Anatomy of the sinoatrial node and the supply of its vascularization in man

Seventy heart preparations of persons belonging to different sex and age have been investigated, using a complex of anatomical and histological techniques. The dimensions of the sinoatrial node (SAN) vary with age and depend on various size and form of the heart. The large atrial branch of the right and left coronary arteries supplies mainly the SAN with blood. More seldom the atrial branches of both cardiac arteries, having anastomoses, realize the SAN blood supply. The character of the SAN vascularization depends on branching variations of the atrial vessels. At the right coronary variant the sources of the SAN blood supply are the SAN branch, the right intermediate or right posterior atrial branches, and at the left coronary variant--the anterior left, the posterior left and the intermediate left atrial branches. At the even variant the SAN blood supply sources are the right intermediate and the anterior left atrial or the right posterior and the left posterior atrial branches. The data obtained can be used for comparison with the results of coronography to make a skilled analysis of clinical-roentgenological observations.     

Atrial natriuretic peptide binding sites in the mammalian heart: Localization to endomural vessels

Summary The distribution of binding sites for atrial natriuretic peptide in cardiac ventricles of several mammalian species, including rat and human, was determined by in vitro autoradiography. The results revealed a unique anatomic localization of atrial natriuretic peptide binding sites to endomural vessels (Thebesian vessels), which communicate directly with the ventricular chambers. Digital image analysis indicated that these vascular channels possessed binding site densities comparable to those of the renal glomeruli a major target site for circulating atrial natriuretic peptide. In contrast, no specific labeling of branches of the coronary arteries and veins was detected. The discrete localization of atrial natriuretic peptide binding sites to this primitive cardiac circulatory system allows speculation as to the role of this hormone in the regulation of endocardialcirculation during cardiac development, normal ventricular function, and in coronary insufficiency.     

Atrioventricular and ventriculoatrial branches of the coronary arteries in human hearts

Atrioventricular (AV) and ventriculoatrial (VA) branches of the coronary arteries are vessels which supply simultaneously atrial and ventricular walls by means of recurrent rami. The terminology indicates the name of the main vessel followed by the name of the recurrent vessel both combined in an adjective. These branches establish a vascular 'suture' across the coronary sulcus in front (superficially to) or behind (deeply to) the trunks of the right coronary artery and of the left coronary artery (circumflex artery). The AV and VA branches, found in 95% of 40 human hearts, should be considered a normal characteristic of the coronary circulation and an important anatomical factor for the clinical interpretation of pathological cardiac phenomena.     

猪冠状动脉的解剖学观察

本文对50例健康的商品猪心脏的铸型标本进行了观察,结果如下:左冠状动脉旋枝与锥旁室间枝的夹角为74.4±2.07度。对角枝出现率为24％,并证明了对角枝出现率与其夹角大小呈正比关系。窦房结枝84％来自右冠状动脉。房室结枝98％来自右冠状动脉。左房旋枝出现率为8％。室间隔的供血由锥旁室间枝的分枝负担61％,约为3/5,窦下室间枝的分技负担39％,约为2/5。室上嵴技、Kugel动脉、室间隔中枝和室间隔背倒前枝的出现率分别为78％、20％、68％和28％。心尖区的血液由左、右冠状动脉共同供应。50例左、右冠状动脉始部外径之比为1.2∶1。左、右冠状动脉在心膈面的分布类型以右强型为主。本文还讨论了猪冠状动脉与狗、人冠状动脉的异同。     

Immunocytochemical detection of atrial natriuretic peptide in periarterial myocardiocytes of cardiac ventricles of adult normotensive rat

The cardiac hormone atrial natriuretic peptide (ANP) is known to be produced by the atrial myocardiocytes. In the ventricles, the concentrations of ANP are very low and are often undetectable by immunocytochemistry. Apart from recent reports of ANP in the various Purkinje cell types, the histological distribution of the small amounts of ANP in the ventricular myocardium has not been well established. In this study, the distribution of ANP immunoreactivity in the ventricles of normotensive adult rats was examined with a modified version of an immunostaining procedure. ANP immunoreactivity was present, in addition to typical myocardial cells, in the myocardiocytes surrounding the arteries and arterioles, particularly at their bifurcations. The specificity of the immunostaining was confirmed with pre-absorption controls. Such a distribution indicates that in addition to being an endocrine hormone ANP may have a paracrine function. The periarterial myocardiocytes may be able to sense the pressure and/or volume changes of the surrounded blood vessels and to release ANP, which may in turn affect these blood vessels and thereby regulate coronary perfusion. The physiological and pathological significance of periarterial ANP distribution warrants further investigation.     

Anomalous course and branches of human coronary arteries

132 hearts obtained from cadavers were dissected in order to study anomalies in the course and branches of human coronary arteries. Only in 1 heart was a deviation of the circumflex branch of the left coronary artery taking a course inferior to the coronary sulcus observed. The right coronary artery travelled the entire length of the coronary sulcus on the back of the heart and gave both a posterior ventricular and a collateral branch. Circumflex branches of the right and left coronary arteries did not anastomose.     

Angioarchitectonics of the auricular and atrial walls of the human heart

Preparations of 103 human hearts at various ages have been investigated. The coronary veins are injected with contrast lead mass and a successive roentgenoangiography of the preparations is performed. The sources of blood supply of the atrial and auricular walls are determined taking into account branching variants of the atrial vessels. Vascularization peculiarities of the atrii and auriculae are described at the sinistrocoronary, dextrocoronary and even variants of the atrial branches. With age the diameter, length of the main atrial and auxillary auricular branches increase, as does their convolutivness. In the atrial and auricular walls there are areas comparatively poor in blood vessels. The branching variants do not always coinside with the types of the cardiac blood supply.     

Human cardiac myosin heavy chain isoforms in fetal and failing adult atria and ventricles

The goal of this study was to test the hypothesis that the relative amounts of the cardiac myosin heavy chain (MHC) isoforms MHC-alpha and MHC-beta change during development and transition to heart failure in the human myocardium. The relative amounts of MHC-alpha and MHC-beta in ventricular and atrial samples from fetal (gestational days 47--110) and nonfailing and failing adult hearts were determined. The majority of the fetal right and left ventricular samples contained small relative amounts of MHC-alpha (mean < 5% of total MHC). There was a small significant decrease in the level of MHC-alpha in the ventricles between 7 and 12 wk of gestation. Fetal atria expressed predominantly MHC-alpha (mean > 95%), with MHC-beta being detected in most samples. The majority of adult nonfailing right and left ventricular samples had detectable levels of MHC-alpha ranging from 1 to 10%. Failing right and left ventricles expressed a significantly lower level of MHC-alpha. MHC-alpha comprised approximately 90% of the total MHC in adult nonfailing left atria, whereas the relative amount of MHC-alpha in the left atria of individuals with dilated or ischemic cardiomyopathy was approximately 50%. The differences in MHC isoform composition between fetal and nonfailing adult atria and between fetal and nonfailing adult ventricles were not statistically significant. We concluded that the MHC isoform compositions of fetal human atria are the same as those of nonfailing adult atria and that the ventricular MHC isoform composition is different between adult nonfailing and failing hearts. Furthermore, the marked alteration in atrial MHC isoform composition, associated with cardiomyopathy, does not represent a regression to a pattern that is uniquely characteristic of the fetal stage.     

Homology of lungs and gas bladders: Insights from arterial vasculature

Gas bladders of ray‐finned fishes serve a variety of vital functions and are thus an important novelty of most living vertebrates. The gas bladder has long been regarded as an evolutionary modification of lungs. Critical evidence for this hypothesized homology is whether pulmonary arteries supply the gas bladder as well as the lungs. Pulmonary arteries, paired branches of the fourth efferent branchial arteries, deliver blood to the lungs in osteichthyans with functional lungs (lungfishes, tetrapods, and the ray‐finned polypterid fishes). The fact that pulmonary arteries also supply the respiratory gas bladder of Amia calva (bowfin) has been used to support the homology of lungs and gas bladders, collectively termed air‐filled organs (AO). However, the homology of pulmonary arteries in bowfin and lunged osteichthyans has been uncertain, given the apparent lack of pulmonary arteries in critical taxa. To re‐evaluate the homology of pulmonary arteries in bowfin and lunged osteichthyans, we studied, using micro‐CT technology, the arterial vasculature of Protopterus, Polypterus, Acipenser, Polyodon, Amia, and Lepisosteus, and analyzed these data using a phylogenetic approach. Our data reveal that Acipenser and Polyodon have paired posterior branches of the fourth efferent branchial arteries, which are thus similar in origin to pulmonary arteries. We hypothesize that these arteries are vestigial pulmonary arteries that have been coopted for new functions due to the dorsal shift of the AO and/or the loss of respiration in these taxa. Ancestral state reconstructions support pulmonary arteries as a synapomorphy of the Osteichthyes, provide the first concrete evidence for the retention of pulmonary arteries in Amia, and support thehomology of lungs and gas bladders due to a shared vascular supply. Finally, we use ancestral state reconstructions to show that arterial AO supplies from the celiacomesenteric artery or dorsal aorta appear to be convergent between teleosts and nonteleost actinopterygians. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Histamine receptors in the human heart

Histamine receptor subtypes in $\text{in vitro}$ isolated human coronary arteries and in $\text{in vitro}$ human atrial and ventricular myocardium were studied. The H₁ receptor mediates contraction of coronary vascular smooth muscle but has no effect on atrial or ventricular tissue. The H₂ receptor mediates relaxation of human coronary artery vascular smooth muscle and mediates a positive inotropic response in atrial and ventricular myocardium.     

Differences between atrial and ventricular protein profiling in children with congenital heart disease

The purpose of the present study was to compare protein profiling of atria and ventricles in children operated for congenital heart disease. Tissue samples were obtained during surgery from patients with normoxemic (ventricular and atrial septal defects) and hypoxemic (tetralogy of Fallot) diseases. Protein fractions were isolated by stepwise extraction from both fight ventricular and atrial musculature. The concentration of total atrial protein in the normoxemic patients exceeded the ventricular value (110±2.1 vs 99.9±4.0mg.g^–1 wet weight, respectively); in the hypoxemic group this atrio-ventricular difference disappeared. The concentration of contractile proteins in all cardiac samples was significantly higher in the ventricles as compared with atria, while the concentration of collagenous proteins was significantly higher in the atria (due to a higher amount of the insoluble collagenous fraction). The concentration of sarcoplasmic proteins (containing predominantly enzyme systems for aerobic and anaerobic substrate utilization), however did not differ between ventricles and atria. Furthermore, ventricular contractile fractions obtained from both normoxemic and hypoxemic patients were contaminated with the myosin light chain of atrial origin. Soluble collagenous fractions (containing newly synthesized collagenous proteins, predominantly collagen I and III), derived from all ventricular samples, were contaminated by low molecular weight fragments (mol. weight 29–35 kDa). The proportion of the soluble collagenous fraction was significantly higher in atrial but not in ventricular myocardium of hypoxemic children as compared with the normoxemic group. It seems, therefore, that lower oxygen saturation affects the svnthesis of collagen preferentially in atrial tissue.     

Epicardial coronary blood flow including the presence of stenoses and aorto-coronary bypasses--I: Model and numerical method

A computer model and numerical method for calculating left epicardial coronary blood flow has been developed. This model employs a finite-branching geometry of the coronary vasculature and the one-dimensional, unsteady equations for flow with friction. The epicardial coronary geometry includes the left main and its bifurcation, the left anterior descending and left circumflex coronary arteries, and a selected number of small branches. Each of the latter terminate in an impedance, whose resistive component is related to intramyocardial compression through a linear dependence on left ventricular pressure. The elastic properties of the epicardial arteries are taken to be non-linear and are prescribed by specifying the local small-disturbance wave speed. The model allows for the incorporation of multiple stenoses as well as aorto-coronary bypasses. Calculations using this model predict pressure and flow waveform development and allow for the systematic investigation of the dependence of coronary flow on various parameters, e.g., peripheral resistance, wall properties, and branching pattern, as well as the presence of stenoses and bypass grafts. Reasonable comparison between calculations and earlier experiments in horses has been obtained.     

Anatomical studies of the coronary system in elasmobranchs: I. Coronary arteries in lamnoid sharks

A study of the anatomy of coronary arteries has been done in five shark species of the order Lamniformes: Isurus oxyrinchus, Isurus paucus, Lamna nasus, Alopias superciliosus, and Alopias vulpinus. The study, which included 26 specimens, was carried out with the injection-corrosion technique, obtaining internal casts of the main trunks and coronary arterial branches. The results have shown a high degree of constancy in the coronary patterns in all species and a number of general features common to all of them, except for Alopias vulpinus. In this species, a mesh-like ventricular pattern of intramyocardial vessels was found instead of subepicardial ventricular coronary branches with a definite pattern. It was also shown that there is a wide range of variation among the species regarding the relative importance of the dorsal and ventral coronary trunks. Thus, Isurus oxyrinchus showed a clear predominance of the ventral coronary trunk, whereas in Alopias superciliosus, most of the ventricle was supplied by branches derived from the dorsal coronary trunk.     

Distributing and delivering vessels of the human heart

The branching characteristics of the right coronary artery, acute marginal, posterior descending, left anterior descending, circumflex, and obtuse marginal arteries are compared with those of diagonal branches, left and right ventricular branches, septal, and higher-order branches, to test a newly proposed functional classification of the coronary arteries in which the first group rank as distributing vessels and the second as delivering vessels. According to this classification, the function of the first type is merely to convey blood to the borders of myocardial zones, while the function of the second is to implement the actual delivery of blood into these zones. This functional difference is important in the hemodynamic analysis of coronary heart disease, as it provides an assessment of the role of a vessel within the coronary network and hence an assessment of the functional importance of that vessel in a particular heart. Measurements from casts of human coronary arteries are used to examine the relevant characteristics of these vessels and hence to test the basis of this classification.     

Cardiac vessels of human fetuses and newborn infants

The anatomy of the cardiac arteries has been studied in 78 and that of the veins--in 74 total preparations of human fetal hearts 3--10-lunar month-old and in newborns. The cardiac vessels are injected with contrast masses, erythrocytes are stained with benzidine, histotopograms are made. In the fetuses all branches of the 1st-3d order of the coronary arteries and cardiac veins have been formed. Topography and main dimentions of large cardiac vessels are defined. During the prenatal period ramification zones of the coronary arteries do not change. In different age groups of the fetuses and newborns right coronary type of the cardiac blood supply predominates considerably (58-60%), in 27-32%--equal, and in 8-13%--left coronary type is observed. A great variability of the venous cardiac bed, vast intervenous anastomoses and a special importance of the cardiac middle vein in blood outflow are noted.     

A mathematical model of human atrioventricular nodal function incorporating concealed conduction

This work develops a mathematical model for the atrioventricular (AV) node in the human heart, based on recordings of electrical activity in the atria (the upper chambers of the heart) and the ventricles (the lower chambers of the heart). Intracardiac recordings of the atrial and ventricular activities were recorded from one patient with atrial flutter and one with atrial fibrillation. During these arrhythmias, not all beats in the atria are conducted to the ventricles. Some are blocked (concealed). However, the blocked beats can affect the properties of the AV node. The activation times of the atrial events were regarded as inputs to a mathematical model of conduction in the AV node, including a representation of AV nodal concealment. The model output was compared to the recorded ventricular response to search for and identify the best possible parameter combinations of the model. Good agreement between the distribution of interbeat intervals in the model and data for durations of 5 min was achieved. A model of AV nodal behavior during atrial flutter and atrial fibrillation could potentially help to understand the relative roles of atrial input activity and intrinsic AV nodal properties in determining the ventricular response.     

Cell transplantation with a catheter-based approach: an efficient method for the treatment of heart failure with multiple lesions

Cell transplantation is emerging as a potential therapeutic approach for the treatment of heart failure. At present, popular methods of cell delivery may not be efficient in perfusing cells through the whole myocardium. We have developed a novel catheter-based method for global transplantation of cells. Heart failure was induced in rabbit by intravenous administration of doxorubicin. Autologous bone marrow mononuclear cells were transplanted into failing hearts via the root of the aorta. Bilateral sinus aortae and coronary arteries were visualized by angiography during the cell transplantation procedure; there was no intraprocedural death. Four weeks after cell transplantation, there was an improvement in the mean left ventricular ejection fraction from baseline 72.13% to 81.54% (P = 0.034). Transplanted cells were observed throughout the cardiac layers of left and right ventricles. In conclusion, cell transplantation through the root of the aorta is a useful approach to globally supply cells into the heart.     

A new cardiac myosin characterized from the canine atria.

Canine atrial myosin light chains were electrophoretically distinct from myosins of canine ventricles on 5–20% polyacrylamide gradient slab gels (SDS), giving molecular weights of 26,000 and 21,000 as compared to 28,000 and 18,500 for ventricular myosin light chains. While atrial myosin heavy chains were immunologically identical with ventricular myosin heavy chains, in contrast, there was 8.0% relative cross-reactivity of atrial myosin light chains with left ventricular myosin light chains by radioimunoassay. According to charge separation on two-dimensional polyacrylamide urea gels, atrial myosin light chains were different from those of ventricular myosins. Variances in ATPase activities between atrial and ventricular myosins were strongly demonstrated. There was a lower K⁺ activated ATPase activity in atrial myosin, however the Ca²⁺ activated ATPase activity, at ATP saturation levels, was higher in atrial myosin as compared to ventricular myosins.     

Quantification of Blood Supply to the Left Ventricular Myocardium in Normal Subjects and Patients with Coronary Heart Disease

The subjects who underwent diagnostic coronarography and detailed examination included 274 patients with lesions in the left coronary artery and its branches and 50 subjects without pathological changes in the coronary arteries or left ventricle. The authors also examined 149 patients with unchanged coronary arteries (67 with small vessel disease 42 with cardiomyopathy of various etiology; and 40 with other pathologies, such as the WPW syndrome, arterial hypertension, aortic stenosis, etc.). In addition to routine retrograde left heart catheterization and recording of the hemodynamic parameters demonstrated by ventriculography, the coronary blood flow was measured in all patients. Its normalized (specific) values are a basis for the coronary blood flow quantification in normal subjects, patients with the coronary heart disease (with insufficient oxygen supply to the myocardium), and those with cardiomyopathy of various genesis (when the myocardial oxygen demand increases together with the left ventricular myocardium mass).     

Immunohistochemical localization of atrial natriuretic polypeptide (ANP) in human atrial and ventricular myocardiocytes

To date, there have been few immunohistochemical investigations of atrial natriuretic polypeptide (ANP) in human cardiac tissue, especially the ventricles. In this study, myocardial tissue was obtained from two sources: the bilateral atria and ventricles at autopsy; and biopsy tissues from the right auricle and left ventricle of a patient with myocardial infarction undergoing surgery. These tissues were examined by the avidin-biotin immunoperoxidase technique using three kinds of primary ANP-antibodies. ANP-immunoreactivity was observed in the perinuclear region of myocytes of all tissues examined. The intensity of the reaction was stronger in atrial tissue, weaker in ventricular tissue. In the later tissue, the positive-staining myocytes were not part of the pulse-conducting system. Although the tissues we studied were not obtained from normal hearts, our data demonstrates that ANP-reactivity can be detected in ventricular myocytes outside the pulse-conducting system.