Cardiovascular and haemopoietic systems

image of Cardiovascular and haemopoietic systems
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Familiarity with the anatomy and physiology of the reptile cardiovascular system is the key to its diagnosis. This chapter covers specific relevant cardiovascular anatomy, chamber morphology and blood flow through the heart, cardiac conduction, veterinary significance of anatomy and physiology, and diagnosis and treatment of cardiac, vascular and haemopoietic diseases.

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19.1 Post-mortem image of the heart and major blood vessels of a common boa, viewed from the ventral aspect. The pericardium has been opened to reveal the right (RA) and left atria (LA) and single ventricle (V). The truncus arteriosus (TA) corkscrews from the right of the ventricle.
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19.2 The heart and main vessels of a non-crocodilian heart. (a) External view from the ventral aspect. (b) External view from the dorsal aspect. (c) Internal structure, with ventricular and atrial walls removed. CA = cavum cavernosum; CP = cavum pulmonale; CV = cavum venosum; LA = left atrium; LAA = left aortic arch; MR = muscular ridge; PA = main pulmonary artery; RA = right atrium; RAA = right aortic arch; SV = sinus venosus; V = ventricle; VS = vertical septum. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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19.3 Schematic diagrams showing how the differing internal anatomies of the ventricle of (a) squamates, testudines and tuataras, (b) varanid lizards and (c) pythons, variously shunt blood flow with their systemic and pulmonary circulations. av = atrioventricular canal; BL = bulbus lamella; CA = cavum arteriosum; CP = cavum pulmonale; CV = cavum venosum; LAo = left aorta; LAt = left atrium; MR = muscular ridge; PA = main pulmonary artery; RAo = right aorta; RAt = right atrium; VS = vertical septum. (Reproduced from with permission). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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19.4 Echocardiographic long-axis images of a small (approximately 500 g) rock python that attempt to show physiological cardiac hypertrophy: (a) after a 2-week fast; (b) 4 days postprandially. An ECG trace (not shown) was used to synchronize ventricular measurements within the cardiac cycle.
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19.5 (a) Plain lateral radiograph of a corn snake demonstrating cardiomegaly secondary to pulmonary hypertension. (b) Post-mortem photograph of the above demonstrating cardiomegaly. Note the asymmetrical atria; this is normal in several species of snake and should not be misinterpreted as chamber enlargement.
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19.6 Dorsal view of the corn snake whose radiograph and post-mortem are shown in Figure 19.5 . Note the coelomic distension.
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19.7 Heart rate using pulsatile blood flow can be obtained in this case using a Parks Medical 8-MHz Doppler ultrasound flow detector placed directly over the heart. The snake was only turned briefly to show the sensor position. In this healthy individual, handling alone markedly affected heart rate.
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19.8 Plain dorsoventral radiograph of an inland bearded dragon, demonstrating the position of the heart within the pectoral girdle (yellow line), that is obscured by the sternum (dotted line).
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19.9 Plain lateral radiograph of a Meller’s chameleon. Metastatic calcification of the blood vessels is apparent in the great vessels within the coelom.
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19.10 Electrocardiography lead position and placement on a Burmese python, demonstrating different attachment methods. The cranial lead uses a human skin-surface electrode; the caudal leads are placed with crocodile clips.
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19.11 ECG readings taken from (a) a corn snake (385 g) and (b) a rock python (536 g) demonstrating the familiar sinus venosus (SV)–P–QRS–T waveform deflections from the baseline. These can be used for cardiac rate and rhythm measurements, and during echocardiography aid interpretation of the cardiac cycle.
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19.12 Base–apex ECG from the corn snake in Figures 19.5 and 19.6 , demonstrating notched P and QRS complexes. Increased amplitudes are suggestive of generalized cardiomegaly. Tachycardia is also seen: heart rate is approximately 50 beats/min (calculated normal heart rate should be 33.4 x (kg) = 26 beats/min).
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19.13 (a) This Horsfield tortoise habituated to handling allows a lateral cervical window to be used to provide an oblique long-axis view of the heart and great vessels. (b) Two-dimensional echocardiographic oblique long-axis view and (c) line drawing that highlights the left aortic arch (LAA) ventral to the pulmonary artery (PA) as they exit the ventricle (V).  Note the homogeneity of the ventricle wall and blood within due to spongy myocardium.
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19.14 (a) Performing echocardiography on a leopard tortoise using a dorsal nuchal window.  (b) The right atrium (RA) sits dorsal to the pulmonary artery (PA) and left aortic arch (LAA).  (c) The line drawing again highlights the lack of contrast within the chambers between blood and spongy myocardium found in tortoises.
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19.15 (a) Two-dimensional echocardiographic long-axis view from the right side of a green iguana. (b) The line drawing clarifies the relationship of the great vessels as these exit the heart and corkscrew dextrally to the right of the image.  LAA = left aortic arch; PA= pulmonary artery;  RAA= right aortic arch; V= ventricle.
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19.16 (a) Two-dimensional short-axis echocardio-graphic view of the ventricle of a green iguana.  (b) The line drawing shows the horizontal septum (HS), a finger-like projection from the muscular ridge into the ventricle that subdivides the chamber internally.
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19.17 (a) Two-dimensional midline long-axis echocardio-graphic view of a Burmese python. (b) The line drawing demonstrates how the prominent horizontal septum (HS) on the muscular ridge effectively divides the ventricle into distinct subchambers, the cavum pulmonate (CP) and reduced cavum venous (CV).  The right atrium (RA) is separated far more clearly by the AV valves (unlabelled). LAA = left aortic arch; PA = pulmonary artery.
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19.18 Echocardiography of a rock python that was undergoing ecdysis (NB: dead skin may interfere with ultrasound wave transmission) using the ventral window, and in the long axis provides a rapid assessment of cardiac morphology and subjective impression of systolic and diastolic function.
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19.19 These diagrams show how the standard echocardiographic views are obtained. (a) The standard image planes with the probe positioned under the reptile can provide (b) the ventral short-axis view (probe in transverse plane) and (c) the long-axis view (probe in sagittal plane). Moving to the lateral aspect of the patient will allow (d) the intercostal view to be obtained (probe in horizontal plane). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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19.20 (a) Two-dimensional ventral short-axis echocardiographic (‘Mickey Mouse’) view, demonstrating the normal anatomy of a Burmese python.  (b) The line diagram shows the three dorsal heart chambers, the sinus venosus (SV) and the right atrium (RA) and left atrium (LA), with the easily identifiable ‘Mickey Mouse’ face of the pulmonary artery (PA) and left aortic arch (LAA) and right aortic arch (RAA).
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19.21 Long-axis horizontal view annotated echocardiographic image from a video of a yellow anaconda. Note the anaconda’s internal ventricular septation characterized by sheets instead of a single vertical septum. AV = atrioventricular; CA = cavum arteriosum; CP = cavum pulmonale; CV = cavum venosum; MR = muscular ridge; Rt Ao = right aortic arch. (Reproduced from with permission)
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19.22 (a) Two-dimensional, non-standard view and (b) line diagram of a Burmese python that shows the almost complete separation of the cavum pulmonale (CP) by the muscular ridge and its horizontal septum (HS) from the cavum venosum (CV) and cavum arteriosum (CA).
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19.27 Inland bearded dragon with an aneurysm: (a) prior to surgery, demonstrating a swelling caudodorsal to the angle of the jaw on the left side, and (b) during removal.
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