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November 27, 1967

The Rule of Six

JAMA. 1967;202(9):915. doi:10.1001/jama.1967.03130220103032

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To the Editor:—  The art of phonocardiography may seem difficult to many physicians. This is mainly due to inability to remember the time intervals between the various components of the heart sounds. By applying the "rule of six," phonocardiography can be greatly simplified.The interval between the Q-wave of the electrocardiogram and the first heart sound (Q-S1 interval) can normally be up to 0.06 seconds. On inspiration, the aortic (A2) and pulmonic components (P2) of the second sound may normally reach a maximum of 0.06 seconds. The opening snap of mitral stenosis may occur from 0.06 to 0.12 seconds after the aortic component of the second sound. The third heart sound or its pathologic counter part, the protodiastolic gallop, may occur from 0.12 to 0.18 seconds after the aortic component of the second sound.Thus, by using the number six or its multiples the various time intervals