Chapter 2 Heart Sounds & Murmurs

A murmur is the sound generated by the turbulent flow of blood within the heart. This sound can be heard using a stethoscope and is often indicative of an abnormality in the heart valves or chambers. It is different from the S1 and S2 sounds, which are the normal heart sounds produced by the closing of the heart valves during systole. Therefore, the correct answer is murmur.

The closure of the aortic and pulmonary valves is heard during diastole. This is because during diastole, the ventricles of the heart are relaxed and filling with blood. As the ventricles fill, the pressure in the aorta and pulmonary artery decreases, causing the aortic and pulmonary valves to close. This closure produces the S2 sound, which is the second heart sound heard during the cardiac cycle.

The S3 sound is a low frequency sound that occurs in early diastole. It is caused by ventricular wall vibration when atrial blood rushes into the ventricles. This sound is normal in young individuals, but it can also indicate ventricular dysfunction or volume overload.

The closure of the mitral and tricuspid valves at the onset of systole produces the S1 sound. During systole, the ventricles contract and pump blood out of the heart, causing the atrioventricular valves (mitral and tricuspid valves) to close. This closure creates a sound that can be heard as the S1 sound.

Diastole refers to the phase of the cardiac cycle when the heart muscle relaxes and fills with blood. During diastole, the ventricles of the heart "rest" and/or fill with blood. This is in contrast to systole, which is the phase when the heart muscle contracts and pumps blood out of the ventricles. The S4 sound and S2 sound are related to specific events during the cardiac cycle, but they are not directly related to diastole. Therefore, the correct answer is diastole.

Systole refers to the phase of the cardiac cycle when the ventricles contract, pumping blood out of the heart and into the arteries. This contraction is responsible for the main pumping action of the heart, pushing oxygenated blood to the body's organs and tissues. During systole, the heart muscles contract, causing the heart chambers to decrease in size and forcing blood out of the ventricles. This is followed by diastole, the phase when the heart relaxes and refills with blood. S2 sound and murmurs are related to the heart sounds heard during different phases of the cardiac cycle and are not directly related to ventricular contraction.

The S4 sound refers to a low frequency caused by atrial contraction into a "stiff" ventricle in late diastole. This sound is often present in conditions like left ventricular hypertrophy and fibrotic myocardium.

Murmurs can arise from various mechanisms. Flow across a partial obstruction can cause turbulent blood flow, resulting in a murmur. Increased blood flow through a normal structure can also create turbulent flow and cause a murmur. Ejection into a dilated chamber can cause abnormal blood flow patterns and result in a murmur. Regurgitant flow across an incompetent valve, where blood leaks back through the valve, can also cause a murmur. Additionally, shunting of blood from a high pressure to a lower pressure vascular chamber through an abnormal route can lead to turbulent flow and a murmur. Flow through the heart through the atrial valves does not typically cause murmurs.