RESUMO
BACKGROUND: Sentinel node biopsy in vulvar cancer is associated with much less morbidity than inguinofemoral node dissection. Our study focused on describing the morphology of superficial lymphatic drainage of the vulva and its relationship to regional nodes, which may facilitate orientation during surgery. MATERIALS AND METHODS: In 24 female cadavers, injections of patent blue (at various localisations medially, unilaterally and bilaterally) were used to visualise the lymphatic drainage of the vulva. After dissection of lymphatic vessels and nodes, their course was documented by photograph and then analysed. Subsequently, a map of vulvar superficial lymphatics was created. RESULTS: The cutaneous and subcutaneous tissue of the vulva primarily drained to superficial inguinal nodes. There was no evidence of a solitary lymph node that drained the unilateral vulva. Each area of the vulva drained to its own lymph node, which was variably localised in the subcutaneous groin around the great saphenous vein. Anastomoses between individual inguinal superficial lymph nodes are likely. Right-left symmetry in the course of lymphatic collectors was not detected. Natural drainage of the medial and paramedial areas to contralateral inguinal nodes was also not detected. The drainage pattern to ipsilateral inguinal nodes was consistent in cadavers without evidence of vulvar disease and may be applicable in the early stages of vulvar cancer. CONCLUSIONS: There was no evidence of a solitary node that drained the unilateral vulva. Each part of the vulva may drain to a corresponding lymph node in a different localisation of the groin. The surgeon should take this variability into account.
Assuntos
Vasos Linfáticos , Neoplasias Vulvares , Feminino , Humanos , Neoplasias Vulvares/patologia , Biópsia de Linfonodo Sentinela , Linfonodos/patologia , Vasos Linfáticos/patologia , Virilha/patologiaRESUMO
In Memoriam: With deep sadness the world of Lymphology learned of the death of Prof. Prof. h.c. Dr. med. Michael Földi, a ground breaking pioneer of modern Lymphology. Words alone will never fully describe or capture the breadth and depth of Michael's contribution to our lymphatic knowledge and the legacy he has left for us all.
Assuntos
Sistema Linfático/patologia , Linfedema/história , História do Século XX , História do Século XXI , HumanosRESUMO
OBJECTIVE: Lymphatic mapping is a method to find and preserve upper extremity lymphatics during axillary surgery (axilla clearance and sentinel node biopsy) in breast cancer patients. This may reduce the incidence of lymphedema. We examined on anatomical model, if the lymphatic drainage of the upper extremity is fully separable from the lymphatic drainage of the breast. We further endeavored to find an explanation as to why lymphedema occurs in the upper extremity after sentinel node biopsy in breast carcinoma. DESIGN: Pilot study. SETTING: Oncogynecologic Center, Department of Obstetrics and Gynecology, First Faculty of Medicine, Charles University in Prague and General University Hospital, Prague. METHODS: Patent blue dye was injected deep and superficially in arm and breast bilaterally in 9 cadavers. After visualization and precise dissection of the lymphatic vessels and nodes, a record of their routes was made. A scheme of arm and breast lymphatics was constructed. RESULTS: The lymph from arm is drained by 2-4 main afferent collectors. As opposed to cranial and medial collectors, caudal collectors diverged from the axillary vein and entered the caudal axilla. In one case the caudal collector entered a node, which was considered to be the sentinel node of the breast. The other important finding is the demonstration of lymphatic anastomoses that take place between imaged nodes in the caudal axilla, which is the most frequent localization of the breast sentinel lymph node. CONCLUSION: The relationship of lymphatic drainage of the arm and breast are closely related and share connections. These connections represent the main problem, which could explain lymphedema following surgery if damaged. Further studies are necessary to improve understanding of this method and to increase the number of observations.
Assuntos
Neoplasias da Mama/patologia , Linfonodos/anatomia & histologia , Vasos Linfáticos/anatomia & histologia , Linfedema/prevenção & controle , Corantes de Rosanilina , Idoso , Braço , Axila , Mama , Neoplasias da Mama/cirurgia , Feminino , Humanos , Excisão de Linfonodo , Linfedema/etiologia , Biópsia de Linfonodo Sentinela/efeitos adversosRESUMO
INTRODUCTION: Axillary reverse mapping (ARM) is a method to preserve upper extremity (UE) lymphatics during axillary surgery in breast cancer patients. This may reduce the incidence of lymphedema. Very precise method to demonstrate lymphatic drainage is direct X-ray lymphography. MATERIALS AND METHODS: The evaluation of direct lymphography X-ray images of the axilla and proximal part of the upper extremity was performed in 9 subjects. As contrast was used Lipiodoil injected on the dorsal side of hand. RESULTS: The lymph from UE is drained by 2-4 main afferent collectors, which in 5 of 9 cases entered into one node in the lateral axilla (ARM node). This node was considered to be the sentinel lymph node for the UE. In 4 cases a cranial collector was shown, which led directly to nodes in the upper part of the axilla. This collector had numerous anastomoses with other collectors before entering the axillary nodes. The most important finding is the demonstration of numerous lymphatic anastomoses that take place between all imaged nodes in the axilla including the caudal nodes, which is the most frequent localization of the breast sentinel lymph node. CONCLUSION: The relationship of lymphatic drainage of the UE and breast are closely related and share numerous connections. These connections represent the main problem of the ARM concept because they may pose potencional route for metastatic cancer cells in sentinel node positive breast cancer patients. Further studies are necessary to improve understanding of this method. Axillary reverse mapping - breast cancer - lymphedema - sentinel node biopsy.
Assuntos
Axila , Neoplasias da Mama/patologia , Meios de Contraste , Óleo Etiodado , Linfonodos/patologia , Linfografia , Biópsia de Linfonodo Sentinela , Adulto , Idoso , Neoplasias da Mama/cirurgia , Feminino , Humanos , Excisão de Linfonodo/métodos , Metástase Linfática/diagnóstico , Linfedema/etiologia , Linfografia/efeitos adversos , Linfografia/métodos , Pessoa de Meia-Idade , Biópsia de Linfonodo Sentinela/métodosRESUMO
OBJECTIVE: The axillary reverse mapping (ARM) technique has been developed to map and preserve arm lymphatic drainage during axillary lymph node dissection (ALND) and/or sentinel lymph node (SLN) biopsy, thereby minimizing arm lymphedema. However, several problems remain to be resolved in the practical application of this technique. This article presents a review of current knowledge regarding ARM and discusses the practical applicability and relevance of this technique. TYPE OF STUDY: Review. SETTING: Oncogynecologic center, Gynecology-Obstetrics Clinic, 1st Medical Faculty and General Teaching Hospital, Prague. CONCLUSIONS: The axillary reverse mapping (ARM) procedure is based on the hypothesis that the lymphatic drainage from the upper arm is different from that of the breast and offers the opportunity to prevent lymphedema in breast cancer patients. However, the oncologic safety of the procedure has not yet been determined.
Assuntos
Neoplasias da Mama/cirurgia , Excisão de Linfonodo , Linfedema/prevenção & controle , Biópsia de Linfonodo Sentinela , Braço , Axila , Neoplasias da Mama/patologia , Feminino , Humanos , Excisão de Linfonodo/efeitos adversos , Linfedema/etiologia , Biópsia de Linfonodo Sentinela/métodosRESUMO
It has been suggested by various investigators that the impairment of lymphatic drainage from the coronary arteries may play a role in predisposition to coronary atherosclerosis, the pathogenesis of which is certainly multifactorial. In our study, no lymphatic vessels were found in the walls of the coronary arteries (adventitia, media and intima) in 51 human hearts from patients ranging in ages from 3 months to 83 years with normal coronary arteries, coronary atherosclerosis, and cardiomyopathy. Visualized lymphatics were located solely in the periadventitial area, and these lymphatics were more irregular in hearts from older persons. With injection, histology, and electronmicroscopy methods we could not detect penetration of lymphatics into the wall of coronary trunks in normal as well atherosclerotic arteries. In all coronary arteries studied, and particularly in the atherosclerotic lesions, blood vasa vasorum could be visualized. In the atherosclerotic areas, vasa vasorum (angiogenesis) could be seen penetrating into the media and intima. Many of the thin-walled vasa vasorum could easily be mistaken for lymphatics. The absence of lymphatics draining the epicardial coronary arteries may be a predisposing factor to coronary atherosclerosis.
Assuntos
Doença da Artéria Coronariana/patologia , Vasos Coronários/anatomia & histologia , Sistema Linfático/anatomia & histologia , Vasa Vasorum/anatomia & histologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Vasos Coronários/fisiologia , Vasos Coronários/ultraestrutura , Feminino , Humanos , Lactente , Sistema Linfático/fisiologia , Sistema Linfático/ultraestrutura , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/patologia , Vasa Vasorum/fisiologia , Vasa Vasorum/ultraestruturaRESUMO
It has been 160 years now since Purkynje published the finding of conduction fibers in the heart in Archiv f. Anatomie u. Physiologie and it has been 166 years since his publication in polish version. Already during Purkynje's life, some anatomists had solved the morphology of these fibers but nobody at that time knew of what great physiological and medical importance this discovery would be for medicine. It was seen as late as in the 20th century and in contemporary times. Purkynje's work indicated the cascade of these discoveries, which were leading in the beginning of the previous century to the formulation of the basic scheme of the conduction system. Purkynje fibers or Purkynje cardiomyocytes are part of the whole complex of the cardiac conduction system which today is classified as specific heart muscle tissue, being responsible for the generation of the heart impulses. From the point of view of ultrastructural composition, the cells of different parts of the cardiac conduction system are partly similar. In contrast to the heart contractile cardiomyocytes, the cells of the cardiac conduction system including Purkynje fibers have a small amount of myofibrils,small mitochondrias, light cytoplasm and a higher glycogen content, but no T-tubular system. They can be detected with some morphological methods. Nevertheless the cells of the conduction system are not completely uniform. They differ in size, number of nexuses-gaps and intercalar discs in individual parts of the conduction system. Nevertheless, these specialized cells work as a whole-unit. Nowadays, the morphology research of all the parts of cardiac conduction system, including Purkynje fibers, is focused on ultrastructural, histochemical and genetical problems. The question is, wheather with future gene/cell therapy disturbances of the conduction system such as arrythmias, can be prevented and cured by replacing the electrical pacemakers with biological ones. If Jan Evangelista Purkynje lived today, he would be surprised but surely delighted with the high degree of research concerning his discovery and its clinical application.
Assuntos
Cardiologia/história , Ramos Subendocárdicos/anatomia & histologia , Animais , República Tcheca , Sistema de Condução Cardíaco/anatomia & histologia , História do Século XIX , História do Século XX , HumanosRESUMO
The aim of this study was to topographically map the superficial lymphatic drainage of the breast. The study was performed on 24 female cadavers. Patent blue dye was administered intradermally and subcutaneously. After visualization and dissection of the lymphatics, a schematic record of their routes was made on a transparency folio of the breast map. Afterwards, a summation was performed of all schematic records, and a map of the lymphatic vessels of the breast was derived. The natural dominant drainage for the outflow of lymph from the superficial areas of the breast is to the axillary nodes. This pathway plays a primary role in the initial stages of breast cancer. This observation does not exclude other pathways of lymph drainage, which probably play a secondary role except in cases where flow is limited in the primary lymphatic pathway. Although each quadrant is dominantly drained by one or two of its own collectors, it is also interconnected via the subareolar plexus with the other quadrants of the breast, and lymph collectors of the upper medial quadrant pass to the lower medial quadrant and vice versa. Lymphatic collectors from the medial quadrants followed the medial, cranial and caudal margins of the breast and afterwards ran into the axilla. The common interconnections of the individual quadrants of the breast with one or two collectors, which circumscribe the breast, but run outside the subareolar plexus, further increase the risk of developing locoregional recurrences. In some cases, the marginal lymphatic collectors of the breast may even run beyond the anatomical boundaries of the breast--particularly apparent in the submammary region.
Assuntos
Mama/anatomia & histologia , Sistema Linfático/anatomia & histologia , Idoso , Cadáver , Corantes/administração & dosagem , Feminino , Humanos , Vasos Linfáticos/anatomia & histologia , Corantes de Rosanilina/administração & dosagem , Coloração e Rotulagem , Fatores de TempoRESUMO
AIM: The aim of study was to topographically map the superficial lymphatic drainage of the breast and its relation to sentinel node. DESIGN: Anatomical study. SETTING: Department of Oncogynecology, Clinic of Obstetric and Gynecology of 1st Medical Faculty of Charles University and General Hospital, Prague. METHODS: The study was performed on 19 female cadavers. After slow intradermal administration of Patent Blau into the periareolar region, into the centers and into the borders of the individual quadrants of the breast, the lymphatics were visualized and a careful resection of these lymphatics and lymph nodes was performed. The lymphatics were drawn onto a schematic map of the breast on a transparent sheet and afterwards a summation of all schematic maps was performed. A map of the lymphatic vessels of the breast was based on this summation. RESULTS: After subcutaneous administration of patent blue were clearly visualized the subareolar plexus and draining sentinel node in the axilla, as well as one or two supplying lymphatics. Despite great variability in the lymphatic drainage of the breast, it was demonstrated that the natural dominant drainage for the outflow of lymph from the superficial areas of the breast are the axillary nodes. CONCLUSION: From the course of the lymphatic vessels it is evident that the breast cannot be divided into functionally separate segments. According to the lymphatic map of the breast, one can assume that in carcinoma of the breast it is the lymphatic drainage and not the localization of the tumor that plays a primary role in the development of metastases. One cannot ignore the existence of alternative drainage pathways of the breast, but their role in the beginning of dissemination of tumor cells in comparison with the axilla is negligible. Subdermal administration of Patent Blau is a reliable and effective method of visualizing lymphatic vessels and the draining lymph nodes of the breast. Due to the meandering course of lymphatics in the breast, we cannot understimate the role of radiation therapy after breast conserving surgery.
Assuntos
Mama , Sistema Linfático/anatomia & histologia , Biópsia de Linfonodo Sentinela , Idoso , Corantes , Feminino , Humanos , Corantes de RosanilinaRESUMO
A morphological evaluation of lymphatic vessels of skin leg ulcers was performed in 39 human subjects with longstanding venous insufficiency and lipodermatosclerosis. Light and electron microscopy demonstrated that the superficial fibrin and inflammatory cell layers and intermediate blood capillary layer of the ulcer bed, which were primarily granulation tissue, did not contain lymphatics. Moreover, lymphatic capillaries were present only sporadically in the transition zone from granulation tissue to the deeper collagenous scar layer of the ulcer. In some instances, in the deepest part of the ulcer bed near the crural fascia, there were one or two thicker lymphatic collectors with valves, which were continuations of collectors from the plantar foot region. Lymphatics were present at the border of the ulcer and in lipodermatosclerotic skin, but the endothelium and muscle lining layer were partially destroyed. Lymphatic capillaries were characterized by open interendothelial junctions in conjunction with subendothelial edema. In lipodermatosclerotic skin, the morphologic changes suggest that absorption of interstitial fluid and lymph is markedly disturbed adjacent to the ulcer bed, which likely contributes to both slow healing and high recurrence of skin ulcers associated with longstanding venous insufficiency.
Assuntos
Úlcera da Perna/patologia , Úlcera da Perna/fisiopatologia , Esclerodermia Localizada/patologia , Insuficiência Venosa/patologia , Adulto , Idoso , Capilares/ultraestrutura , Drenagem , Feminino , Humanos , Masculino , Microscopia Eletrônica , Pessoa de Meia-Idade , Pele/irrigação sanguíneaRESUMO
On the supposition that pericoronary lymphatics play an important role in the efflux of interstitial fluid from the blood vessel wall, we examined the morphology of pericoronary arterial lymphatics in the dog. After ligation of the principal epicardial drainage lymphatics, after ligation of the left anterior descending coronary artery, after induced pericoronary inflammation and after instillation of India Ink into the pericardial sac using light, dissecting, and electron microscopy. The findings were compared with non-operated (control) dogs. Lymphatic drainage of the coronary arteries is via adventitial lymphatics, which do not penetrate to the media and via periadventitial lymphatics consisting of a subepicardial lymphatic plexus overlying the coronary arteries. The smaller arterioles in the ventricular muscle have many more accompanying lymphatics than do epicardial coronary arteries. In the latter arteries, prelymphatic channels formed by collagen fibers in the media likely transport interstitial fluid to the adventitial and periadventitial lymphatics. Arterial contraction also likely plays a role in propulsion of coronary arterial interstitial fluid towards adventitial lymphatics.
Assuntos
Vasos Coronários/anatomia & histologia , Sistema Linfático/anatomia & histologia , Animais , Arteríolas/anatomia & histologia , Doença da Artéria Coronariana/patologia , Doença da Artéria Coronariana/fisiopatologia , Vasos Coronários/fisiologia , Vasos Coronários/ultraestrutura , Cães , Feminino , Sistema Linfático/fisiologia , Sistema Linfático/ultraestrutura , Masculino , Vasa Vasorum/anatomia & histologiaRESUMO
We transected the principal ascending anterior epicardial cardiac lymphatic in 10 dogs, and after varying time intervals reoperated to look for lymphatic regeneration using dye injection. Photographs and sketches were made to record the findings, and in six dogs serial histologic sections were also examined. In none of the 10 dogs was regeneration of the transected principal cardiac lymphatic detected although small lymphatic collaterals from the distal side of the lymphatic developed in 2 dogs. Further studies are merited to assess the role of lymphatic insufficiency in the development of coronary vasculopathy and chronic rejection after cardiac transplantation and other heart operations (e.g., coronary artery bypass) that may injure lymphatic drainage capacity.
Assuntos
Sistema Linfático/fisiologia , Pericárdio/anatomia & histologia , Regeneração , Animais , Cães , Feminino , Sistema Linfático/cirurgia , MasculinoRESUMO
Our interest in the effects of impaired cardiac lymph drainage on coronary atherosclerosis led us to study the cardiac lymphatic anatomy in the monkey, generally considered the ideal experimental animal for examining coronary artery disorders. Short-term and long-term studies to visualize the cardiac lymphatic system and its mediastinal drainage pathways in 14 living monkeys confirmed that the epicardial collecting lymphatic anatomy is comparable to that of man, dog, and pig. These lymphatics, and particular lymphatic drainage to the cardiac lymph node in the right mediastinum, are difficult to visualize, in good part, because lymph uptake of such tracers as India Ink and T1824 blue dye is extremely slow. By modifying our techniques and taking cognizance of the slow lymphatic uptake of the tracers, we have been more successful in visualizing the mediastinal cardiac lymph node. Though our studies confirm that the lymphatic drainage of the monkey heart is similar to that in other mammals, we conclude that the "monkey model" has several drawbacks to study the effects of impaired cardiac lymph flow because of the laborious requirements to visualize successfully the cardiac lymph node. Perhaps the development of new markers would make this lymphatic system more approachable for experimental investigation.
Assuntos
Coração/anatomia & histologia , Sistema Linfático/anatomia & histologia , Mediastino/anatomia & histologia , Animais , Macaca mulattaRESUMO
Parietal pericardial lymphatics were visualized by indirect and direct India ink injections in 35 human cadavers. Studies included examination of cleared specimens under the dissecting microscope and standard light microscopy. The lymphatic vessels of the ventral pericardial surface most often pass along the phrenic nerves cranially to terminate in the anterior right and left and transverse mediastinal nodes, or caudally to the diaphragm or prepericardial lymph nodes. The lymphatics draining the lateral parts of pericardium pass to the anterior mediastinal, tracheobronchial, lateropericardial, prepericardial and posterior mediastinal (juxtaesophageal) lymph nodes. The posterior part of the pericardium drains to the juxtaesophageal and tracheobronchial nodes. Lymphatics from the diaphragmatic part of the pericardium pass to the right lateropericardial and prepericardial, juxtaesophageal and tracheobronchial nodes. The pericardial cupula is anteriorly drained to the anterior mediastinal nodes, and posteriorly to the tracheobronchial nodes. In cleared specimens two networks of lymphatic vessels are seen to surround the pericardial space. On the ventral surface, the lymphatics of the parietal pericardium connect to lymphatics in the pericardial fat and areolar tissue. On the lateral and posterior surfaces, the lymphatics of the parietal pericardium anastomose with lymphatics of the reflected mediastinal pleura. These anatomical observations offer new insights into the mechanisms of turnover of pericardial fluid and into the mechanisms of occurrence of chylopericardium.
Assuntos
Sistema Linfático/anatomia & histologia , Pericárdio/anatomia & histologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Pessoa de Meia-IdadeRESUMO
Massage of the foot in men and the hindpaw in dogs was performed by applying external pressures of 70-100 mmHg for a period of one, three, five, and ten minutes with a frequency of 25 strokes per minute. This protocol was performed on individuals without edema, on dogs with experimental lymphedema and men with post-thrombotic venous edema. After ten minutes of forceful massage, focal damage of lymphatics was present. In a group of dogs with lymphedema and men with post-thrombotic venous edema, the alteration of lymphatics was greater than in normal individuals and evident only after 3 to 5 minutes of massage. At first, the forceful massage affected the endothelial lining of the initial lymphatics. Alterations of lymphatic collectors were visible later. The fluid in lymphedema was translocated by massage using high pressure from the interstitium into the lumen of lymphatics by means of the open junctions and by artificial cracks that develop from injury to the lymphatic wall. Vigorous massage in lymphedema also produces loosening of subcutaneous connective tissue, formation of large tissue channels and release of lipid droplets that enter the lymphatics. By this mechanism, massage helps reduce the amount of fat cells in the lymphedematous leg.
Assuntos
Sistema Linfático/lesões , Linfedema/terapia , Massagem/efeitos adversos , Síndrome Pós-Flebítica/terapia , Adulto , Idoso , Animais , Cães , Endotélio Linfático/lesões , Endotélio Linfático/ultraestrutura , Feminino , Pé , Membro Posterior , Humanos , Sistema Linfático/ultraestrutura , Masculino , Microscopia Eletrônica , Pessoa de Meia-Idade , Pressão/efeitos adversos , Fatores de TempoRESUMO
A careful anatomical study of the lymphatic drainage from the parietal pericardium reveals a complicated network that is notably different from that defined by the instillation of markers into the pericardial sac. The pericardial cupola and the posterior (dorsal) area of the parietal pericardium drain directly to the cardiac lymph node in the right upper mediastinum by relatively short lymphatics. The lymphatics of the anterior and lateral areas of the parietal pericardium pass to collecting vessels that travel cranially or caudally along the phrenic nerves. The former traverse specific lymph nodes and then enter the right or left venous angles. The latter pass caudally and then drain to the major collecting systems from the area of the diaphragm.
Assuntos
Cães/anatomia & histologia , Coração/anatomia & histologia , Sistema Linfático/anatomia & histologia , Pericárdio/anatomia & histologia , AnimaisRESUMO
In ten postmortem hearts of the Macaque monkey (M. mulatta), the coronary lymphatics were visualized using an India ink suspension in 2% gelatin. The left coronary lymphatic initially passed to the dorsal surface of the aortic arch. In five hearts, this lymphatic went directly to the cardiac lymph node, whereas in the others, it first ascended to the left superior tracheobronchial node and then interconnected with the cardiac lymph node. The right coronary lymphatic usually passed in front of the ascending aorta and common arterial (brachiocephalic) trunk and entered the cardiac lymph node. In two hearts, however, the right coronary lymphatic first ascended to an anterior transverse mediastinal node and from here lymphatics joined the cardiac lymph node. Those lymphatics that passed cephalad from the cardiac lymph node to the right anterior mediastinal nodes and the right paratracheal nodes ultimately emptied into the right venous angle. Those lymphatics that passed cephalad from the cardiac lymph node to the anterior transverse mediastinal nodes ultimately emptied into the left venous angle. In five other Macaque monkeys (M. mulatta and M. fascicularis) after marker injection (T1824 blue dye and micropulverized barium sulfate) into the living heart or pericardium, lymphatic drainage beyond the base of the heart could not be demonstrated. Whereas postmortem morphologic studies suggest that the monkey coronary lymphatic system is amenable to obstruction by removal of the cardiac lymph node and interruption of its adjacent lymphatic connections, effective methods for visualizing the mediastinal lymphatic collecting system in the living monkey must be developed before experimental cardiac lymphatic ablation can be accomplished in this species.
Assuntos
Coração/anatomia & histologia , Sistema Linfático/anatomia & histologia , Macaca mulatta/anatomia & histologia , Animais , Linfonodos/anatomia & histologia , Macaca fascicularis , Mediastino/anatomia & histologiaRESUMO
The arterial supply to the region of the coronary sinus and the interatrial septum was examined in 18 normal canine hearts. In 13 of a further 18 dogs, coronary sinus rhythm was evoked by the ligation of atrial arteries, subsequent to which the arteries were visualized by injection of latex. A stable coronary sinus rhythm is evoked by producing ischaemia in an extensive area of the right atrium, including the sinus node, the interatrial septum and Bachmann's bundle, but preserving from ischaemia the posteroinferior part of the right atrium. Microscopical examination of the hearts with coronary sinus rhythm, and comparison with 9 control hearts, failed to demonstrate any morphological centre, in the form of nodal cells, which might have been responsible for the abnormal rhythm. In the posterior part of the right atrium, the ischaemic changes failed to affect the approaches of the atrioventricular node. The approaches were predominantly composed of cells poor in myofibrils mixed to a variable degree with cells of the working myocardium. We discuss the possibilities of the development of coronary sinus rhythm and "circus movement" with regard to the participation of the approaches to the atrioventricular node.