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| | ===[[Ventricular Septal Defect]]=== | | ===[[Ventricular Septal Defect]]=== |
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| − | ===Patent Ductus Arteriosus=== | + | ===[[Patent Ductus Arteriosus]]=== |
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| − | Ductus Arteriosus shunts blood from the Pulmonary Artery to the Aorta in the foetus to bypass the lungs. Usually closes shortly after birth due to smooth muscle contraction in repsonse to increased arterial oxygen tension. When patent after birth, blood flows along the pressure gradient, left to right, leading to pulmonary hypertension. If the hypertension is significant, as with larger defects, right sided pressure may increase enough to allow reversal of flow through the PDA and will result in cyanosis. Reverse shunting is rare.
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| − | ''Incidence:''
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| − | [[Image:patent_ductus_goat.jpg|right|thumb|200px|<small><center>'''Patent ductus arteriosus'''. Courtesy of A. Jefferies</center></small>]]
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| − | *Uncommon in cats.
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| − | *More common in dogs with distinct '''female predisposition'''.
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| − | *Predisposed breeds include; CKCS, Border Collie, GSD, Poodles.
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| − | *Research into PDAs in dogs has revealed a genetic component influencing the maturation of collagen.
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| − | *May be a normal finding in lambs and piglets up to 2 weeks of age.
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| − | ''Clinical Signs:''
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| − | *Continuous '''machinery murmur''' at left heart base.
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| − | *'''Water-Hammer pulse''' (rapid diastolic decline).
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| − | *Variable other signs depending on size of defect E.g. syncope, cyanosis, exercise intolerance etc.
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| − | *May progress to left sided heart failure and so pulmonary oedema.
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| − | ''Diagnosis:''
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| − | *Left atrial and left ventricular enlargement radiologically and on ECG due to volume overload.
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| − | *Pulmonary overcirculation (enlargement of pulmonary arteries and veins) on radiology.
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| − | *DV radiographs show a '''three knuckled appearance'''; enlargement of:
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| − | **Aortic arch.
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| − | **Pulmonary artery.
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| − | **Left auricular appendage.
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| − | *PDA difficult to image on echocardiography but Doppler imaging may be useful.
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| − | ''Treatment:''
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| − | *'''Surgical ligation''' for left to right shunts. Needs stabilisation first.
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| − | *Right to left shunts are not operable.
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| − | *Untreated dogs face 60-70% mortality during their first year of life.
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| | ==Great Vessels== | | ==Great Vessels== |