2014. január 5., vasárnap

Heart sound

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The essential qualifications for an author of such a work as the present are an actual acquaintance with the persons mentioned, an intimate knowledge of their daily lives, and a personal familiarity with the scenes described. Auscultation of heart sounds should usually follow the general medical assessment and the general assessment of the cardiovascular system. The nurse should first think about the results of the general assessment and then proceed to listen to heart sounds. In many cases, the first part of the assessment will give you a clue of what to listen for upon auscultation. For example, if the patient states in his/her history that he/she has had cardiac surgery, or a valve replaced, etc., then it will alert the nurse to listen for particular sounds or murmurs.In most persons, there are two major sounds that can be heard. The “lub” and “dub” are called S1 and S2 respectively, and are the two most prominent and easily heard sounds. S1 and S2 follow each other closely. Begin to auscultate the heart sounds, by having the patient lie comfortably on his/her back at about a 45 degree angle. Have them put their hands at their sides and then explain what you are going to do. You may have to tell some patients to relax and to breathe normally, as anxiety may sometimes make them breathe rapidly and noisily and interfere with your procedure. First, start at point number one, above the aortic area. Then proceed to the pulmonic, 2nd pulmonic, right ventricular, apical and then epigastric area. Each of these areas allows for the clearest heart sound for that valve it is named for. The aortic region, for example, is the best place to listen to the aortic valve, tec., even though the valve is not actually located at that precise area. Heart sounds are generally easy to hear; but sometimes due to patient and other conditions, it may be difficult to hear clearly. Use the diaphragm of the stethoscope and place it gently on the chest in the areas indicated. The diaphragm will be best for listening to the high-pitched sounds of S1, so auscultate using the diaphragm at all points. Do not “drag” the stethoscope along the skin. Excess noise will be generated by this action. Have the patient breath normally and put them in a supine position. Sometimes the sounds may be better heard in a sitting position. Try both ways if you have difficulty hearing the sounds. The most fundamental heart sounds are the first and second sounds, usually abbreviated as S1 and S2. S1 is caused by closure of the mitral and tricuspid valves at the beginning of isovolumetric ventricular contraction. S1 is normally slightly split (~0.04 sec) because mitral valve closure precedes tricuspid valve closure; however, this very short time interval cannot normally be heard with a stethoscope so only a single sound is perceived.  S2 is caused by closure of the aortic and pulmonic valves at the beginning of isovolumetric ventricular relaxation. S2 is physiologically split because aortic valve closure normally precedes pulmonic valve closure. This splitting is not of fixed duration.  S2 splitting changes depending on respiration, body posture and certain pathological conditions. The third heart sound (S3), when audible, occurs early in ventricular filling, and may represent tensing of the chordae tendineae and the atrioventricular ring, which is the connective tissue supporting the AV valve leaflets. This sound is normal in children, but when heard in adults it is often associated with ventricular dilation as occurs in systolic ventricular failure. The fourth heart sound (S4), when audible, is caused by vibration of the ventricular wall during atrial contraction. This sound is usually associated with a stiffened ventricle (low ventricular compliance), and therefore is heard in patients with ventricular hypertrophy, myocardial ischemia, or in older adults.

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