Physiology of Cardiovascular Murmur (Heart Murmur)

Hello everyone, it is a great day here, and I hope it is a great day from your end. Today, I will be taking time to explain the physiology, location, clinical significance, and everything you need to know about Cardiovascular murmur, or heart murmur (which ever name you are familiar with).

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Okay, let's do a little bit of English learning. Murmur according to Cambridge Dictionary is defined as a soft continuous sound from something, or someone with this, heart murmur, when combining heart and murmur would mean a continuous sound from the heart. Since we have a literal understanding of Heart Murmur, let's go do justice to the topic.

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Understanding A Normal Heart Function

I have been able to explain the heart (basically not as a topic, but part of a topic) in many of my previous posts, which I would recommend that you read through, and soon, I will be making a post about the physiology of the heart, but if you need to understand the heart, my previous posts have done justice to giving an explicit explanation into the heart in one way or another. First, let's understand the normal heart sound. Cardiac events are responsible for cardiac sounds. The heart sound is divided into S1 and S2.

S1 is a heart sound caused as a result of the closing of the Atrioventricular valves (the mitral valve, and the tricuspid valve) in the heart, when systolic contraction of the ventricles starts. The S2 sound occurs when the Semilunar valve closes as a result of a lower ventricular pressure (the pulmonary artery, and the aortic valve), preventing blood from the pulmonary artery and the aorta, back to the ventricles. Using a stethoscope during Auscultation, the heart gives a Lub Dub sound.

Heart Murmur Physiology

Heart Murmur basically describes the blowing, or whooshing sounds, as a result of turbulence in the flow of blood through the heart, or vessels to the heart. Heart Murmur would be triggered/caused by higher velocity of blood flow as a result of high contractile strength, reduced valve diameter or vessels towards the heart, reduced viscosity of blood basically from anemia, and valve incompetence..

Higher velocity of blood flow as a result of high contractile strength, increasing turbulent could occur under conditions where there is a high flow in the ascending aorta as a result of small diameter valves, due to stenotic or partial obstruction. An increase in velocity would increase the Reynolds Number, which is a way to identify turbulence. The smaller the diameter of the valve, the higher the velocity of blood, increasing the murmur of the heart, and the larger the diameter of the valve, the lower the velocity of blood. This could happen with Ventricular septal defect, causing turbulence in blood flow..

Coarctation of the aorta is another reason. When the Aorta is narrowed, blood flowing from the left ventricle will need to squeeze through the narrowed aorta to get to the body. When the aorta is narrowed, it causes an increase in velocity of blood from the Left ventricle to the body, causing an increase in turbulence which would mean an increase in murmur.

Aortic Stenosis is another cause for murmur in the heart. This happens when the valve between the left chamber of the heart and the aorta is narrowed, causing the left ventricular outflow obstruction, thereby increasing the velocity of blood passing through. Conditions such as Hypertrophic obstructive Cardiomyopathy can cause Aortic stenosis, which causes a murmur..

Heart Murmur can occur due to the viscosity of blood. When the blood is thick, its movement isn't fast and this doesn't cause turbulence, but when the blood is thin as a result of reduced viscosity due to lack of components such as red blood cell in the blood, in cases of anemia, it would lead to increase in turbulence, causing an increase in murmur..

Blood flow in an incompetent valve can also cause heart murmur. Disorders such as Pulmonic Valve Regurgitation, Aortic regurgitation, Mitral regurgitation, and tricuspid regurgitation whereby blood is flowing back from any of the valves, into the heart could lead to turbulence of blood flow, causing heart murmur..

Identifying Murmur Location

When listening to murmurs, using the bell of the stethoscope will help identify low-pitched sound, and using the diaphragm of the Stethoscope will help listen to high-pitched murmur sound.. The location of the murmur is dependent on the area where the valve location. The murmur could occur at the Pulmonary valve area, Aortic valve Area, Tricuspid valve Area, and the Mitral Valve Area.

Finding murmur in the Aortic Valve is identified at the second intercostal space on the right sternal border. This includes identifying Aortic stenosis, Aortic regurgitation, and co-arctic aorta. With Aortic stenosis, the blood is being obstructed from a forward flow, leaving the heart into the carotid. With Aortic regurgitation, blood is going back into the left ventricle.

The Pulmonic valve murmur is located at the second intercostal space on the left sternal border, these murmurs would be as a result of Pulmonic stenosis, Pulmonic regurgitation, and Atrial Septal defects.

The Tricuspid valve murmur can be identified at the fourth intercostal space on the left sternal border, murmurs in this valve are as a result of Tricuspid stenosis, tricuspid regurgitation, and Ventricular Septal defect.

The mitral valve murmur can be identified at the fifth midline level of the clavicle line. Murmurs in the mitral valve can be as a result of Mitral valve Stenosis, Mitral regurgitation, and Mitral valve prolapse.

ERBs Point murmur can be identified at the third intercostal space on the left sternal border. Erbs point allows for easy identifying of the S1 and S2 sound, as well as identifying any murmur, especially murmurs from Hypertrophic Obstructive Cardiomyopathy.

Cardiovascular Murmur Intensity

The intensity of cardiovascular murmur can be divided into 6 grades. The grade starts with grade 1 to grade 6. Grade 1 murmur is difficult to identify because the murmur is very faint. It can only be audible to an expert. In grade 2, the murmur is faint, but can still be audible by non-experts. A grade 3 murmur can be heard with a stethoscope than a grade 2 murmur. Grade 3 murmurs can cause little vibrations/thrill in the chest. Grade 4 murmurs are loud, and causes vibration/thrill in the chest. The vibratory sensation can be felt easily with a hand or a stethoscope. Grade 5 murmurs are super loud and have a palpable vibration/thrill. The murmur can be heard across wide areas, and in this grade of murmur, the stethoscope do not need to be placed fully on the chest to hear the murmur, it only needs to be placed slightly close to the chest. With grade 6 murmur, there is a palpable thrill or heavy vibration, that can be heard without placing the stethoscope on the chest. Hovering the stethoscope around the chest is enough to hear the murmur. The murmur can also be heard without a stethoscope. Grade 1 to 3 murmurs are not likely pathological, it could be benign while grade 4 to 6 are basically pathological., .

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