Part 44

The pulse at the radial artery should be about synchronous with the beat of the heart. If retarded it may be held to indicate the existence on the anterior aorta or its primary divisions of an aneurism with elastic walls or more probably an imperfection of the aortic valves, which allows a regurgitation of the blood into the heart.

=Venous pulse.= A venous pulse seen in the lower end of the jugular veins is common in the domestic animals. In the ox it is quite compatible with health and is only to be judged by its amplitude and force. In other animals it often coexists with congestion of the lungs which impedes the circulation through the right side of the heart and leads to engorgement of the venous system. In the absence of this condition it frequently indicates an imperfection of the auriculo-ventricular valves in the right heart and a reflux of blood from the contracting ventricle which checks the descending current in the veins.

=Percussion.= In the =horse= a dull, dead sound is emitted when percussion is made over the left side for about four inches above the breast bone and in the space corresponding to the lower ends and the cartilages of prolongation of the fourth, fifth and sixth ribs. In the ox this dulness is less marked on the level of the sixth rib. The same results can be obtained on the right side by imparting heavier blows to the chest walls so as to derive the sound from the deeper parts.

The area of dulness is increased in cases of hypertrophy or in dilatation of the heart when the enlarged organ presses aside the lung tissue and exposes a greater amount of its substance to the chest walls. The same result takes place in hydropericardium.

The area of dullness is diminished in cases of ruptured air cells (as in “heaves”) when the inflated and expanded lung tissue envelopes the heart more completely and gives out its own clear resonance where the dull sound of the heart is usually obtained.

=Application of the hand.= =Palpation.= In conditions of health and in quietude the hand applied on the side of the chest, close behind the left elbow only just perceives the beat of the heart with each contraction. If the animal is excited whether from fear, joy or physical suffering the heart’s impulse becomes more powerful and by this alone the state of its function may be very satisfactorily ascertained. The impulse is strong in all active fevers and extensive inflammations of important organs, but it is especially marked in diseases of the heart and lungs. Irregularity in the force of successive beats is seen in various heart diseases and debilitated conditions are recognized in the same way.

Any want of harmony between the heart’s action and the pulse may be observed by laying the right hand over the region of the heart and applying the fingers of the left on the radial artery. In debility and especially if from a deficiency of blood the violent or tumultuous action of the heart contrasts strangely with the weak jerking and compressible pulse. The same symptoms are noticed when the valves of the heart close their orifices imperfectly. In convalescence from lung diseases and in certain diseases of the heart a beat may be felt by the right hand for which no corresponding pulsation is felt in the radial artery by the left.

When the heart is hypertrophied the impulse is stronger and is associated with a full, strong, and rolling pulse. When it is atrophied the impulse on the chest and pulse beat are equally weak. When water exists in the pericardium the heart strikes the ribs with less force.

=Sounds of the Heart.= Synchronous with each beat of the heart two distinct sounds are heard, separated by a short interval, inappreciable to most ears, and followed by a period of silence. These sounds are distinct alike in character and duration. The first sound is dull and prolonged; the second is short and quick. Some idea of these sounds may be formed by the pronunciation of the two syllables, lub—tip, but an acquaintance with the sounds themselves is essential to a correct conception of them. The period of time occupied by the first sound is double that taken up by the second and in man and the smaller quadrupeds the subsequent period of silence is of equal duration with the second sound. Dividing the time belonging to one revolution of the heart into four equal periods the first two are taken up by the first sound, the third by the second sound and the fourth by the interval of silence. In the horse the silence is more prolonged, and occupies the entire latter half of the period of a revolution. The relations stand thus:—the first sound extends over two-sixths of the time, the second sound over one-sixth, and the silence over three-sixths.

The first sound, synchronous with the beat of the heart against the ribs corresponds also in point of time with the contraction of the ventricles, the closure and tension of the auriculo-ventricular valves and the rush of the blood into the great arteries. The second sound corresponds to the reflux of blood in the arteries and the closure of the valves between them and the heart. The period of silence represents the period of rest during which the heart is being filled from the veins.

In the horse, at rest, the first is the only sound that can be distinctly heard in many cases, but during the excitement of exercise, or in febrile conditions the second is sufficiently apparent and any deviation from the natural character is easily noted.

These sounds are most distinct over the lower end of the fifth and sixth ribs on the left side, but they may be heard distinctly behind the middle of the shoulder on either side when the corresponding limb is advanced. In birds they may be heard beneath the wings but above all and most clearly over the breastbone.

In =disease= these =sounds= may be heard in unusual situations, they may be altered in force duration or rythm, or they may be associated with other sounds or superseded by them.

The sounds may be heard in new situations, in displacements of the heart from tumors or effusions in the chest, structural changes in the lungs, pleuræ, or pericardium, aneurism of the aorta, etc., etc.

The heart sounds are clearly heard over any part of the chest when the lung tissue intervening between that part of the surface and the heart is solid (hepatized). They are heard distinctly behind the median part of the right shoulder, when liquid effusion into the left pleural sac has displaced the heart to the right; and when the right cavities of the heart are extensively dilated as exists so commonly in the advanced stages of “heaves.”

The =extent= over which the sounds may be heard is increased when the lung surrounding the heart is solidified (hepatisation, splenisation, etc.), or when liquid effusion exists in the chest. A liquid but more especially a solid is a better conductor of sound than the spongy lung. Enlargement (hypertrophy) of the heart equally increases the area of sound. The area of sound is lessened by atrophy of the heart, and by an emphysematous condition of the lungs by which the heart is more extensively covered and further separated from the walls of the chest.

The =force= or =intensity= of the heart sounds is increased in high fever, in acute inflammation, in increase of the muscular walls of the heart with enlargement of the internal cavities, in functional disturbance from fear or other exciting cause, and in palpitation. Often in a weak and bloodless patient the heart sounds can be clearly heard at several yards distance from the animal. The intensity of the sounds is diminished in debility when not associated with palpitation, in atrophy of the muscular substance of the heart, in hypertrophy of the muscular tissue of the heart with diminution of its internal cavities, in broken wind when the emphysematous lung more completely envelopes the heart, and in cases of extensive liquid effusion into the pericardium which prevents the apex of the heart from striking against the side of the chest.

The regular =rythm=, normally manifested by the two sounds and the silence, may be modified in the unequal irregular or intermittent contractions of the heart. Küssmaul’s paradoxical pulse is one in which the pulse is more frequent but less full during inspiration than expiration. Seen in weak heart, during recovery from chest diseases, in chronic pericarditis, and when fibrous bands encircle the root of the aorta. Bigeminal and trigeminal when two or three beats follow each other rapidly, and are separated from the preceding and succeeding beats by longer intervals. This occurs in disease of the mitral valve, and in other weak states of the heart. Fœtal heart rythm in which the pause is shortened and the two sounds of the heart are almost identical, is seen in the later stages of fevers, and in extreme dilation. A curious aberration of rythm is the repetition of either the first or second sound. If of the first sound (anapestic bruit) each beat will be accompanied by three sounds the first two of which resemble the first sound of health. If the second sound is repeated (dactylic bruit, bruit de galop) the first sound only will be prolonged and the last two sharp and quick. The repetition of the last sound is probably due to impaired nervous supply which allows the completion of the contraction of the ventricle and the closure of the arterial (semilunar) valves sooner on one side than the other. If due to diminution of the arterial orifice which retarded the emptying of one of the ventricles, the first sound would probably be accompanied by a blowing murmur. If the auriculo-ventricular valves on one side were imperfect, allowing a reflux into the auricle and a more rapid emptying of the ventricle a blowing murmur would equally accompany the first sound. In either of these two last mentioned cases the murmur would mask or hide the first of two doubled sounds.

The repetition of the 1st sound is often due to dilatation of one ventricle, which in consequence is longer in reaching the same sensation of plenitude, and in receiving the stimulus to contraction.

=Morbid Sounds.= =Murmurs.= The distinct and superadded sounds heard in disease are usually designated murmurs. They originate in the interior of the heart (endocardial) or externally to the heart (pericardial). The =endocardial= sounds mostly arise from some abnormal conditions of the valves or orifices and consist in a blowing or rushing noise which usually accompanies or displaces one of the heart sounds, though it may precede or succeed these. The following table modified from that of Bartle and Roger presents at a glance the relations of these different sounds and their significance.

Blowing or Hissing Murmurs.

Blowing murmur before │Narrowing of the auriculo-ventricular orifice. the first sound. │ Vegetations or coagula on the valves.

│Strongest toward the │ Blowing murmur with the│ base of the heart. │Narrowing of the aortic first sound. │ Propagated along the │ opening. │ great arteries. │ │Strongest toward the │Narrowing of the │ apex of the heart. │ pulmonary artery or │ Not propagated in the│ insufficiency of the │ great arteries. │ auriculo-ventricular │ │ valves.

│Double rushing sound │Insufficiency of the Blowing murmur with the│ heard over the great │ arterial (semilunar) second sound. │ arteries at each beat│ valves. │ of the heart. │

│Double rushing sound in│ Blowing murmur after │ the arteries with │Aneurism (dilatation of the second sound. │ each beat of the │ the great aorta.) │ heart. │

From the table it will be seen that each orifice in the heart may become the seat of two perfectly distinct and independent murmurs; one due to constriction of the orifice in which case the sound is produced with the onward progress of the blood wave; and one due to dilatation of the orifice or insufficient closure of it by the valves, when the sound is due to a recoil or regurgitation of the blood. There is a further sound due to mere roughness of the valves in cases of disease when the sound will be with the normal current of blood, though a second or regurgitant hiss is often heard from the valves being at the same time insufficient to close the orifice. Another blowing murmur is usually heard over the heart and coincident with its first sound in the bloodless state (anæmia). This is not necessarily connected with any diseased condition of the heart itself.

The nature of these murmurs differs in special instances. They may resemble the soft whisper of the words who or awe, of the double letter ss, or the single letter r, according as they are soft or hard and purring.

The =pericardial murmur=, caused by the rubbing of the dry roughened surface of the serous membrane covering the heart on the correspondingly dry rough surface of the same membrane, reflected on the investing sac, resembles that caused by passing the palm of the one hand over the other which lies on the ear. It is distinguished from the friction sound of pleurisy by its coinciding with the movements of the heart and not with those of respiration. It is usually heard alike during the sounds of the heart and during the period of silence or in other words during the movements of contraction and dilatation in that organ.