Malformations of the sacculus and the semicircular canals in spider morph pythons.

Spider morph ball pythons are a frequently-bred designer morph with striking alterations of the skin color pattern. We created high-resolution µCT-image series through the otic region of the skulls, used 3D-reconstruction software for rendering anatomical models, and compared the anatomy of the semicircular ducts, sacculus and ampullae of wildtype Python regius (ball python) with spider morph snakes. All spider morph snakes showed the wobble condition (i.e., twisting movements of the head, impaired locomotion, difficulty striking or constricting prey items). We describe the inner ear structures in wildtype and spider morph snakes and report a deviant morphology of semicircular canals, ampullae and sacculus in the latter. We also report about associated differences in the desmal skull bones of spider morph snakes, which were characterized by wider semicircular canals, ampullae widened and difficult to discern in µCT, a deformed crus communis, and a small sacculus with a highly deviant X-ray morphology as compared to wildtype individuals. We observed considerable intra- and interindividual variability of these features. This deviant morphology in spider morph snakes could easily be associated with an impairment of sense of equilibrium and the observed neurological wobble condition. Limitations in sample size prevent statistical analyses, but the anatomical evidence is strong enough to support an association between the wobble condition and a malformation of the inner ear structures. A link between artificially selected alterations in pattern and specific color design with neural-crest associated developmental malformations of the statoacoustic organ as known from other vertebrates is discussed.

Comparative Assessment of Computed Tomography and Magnetic Resonance Imaging of Spider Morph and Wild Type Ball Pythons (Python regius) for Evaluation of the Morphological Correlate of Wobble Syndrome.

There is general awareness of artificial selection and its potential implications on the health and welfare of animals. Despite growing popularity and increasing numbers of reptile breeds of atypical colour and pattern variants, only a few studies have investigated the appearance and causes of diseases associated with colour morphs. Ball pythons (Python regius) are among the most frequently bred reptiles and breeders have selected for a multitude of different colour and pattern morphs. Among those colour variants, the spider morph of the ball python is frequently associated with wobble syndrome. The aim of this study was to determine whether a morphological variant can be found and associated with the clinical occurrence of wobble syndrome in spider ball pythons, using computed tomography and magnetic resonance imaging as in-vivo diagnostic methods. Data from five spider and three wild type ball pythons was assessed and evaluated comparatively. We were able to identify distinctive structural differences in inner ear morphology in spider ball pythons, which were highly likely related to wobble syndrome. To our knowledge, this is the first report of these anomalies and provides a basis for further anatomical and genetic studies and discussion of the implications for animal welfare in reptile breeding.

Comparative and Functional Anatomy of the Ectothermic Sauropsid Heart.

The heart development, form, and functional specializations of chelonians, squamates, crocodilians, and birds characterize how diverse structure and specializations arise from similar foundations. This review aims to summarize the morphologic diversity of sauropsid hearts and present it in an integrative functional and phylogenetic context. Besides the detailed morphologic descriptions, the integrative view of function, evolution, and development will aid understanding of the surprising diversity of sauropsid hearts. This integrated perspective is a foundation that strengthens appreciation that the sauropsid hearts are the outcome of biological evolution; disease often is linked to arising mismatch between adaptations and modern environments.

Phylogeny and evolutionary history of the amniote egg.

We review morphological features of the amniote egg and embryos in a comparative phylogenetic framework, including all major clades of extant vertebrates. We discuss 40 characters that are relevant for an analysis of the evolutionary history of the vertebrate egg. Special attention is given to the morphology of the cellular yolk sac, the eggshell, and extraembryonic membranes. Many features that are typically assigned to amniotes, such as a large yolk sac, delayed egg deposition, and terrestrial reproduction have evolved independently and convergently in numerous clades of vertebrates. We use phylogenetic character mapping and ancestral character state reconstruction as tools to recognize sequence, order, and patterns of morphological evolution and deduce a hypothesis of the evolutionary history of the amniote egg. Besides amnion and chorioallantois, amniotes ancestrally possess copulatory organs (secondarily reduced in most birds), internal fertilization, and delayed deposition of eggs that contain an embryo in the primitive streak or early somite stage. Except for the amnion, chorioallantois, and amniote type of eggshell, these features evolved convergently in almost all major clades of aquatic vertebrates possibly in response to selective factors such as egg predation, hostile environmental conditions for egg development, or to adjust hatching of young to favorable season. A functionally important feature of the amnion membrane is its myogenic contractility that moves the (early) embryo and prevents adhering of the growing embryo to extraembryonic materials. This function of the amnion membrane and the liquid-filled amnion cavity may have evolved under the requirements of delayed deposition of eggs that contain developing embryos. The chorioallantois is a temporary embryonic exchange organ that supports embryonic development. A possible evolutionary scenario is that the amniote egg presents an exaptation that paved the evolutionary pathway for reproduction on land. As shown by numerous examples from anamniotes, reproduction on land has occurred multiple times among vertebrates-the amniote egg presenting one "solution" that enabled the conquest of land for reproduction.

Morphology of the avian yolk sac.

The avian yolk sac is a multifunctional extraembryonic organ that serves not only as a site of nutrient (yolk) absorption, but also for early hemopoiesis, and formation of blood vessels. Although the yolk sac membrane being specialized to function as an extraembryonic absorptive organ, it is neither morphologically nor functionally part of the embryonic gut. Yolk absorption is by the phagocytic activity of the extraembryonic endoderm. I used cryohistology and resin embedding histology of complete developmental series of Japanese quail to document the development of the avian yolk sac and changes of the microscopic anatomy throughout development. This material is complemented by complete series of MRT-scans of live ostrich embryos from beginning of incubation through hatching. Considerable changes of size and shape of the yolk mass are documented and discussed as resulting from water flux from albumen to yolk associated with the biochemical activation of yolk sac proteins. During embryogenesis, the yolk sac endoderm forms villi that increase the absorptive surface and reach into the yolk ball. The histology of the absorptive epithelium is specialized for phagocytic absorption of yolk. During early developmental stages, the extraembryonic endoderm is single layered, but it eventually becomes several layers thick during later stages. The extraembryonic mesoderm forms an extensive layer of hematopoietic tissue; deep in this tissue lie the yolk sac vessels. During late stages of development, the erythropoietic tissue disappears, blood vessels are obliterated, and the yolk sac epithelium becomes apoptotic. Results are discussed in the light of the evolutionary history and phylogeny of the amniote egg.

Three genetically distinct ferlaviruses have varying effects on infected corn snakes (Pantherophis guttatus).

Ferlaviruses are important pathogens in snakes and other reptiles. They cause respiratory and neurological disease in infected animals and can cause severe disease outbreaks. Isolates from this genus can be divided into four genogroups-A, B, and C, as well as a more distantly related sister group, "tortoise". Sequences from large portions (5.3 kb) of the genomes of a variety of ferlavirus isolates from genogroups A, B, and C, including the genes coding the surface glycoproteins F and HN as well as the L protein were determined and compared. In silico analyses of the glycoproteins of genogroup A, B, and C isolates were carried out. Three isolates representing these three genogroups were used in transmission studies with corn snakes (Pantherophis guttatus), and clinical signs, gross and histopathology, electronmicroscopic changes in the lungs, and isolation of bacteria from the lungs were evaluated. Analysis of the sequences supported the previous categorization of ferlaviruses into four genogroups, and criteria for definition of ferlavirus genogroups and species were established based on sequence identities (80% resp. 90%). Analysis of the ferlavirus glycoprotein models showed parallels to corresponding regions of other paramyxoviruses. The transmission studies showed clear differences in the pathogenicities of the three virus isolates used. The genogroup B isolate was the most and the group A virus the least pathogenic. Reasons for these differences were not clear based on the differences in the putative structures of their respective glycoproteins, although e.g. residue and consequential structure variation of an extended cleavage site or changes in electrostatic charges at enzyme binding sites could play a role. The presence of bacteria in the lungs of the infected animals also clearly corresponded to increased pathogenicity. This study contributes to knowledge about the structure and phylogeny of ferlaviruses and lucidly demonstrates differences in pathogenicity between strains of different genogroups.

Morphological responses to feeding in ticks (Ixodes ricinus).

BACKGROUND: Ticks can survive long periods without feeding but, when feeding, ingest large quantities of blood, resulting in a more than 100-fold increase of body volume. We study morphological adaptations to changes in opisthosoma volume during feeding in the castor bean tick, Ixodes ricinus. We aim to understand the functional morphological features that accommodate enormous changes in volume changes. METHODS: Using light and electron microscopy, we compare the cuticle and epidermis of the alloscutum, the epithelium of the midgut diverticula, and the tracheae of adult female ticks when fasting, semi-engorged, and fully engorged. RESULTS: Our results add to an existing body of knowledge that the area of the epidermis increases by cellular differentiation, cellular hypertrophy, and changes in the shape of epithelial cells from pseudostratified to single layered prismatic in semi-engorged ticks, and to thin squamous epithelium in fully engorged ticks. We did not find evidence for cell proliferation. The midgut diverticula accommodate the volume increase by cellular hypertrophy and changes in cell shape. In fully engorged ticks, the epithelial cells of the midgut diverticula are stretched to an extremely thin, squamous epithelium. Changes in size and shape (and cell divisions) contribute to the accommodation of volume changes. Tracheae do not increase in size, but extend in length, thus following the volume changes of the opisthosoma in feeding ticks to secure oxygen supply to the internal organs. CONCLUSIONS: Changes of epithelial tissue configuration in the epidermis and the midgut diverticula are described as important components of the morphological response to feeding in ticks. We provide evidence for a previously unknown mechanism hosted in the endocuticle of the tracheae that allows the tracheae of castor bean ticks to expand when the body volume increases and the distance between the respiratory spiracle and the oxygen demanding tissue enlarges. This is the first report of expandable tracheae in arthropods.

Open data and digital morphology.

Over the past two decades, the development of methods for visualizing and analysing specimens digitally, in three and even four dimensions, has transformed the study of living and fossil organisms. However, the initial promise that the widespread application of such methods would facilitate access to the underlying digital data has not been fully achieved. The underlying datasets for many published studies are not readily or freely available, introducing a barrier to verification and reproducibility, and the reuse of data. There is no current agreement or policy on the amount and type of data that should be made available alongside studies that use, and in some cases are wholly reliant on, digital morphology. Here, we propose a set of recommendations for minimum standards and additional best practice for three-dimensional digital data publication, and review the issues around data storage, management and accessibility.

Morphology and Morphometry of the Lung in Corn Snakes (Pantherophis guttatus) Infected with Three Different Strains of Ferlavirus.

Ophidian paramyxovirus (ferlavirus) is a global threat to reptilian sauropsids in herpetological collections, with occasional but fatal effects. This study characterizes the effects of three different genetic strains of ferlavirus on the dynamic changes of histology and morphometry of the lung of corn snakes (Pantherophis guttatus). Lungs from 42 corn snakes were either sham-infected or infected experimentally under standardized conditions. From 4 to 49 days after intratracheal inoculation, the lungs were examined qualitatively and quantitatively. Progressive microscopical changes were seen in the lung. Initially, increased numbers of heterophils were observed in the interstitium followed by proliferation and vacuolation of epithelial cells lining faveoli. Electron microscopy revealed loss of type-I pneumocytes, hyperplasia of type-II pneumocytes, and interstitial infiltrates of heterophils and mononuclear cells. With progression of disease the respiratory epithelium was initially overgrown by transformed type-II pneumocytes and later became multilayered. The results of the study suggest that the respiratory capacity of the lungs declines with disease development. The dynamics of disease development and histopathology differed in snakes infected with different ferlavirus genogroups. Animals infected with virus genogroup B developed histopathological changes and morphometric changes more rapidly and of greater intensity than snakes infected with viruses from genogroups A or C.

Histological and ultrastructural analysis of the respiratory tracheae of Galeodes granti (Chelicerata: Solifugae).

Solifuges lack oxygen-carrying proteins like hemocyanins found in other chelicerates. For conduction of gases, therefore, we hypothesize that the tracheal system is divided into convective and respiratory parts, the latter having intimate association with respiring cells, tissues and organs. This hypothesis is supported by studies of tracheae in other arthropods. We used light, scanning, and transmission electron microscopy to examine the tracheae of Galeodes granti (Chelicerata, Solifugae). We studied tracheae in cheliceral and leg muscles, midgut and midgut diverticula, the heart and the supra- and subesophageal ganglia of the central nervous system. In all tissues examined, the tracheae penetrate into tissues and can be found between cells. Terminal branches with diameter less than one micron were found embedded into cell bodies of respiring tissue, thus reducing the diffusion distance. We suggest that the terminal branches are specialized for respiratory function due to their thin intima, with reduced endocuticle and exocuticle. Comparison with other tracheate chelicerates suggests parallel evolution of a common tracheal pattern based on homologous cellular building materials within the chelicerates and arthropods.

Morphology of the tracheal system of camel spiders (Chelicerata: Solifugae) based on micro-CT and 3D-reconstruction in exemplar species from three families.

We studied the tracheal system of exemplar species representing three families of Solifugae Sundevall, 1833, i.e., Galeodes granti Pocock, 1903, Ammotrechula wasbaueri Muma, 1962 and Eremobates sp., using µCT-imaging and 3D-reconstruction. This is the first comparative study of the tracheal system of Solifugae in 85 years and the first using high-resolution nondestructive methods. The tracheal system was found to be structurally similar in all three species, with broad major tracheae predominantly in the prosoma as well as anastomoses (i.e., connections between tracheal branches from different stigmata) in the prosoma and opisthosoma. Differences among the three species were observed in the presence or absence of cheliceral air sacs, the number of tracheae supplying the heart, and the ramification of major tracheae in the opisthosoma. The structure of the tracheal system with its extensive branches and some anastomoses is assumed to aid rapid and efficient gas exchange in the respiratory tissues of these active predators. The large diameter of cheliceral tracheae (air sacs) of taxa with disproportionally heavier chelicerae suggests a role in weight reduction, enabling solifuges to reach greater speeds during predation. The air sacs may also permit more rapid and efficient gaseous exchange, necessary to operate the musculature of these structures, thereby improving their use for predation in an environment where prey is scarce.

Using heart rate to predict energy expenditure in large domestic dogs.

The aim of this study was to establish heart rate as a measure of energy expenditure in large active kennel dogs (28 ± 3 kg bw). Therefore, the heart rate (HR)-oxygen consumption (V˙O2) relationship was analysed in Foxhound-Boxer-Ingelheim-Labrador cross-breds (FBI dogs) at rest and graded levels of exercise on a treadmill up to 60-65% of maximal aerobic capacity. To test for effects of training, HR and V˙O2 were measured in female dogs, before and after a training period, and after an adjacent training pause to test for reversibility of potential effects. Least squares regression was applied to describe the relationship between HR and V˙O2. The applied training had no statistically significant effect on the HR-V˙O2 regression. A general regression line from all data collected was prepared to establish a general predictive equation for energy expenditure from HR in FBI dogs. The regression equation established in this study enables fast estimation of energy requirement for running activity. The equation is valid for large dogs weighing around 30 kg that run at ground level up to 15 km/h with a heart rate maximum of 190 bpm irrespective of the training level.

Morphological Pulmonary Diffusion Capacity for Oxygen of Burmese Pythons (Python molurus): a Comparison of Animals in Healthy Condition and with Different Pulmonary Infections.

A qualitative and quantitative morphological study of the pulmonary exchange capacity of healthy and diseased Burmese pythons (Python molurus) was carried out in order to test the hypothesis that the high morphological excess capacity for oxygen exchange in the lungs of these snakes is one of the reasons why pathological processes extend throughout the lung parenchyma and impair major parts of the lungs before clinical signs of respiratory disease become apparent. Twenty-four Burmese pythons (12 healthy and 12 diseased) were included in the study. A stereology-based approach was used to quantify the lung parenchyma using computed tomography. Light microscopy was used to quantify tissue compartments and the respiratory exchange surface, and transmission electron microscopy was used to measure the thickness of the diffusion barrier. The morphological diffusion capacity for oxygen of the lungs and the anatomical diffusion factor were calculated. The calculated anatomical diffusion capacity was compared with published values for oxygen consumption of healthy snakes, and the degree to which the exchange capacity can be obstructed before normal physiological function is impaired was estimated. Heterogeneous pulmonary infections result in graded morphological transformations of pulmonary parenchyma involving lymphocyte migration into the connective tissue and thickening of the septal connective tissue, increasing thickness of the diffusion barrier and increasing transformation of the pulmonary epithelium into a columnar pseudostratified or stratified epithelium. The transformed epithelium developed by hyperplasia of ciliated cells arising from the tip of the faveolar septa and by hyperplasia of type II pneumocytes. These results support the idea that the lungs have a remarkable overcapacity for oxygen consumption and that the development of pulmonary disease continuously reduces the capacity for oxygen consumption. However, due to the overcapacity of the lungs, this reduction does not result in clinical signs and disease can progress unrecognized for an extended period.

Morphological specializations for fetal maintenance in viviparous vertebrates: An introduction and historical retrospective.

In many viviparous vertebrates, pregnant females sustain their developing embryos and provide them with nutrients by means of placentas and a diversity of other types of specializations. With this article, we introduce a virtual (online) issue of the Journal of Morphology that presents 12 recent papers on fetal maintenance in viviparous vertebrates. We also outline the history of research in this area and document the central role of morphology in helping to explain the function and evolution of specializations for fetal nutrition. This virtual issue of the Journal of Morphology is an outgrowth of a symposium held under auspices of the International Congress of Vertebrate Morphology. The included papers reflect a diversity of taxa, research methods, and biological issues. To celebrate the publication of this virtual issue of the Journal of Morphology, the publisher is making freely available to readers a number of other relevant papers published in the journal over the past 128 years.

Alligators and Crocodiles Have High Paracellular Absorption of Nutrients, But Differ in Digestive Morphology and Physiology.

Much of what is known about crocodilian nutrition and growth has come from animals propagated in captivity, but captive animals from the families Crocodilidae and Alligatoridae respond differently to similar diets. Since there are few comparative studies of crocodilian digestive physiology to help explain these differences, we investigated young Alligator mississippiensis and Crocodylus porosus in terms of (1) gross and microscopic morphology of the intestine, (2) activity of the membrane-bound digestive enzymes aminopeptidase-N, maltase, and sucrase, and (3) nutrient absorption by carrier-mediated and paracellular pathways. We also measured gut morphology of animals over a larger range of body sizes. The two species showed different allometry of length and mass of the gut, with A. mississippiensis having a steeper increase in intestinal mass with body size, and C. porosus having a steeper increase in intestinal length with body size. Both species showed similar patterns of magnification of the intestinal surface area, with decreasing magnification from the proximal to distal ends of the intestine. Although A. mississippiensis had significantly greater surface-area magnification overall, a compensating significant difference in gut length between species meant that total surface area of the intestine was not significantly different from that of C. porosus. The species differed in enzyme activities, with A. mississippiensis having significantly greater ability to digest carbohydrates relative to protein than did C. porosus. These differences in enzyme activity may help explain the differences in performance between the crocodilian families when on artificial diets. Both A. mississippiensis and C. porosus showed high absorption of 3-O methyl d-glucose (absorbed via both carrier-mediated and paracellular transport), as expected. Both species also showed surprisingly high levels of l-glucose-uptake (absorbed paracellularly), with fractional absorptions as high as those previously seen only in small birds and bats. Analyses of absorption rates suggested a relatively high proportional contribution of paracellular (i.e., non-mediated) uptake to total uptake of nutrients in both species. Because we measured juveniles, and most paracellular studies to date have been on adults, it is unclear whether high paracellular absorption is generally high within crocodilians or whether these high values are specific to juveniles.

A new NMR technique to probe protein-ligand interaction.

Non covalent grafting of proteins on affinity phases is a very common approach for isolation, purification and re-concentration of tagged proteins. Many biophysical studies are conducted on these grafted proteins (surface plasmon resonance, quartz crystal microbalance, etc.) showing that the integrity and function of the protein is usually maintained. However, NMR studies of such samples were not undertaken so far, due to the broadening observed on this kind of heterogeneous samples. We present here the use of the HR-MAS technology to obtain 2D NMR spectra of the MAGI-1 PDZ2/6 protein domain, C13-labeled, tagged with a His-tag and grafted on a Nickel affinity resin. We optimized the C13 Methyl SOFAST HMQC experiment allowing important gains in terms of signal-to-noise. The gain comes from the gathering of proton magnetization from the resin material to the protein under study. Several methyl signals from the unstructured C-terminal tail, which is involved in the binding of the PDZ domain to C-terminal peptides of its partners, were observed and measured. The interaction of the bound PDZ domain with cognate peptides was monitored using <500µg of protein sample. A response proportional to the peptide Kd is obtained, indicating that the method can be used to rapidly and efficiently monitor protein-ligand interactions.

Morphological respiratory diffusion capacity of the lungs of ball pythons (Python regius).

This study aims at a functional and morphological characterization of the lung of a boid snake. In particular, we were interested to see if the python's lungs are designed with excess capacity as compared to resting and working oxygen demands. Therefore, the morphological respiratory diffusion capacity of ball pythons (Python regius) was examined following a stereological, hierarchically nested approach. The volume of the respiratory exchange tissue was determined using computed tomography. Tissue compartments were quantified using stereological methods on light microscopic images. The tissue diffusion barrier for oxygen transport was characterized and measured using transmission electron micrographs. We found a significant negative correlation between body mass and the volume of respiratory tissue; the lungs of larger snakes had relatively less respiratory tissue. Therefore, mass-specific respiratory tissue was calculated to exclude effects of body mass. The volume of the lung that contains parenchyma was 11.9±5.0mm(3)g(-1). The volume fraction, i.e., the actual pulmonary exchange tissue per lung parenchyma, was 63.22±7.3%; the total respiratory surface was, on average, 0.214±0.129m(2); it was significantly negatively correlated to body mass, with larger snakes having proportionally smaller respiratory surfaces. For the air-blood barrier, a harmonic mean of 0.78±0.05µm was found, with the epithelial layer representing the thickest part of the barrier. Based on these findings, a median diffusion capacity of the tissue barrier ( [Formula: see text] ) of 0.69±0.38ml O(2)min(-1)mmHg(-1) was calculated. Based on published values for blood oxygen concentration, a total oxygen uptake capacity of 61.16mlO(2)min(-1)kg(-1) can be assumed. This value exceeds the maximum demand for oxygen in ball pythons by a factor of 12. We conclude that healthy individuals of P. regius possess a considerable spare capacity for tissue oxygen exchange.

[Echocardiography in Boid snakes: Demonstration and blood flow measurements]. / Echokardiographische Untersuchungen bei Boiden: Darstellung und Blutflussmessungen.

OBJECTIVE: Comparative echocardiography and blood flow measurements in different boid species. MATERIALS AND METHODS: 51 healthy snakes from seven different species were examined echocardiographically under standardized conditions. The heart and the great vessels were displayed using 2-D-ultrasonography. Pulsed-wave doppler technique measurements of the blood flow within the vessels were performed and results analyzed statistically. RESULTS: The examinations could be performed in non-sedated snakes in ventral recumbency. The best image quality was obtained using the ventrolateral coupling site. An examination scheme applicable to all examined snake species was established. Diversity in the anatomy of vessels could be detected in different snake species. A characteristic shape of the curve demonstrating the blood flow against time could be shown for the respective vessels. There were positive correlations between the size of the snakes and the absolute blood flow (total flow, systemic flow, pulmonary flow to body length: p<0.001; r=0.770; r=0.627; r=0.766; respectively to body mass: p<0.001; r=0.815; r=0.698; r=0.788), as well as negative correlations between the size of the animals and the blood flow relative to body mass (total flow, systemic flow, pulmonary flow to body length: p<0.001; r=-0.533; r=-0.512; r=-0.478; respectively total flow to body mass: p<0.001; r=-0.768). CONCLUSION AND CLINICAL RELEVANCE: When using standardized conditions, echocardiography in boid snakes is a useful diagnostic tool for the assessment of cardiac function. Reference values provided in this study serve as a basis for ultrasound examination in veterinary practice.

Dual-Source computed tomography of the chest in the surgical planning of repeated cardiac surgery.

AIM: When reoperative cardiac surgery is indicated, detailed, three-dimensional imaging of the thorax permits accurate depiction of cardiac anatomy and vascular structures potentially increasing the safety of the surgical procedure. We sought to evaluate the contribution of dual-source multidetector-row computed tomography (DSCT) of the heart and thorax in planning repeated open heart surgery. METHODS: Twenty-eight patients (mean age, 68 years) scheduled for repeated cardiac surgery who had undergone previous coronary artery bypass grafting (n=19) or cardiac valve replacement (8) or combined valvular and bypass surgery (1) underwent contrast-enhanced ECG-gated DSCT (Somatom Definition, Siemens Medical Solutions) of the whole thorax with a temporal resolution of 82 ms and a spatial resolution of 0.4 mm³. The indication for repeated surgery was bypass surgery (N.=6), valve replacement (16), combined bypass and valvular surgery (5) or other reasons (1). Assessment of surgical risk based on DSCT data were performed in terms of the relation of the ascending aorta and cardiac structures to the expected median sternotomy line, graft patency and anatomic course, and the degree of calcification of the ascending aorta and coronary arteries. RESULTS: DSCT findings led to a change of surgical approach for 9/28 (32.1%) patients (non-midline incision, N.=3; surgery performed under circulatory arrest, N.=5; peripheral arterial cannulation before sternotomy, N.=1) and cancellation of surgery for 4/28 (14.3%) patients (heavy aortic and coronary calcifications impeding bypass surgery, N.=2; right heart or aortic aneurysm in close proximity to the sternum in high risk patients, N.=2). The planned surgical approach remained unchanged after DSCT for the remaining15/28 (53.6%) patients. Of 54 bypass graft conduits (20 arterial, 34 venous) visualized on DSCT in 20 patients after previous bypass grafting, 16 arterial and 24 venous grafts were patent, while 4 arterial and 10 venous grafts were occluded. CONCLUSION: DSCT of the heart and thorax is an effective, non-invasive tool for the preoperative planning of repeated cardiac surgery. The technique provides significant information to modify the surgical approach and may increase the safety of the procedure.