Clinical assessment of cardiovascular system

CLINICAL ASSESSMENT OF CARDIOVASCULAR SYSTEM

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
Equines
Ruminants
Base
From 2nd to 6th intercostal space
From 3rd to 6th rib
Apex
Half an inch from the last sternal segment
One inch from the diaphragm
Posterior border
Opposite to the 6th rib
Opposite to the 5th rib
Left surface
Composed of left ventricle and extends from 3rd to 6th rib
Extends from 3rd to 4th rib
Right surface
Extends from 3rd to 4th rib
Not examined

Position of valves

  • Mitral valves
    • Examined on the left side in the 5th intercostals space, 4 inches above the sternal extremity of 5th rib.
  • Tricuspid valves
    • Present on the right side in the 3rd intercostals space and 3 inches above the sternal extremity of the 4th rib.
  • Aortic semi-lunar valve
    • Present on the left side in the 4th intercostals space level with the shoulder point.
  • Pulmonary semi-lunar valve
    • Present on the left side in the 3rd intercostals space at the level of olecranon process of the ulna.
    • Examination of the circulatory system includes examining the heart, pulse and blood vessels.
    • Chest movement is noticeable in small and young animals (normal animals). Visible evidence of cardiac activity is noted in over-exertion, haemolytic anaemia and some cardiac diseases.
    • The strength of cardiac impulse can be determined by placing the palm of the hand over the cardiac area on the left side.
    • The point of maximum impact is increased in area and displaced posteriorly in cardiac hypertrophy or dilatation associated with insufficiency or anaemia; anteriorly in ascitis, hepatomegally, distention of stomach or intestine with food or gases. It cannot be palpated when the heart has been displaced away from the thoracic wall as in serous pericarditis, pleurisy, hydropericaritis, hydrothorax and mediastinal or pulmonary neoplasia or hydatosis.
    • The character of heart sounds and presence of abnormal sounds is detected by auscultation. Two main sounds must be differentiated:
    • The first heart sound is dull, loud and prolonged. Followed immediately by the second heart sound, which is shorter and sharper. The second heart sound is followed by a pause. The first heart sound is the result of contraction of the cardiac muscle together with closure of the atrio-ventricular valves. It corresponds to the phase of cardiac systole and is referred to as systolic sound. The second heart sound is produced by closure of the semi-lunar valves. It occurs during the cardiac diastole and is therefore termed the diastolic sound.
    • When the heart rate is slow, the first and the second sounds are readily recognized by their characteristic and by the fact that the first sound occurs after a pause whereas the second sound occurs directly after the first. If the heart rate is increased, the sounds cannot be easily distinguished from each other. In these cases, palpating the wall and detecting which sound coincides with the apex beat with help distinguish systolic sound.

Abnormal heart sounds

  • Abnormal heart rate
    • Increased rate with loud sounds occur in cardiac hypertrophy, anaemia, febrile conditions, exertion.
    • Decreased rate with weak sounds occur in cardiac insufficiency, congestive heart failure, all conditions in which the heart is displaced away from the thoracic wall or fluid is present in the pleural or pericardial sac (hydro pericardium, hydrothorax and pleurisy).
  • Abnormalities in intensity of heart sounds
    • The intensity of the first heart sound is related to the force of the ventricular contraction, so that it is increased in ventricular hypertrophy and decreased in myocardial weakness.
    • The intensity of the second heart sound is dependent upon the arterial and pulmonary blood pressures. Accentuation of the second heart sound is usually the result of an increase in the backpressure of the blood against the closed valves. This occurs when the blood is expelled from the ventricles with greater force than usual producing a variable degree of hypertension. This hypertension is observed in bronchitis, pneumonia and pulmonary emphysema, which result in increased resistance in the pulmonary circulation. Less often, the accentuated second heart sound involves the aortic valve at which instance it is attributable to increased resistance in the systemic circulation as in renal disease.
  • Reduplication of the heart sounds
    • Reduplication of the first sound occurs in elevated blood pressure and in asynchronous contraction of the ventricles. This is observed in disturbance in the conductivity of one branch of the bundle of hiss or severe damage of the myocardium (myocarditis).
    • Reduplication of the second heart sound occurs when the semi-lunar valves fail to close simultaneously, seen in pulmonary hypertension where the pulmonary semi-lunar valves are rarely closed. Reduplication also occurs in asynchronous ventricular contraction.

Other abnormal heart sounds

  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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).
  • 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.
  • 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

  • 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.
  • 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.
Last modified: Tuesday, 5 June 2012, 12:34 PM