Cardiac Cycle - Heart Sounds 2 (Ozansoy) PDF

HEART SOUNDS-II MEHMET OZANSOY, Ph.D. Dept. of Physiology  Closing of the AV and semilunar valves produces sounds that can be heard by listening through a stethoscope placed on the chest.  These sounds are often verbalized as “lub-dub.”  The “lub,”or first sound, is produced by closing of th...

HEART SOUNDS-II MEHMET OZANSOY, Ph.D. Dept. of Physiology  Closing of the AV and semilunar valves produces sounds that can be heard by listening through a stethoscope placed on the chest.  These sounds are often verbalized as “lub-dub.”  The “lub,”or first sound, is produced by closing of the AV valves during isovolumetric contraction of the ventricles.  The “dub,” or second sound, is produced by closing of the semilunar valves when the pressure in the ventricles falls below the pressure in the arteries.  The first sound is thus heard when the ventricles contract at systole, and the second sound is heard when the ventricles relax at the beginning of diastole. Heart Murmurs  Murmurs are abnormal heart sounds produced by abnormal patterns of blood flow in the heart.  Many murmurs are caused by defective heart valves.  Defective heart valves may be congenital, or they may occur as a result of rheumatic endocarditis, associated with rheumatic fever.  In this disease, the valves become damaged by antibodies made in response to an infection caused by streptococcus bacteria (the bacteria that produce strep throat).  In mitral stenosis, for example, the mitral valve becomes thickened and calcified.  This can impair the blood flow from the left atrium to the left ventricle.  An accumulation of blood in the left atrium may cause a rise in left atrial and pulmonary vein pressure, resulting in pulmonary hypertension.  To compensate for the increased pulmonary pressure, the right ventricle grows thicker and stronger: right ventricular hypertrophy!!!  Mitral valve prolapse (with a prevalence estimated at 2.5%) is the most common cause of chronic mitral regurgitation, where blood flows backward into the left atrium.  It has both congenital and acquired forms  In younger people with mitral valve prolapse, it is usually caused by excess valve leaflet material.  Although most people with this condition lack symptoms and have an apparently normal lifespan, in some people the condition can progress.  Regurgitation can worsen if there is lengthening and rupture of the chordae tendinae extending from the papillary muscles to the valve flaps  Murmurs also can be produced by the flow of blood through septal defects —holes in the septum between the right and left sides of the heart.  These are usually congenital and may occur either in the interatrial or interventricular septum  When a septal defect is not accompanied by other abnormalities, blood will usually pass through the defect from the left to the right side, due to the higher pressure on the left side.  The buildup of blood and pressure on the right side of the heart that results may lead to pulmonary hypertension and edema (fluid in the lungs).