Auscultation of the Chest
Note the quality of the first and second heart sounds at each site, and whether there are any additional sounds. The first heart sound has two components, caused by mitral and tricuspid valve closure. Mitral closure occurs slightly before tricuspid but this does not normally cause splitting of the sound. The second heart sound is a slightly lower pitch than the first, it occurs at the end of systole. It comprises both aortic and pulmonary valve closure. A useful mnemonic is that the valves close in alphabetical order, i.e. aortic before pulmonary and mitral before tricuspid.
During inspiration, splitting of the second sound may be detected over the pulmonary area: this is due to the increased venous return to the right ventricle, leading to more prolonged systole on the right side of the heart. Splitting of the first heart sound may indicate complete right bundle branch block, whereas increase of the normal splitting of the second heart sound occurs if there is delay in right ventricular emptying, as in right bundle branch block, pulmonary stenosis, ventricular septal defects and mitral incompetence.
Atrial septal defects typically cause a fixed splitting of the second sound. Reverse splitting of the second sound (i.e. splitting occurring in expiration, as opposed to inspiration) is due to delayed left ventricle depolarization (e.g. left bundle branch block) and delayed left ventricular emptying (e.g. aortic stenosis, coarctation of the aorta and patent ductus arteriosus).
Auscultation starts over the apex, where the mitral valve is assessed. In this mitral area, apply the bell of the stethoscope (figure 51a). It produces a resonating chamber that is particularly efficient in amplifying the low pitched sounds, that may occur with mitral diastolic murmurs and a fourth heart sound.
Next change to the diaphragm (figure 51b). This is appropriate for detecting high pitched sounds, such as those generated by systolic murmurs.
Follow this by applying the stethoscope systematically over the aortic area (second right intercostal space), the pulmonary area (second left intercostal space) and finally the tricuspid areas (fifth left intercostal space). At each site use both the bell and the diaphragm (figure 52a–c).
The above order of auscultation links the mitral and aortic valves, and the pulmonary with the tricuspid, i.e. the valves on the respective sides of the heart. Auscultation must not be limited to these four sites. When abnormalities are found or suspected, move the stethoscope over each area to identify the positions of optimal sound, and also to follow the radiation of sound: typical sites are along the left sternal border, radiation from the apex into the left axilla and from the aortic area into the right side of the neck (figure 53).
Repositioning a patient may accentuate sounds, such as turning to the left lateral position or sitting upright (figure 54a,b); sounds may further be accentuated by deep inspiration, deep expiration or a Valsalva manoeuvre. A Valsalva manoeuvre is performed by asking the patient to blow hard on the back of their hand or forearm, without releasing air (figure 55).