What we observed at the apex is three impulses. There is one that occurs just prior to systole, one during systole and one in early diastole. Let's again use the cotton swab to reinforce that. A presystolic movement, a systolic movement, timed with the carotid, and an early diastolic movement. Let's look together. [Cut-away]

Let's go through these three movements we felt one at a time and try to decide their best explanation. The presystolic impulse is the palpable equivalent of a fourth heart sound, and it is due to the left atrium struggling to get blood into a left ventricle that is less accepting, less compliant. The systolic impulse is that impulse that usually occurs as the left ventricle hits the chest wall. The third impulse, in early diastole, is the palpable equivalent of a third heart sound, and that is due to the fact that blood is rushing into the left ventricle. And the relationship between that rushing in in early diastole and its deceleration sets up vibrations, and it can be due to either excess flow accros the valve, as in the case of a patient with mitral regurgitation, there is great flow in early diastole into the left ventricle, or due to poor compliance, failure, stiffness of the left ventricle. Three impulses in our patient.