Which Of The Following Heart Valves Has The Pmi On The Right Side Of The Animal's Chest

Auscultation is a inexpensive and easy diagnostic tool available in every veterinary practice. Withal if we ask ourselves if it is used to its full potential, the answer is probably no. While it seems like an easy enough task to perform, information technology is frequently over complicated. Two things hinder auscultation technique. First, optimal listening weather are rarely achieved; and 2d, cardiologists hold that recognising abnormal center sounds, and gaining proficiency in the technique is hard (Pedersen et al, 1999; Naylor et al, 2001; Ware, 2007).

Primarily, auscultation of the eye is used to record heart charge per unit and rhythm, and to determine middle sounds. As with most things in life, practise is fundamental, and then that abnormal sounds can be readily distinguished from normal heart sounds. If abnormal sounds are heard, it is recommended to make up one's mind the timing of the additional sounds, the point of maximal intensity (PMI) — or where the sound is heard the loudest — and finally, the intensity or loudness of the sounds in relation to a grading system.

Equipment

There are a few different types of stethoscopes available on the market place (Effigy 1). The better quality stethoscopes are adequate for veterinary use. Paediatric stethoscopes are not recommended for most auscultation because a larger bong is needed to maximise amplification of heart sounds. The main components are ear pieces, tubing, bell, and diaphragm (Figure 2).

Figure 1. Examples of stethoscopes available for utilize in veterinary do.

Effigy two. Labelled diagram of a stethoscope.

The binaurals should face up frontward (Effigy 3) and be placed snugly into the ears. Information technology may be necessary to motion the tubing to better fit the ear canal and minimise sound leakage. Audio leakage and/or environmental sounds are a common problem when attempting to detect lower heart sounds or identify eye murmurs. The diaphragm is used to hear high-pitched sounds in the lungs and heart. It is best for heart sounds i and two (S1 and S2). The bell is used for lower-pitched center sounds and actress heart sounds (S3 and S4). Some stethoscopes exercise not take a separate bell and diaphragm, and so fingertip pressure should exist used to distinguish high and depression pitched sounds.

Figure 3. This image shows how to identify the ear pieces into the ears correctly.

Environment

Consider where the auscultation is to be performed. Ideally, a tranquility room and gentle handling is recommended, then as not to excite or distress the patient. Panting dogs can be a trouble; gentle closing of the mouth can allow a few seconds of undisturbed auscultation. Sometimes cats may purr, which tin can make auscultation impossible. Holding a finger beyond the nose may stop purring for a moment, or turning on a tap near to the true cat may provide some lark. If the owner happens to be present during auscultation, information technology may demand to exist explained that silence is required for optimal auscultation. Owners quite often similar to talk during quiet periods.

Technique

Commencement, it is important to know what is expected to exist heard. There are two normal centre sounds in the canis familiaris and cat:

• The 'lub' (S1), when the atrioventricular valves close

• And the 'dub' (S2), when the semilunar valves close.

S1 is a louder, longer, and duller sound than S2. It is best heard in thin and young animals, or those with high sympathetic tone, and those with tachycardia, mitral regurgitation, systemic hypertension, or anaemia. S2 is a shorter college pitched sound, which is loudest over the pulmonic and aortic areas. Whatsoever other sounds are described as additional heart sounds. These extra sounds are described by location (the PMI), timing in the cardiac wheel, and intensity of the audio (loudness). Table 1 outlines the PMI in dogs and cats.

Tabular array 1. PMI locations in the domestic dog and cat

Structure	Location
Mitral valve (left noon)	Canis familiaris — left side, 5th intercostal space at costochondral junction. Cat — left side, 5th–6th intercostal space, near sternum
Aortic valve (left base)	Dog — left side, 4th intercostal space, just above costochondral junction
Pulmonic valve (left base)	Dog — left side, 2nd–4th intercostal space, just in a higher place sternum. Cat — left side, 2nd–tertiary intercostal space, one third of the manner up from sternum
Tricuspid valve (right noon)	Dog — correct side, 3rd–5th intercostal space virtually costochondral junction True cat — right side, quaternary–5th intercostal space most sternum

Timing of additional heart sounds is important. Sounds heard betwixt S1 and S2 occur during systole. This is the most common type of heart murmur recorded in small animals. Sounds heard between S2 and S1 are diastolic. Diastolic murmurs are rare in small-scale-animal medicine. Murmurs throughout systole and diastole are chosen continuous murmurs. The almost common crusade of a continuous murmur is a patent ductus arteriosus. Distinguishing when additional eye sounds occur, will help the veterinary surgeon to focus their differential diagnosis. An approach, such as the one described below, should be followed to reliably perform auscultation:

• A systematic arroyo should be used from the showtime. The patient should exist in a standing position in a repose room (Effigy 4)

• Both sides of the entire thorax should be auscultated

• The centre should exist auscultated separately from the lungs

• Commencement, the heart charge per unit and rhythm should be noted. It should also exist noted whether respiratory pattern changes the rate or rhythm

• It is critical to recognise normal heart sounds, S1 and S2 in the patient, or the 'lub' and 'dub'. Time should be taken to be sure

• If extra heart sounds are identified, the next steps are to localise and identify the PMI, timing, and intensity. Effigy 5 shows PMI location

• All valve areas, should be auscultated in order if possible. Fourth dimension should be taken to listen to the pulmonic, aortic, mitral, and tricuspid areas. Starting with the pulmonic expanse of the left side of the thorax, the stethoscope should be moved from base to noon (Effigy half-dozen). It may exist necessary to motility the left leg forwards so that the third intercostal space, the site of the pulmonic valve, can be better heard

• To maximise the area of the aortic valve, the stethoscope should then be moved slightly upwards and dorsum 1 intercostal space. It may not be possible to distinguish the aortic and pulmonic areas in small dogs and cats

• The sternum in cats should besides be auscultated

• Nevertheless on the left side of the thorax, the stethoscope should then be moved a petty lower to the level of the costochondral junctions at the fifth to seventh intercostal spaces. This is the PMI of the mitral valve

• Next, the stethoscope should be placed on the correct side of the thorax betwixt the tertiary to 5th intercostal spaces, over again at the level of the costochondral junctions (Figure 6). This is the PMI for the tricuspid valve

• Timing of the boosted heart sounds needs to be noted. To assistance place when systole occurs, a pulse should be palpated at the same time every bit auscultation. An arterial pulse should exist felt during systole, betwixt S1 and S2

• Finally, the intensity, or loudness should exist noted. Table 2 shows the grading organisation used in small animals

• Mutual artefacts that tin can hamper auscultation include shaking, movement, panting, purring, and increased respiratory noise. The patient should exist calmed as much as possible to create optimal listening weather.

Effigy four. Expert auscultation technique

Figure v. PMIs on the left (A) and right (B) side of the thorax. AV, aortic valve; PV, pulmonic valve; MV, mitral valve; Television receiver tricuspid valve

Figure six. Move the stethoscope from base to apex starting with the left side of the thorax.

Table 2. Center murmur grading

Intensity	Grade	Loudness
Depression intensity	I	Low intensity murmur heard in a quiet surround simply after conscientious auscultation over a localised cardiac expanse
	2	Depression intensity murmur heard immediately when the stethoscope is placed over the PMI
Moderate intensity	Three	Murmur of moderate intensity
	4	High intensity murmur that tin can be auscultated over several areas without whatever palpable precordial thrill
Loftier intensity	V	High intensity murmur with a palpable precordial thrill
	VI	High intensity murmur with a palpable precordial thrill that may even be heard when the stethoscope is slightly lifted off the chest wall

Grading

The loudness of a centre murmur is graded between I and VI (Tabular array 2). Grading can exist useful to assess illness progression and/or severity of certain cardiac weather, such every bit aortic or pulmonic stenosis or mitral regurgitation. However, information technology is less useful to assess myocardial disease severity. Furthermore, ventricular septal defects will give a louder sound when the hole is smaller considering of the higher pressure level across the hole. Therefore, grade does not always point disease severity.

It is also of import to call up that veterinary professionals will not e'er agree on the presence or loudness of a murmur. Pedersen et al (1999) conducted a written report evaluating unlike people and their auscultation. The study used dogs diagnosed with mitral valve disease, and they constitute that interobserver understanding on presence and absence of mildly-diseased dogs varied betwixt 63–88%. In a like report, Höglund et al (2004) showed high interobserver variance in dogs with aortic stenosis. Another study looking at the comparing of cat cardiac auscultation, showed simply moderate interobserver agreement (Wagner et al, 2010).

What is a murmur?

A murmur can be best described as an abnormal middle sound of prolonged duration (Ware, 2007). Blood menstruation commonly passes through claret vessels and the heart with minimal turbulence, which does not crusade a murmur. A murmur arises from a vibration of structures within the heart, created past high velocity, abnormal blood flow, turbulence or reduced blood viscosity. Eye murmurs can occur without the presence of heart disease. Innocent or physiological murmurs can be quite normal for puppies and kittens, and disappear by the age of 6 months. These murmurs are unremarkably left sided and between grades I–Three/VI. Innocent murmurs can still be present in developed cats and dogs, merely if no affliction is suspected, no handling is required.

Also, in cases of severe anaemia a center murmur can exist caused past low viscosity of the blood. When the anaemia is corrected, the murmur tin disappear. Eye murmurs acquired by center disease are seen when there is an obstruction to blood flow, seen with aortic stenosis, or valvular incompetence such as mitral valve affliction. For a summary of heart murmur causes encounter Table 3.

Table 3. Causes of heart murmurs

Middle disease	Flow murmurs	Other causes
Leaking valves (eastward.g. mitral valve disease)	Innocent murmurs	Anaemia
Stenotic valves (east.g. pulmonic stenosis)	Physiological murmurs	Hyperthyroidism
Holes in the heart (e.one thousand. ventricular septal defects)

Other eye sounds

Occasionally, it is possible to hear other heart sounds. These sounds, either an S3 or S4, are known as gallop sounds. They are lower pitched than the S2 audio and, when heard, can sound similar a galloping horse. They are both heard in diastole; distinguishing one from the other is very difficult, and requires some experience and practice. An S3 audio occurs because of ventricular dilation and myocardial failure. It tin sometimes be heard in dilated cardiomyopathy, or advanced valvular heart disease. An S4 sound is associated with atrial contraction in dogs and cats that take aberrant ventricular relaxation and stiffness. In cats, it can be heard with advanced hyperthyroidism or hypertrophic cardiomyopathy. Sometimes, information technology can be a transient finding in older, stressed, or anaemic cats.

When a center murmur is detected in a cat or dog

Equally already discussed, a eye murmur does not always signify heart disease. For example, a 2010 study in good for you cats, showed that 34% of evidently healthy cats had heart murmurs (Wagner et al, 2010). The aforementioned report too showed that of those recorded equally having a murmur, merely half had heart disease on echocardiographic examination. Furthermore, of those that did not accept a heart murmur, sixteen% did take center illness when echocardiography was performed.

Payne et al (2010) even showed that a eye murmur was a good prognostic indicator in cats. Nonetheless, in dogs with mitral valve affliction, heart murmurs can be an indicator of disease severity; for example, the more degeneration of the mitral valve, the louder the murmur. However, a written report published in 2015 showed that only 46% of dogs with mitral valve disease died every bit a result of their illness (Lopez-Alvarez et al, 2015). They too showed that a murmur of course Iii/VI or above was associated with a college risk of mortality.

Determination

As with many things in life, practice makes perfect in the example of carrying out auscultation. Using a quiet room with a continuing, at-home and complicit beast is recommended. Using a systematic approach is helpful, starting with heart charge per unit and rhythm, then recognising normal heart sounds, moving from left to right side beyond the thorax, focusing auscultation over the PMI areas.

If a murmur or additional centre sounds are auscultated, location, timing and intensity should be noted, recorded on the patient file, and highlighted to the veterinary surgeon. It is to be expected that there volition exist interobserver differences, just taking a calm and systematic approach volition help reliability. A heart murmur can be an indicator of middle illness, simply does not necessarily hateful a capital punishment.

KEY POINTS

• Using a calm and systematic arroyo will greatly assist auscultation technique.

• Regular practice volition help identify aberrant and normal heart sounds.

• Identifying S1 and S2 is a crucial part of identifying other sounds.

• Center murmurs can indicate heart disease, and should be noted in terms of location, timing and intensity, and the veterinary surgeon informed.

• Middle murmurs can be present without heart affliction.

Disharmonize of involvement: none.

References

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Source: https://www.magonlinelibrary.com/doi/10.12968/vetn.2017.8.9.512

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