EXAMINATION OF CARDIAC (HEART) AREA IN ANIMALS (CATTLE, HORSE, DOG)

 EXAMINATION OF CARDIAC (HEART) AREA IN ANIMALS (CATTLE, HORSE, DOG)



CATTLE- On the left side heart is in contact with thoracic wall from 3rd  rib to 4th intercostal space and on the right side, area of contact is limited to 3rd and 4th  intercostal space.

The left atrioventricular orifice is mainly at the level of 4th intercostal space, arotic orifice with 4th rib, pulmonary orifice at the 3rd intercostal space, the right atrioventricular orifice at 4th rib.

 

HORSE- The left surface of the heart is in contact with ventral 3rd of the thoracic wall from 3rd  to 6th  rib and in the right side from 3rd  to 4th intercostal space.

The left A.V. orifice is situated at 5th   intercostal space, arotic orifice at 4th  intercostal space on a line horizontal with a point of shoulder. Pulmonary orifice of the right ventricle is at level with 3rd  intercostal space and right A.V. orifice guarded by the tricuspid valve is situated opposite to the 4th  intercostal space.

 

DOG- The area of contact between heart and left thoracic wall extend from the level of ventral parts of the 3rd  to 6th  rib.

The left A. V. valve is located at 5th  intercostal space, arotic valve at left 4th  intercostal space, the pulmonic valve at 3rd intercostal space and right A.V. valve at right 3rd  to 5th  intercostal space.

 

PALPATION- The animal should be in a standing position and bearing weight on all four limbs. The palpation is to be carried out with the palm of the hand and should be performed on both ribs. The objective of palpation is to determine the location and characters of the apex beat (Cardiac impulse) and to determine whether adventitious vibration associated with the cardiac cycle, is present.

The apex beat is a low-frequency vibration produced during contraction and rotation of the heart in early systole. It is synchronous with 1st heart sound. It is best felt on the left side at 4th or 5th  intercostal space in the horse, 5th  intercostal space in cow and sheep, goat at 5th  intercostal space. Acaudal shifting of cardiac impulse is suggestive of cardiac enlargement, displacement of the heart.

 

Precardial thrill - This is a sensation of vibration felt on palpation of a thoracic wall over the area of heart associated with the kinetic energy generated by the turbulent flow of intracardiac or intravascular origin.

 

PERCUSSION- It is of little value in large animals because most of the heart underlies the muscle of the forelimb and, the thoracic wall underlying the heart can not be resonated. However, the heart is percussed using the same technique as for the lung. The area of cardiac dullness in normal cattle is about 6-8 cm in diameter between 3rd  and 4th  intercostal space at the level of point of elbow. An increase in the area of cardiac dullness occurs in:

-        Enlargement of heart

-        Pericardial effusion

-        Lateral displacement of the heart.

-        Neoplasm of heart

Decrease in the size of cardiac dullness occurs in emphysema. A pain reaction during percussion of the cardiac area suggests presence of pericarditis or pleurisy.

 

Auscultation- Auscultation of the heart is performed to determine the heart rate, the character of normal heart sounds, and the presence of abnormal heart sound viz. Cardiac murmurs, pericardial frictional rub, etc.

Manual extension of forelimbs can facilitate auscultation of the heart.

The heart must be examined in a systematic manner for best results on the left side of the animal.

 

Normal heart sounds- The first and second heart sounds are clearly audible in a normal animals unless they are exceptionally fat. A 3rd and 4th  heart sound may be heard in large animals, particularly horses. The 1st and 2nd  heart sounds are the only sound normal audible in the dog and cat.

The 1st  heart sound (S1) is associated with the closer of A.V. valve and sounds like "lubb”.

The second heart sound (S2) is associated with closer of arotic and pulmonary valves and sounds like “dupp".

Third heart sound (S3) is associated with rapid filling of the ventricle in early diastole and is audible on the left side just caudal to area of maximum audibility of the 1st  heart sound.

The fourth heart sound (S4) is a gentle sound that happens just before the first heart sound and is most audible on the left and right sides of the heart.

 

Heart rate- It is determined by counting the number of beats per one minute (S1 and S2 or in some animals four heart sound constitute 1 heartbeat).

An increase in the absolute intensity of heart sound occurs with cardiac hypertrophy, hypomagnesemia, etc.

Muffling of heart sound suggests an increase in tissue and fluid interfaces between the heart and stethoscope.

Normal cardiac rhythm can be described as lubb- dupp-pause, the first sound being long, loud and the second being sharper and shorter.

In many small animals the heart rate is so rapid that the events of early systolic feeling and atrial contraction fuse which is known as summation gallop. Variation in the cardiac rate and rhythm causes tachycardia, bradycardia, and arrhythmia.

 

Abnormal heart sounds- In animals abnormal heart sounds include cardiac murmurs, pericardial frictional rub, and other adventitious heart sounds(systolic click).

 

Cardiac murmurs- Are audible vibrations caused by turbulent blood flow produced from a sudden change in the diameter of the vessel through which the blood is flowing resulting in the generation of murmur.

Cardiac sounds- A murmur is a prolonged series of auditory vibrations emanating from the heart or blood vessels during a normally a silent period of the cardiac cycle. Turbulence in flowing blood is generally considered as the major source of murmurs or prolonged vibrations. 

Causes of turbulence-

1. alteration of the morphology of any one of the four heart valves (stenosis or insufficiency)

2. abnormal communication between two sides of the heart and/or great vessels (inter-atrial septal

defect, inter-ventricular septal defect, or patent ductus arteriosus), 

3.increased blood flow velocity through a normal valve orifice or vessel.

Murmurs can be classified on the basis of location, timing, quality, radiation, and intensity. Murmurs occur during systole, diastole, or both. The intensity of the murmur is commonly graded from 1-6.

The cardiac murmur can be heard in stenosis or valve incompetence, congenital cardiac abnormalities.

 

Innocent murmurs - Murmurs not associated with a cardiac defect is called innocent murmurs. Those caused by turbulence during periods of high-velocity flow is called functional or flow murmurs, those associated with turbulence due to decreased viscosity and increased flow is called physiological innocent murmurs, occur in all large animal and particular in the horse.

Hemic murmurs - occur in animals that are anemic and hypoproteinemia. They are detected at the area of the tricuspid valve. The intensity fluctuates with respiration, increasing with inspiration and decreasing with expiration.

Murmurs in newborn animal - A continuous or a systolic murmur is frequently audible over the base of the heart in newborn animals owing to partial temporary patency of the closing ductus arteriosus.


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By- Dr. Jitendra kumar sahu (B.V.Sc & A.H.)


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