A heartbeat heard through a stethoscope sounds like "lubb-dupp." These sounds are due to vibrations in the heart tissues produced as the blood flow is suddenly speeded or slowed with the contraction and relaxation of the heart chambers, and with the opening and closing of the valves.
The first part of a heart sound (lubb) occurs during the ventricular contraction, when the A-V valves are closing. The second part (dupp) occurs during ventricular relaxation, when the pulmonary and aortic valves are closing (fig. 15.16).
Sometimes during inspiration, the interval between the closure of the pulmonary and the aortic valves is long enough that a sound coming from each of these events can be heard. In this case, the second heart sound is said to be split.
Heart sounds are of particular interest because they can indicate the condition of the heart valves. For exam ple, inflammation of the endocardium (endocarditis) may change the shapes of the valvular cusps). Then, the cusps may close incompletely, and some blood may leak back through the valve. This produces an abnormal sound called a murmur. The seriousness of a murmur depends on the extent of valvular damage. Many heart murmurs are harmless. Fortunately for those who have serious problems, it is often possible to repair the damaged valves or to replace them. Clinical Application 15.1 describes more severe heart problems.
Using a stethoscope, it is possible to hear sounds associated with the aortic and pulmonary valves by listening from the second intercostal space on either side of the sternum. The aortic sound comes from the right, and the pulmonic sound from the left. The sound associated with the bicuspid (mitral) valve can be heard from the fifth intercostal space at the nipple line on the left. The sound of the tricuspid valve can be heard at the fifth intercostal space just to the right of the sternum (fig. 15.17).
Was this article helpful?