In an age of complex diagnostic technology, any news of a new use for a simple old physical sign is bound to quicken the pulse. It is thrilling to see little David take on Goliath.
Pulsus paradoxus was first named and described by Kussmaul in 1873. The name persisted, even though it has been shown since that the observed decrease in the amplitude of the pulse on deep inspiration is not a paradoxical phenomenon, but an exaggeration of the normal response.1 The difference is that of degree. Normally, the decrease is less than 5 mm Hg, whereas in pulsus paradoxus it may well exceed 10, even 20, mm Hg and then be detectable without the aid of the sphygmomanometer by palpation alone.
Not only did the name persist, but also its association with the originally described condition. Much as an actor who gets "typed" early in his career, pulsus