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Ep002: Cardiac Blood Flow and Murmurs

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Understanding the blood flow through the heart is foundational to understanding cardiac pathophysiology.  Blood returning from the body enters the heart through the Superior and Inferior Vena Cavae and spills into the Right Atrium. From the Right Atrium blood is pushed through the tricuspid valve into the right ventricle.  The right ventricle contracts and forces blood out of the heart through the pulmonic valve into the pulmonary artery which carries the blood to the lungs to be oxygenated. Oxygenated blood then flows out of the lungs through the pulmonary veins into the left atrium.  Blood is squeezed out of the left atrium through the mitral valve into the left ventricle. Then the left ventricle contracts and forces blood out of the heart through the aortic valve into the aorta and out into the rest of the body.

Understanding where the valves are located will also help you to understand murmurs. If a valve is fully open when it should be indicative of stenosis.  When a valve doesn’t close like it should that causes regurgitation. When we discussed heart sounds, we mentioned that the tricuspid and mitral valves are closing during systole or S1. So if you hear a murmur during S1 in either of these locations it indicates improper closing therefore regurgitation. If the murmur is heard during S2 in these locations, it indicates stenosis (or incomplete opening). In the opposite way, an S1 murmur in the aortic or pulmonic locations indicate stenosis (because the valve isn’t opening fully); and an S2 murmur in aortic or pulmonic would indicate regurgitation from a valve that didn’t close fully.

By understanding how the blood flows through the heart and the physiology behind murmurs, you will better be able to understand the signs and symptoms you see in your patient.

Date Published - Apr 26, 2018
Date Modified - Apr 26, 2018