Practical Application 4.2
Auscultation of the Human Heart
Auscultation of, or listening to the sounds made by, the heart is but one part of a comprehensive cardiac examination. Begin a habit of auscultating the heart in a systematic fashion that is the same for every patient whom you evaluate. Establishing a uniform approach will more quickly familiarize you with normal heart sounds and help you identify abnormal sounds. To aid your concentration, try to auscultate the heart in a quiet room. Approach the patient from the right side and do all that you can to minimize anxiety. Attempt to warm your stethoscope before using it and communicate with the patient as you progress through this part of the physical examination. Remember that maintaining patient modesty is always a priority.
Auscultation is usually done with the patient lying on his back, before an exercise test; however, auscultation can be performed with the patient in the sitting position. As mentioned earlier, when you auscultate the heart for cardiac sounds, you should do so systematically. Begin by placing the diaphragm of the stethoscope firmly on the chest wall in the lower-left parasternal region. First, characterize the rhythm as regular, occasionally irregular, or irregular. An irregular rhythm is usually attributable to atrial fibrillation. The diaphragm of the stethoscope is best used to hear high-pitched sounds, whereas the bell portion is used for low-pitched sounds.
Next, move the stethoscope to the point on the chest where the first heart sound (S1, the sounds of mitral and tricuspid valves closing) is best characterized. For most people, this location is found at the apex of the heart at the left midclavicular line and near the fourth and fifth intercostal spaces. You will hear two sounds. The first sound (S1) is the louder and more distinct sound of the two. Then, move your stethoscope upward and to the right side of the sternal border at the second intercostal space. This location is generally the best place to characterize the second heart sound (S2, the sounds of aortic and pulmonic valves closing) because it is louder and more pronounced here.
Soft heart sounds occur with low cardiac output states, obesity, and significant pulmonary disease (e.g., diseased or hyperinflated lung tissue between the chest wall and the heart). Loud heart tones occur in thin people and in hyperdynamic states such as pregnancy. The second heart sound normally splits with inspiration as right ventricular ejection is delayed with the increased volume it receives from the augmented venous return of inspiration. This delays or splits the pulmonic component of S2 (sometimes referred to as P2) from the aortic component of S2 (referred to as A2, figure 4.3).
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With practice and as you begin to care for patients with various cardiac problems, you will become exposed to and appreciate third (S3) and fourth (S4) heart sounds. S3 and S4 are low-pitched sounds that are heard during diastole and best appreciated with use of the bell portion of the stethoscope. The presence of either of these two heart sounds is most often associated with a heart problem and, if not previously noted in the patient’s medical record, should be brought to the attention of a physician. S3 is best heard at the apex and occurs right after S2. S4 is also well heard at the apex and occurs just before S1. An S3 commonly indicates severe left ventricular systolic impairment with volume overload and dilation. An S4 commonly indicates chronic stiffness or poor compliance of the left ventricle, usually attributable to long-term hypertension. As you can appreciate, learning and identifying heart sounds require a great deal of practice.
The clinical exercise physiologist should be able to appreciate systole and diastole and, with advanced training, listen for murmurs in the mitral, tricuspid, pulmonic, and aortic areas (figure 4.4). Murmurs are characterized by the timing in the cardiac cycle (systolic, diastolic, or both), location where best heard, radiation, duration (short or long), intensity, pitch (low, high), quality (musical, rumbling, blowing), and change with respiration (8). A central concept to keep in mind while listening with the stethoscope is that the sounds heard are attributable to changes in blood velocity and the movement of cardiac valve leaflets, both of which are driven by pressure gradients and result in flow. Systolic murmurs are more common and are often characterized as ejection type (e.g., diamond shaped or holosystolic). Diastolic murmurs are distinctly less common and are always abnormal.
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Exercise physiologists working in the clinical exercise testing setting would be well served to acquire the basic skills needed to auscultate the heart. For further information and to hear audio clips of murmurs go to www.blaufuss.org or Heart Songs 3 at www.cardiosource.org.
