The y-axis represents pressure. The term murmur is used to describe an unusual sound coming from the heart that is caused by the turbulent flow of blood. Murmurs are graded on a scale of 1 to 6, with 1 being the most common, the most difficult sound to detect, and the least serious. The most severe is a 6. Phonocardiograms or auscultograms can be used to record both normal and abnormal sounds using specialized electronic stethoscopes. During auscultation, it is common practice for the clinician to ask the patient to breathe deeply.
This procedure not only allows for listening to airflow, but it may also amplify heart murmurs. Inhalation increases blood flow into the right side of the heart and may increase the amplitude of right-sided heart murmurs. Expiration partially restricts blood flow into the left side of the heart and may amplify left-sided heart murmurs. Figure 4 indicates proper placement of the bell of the stethoscope to facilitate auscultation.
Figure 4. Proper placement of the bell of the stethoscope facilitates auscultation. At each of the four locations on the chest, a different valve can be heard. The cardiac cycle comprises a complete relaxation and contraction of both the atria and ventricles, and lasts approximately 0. Beginning with all chambers in diastole, blood flows passively from the veins into the atria and past the atrioventricular valves into the ventricles.
The atria begin to contract atrial systole , following depolarization of the atria, and pump blood into the ventricles. The ventricles begin to contract ventricular systole , raising pressure within the ventricles. When ventricular pressure rises above the pressure in the atria, blood flows toward the atria, producing the first heart sound, S 1 or lub. As pressure in the ventricles rises above two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase.
Following ventricular repolarization, the ventricles begin to relax ventricular diastole , and pressure within the ventricles drops. As ventricular pressure drops, there is a tendency for blood to flow back into the atria from the major arteries, producing the dicrotic notch in the ECG and closing the two semilunar valves. The second heart sound, S 2 or dub, occurs when the semilunar valves close. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart cycle.
The valves prevent backflow of blood. Failure of the valves to operate properly produces turbulent blood flow within the heart; the resulting heart murmur can often be heard with a stethoscope. Answer the question s below to see how well you understand the topics covered in the previous section. Skip to main content.
Search for:. Critical Thinking Question Describe one cardiac cycle, beginning with both atria and ventricles relaxed. Show an Example Answer The cardiac cycle comprises a complete relaxation and contraction of both the atria and ventricles, and lasts approximately 0. The atria begin to contract following depolarization of the atria and pump blood into the ventricles.
The ventricles begin to contract, raising pressure within the ventricles. When ventricular pressure rises above the pressure in the two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase.
Following ventricular repolarization, the ventricles begin to relax, and pressure within the ventricles drops. Licenses and Attributions. In both conditions, the aortic valve A2 closes after the pulmonary valve P2.
Since the respiration only affects P2, its effect in paradoxical splitting is the opposite of normal, i. Murmurs are additional sounds generated by turbulent blood flow in the heart and blood vessels. Murmurs may be systolic, diastolic or continuous. Systolic murmurs are the most common types of murmurs in children and based on their timing within systole, they are classified into:.
The murmur is heard shortly after S1 pulse. The intensity of the murmur increases as more blood flows across an obstruction and then decreases crescendo-decrescendo or diamond shaped.
Innocent murmurs are the most common cause of SEM see below. Other causes include stenotic lesions aortic and pulmonary stenosis, coarctation of the aorta, Tetralogy of Fallot TOF or relative pulmonary stenosis due to increased flow from an ASD. Crescendo decrescendo murmur. Examples: ventricular septal defect VSD , mitral and tricuspid valve regurgitation. Holosystolic murmur. In the latter part of systole, the small VSD may close or become so small to not allow discernible flow through and the murmur is no longer audible.
Decrescendo murmur. Diastolic murmurs are usually abnormal, and may be early, mid or late diastolic. Continuous murmurs are heard during both systole and diastole. They occur when there is a constant shunt between a high and low pressure blood vessel. However, some forward flow of blood continues secondary to remnant kinetic energy from the previous phase. Isovolumetric relaxation d-e : When the ventricular pressures drop below the diastolic aortic and pulmonary pressures 80 mmHg and 10 mmHg respectively , the aortic and pulmonary valves close producing the second heart sound point d.
This marks the beginning of diastole. The ventricles generate negative pressure without changing their volume isovolumetric so that the ventricular pressure becomes lower than the atrial pressure. Ventricular filling e-a : As the AV valves open at point e , ventricular filling starts. The initial rapid filling is mainly augmented by ventricular suction which results from ventricular untwisting and the return of each ventricular muscle fiber to its slack length. The ventricular pressure gradually increases until it equals the atrial pressure and the AV valves close point a.
This is represented by the P wave on the EKG of the following cycle.
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