Murmurs recognition – part 1

This is a guest post from vanumu . You can also find and follow him on twitter @vanstar7. I am a huge fan of his work.

Let’s review the basics!

Blood flow through the heart

Let’s look at the basic flow of blood through the heart using a simple diagram.

Deoxygenated Blood flows from the body into the right atrium (RA).

Then it travels through the the tricuspid valve to the right ventricle(RV).

From the right ventricle, blood is pumped through the pulmonary valve into the blood vessel that goes to the lungs.

Oxygenated Blood flows from the lungs through blood vessels back to the heart’s left atrium(LA).

From the left atrium, blood goes through the mitral valve and into the left ventricle.

The left ventricle pumps blood through the aortic valve to a major blood vessel called the aorta and out to the body.

The Valves of the Heart

The heart has a series of valves that ensure forward blood flow.

Atrioventricular Valves (tricuspid and bicuspid)

The bicuspid (mitral) and tricuspid valves are composed of similar components: leaflets (3 for the tricuspid valve, 2 for the bicuspid valve), annulus – a fibrous ring that encircles the valve, chordae tendanae – fibrous ligaments that connect the leaflets to the papillary muscles which in turn flex when the ventricles contract to stabilize the AV valves.

Semilunar Valves (pulmonic and aortic valves)

The pulmonic and aortic valves are virtually identical although the aortic valve consists of a thicker fibrous structure than the pulmonic valve.

Heart sounds

The heart sounds are the noises (sound) generated by the beating heart and the resultant flow of blood through it.

heartbeat = vibrations caused by the closing valves, not by the valves snapping shut.

In healthy adults there are two normal heart sounds- S1 and S2 “lub – dub”

First Heart sound: S1 is produced by the closure of closing of the AV valves.

Second Heart sound: S2 is produced by the closure of closing of the semilunar valves.

In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, gallop rhythms (S3, S4) and adventitious sounds.

A gallop rhythm refers to a (usually abnormal) rhythm of the heart on auscultation. It includes three or four sounds,  thus resembling the sounds of a gallop.

Third Heart sound: S3 occurs at the beginning of diastole after S2. It is caused by the oscillation of blood back and forth between the walls of the ventricles initiated by inrushing blood from the atria.

S3 is usually associated with

• HEART FAILURE.

Fourth Heart sound: S4 a rare extra heart sound that occurs immediately before S1. It is physiologically seen sometimes in healthy children and trained athletes but when audible in an adult is called a presystolic gallop or atrial gallop. This gallop is produced by the sound of blood being forced into a stiff/hypertrophic ventricle.

S4 is usually associated with

• Hypertrophy of the ventricle

(athletes, long-standing hypertension, aortic stenosis, overloading of the ventricle)

• Restrictive cardiomyopathy (fibrosis of the ventricle i.e. post-MI)
• Congestive Heart Failure (failing left ventricle)

Assessment points for heart auscultation

ICS = Intercostal space

Erb’s point refers to the third intercostal space on the left sternal border where S2 is best auscultated.

Heart murmurs

Murmurs are extra heart sounds that are produced as a result of turbulent blood flow which is sufficient to produce audible noise

Murmurs can be classified by six different characteristics:

• Timing: whether the murmur is a systolic or diastolic murmur.
• Shape: intensity over time; murmurs can be crescendo, crescendo-decrescendo, or decrescendo.
• Location: where the heart murmur is auscultated best.
• Radiation: where the sound of the murmur radiates.
• Intensity: loudness of the murmur, and is graded on a scale from 1-6.
• Pitch: low, medium or high -determined by whether it can be auscultated best with the bell or diaphragm of a stethoscope.

Grading of a murmur

Six grades are used to classify the intensity of a murmur:

• Grade I is the faintest murmur that can be heard (with difficulty)
• Grade II murmur is also a faint murmur but can be identified immediately
• Grade III murmur is moderately loud
• Grade IV murmur is loud and is associated with a palpable thrill
• Grade V murmur is very loud but cannot be heard without the stethoscope.
• Grade VI murmur is the loudest and can be heard without a stethoscope

Timing of a murmur

The following classification is useful:

For systolic murmurs

• Holosystolic (or pansystolic)
• Early systolic
• Midsystolic (or systolic ejection)
• Late systolic

For diastolic murmurs:

• Early diastolic
• Mid-diastolic
• Late diastolic (or presystolic)

Continuous murmurs

Let’s look at an overview of the most common murmurs seen in relation to their timing..

We will explore each murmur separately in “Murmurs recognition –part 2”. Please try to get an overall idea of the various murmurs for now.

Holosystolic and early systolic murmurs

Holosystolic murmurs are usually regurgitant murmurs

They usually occur when blood flows from a chamber whose pressure throughout systole is higher than pressure in the chamber receiving the flow.

Types of holosystolic murmurs:

• Mitral regurgitation – high pitched and best heard with the diaphragm of the stethoscope and the patient in the left lateral decubitus position
• Tricuspid regurgitation – best heard with the diaphragm of the stethoscope over the lower left second and third interspaces and along the left sternal border.
• Ventricular septal defect – VSDs cause a holosystolic murmur if pressure in the right ventricle is lower than the left ventricle throughout systole, resulting in a continuous left-to-right shunt.

Midsystolic ejection murmurs

The ejection or midsystolic murmur (MSM) is related to flow of blood across the semilunar valves

The onset of the MSM coincides with the beginning of ejection and termination occurs with the cessation of forward flow.

Types of midsystolic ejection murmurs:

• Innocent midsystolic murmurs – 60 percent of patients have a systolic murmur. The “innocence” of an MSM should depends on the absence of other abnormal findings.

Still’s murmur is an innocent murmur heard as a short vibrating murmur over the mid precordium in children in the absence of any other abnormality.

• Increased semilunar blood flow – MSM also occurs in the presence of normal valves when flow across the semilunar valve is significantly increased.

This can be seen in patients with anemia, thyrotoxicosis, pure aortic regurgitation, and pregnancy (MSM is seen in 80% of normal preganant women).

• Dilation of the aortic root or pulmonary artery – Aortic root dilatation or dilatation of the proximal pulmonary artery may be associated with an MSM.
• Aortic outflow obstruction – MSM associated with fixed aortic obstruction due to valvular, subvalvular, or supravalvular stenosis or hypertrophic cardiomyopathy (HCM) typically is harsh and medium pitch.
• Atrial septal defect with left to right shunting causes increased flow across the pulmonary valve elicited as an MSM.
• Aortic valve sclerosis – it must be considered in the differential diagnosis of aortic stenosis in elderly patients.
• Pulmonic valve stenosis -  The murmur duration correlates reasonably well with the severity of stenosis and is harsh and best heard over the left second interspace. When the murmur is loud it radiates to the left side of the neck and is frequently accompanied by a palpable thrill.
• Bicuspid aortic valve – murmur is best heard over the right second interspace with little or no radiation.

Late systolic murmurs

A late systolic murmur starts after S1 and, if left-sided, extends to A2, usually in a crescendo manner .

Types of late systolic murmurs:

• Mitral valve prolapse – the most common cause of a late systolic murmur and best heard with the diaphragm of the stethoscope, over or just medial to the cardiac apex.
• Tricuspid valve prolapse – uncommon in the absence of mitral valve prolapse and best heard over the left lower sternal border.
• Papillary muscle displacement – mild mitral regurgitation due to papillary muscle displacement (previously known as papillary muscle dysfunction) in acute myocardial infarction.

Early diastolic murmurs

Early diastolic murmurs typically start at the time of semilunar valve closure and their onset coincides with S2. An aortic regurgitation murmur begins with A2; pulmonary regurgitation begins with P2.

Types of early diastolic murmurs:

• Aortic regurgitation – best heard with the diaphragm of the stethoscope over the left sternal border or over the right second interspace, while the patient sits and leans forward with the breath held in full expiration.
• Pulmonary regurgitation – it is occasionally can be heard in thin subjects where a mild pulmonary regurgitation may be present. Pathologic pulmonary regurgitation is most frequently a result of pulmonary hypertension (Graham-Steell murmur) or residual after Tetralogy of Fallot repair in adults.
• Left anterior descending artery stenosis – also know as “Dock’s murmur” is a rare diastolic murmur similar to AR seen in patients with LAD artery stenosis.

Mid-Diastolic and late diastolic murmurs

Mid-diastolic murmurs result from turbulent flow across the AV valves during the rapid filling phase because of mitral or tricuspid valve stenosis and an abnormal pattern of flow across these valves.  AV valve stenosis can also present as presystolic murmurs occurring in late diastole and extending up to S1. They usually have a crescendo configuration .

Types of Mid-Diastolic and late diastolic murmurs:

• Mitral stenosis has a rumbling character that starts with an opening snap and is best heard with the bell of the stethoscope over the left ventricular impulse with the patient in the left lateral decubitus position(lying on your left side).
• Tricuspid stenosis is associated with a mid-diastolic rumble that is best heard along the left sternal border that increases in intensity of the murmur with inspiration (Carvallo’s sign).
• Increased flow across the AV valve may cause mid-diastolic murmurs in the presence of normal atrioventricular valves when the flow across the valve is markedly increased in mid-diastole (flow murmurs). The intensity of the tricuspid flow murmur tends to increase during inspiration.
• Atrial myxoma may cause obstruction of the atrioventricular valves. In left atrial myxoma, the auscultatory findings can be similar to those of mitral stenosis. Right atrial myxoma is less common and auscultatory findings may be similar to those of tricuspid stenosis.
• Austin Flint murmur is usually described in patients with pure aortic regurgitation. Several mechanisms have been proposed to explain the genesis of this murmur, including fluttering of the mitral valve from the impingement by the aortic regurgitant jet, relative (functional) mitral stenosis, and regurgitant jets directed against the left ventricular free wall.
• Carey-Coombs murmur has been attributed to acute mitral valvulitis and is usually seen in In acute rheumatic fever.

Types of late diastolic murmurs:

• Rytand’s murmur is usually seen in a complete AV block with a slow idioventricular rhythm and is heard as a short late diastolic murmur. The precise mechanism of Rytand’s murmur is not known but has been postulated to be due to a diastolic mitral regurgitation.

Continuous Murmurs

Continuous murmurs are defined as murmurs that begin in systole and extend up to diastole without interruption. Continuous murmurs result from blood flow from a higher pressure chamber or vessel to a lower system associated with a persistent pressure gradient between these areas.

Types of Mid-Diastolic and late diastolic murmurs:

• Patent ductus arteriosus is a relatively common cause of a continuous murmur in adults that causes a continuous murmur know as Gibson’s murmur or machinery murmur.
• Aortopulmonary window is a small space between the aortic arch and the pulmonary artery that is visible in the lateral chest radiograph.
• Coronary arteriovenous fistulas may produce a continuous murmur with its location, duration, and character dependant on the anatomical type of fistulas.

~~Review illustrations~~

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