina is surmised as one of barriers that control the movement of ANP, a large molecule. This study was attempted to elucidate the morphological characteristics of basal lamina and connective tissue fibers of atrial endocardial layer by scanning electron microscopy. Basal lamina was exposed by removal of the overlying endothelium. This was achieved by using OsO4 maceration, immersion in aqueous boric acid or EDTA treatment. After removal of the endothelial cell, the specimens were exposed to ultrasonic vibration in case of need. The external surface of basal lamina showed a fairly smooth appearance on the whole, although a few irregular folds are often encountered. Fenestrations, 0.1-1 micrometer in diameter, were randomly observed on the basal lamina, and they were circular to oval in shape. Margin of fenestrations was somewhat distinct and some was divided into two parts by linear structures. The structural differences of fenestrations between right and left atria were not found. The fibroreticular lamina under the basal lamina was revealed by removal of the endothelial cells and their basal lamina. This layer was consisted of interwoven fine fibers. These fine fibers were repeatedly divided and fused, forming reticular network. Some fine fibers connected with basal lamina. Some connective tissue fibers below fibroreticular layer were collected into thick bundles running parallel to myocytes. Above results may serve as a basis for the physiological and morphological studies of atrium.