We're now going to learn essential bedside cardiology by examining Harvey, the cardiology patient simulator. You know, the use of a simulator for medical training is analogous to the use of books and articles for cognitive knowledge and then, of course, you have to see patients. It's the same with a simulator. It's a wonderful place to begin, and the skills learned on a simulator in fact do transfer to live patients. Now, a word before we examine Harvey about the stethoscope. The bell of the stethoscope is critical. It is imperative to use this to listen for low-frequency sounds such as filling sounds, and we will practice that together, and use the proper head of the stethoscope, the diaphragm, for the more high-frequency sounds and the bell for the more low-frequency. Now, we're going to begin by listening at the upper right sternal edge to get the cadence of the first and second heart sounds. Those can be mimicked by [sounds]. What we're going to do is use the carotid as a timing device. You don't do this with patients, but it's very helpful for timing here, and when the cotton swab moves, it's systole, and as it moves you'll be able to hear the first and second sounds at the upper right sternal edge, and you'll be able to think of the hemodynamic curves, and you'll be able to envision why the mitral valve is closing to cause the first sound, the AV valves, and the second sounds are caused by the closure of the semilunar valves. Everyone listen together [sounds]. What we heard was [sounds]. You should mimic that. Go ahead and do it. [sounds]
It's [lup systole dub]. We're on our way to learn essential bedside cardiology.
Ausculation Areas
Auscultation is usually begun at the aortic area. The stethoscope is then sequentially moved to the pulmonary, tricuspid and mitral areas. Keep in mind that murmurs may radiate widely and that they may be present in areas other than the classic ones described. Inching the stethoscope across the chest is a useful technique to define the area where a given acoustic event is best heard. For best results, one should selectively tune in on the individual sounds and murmurs that may be present.
S1+S2
The first and second heart sounds we heard at the upper right sternal edge are normal. They are single and are normal in intensity. The second sound, S2, is normally louder than the first sound, S1, in the aortic area because the stethoscope is closer to the aorta than it is to the left ventricle. The relative intensities of heart sounds may be clues to pathology. For example, a loud aortic closure may be seen in some patients with hypertension.
S1+S2 Heart Animation
This is a graphic example of the left heart in the normal patient. In the animation that follows, we can appreciate that the first heart sound on the left side is associated with closure and tensing of the mitral valve. And the second heart sound on the left side is associated with closure and tensing of the aortic valve.
S1+S2 Pressure Curves
Always keep in mind the events of the cardiac cycle. In these left heart pressure tracings, S1 indicates the beginning of systole and coincides with closure of the mitral valve. S2 indicates the end of systole and the beginning of diastole and coincides with closure of the aortic valve. Both sounds are due to vibrations of the valve apparatus and surrounding cardiac structures and blood that result from valve closure and the ensuing deceleration of blood flow.