CLINICAL ASSESSMENT OF CARDIOVASCULAR SYSTEM
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The circulatory system consists of two main functional units, the heart and the blood vessels. The function of the cardiovascular system is to maintain the normal exchange of oxygen, carbon dioxide, electrolytes, nutrients, fluids and excretory products between blood and tissues.
Area of examination of the heart in equines and ruminants
Area
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Equines
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Ruminants
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Base
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From 2nd to 6th intercostal space
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From 3rd to 6th rib
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Apex
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Half an inch from the last sternal segment
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One inch from the diaphragm
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Posterior border
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Opposite to the 6th rib
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Opposite to the 5th rib
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Left surface
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Composed of left ventricle and extends from 3rd to 6th rib
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Extends from 3rd to 4th rib
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Right surface
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Extends from 3rd to 4th rib
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Not examined
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Position of valves
Abnormal heart sounds
Other abnormal heart sounds
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These may replace one or both heart sounds or accompany them. They may originate from the cavities of the heart or from the pericardium. Those that arise from the inside of the heart are classified as murmurs and are caused by endocardial lesions such as valvular vegetation or adhesions, valvular insufficiency and by abnormal orifices such as ventricular septal defect.
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Cardiac murmurs caused by these conditions maybe hissing, humming, whirring or vibrant in tone. Such sounds are produced by stenosis of the valvular orifice or insufficiency of the valves.
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Theoretically there are eight possible separate valvular defects but several of the possibilities are extremely rare in animals. The murmur arising from stenosis is produced when the valve is open and that of insufficiency when the valve is closed. Valvular endocardial murmurs are caused by chronic valvular endocarditis, cardiac dilatation, acute endocarditis and neoplasia.
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Endocardial murmurs occur during either systole or diastole. Systolic murmurs indicated either stenosis of the semi-lunar orifices or insufficiency of the atrioventricular valves. Diastolic murmurs suggest the opposite; either stenosis of the atrioventricular orifice or insufficiency of the semi-lunar valves. These endocardial murmurs are heard at the site of the valve.
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The continuous machinery murmur of the patent ductus arteriosus maybe heard during both systole and diastole over a wide area of the thorax but most intensely in the 3rd left intercostals space in the region of the pulmonary valve.
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Murmurs that originate at the valves or other cardiac structures are classified as organic murmurs, whereas those that occur in the absence of primary heart disease are known as functional murmurs (non-organic).
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Functional murmurs are best heard in anaemia where the reduction of haemoglobin and red blood cells, the oxygen-carrying capacity of the blood is greatly reduced, with the result that the circulation time is shortened in an attempt to prevent tissue anoxia, this leads to increased heart rate.
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Functional murmurs are usually systolic, rather faint and organic murmurs in contrast are loud and maybe either systolic or diastolic, audible at a precise phase of the cardiac cycle.
Pericardial sounds
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Frictional sound is heard at the beginning of pericarditis where its surface becomes rough and dry. The exudation into the pericardial sac results in presence of fluid that sets in motion by the movement of the heart; the heart sounds then becomes muffled.
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Appearance of gas on the surface of fluid in the pericardial sac results in presence of tinkling or splashing sounds. These sounds are observed in traumatic pericarditis in cattle.
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