What did we observe when we assessed the contour of our patient's precordial impulse? We saw something very unusual. Three impulses at the apex. The first was prior to systole, presystolic, and the other two were during systole. Let's all concentrate together, using the cotton swabs, timing the apical impulse with the systolic carotid impulse. Everybody look together. [Cut-away]

Three impulses at the apex. The first is presystolic, just before the carotid impulse. That is the palpable equivalent of a fourth heart sound. It tells us something. It tells us that the atrium, in late diastole, is struggling to get blood into the left ventricle and, as blood goes into the left ventricle and decelerates more rapidly because of a stiff less compliant ventricle, you can palpate a presystolic impulse and likely will be able to hear a fourth heart sound. And then we saw the very unusual two systolic impulses. That can be a clue to a specific diagnosis.