Spontaneously Arising Tumours and Tumour-like Lesions of the Cervix and Uterus in 83 Pet Guinea Pigs (Cavia porcellus).

Tumours and tumour-like lesions are rare findings in the genital system of guinea pigs. The aim of the present study was to characterize nodular lesions in the cervix and uterus of guinea pigs submitted for histopathological diagnosis. Samples from 83 pet animals were investigated. Cases included 64 surgically excised masses including complete uteri (n = 37), parts from uteri containing masses (n = 8), complete masses (n = 12) or samples from masses (n = 7) and 19 complete necropsy examinations. In 55 of the cases, only solitary changes were observed; in 28 cases two or more lesions were diagnosed. Histopathological diagnoses included polyps in the vagina, cervix or uterus (n = 8), hyperplastic lesions of the endocervix (n = 10) and seven adenomas and two adenocarcinomas of the endocervix. Endometrial alterations included single small glandular cysts (n = 3), nodular glandular-cystic hyperplasia (n = 8), adenoma (n = 20) and adenocarcinoma (n = 3). Four placentas, 10 focal decidualizations and six deciduomas were found. Furthermore, 18 leiomyomas and nine leiomyosarcomas were diagnosed. Uterine malignant mixed Müllerian tumours were observed in seven cases. Overall, benign lesions outnumbered malignant tumours in the female genital tract of pet guinea pigs. Therefore, surgical excision or ovariohysterectomy should be recommended as therapy.

Cutaneous and Subcutaneous Soft Tissue Tumours in Snakes: A Retrospective Study of 33 Cases.

Cutaneous and subcutaneous soft tissue tumours have been rarely described in detail in snakes. Several malignant entities show strikingly similar histological patterns and therefore the term soft tissue sarcoma (STS) has become a standard histopathological diagnosis. The present study characterizes soft tissue tumours in 33 snakes. Samples included 29 surgically excised masses and four carcasses. Additionally, six animals were humanely destroyed and submitted for necropsy examination following tumour recurrence. Benign neoplasms (n = 8) were described as lipomas of varying differentiation. Recurrence was observed in two of five snakes in which the clinical course was recorded. Malignant neoplasms (n = 25) were diagnosed as STS and graded according to a three-point system previously applied to canine STS. Five (20%) of the primary tumours were classified as grade 1, eleven (44%) as grade 2 and nine (36%) as grade 3 sarcomas. Clinically, recurrence of STS was observed in 11 of 17 cases with available follow-up information. Pathologically, multiple cutaneous metastases were found in one grass snake (Natrix natrix), while visceral metastases were observed in one carpet python (Morelia spilota) and two corn snakes (Pantherophis guttatus). Metastatic risk appears to increase with histological grade. Surgical excision generally represents the current therapy of choice for STS. This study includes the first reports of conventional lipomas in a ribbon snake (Thamnophis radix), angiolipomas in a black-headed python (Aspidites melanocephalus) and a corn snake as well as of STS in a Jamaican boa (Epicrates subflavus), emerald tree boa (Corallus caninus), grass snake (N. natrix), African house snake (Lamprophis fuliginosus), California kingsnake (Lampropeltis getula californiae) and common garter snake (Thamnophis sirtalis).

Cardiac pathology in Irish wolfhounds with heart disease.

OBJECTIVES: To evaluate gross and histopathologic lesions in Irish wolfhounds (IWs) with atrial fibrillation (AF) and/or primary dilated cardiomyopathy (DCM) in different stages of disease. METHODS: Twenty-six formalin-fixed IW hearts were studied. Clinical diagnosis was based upon results of their most recent cardiovascular examinations including electrocardiography and echocardiography and categorized as normal (n = 4); preclinical (asymptomatic) DCM with AF (n = 6); DCM with congestive heart failure and AF (n = 4); AF with left ventricular reverse remodeling after DCM diagnosis (n = 3); AF without DCM (n = 7); and DCM with sinus rhythm (n = 2). All hearts were evaluated by one pathologist (HA) blinded to the clinical diagnosis. RESULTS: Ten of 15 DCM hearts showed mild to moderate multifocal myocardial fibrosis with variable diffuse adipocyte infiltration within the left and right ventricular myocardium. In five DCM hearts, there were no histopathological findings identified. Right atrial appendages from AF dogs with and without DCM had significantly more myocardial fibrosis and adipocyte infiltration compared with normal hearts and compared to left atrial appendages. CONCLUSIONS: Gross and histological findings in the ventricular myocardium of IWs with clinical diagnosis of DCM were variable; in some dogs, histopathology was normal. In IWs, the etiology of DCM might be different from that in other breeds with conditions causing functional impairment rather than evident histological changes. Right and left atrial appendages from IWs with AF displayed substantial pathology (interstitial fibrosis and adipocytes) most prevalent in the right atrial appendages which may be correlated to the pathogenesis of AF. These preliminary findings merit further study.

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.

Alpha-smooth muscle actin and serotonin receptors 2A and 2B in dogs with myxomatous mitral valve disease.

Canine Myxomatous mitral valve disease (MMVD) is an age-related disease. Serotonin (5-HT) is implicated in the pathogenesis as locally-produced or platelet-derived. Involvement of the 5-HT2A receptor (R) and 5-HT2BR in the induction of myxomatous-mediating valvular myofibroblasts (MF) has been suggested. In an age-matched population of dogs with non-clinical and clinical MMVD, the objectives were to investigate (1) gene expression of 5-HT2AR and 5-HT2BR, (2) protein expression and spatial relationship of 5-HT2AR, 5-HT2BR and MF in the mitral valve (MV) and the cardiac anterior papillary muscle (AP) and (3) serum 5-HT concentrations. Gene expression of 5-HT2BR was significantly higher in MV and AP among dogs with clinical MMVD. This was not found for 5-HT2BR protein expression, though association of 5-HT2BR with myxomatous pathology and co-localization of 5-HT2BR and MF in MV and AP support a functional relationship, perhaps perpetuation of clinical MMVD. 5-HT2AR-expression and serum 5-HT showed no differences between groups.

[Bone tumours in lizards and snakes. A rare clinical finding]. / Knochentumoren bei Echsen und Schlangen. Ein seltener klinischer Befund in der Reptilienpraxis.

OBJECTIVE: This article presents the pathological findings of 13 bone and cartilage tumours in lizards (n=8) and snakes (n=5) within the clinical context. MATERIAL AND METHODS: Within a 12-year period (2001-2013), 13 cases of bone tumours in reptiles were diagnosed from 358 submitted tumour specimens. Pathological examination was performed on eight excisions, two biopsies, two amputates and four carcasses. Macroscopically, the samples displayed a light-coloured surface when cut and had a generally solid consistency. For the histological examination, representative specimens were decalcified when necessary, embedded in paraffin and stained using haematoxylin and eosin. Diagnosis was made based on the World Health Organisation classification for veterinary and human medicine. RESULTS: Benign proliferations of the bone (ossifying fibroma [n=2], fibrous dysplasia [n=1]) as well as malignant cartilage (chondrosarcoma [n=2]) and bone tumours (fibroblastic osteosarcoma [n=2], small cell osteosarcoma [n=1]) were found on the head (n=5) and limbs (n=3) of various lizard species. In snakes only malignant cartilage neoplasms (chondrosarcoma [n=2], dedifferentiated chondrosarcoma [n=3]) of the spine were diagnosed. The histological appearance of the malignant tumours ranged from low to highly malignant differentiated aggregations of tumour cells, that produced varying amounts of osteoid or a hyaline matrix. Curative therapy was achieved in one ossifying fibroma by complete surgical removal and in two chondrosarcomas through amputation. No metastasis was observed in any of the four necropsies. CONCLUSION AND CLINICAL RELEVANCE: Primary neoplasias of the bone are rare tumours in reptiles. Considering the information on therapeutic procedures and clinical course, the therapy of choice in lizards is complete surgical removal whereas in snakes reductive surgery may prolong the survival time.

Histological study of the external, middle and inner ear of horses.

Clinical, anatomical and histological aspects of the equine acoustic organ have been poorly investigated and illustrated in literature so far. It is understood that an intact acoustic organ and hearing function are of vital importance for the well-being of flight animals like horses. The knowledge of the acoustic organ is usually transferred analogously from other mammals to horses. The purpose of this study was to provide a detailed and complete histological description of the healthy equine auditory organ, and to determine its congruity to other mammalians. Anatomical dissections and histological preparations were carried out on ten cadaver heads. Specimens of various parts of the equine acoustic organ were taken and evaluated histologically. The histological composition of external, middle and inner ear structures are predominantly congruent to those of other mammals, especially to human beings. Unique inwardly directed rete pegs within the osseous ear canal and the prominent tensor tympani muscle are described for the first time. Results obtained in this study can be employed as references for further research on the equine acoustic organ and improve the understanding of the clinical development of hearing loss, otitis externa/media/interna or tympanosclerosis.

Matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs) and transforming growth factor-ß (TGF-ß) in advanced canine myxomatous mitral valve disease.

This study investigated mitral valve and myocardial protein and gene expression of matrix metalloproteinases (MMPs), their tissue inhibitors (TIMPs) and transforming growth factor-ß (TGF-ß) and plasma MMP and TGF-ß concentrations in age-matched dog groups euthanized due to either advanced myxomatous mitral valve disease (MMVD) or other reasons. Furthermore, echocardiographic data and lumen/area ratio were correlated with tissue and plasma levels of MMPs, TIMPs and TGF-ßs. Mitral valve and myocardial gene expression of MMP2, MMP14, TGF-ß1 and TGF-ß2 were increased and plasma MMP9 was decreased in advanced MMVD dogs. Myocardial gene expression of TIMP2 and TIMP3 were increased in advanced MMVD. All affected markers correlated to echocardiographic parameters. Significantly narrowed lumen/area ratio was associated with increased myocardial expression of MMP2, MMP14, TIMP2 and TIMP3. No differences in tissue protein expression were recorded. MMP2, MMP14, TIMP2, TIMP3, TGF-ß1 and TGF-ß2 appear to play a local role in the development of advanced MMVD.

Melanophoromas and iridophoromas in reptiles.

Chromatophoromas are tumours of pigment-producing cells of the skin and are rarely reported in reptiles. These tumours are subclassified on the basis of the type of pigment. The present study characterizes chromatophoromas arising in 26 reptiles, including six snakes, 19 lizards and a tortoise. These include the first reports of melanophoromas in a yellow anaconda (Eunectes notaeus), pigmy rattlesnake (Sistrurus spp.), southern water snake (Nerodia fasciata), veiled chameleon (Chamaeleo calyptratus) and leopard gecko (Eublepharis macularius); the first reports of benign iridophoromas in a savannah monitor (Varanus exanthematicus), veiled chameleon and bearded dragon (Pogona vitticeps); and the first description of a malignant iridophoroma in a bearded dragon. Additionally, in three bearded dragons a 'mucinous' type of melanophoroma is described for the first time. Chromatophoromas generally arose from the skin of the body and head and ranged in size from 0.2 to 2.0cm in diameter. In six cases the animals were humanely destroyed immediately after diagnosis. Three further animals were humanely destroyed following recurrence of their tumour. Six of these nine reptiles had visceral metastases. Grossly, melanophoromas (n=20) were grey or black, while iridophoromas (n=6) were white in colour. Microscopically, most of the tumours were composed of spindle cells with varying pigmentation and 0-2 mitoses per 10 high power fields. Six of the 20 melanophoromas were classified as malignant due to the presence of intravascular tumour cells, visceral metastases, high pleomorphism and/or mitotic figures. Five of the six iridophoromas were classified as benign and the one malignant tumour was defined by the presence of intravascular tumour cells and visceral metastases. Immunohistochemically, melan A and S100 were coexpressed by all of the chromatophoromas.

Fungal contamination of paraffin wax blocks in a pathology archive.

While searching for paraffin wax blocks for research purposes in our archive we detected numerous larval and some dead adult moths. Some wax blocks were riddled with a white-brown crumbling substance. The entire archive was checked and profoundly-infested blocks were separated from unaffected blocks. Mycological and parasitological investigations were performed. Fungi were identified by culture and polymerase chain reaction, which revealed high sequence homology to six different fungal species. The moths were determined to be Nemapogon personellus. A total of 8,484 wax blocks had to be removed from the archive and destroyed. Pathologists should be alerted to the importance of checking the humidity of the air where archival material is stored.

An immunohistochemical study of feline myocardial fibrosis.

The aim of the present study was to investigate the pathology of feline myocardial fibrosis. The hearts from 40 cats with myocardial fibrosis were compared with the hearts from 25 normal cats. Clinical data were available in 11 cases. Hearts with myocardial fibrosis were hypomotile and there were hyperechoic areas in the ventricular wall on echocardiography. The presence of myocardial fibrosis was correlated significantly with hypertrophy of the ventricles, atrial dilation and angiosclerosis. Immunohistochemical studies demonstrated that normal feline cardiomyocytes expressed matrix metalloproteinase (MMP)-2, MMP-9, MMP-14, tissue inhibitor of matrix metalloproteinase (TIMP)-2 and transforming growth factor (TGF)-ß2. Fibroblasts in normal hearts expressed only TIMP-2. In the hearts with myocardial fibrosis, expression of MMP-2, TIMP-3 and TGF-ß2 by cardiomyocytes was significantly increased, but TIMP-2 expression was diminished. Fibroblasts in the affected hearts showed expression of MMP-14 in several cases. These findings suggest that a complex fibrotic remodelling of the feline myocardium occurs in this disease and that cardiomyocytes are involved in this process.

Cardiac remodeling and MMPs on the model of chronic daunorubicin-induced cardiomyopathy in rabbits.

The matrix metalloproteinases (MMPs) play a key role during cardiac remodeling. The aim of the study was to investigate the changes in collagenous proteins and MMPs in the model of non-ischemic, anthracycline-induced chronic cardiomyopathy in rabbits using both biochemical and histological approaches. The study was carried out in three groups of Chinchilla male rabbits: 1) daunorubicin (3 mg/kg, once weekly for 10 weeks), 2) control (saline in the same schedule), 3) daunorubicin with the cardioprotectant dexrazoxane (60 mg/kg, before each daunorubicin). Morphological changes in the myocardium of daunorubicin-treated animals were characterized by focal myocardial interstitial fibrosis of different intensity. The subsequent proliferation of the fibrotic tissue was marked by an increased content of both collagen types I and III, which resulted in their typical coexpression in the majority of bundles of fibers forming either smaller or larger scars. Biochemical analysis showed a significantly increased concentration of hydroxyproline, mainly in the pepsin-insoluble fraction of collagenous proteins, in the daunorubicin-treated group (1.42+/-0.12 mg/g) as compared with the control (1.03+/-0.04 mg/g) and dexrazoxane (1.07+/-0.07 mg/g) groups. Dexrazoxane co-administration remarkably reduced the cardiotoxic effects of daunorubicin to the extent comparable with the controls in all evaluated parameters. Using zymography, it was possible to detect only a gelatinolytic band corresponding to MMP-2 (MMP-9 activity was not detectable). However, no significant changes in MMP-2 activity were determined between individual groups. Immunohistochemical analysis revealed increased MMP-2 expression in both cardiomyocytes and fibroblasts. Thus, this study has revealed specific alterations in the collagen network in chronic anthracycline cardiotoxicity in relationship to the expression and activity of major MMPs.

Disseminated infection with Mycobacterium genavense in a grizzled giant squirrel (Ratufa macroura) associated with the isolation of an unknown Mycobacterium.

Disseminated infection with Mycobacterium genavense was diagnosed in an adult grizzled giant squirrel (Ratufa macroura). Microscopical examination showed granulomatous inflammation in the brain, kidneys, lungs and maxilla with intracellular acid-fast bacilli. M. genavense and a novel species of Mycobacterium (proposed name 'Mycobacterium lipsiensis') were identified.

Distribution of extracellular matrix components in normal and degenerated canine tricuspid valve leaflets.

The aim of the present study was to investigate the composition and distribution of various extracellular matrix (ECM) components in normal canine tricuspid valves (TVs) and in TVs affected by chronic valvular disease (CVD). The parietal (pTV) and septal (sTV) leaflets of the TVs from 27 dogs were investigated immunohistochemically for expression of collagen types I, III, IV and VI, elastin, laminin, fibronectin and heparan sulphate. Normal pTV consisted mainly of elastin and collagen VI in the atrialis, fibronectin in the thin spongiosa and mixed collagens in the fibrosa. The layered structure was less distinct in sTV, with numerous adipocytes and proteoglycans in the spongiosa and collagen III predominating in the fibrosa. The earliest stages of CVD affecting the pTV were recognized in the spongiosa and progression to advanced disease was characterized by nodular accumulation of proteoglycans within the free edge of the leaflet. These nodular lesions of the pTV contained more fibronectin, elastin and collagens I and VI than those affecting the sTV. These findings contrast with those reported in CVD affecting the mitral valve (MV) in which the early lesions affect the atrialis and advanced disease involves the entire leaflet. The pathogenesis of CVD in TV may involve initial alterations of the tricuspid annulus that lead to early lesions within the spongiosa, resulting in further shear stress and proteoglycan accumulation at the free edge of the pTV.

Expression of genes encoding matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in normal and diseased canine mitral valves.

The pathogenesis of canine chronic valvular disease (CVD) is not fully characterized. The present study investigates the expression of genes encoding matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in normal and diseased mitral valves (MVs). Samples from normal (n=15) or diseased (n=10) canine MVs were subject to real-time polymerase chain reaction (PCR) for quantification of mRNA encoding MMP-1, -2, -9 and -14 and TIMP-2, -3 and -4. In normal valves there was low expression of mRNA encoding MMP-2, -9 and -14 and TIMP-3. In the valves from dogs with CVD there was significantly increased transcription of mRNA encoding MMP-1 and -14 and TIMP-2, -3 and -4, but no elevation in mRNA encoding MMP-2 and -9. MMPs and TIMPs are therefore likely to be involved in extracellular matrix metabolism in normal canine MVs and there are significant alterations in the expression of genes encoding these molecules during CVD.

Immunohistochemical and histochemical identification of proteins and carbohydrates in the equine endometrium Expression patterns for mares suffering from endometrosis.

Although alterations in patterns of protein secretion revealed in uterine flushings from mares suffering from endometrosis have been described, little is known about alterations at the cellular level. Hence, the aim of this study was to characterize deviations in patterns of uterine gland secretion patterns using endometrial biopsies, histochemical and newly established immunohistochemical methods. Forty-eight endometrial biopsies were obtained from mares suffering from various types of endometrosis (active and inactive, destructive and non-destructive) and degree (mild to severe) were analyzed for expression of the proteins uteroglobin, uteroferrin, calbindinD9k and uterocalin as representatives of endometrial proteins detectable by immunohistochemistry using polyclonal antibodies. Glycogen was identified using the PAS-reaction and mucopolysaccharides were stained with alcian blue. Uterine glandular epithelia within fibrotic foci mostly revealed a protein and carbohydrate pattern of expression which was independent of hormonal changes during the estrous cycle. In comparison to non-affected glands, most epithelial cells within periglandular fibrosis exhibited decreased immunostaining intensity for proteins, especially when there was destructive endometrosis. However, uteroferrin staining intensity was strong within areas of severe destructive endometrosis. Moreover, only few basal glandular epithelial cells, especially those in cystic glands, stained for mucopolysaccharides that are typically seen within the luminal epithelia. Usually a single fibrotic focus caused only slight alterations in glandular proteins and carbohydrate reaction patterns, so that only more severe endometrosis lead to deviations which were detectable in uterine flushings. The highly sensitive methods used in the present study allow studies of uterine secretion patterns in the context of routine assessment of endometrial biopsies.

Detection and characterization of chondroid metaplasia in canine atrioventricular valves.

The atrioventricular valves of 25 dogs of different breeds and age were examined grossly and microscopically following histochemical staining and immunohistochemical labelling for collagen types I, III and VI, and for fibronectin and laminin. Foci of cartilage were identified in the tricuspid septal leaflet within the fibrosa (n=21) or spongiosa (n=3). These were further characterized as either fibrocartilage, predominantly composed of collagens I and VI, or hyaline cartilage consisting of laminin and collagens III and VI. Eighteen of the dogs were of large breed and seven of small breed. Retrospective echocardiographic findings were available from five cases and in three of these a hyperechogenic structure was identified corresponding to the cartilage focus (0.1, 1.12 and 5.63 mm(2) in size). The clinical significance and mechanism of formation of these cartilaginous foci remain undetermined, although factors such as breed, size and concurrent chronic valvular disease may be significant.

Expression of transforming growth factor-beta1, -beta2 and -beta3 in normal and diseased canine mitral valves.

The pathogenesis of chronic valvular disease (CVD) in dogs remains unclear, but activation and proliferation of valvular stromal cells (VSC) and their transdifferentiation into myofibroblast-like cells has been described. These alterations may be influenced by transforming growth factor-beta (TGF-beta), a cytokine involved in extracellular matrix (ECM) regulation and mesenchymal cell differentiation. The present study investigates immunohistochemically the expression of TGF-beta1, -beta2, -beta3 and smooth muscle alpha actin (alpha-SMA) in normal canine mitral valves (MVs) (n=10) and in the valves of dogs with mild (n=7), moderate (n=14) and severe (n=9) CVD. In normal mitral valves there was no expression of alpha-SMA but VSC displayed variable expression of TGF-beta1 (10% of VSC labelled), TGF-beta2 (1-5% labelled) and TGF-beta3 (50% labelled). In mild CVD the affected atrialis contain activated and proliferating alpha-SMA-positive VSC, which strongly expressed TGF-beta1 and -beta3, but only 10% of these cells expressed TGF-beta2. In unaffected areas of the leaflet there was selective increase in expression of TGF-beta1 and -beta3. In advanced CVD the activated subendothelial VSC strongly expressed alpha-SMA, TGF-beta1 and -beta3. Inactive VSC within the centre of the nodules had much less labelling for TGF-beta1 and -beta3. TGF-beta1 labelling was strong within the ECM. These data suggest that TGF-beta plays a role in the pathogenesis of CVD by inducing myofibroblast-like differentiation of VSC and ECM secretion. Changed haemodynamic forces and expression of matrix metalloproteinases (MMPs) may in turn regulate TGF-beta expression.

[Efficacy and safety of various energy sources and application techniques for the surgical treatment of atrial fibrillation]. / Experimentelle Evaluierung verschiedener Energiequellen und Applikationsverfahren zur chirurgischen Therapie des Vorhofflimmerns.

We investigated efficacy and safety of different energy sources and application techniques for the treatment of atrial fibrillation in an experimental acute sheep model. In particular, we focused on thermal damage to the adjacent structures and tissues. We also attempted to evaluate the efficacy of different application techniques such as endocardial or epicardial approaches. Overall 64 young Merino sheep were examined. It could be shown that endocardial ablation with different energy sources on cardiopulmonary bypass consistently caused histomorphologically and electrophysiologically transmural lesions. Depending on the energy source, different amounts of endocardial damage were induced. Cryoapplication produces the smallest endocardial laceration without thrombus formation. Dry radiofrequency energy and microwave produced very wide and diffuse endocardial damage with carbonisation and disruption of the endothelium. Epicardial ablation on a beating heart (off-pump) with bipolar radiofrequency was consistently effective. Due to the energy flow between the two jaws of the bipolar clamp, no collateral damage was observed. All other energy sources were unable to produce transmural lesions epicardially (off-pump) because the nearby blood flow rewarmed or recooled the myocardium and caused the so called "heat sink phenomenon". Depending on the energy source, different histomorphological changes in the esophagus could be observed. Changes in intraluminal-measured esophageal temperatures were not observed during ablation.