A heart murmur is a sound created by turbulent blood flow within the heart that is most commonly detected when auscultating the heart with a stethoscope, and these can range from normal findings to life-threatening abnormalities. We will look at a systematic approach to describing murmurs as well as some general summaries of valve disorders causing the different murmurs. Normally, blood flowing through the heart is smooth and so generates no audible sound, which is why normal heart sounds are the closing of the valves, specifically the mitral and tricuspid valves in S1, marking the beginning of systole, and aortic then pulmonary in S2, marking the beginning of diastole. However, when blood flow is not smooth, and instead of flowing in the same direction uniformly, It is called turbulent and produces sound waves that can be heard. Some murmurs are termed physiological and are expected findings in some situations.
For example, hyperdynamic states such as anemia, while other murmurs are due to structural changes within the heart causing the turbulent flow. The features of the murmur give clues as to the underlying cause. They can be remembered with the mnemonic script.
We'll use aortic stenosis as an example, where stenosis means narrowing. First is the sight, so where is the murmur best heard? The five main locations highlighted in cardiac auscultation are the aortic area on the right sternal border at the second intercostal space for the aortic valve, and this is where aortic stenosis is best heard.
The pulmonic area is on the left sternal border. second intercostal space for the pulmonary valve, and Erb's point is on the left sternal border at the third intercostal space, where S1 and S2 can normally both be heard. The tricuspid area is at the fourth intercostal space on the left sternal edge, and the mitral area is one lower down at the fifth intercostal space, this time at the midclavicular line.
This is also known as the apex. Next is the character. For example, aortic stenosis features a crescendo-de-crescendo sound, meaning an increasing or decreasing level of intensity, resembling a diamond when graphed on a phonogram. R is for radiation, meaning other locations that the murmur is audible. The classic area for aortic stenosis is the carotid arteries on both sides.
Intensity is next, which is essentially the loudness of the murmur based on grades between 1 and 6. 1 being a faint murmur, barely audible on auscultation, and 6 being audible with the stethoscope not even in contact with the chest. In most cases, non-pathological murmurs will be less than grade 3, which is moderate and easily heard without a thrill, which is a palpable vibration. Then, there is the pitch or frequency.
Generally speaking, a higher velocity flow results from a higher pressure gradient. This is why it's commonly high pitched in aortic stenosis, but it's not always the case, especially when heart failure develops. T is then for timing, when in the cardiac cycle is the murmur heard, divided into systolic, diastolic or continuous. Aortic stenosis is a systolic murmur.
heard between S1 and S2. Extra features of aortic stenosis include a narrow pulse pressure, that is, the difference between systolic and diastolic pressures. Hypertrophic obstructive cardiomyopathy may produce similar murmurs.
However, maneuvers that increase the left ventricular volume, like squatting or valsalva release, make aortic stenosis more prominent. In general, it's useful to remember that right-sided murmurs get louder with inspiration while those on the left side with expiration. The mnemonic ryle helps remember this. Aortic regurgitation instead is where the aortic valve is insufficient and blood flows back from the aorta into the left ventricle during early diastole. Although a murmur of the aortic valve it is best heard at the second to fourth intercostal spaces.
on the left side of the sternum because this is the direction of the turbulent blood flow. It has a blowing, decrescendo character and does not generally radiate, but sometimes a feature known as the Austin-Flint murmur may be heard as blood flowing back from the aorta meets blood being pumped from the left atrium into the left ventricle by the atrial kick, producing a rumbling murmur heard at the apex. It's typically high-pitched. and occurs in early diastole.
There are several suggestive clinical signs of aortic regurgitation, some of which are de Mausset's sign, where the head nods rhythmically with the heartbeat and occurs because the patient becomes aware of the wider pulse pressure, Corrigan's sign, where there is visible distension and collapse of the carotid arteries during the cardiac cycle. Also the water hammer pulse, meaning a forceful pulse with then a quick drop off. Maneuvers that increase the sound of aortic regurgitation are those that increase afterload, such as squatting.
Mitral stenosis is where there is narrowing of the mitral valve, increasing resistance to blood flow from the left atrium to left ventricle. It produces a murmur, best heard at the apex, that has a rumbling character. There is no typical radiation and it's usually low-pitched. It's a mid-diastolic murmur. with an opening click or snap occurring due to buildup of blood in the left atrium, increasing the pressure and forcing open the stenosed valve.
Often there is a low volume pulse that is commonly irregularly irregular due to mitral stenosis predisposing to atrial fibrillation and a red discoloration of the cheeks called a malar flush due to chronic hypoxia. Like the last two, movement increasing return to the left side of the heart increases the murmur, such as valsalva release and squatting. Mitral regurgitation is when blood flows backwards from the left ventricle into the left atrium during systole.
In fact, it's termed pan-systolic, as it can be heard throughout systole. It's best heard at the apex and features radiation to the axilla. and is associated with a blowing, high pitched sound.
Squatting increases the intensity as increasing afterload increases resistance to the left ventricle outflow tract and so promotes more blood to backflow into the left atrium. Mitral valve prolapse is similar but features a mid-systolic click as the mitral valve prolapses. Pulmonic or pulmonary stenosis is where there is narrowing affecting the pulmonary valve and therefore blood moving from the right ventricle to the pulmonary artery.
It is usually congenital but may not present until adulthood and is part of the Tetralogy of Fallot. It is best heard at the pulmonary area and is a crescendo-de-crescendo systolic murmur with a harsh character. Unlike aortic stenosis, it does not generally radiate, but some sources mention it may towards the left shoulder and infraclavicular region. The increased resistance to the outflow of the right ventricle could mean that it takes longer for the blood to be ejected, and so the pulmonary component of the second heart sound is delayed, giving a split S2 sound.
Pulmonary regurgitation, as you can imagine, instead features insufficiency of the pulmonic valve and so blood passes back from the pulmonary artery into the right ventricle. Overall it is rare and usually associated with pulmonary hypertension. When this is the case it is called the Graham steel murmur which is what we'll describe although there are subtle differences when pulmonary hypertension is not present. This murmur is an early diastolic murmur.
best heard at the pulmonic area and is described as having a high-pitched decrescendo character. Tricuspid stenosis is rare and almost exclusively caused by rheumatic fever and occurring together with tricuspid regurgitation. In some rare cases, carcinoid syndrome can cause isolated tricuspid stenosis. It is a mid-diastolic murmur best heard at the tricuspid area and is described typically as a scratching, rumbling sound with soft opening snap.
It often features a raised jugular venous pressure that may be visible on a clinical exam, as well as discomfort in the region of the liver due to congestion and enlargement. Blood leaking back into the right atrium from the right ventricle is tricuspid regurgitation, producing a high-pitched pan-systolic murmur best heard at the tricuspid area. Although not a clear radiation, it can sometimes be heard from the epigastrium.
In severe cases, the pitch tends to be described as medium. Epstein's anomaly can lead to this, and depending on the severity, the regurgitation may be visualised as a prominent jugular venous pressure waveform, up to palpable pulsating in the hepatic region. It becomes louder with inspiration, and this is known as Cavallo's sign.