A 59-year-old man is admitted to the hospital with severe chest pain. During examination a slight rhythmic pulsation on the chest wall at the left fifth intercostal space is noted in the midclavicular line. What part of the heart is responsible for this pulsation?

The apex of the heart is located in the left fifth intercostal space, about 3 1/2 inches to the left of the sternum. When this area of the heart is palpated, any pulsations would be generated by throbbing of the apex of the heart against the thoracic wall. This is also the location for performing auscultation (listening) of the mitral valve, not associated with palpation. The right atrium is located to the right of the sternum. The left atrium is located on the posterior aspect of the heart, thus no direct palpation is realized. The aortic arch would be located posterior to the manubrium of the sternum, above the second intercostal space.