The Mechanism of the Pulsus Bisferiens

The earliest reference in print to the pulsus bisferiens* is in a Latin edition of Galen's De Pulsi- bus, published in Paris in 1532.From this, it is clear that debate concerning the nature and significance of this type of pulse dates from the first and second centuries A.D. Galen was insistent that, when two separate impulses are felt in the pulse, it cannot be assumed that two separate pulse waves are present.He stated that the pulsus bisferiens (as distinct from the dicrotic pulse) is characterized by quies media ictus-a central pause in the stroke.Although clinical observations on the form of the pulse can be found throughout medical literature, it was not until the invention of the sphygmograph by Marey (1860) that more precise information concerning abnormalities in wave-form became available.Mahomed (1872) who used a modification of Marey's instrument, was the first to use the terms percussion wave and tidal wave.These terms are now used to denote the twin peaks of the pulsus bisferiens; the anacrotic pulse is characterized by a small percussion wave followed by an unusually tall and broad tidal wave.Broadbent and Broadbent (1900) were among the first to discuss the pulsus bisferiens in aortic valve disease and mentioned the theory of its causation put forward by d'Espine, who suggested that left ventricular contraction occurred in two phases, producing distinct percussion and tidal waves.Bramwell (1937) was not satisfied with d'Espine's explanation and suggested that the tidal wave represented the summation of outgoing and reflected waves.The slowness of left ventricular ejection in aortic stenosis caused the outgoing wave to be well maintained when the reflected wave returned, the resultant summated tidal wave being very large.Bramwell's explanation of the genesis ofthe abnormal pulse forms in aortic valve disease has been quoted widely.An alternative explanation, offered by Katz et al. (1927), has received less attention.They studied the pressure pulses in the left ventricle and aorta in experimental aortic stenosis in dogs and described a sharp negative deflection occurring on the upstroke of the aortic pressure pulse.This they believed to be due to the suction effect of the high-velocity stream of blood (Venturi effect) and regarded it as the analogue of the anacrotic notch in the peripheral pulse.The introduction of surgical procedures for the relief of aortic stenosis has provided an opportunity of recording pressure pulses in the aorta and left ventricle in cases of aortic stenosis at opera- tion.It is proposed in this paper to study such records in an attempt to elucidate further the mechanism and significance of the abnormal pulse in aortic stenosis-particularly the pulsus bisferiens.None of the previous theories has explained satisfactorily why the pulse associated with pure or dominant aortic stenosis is characterized by a notch on the upstroke and a large tidal wave, whereas if significant aortic regurgitation is superadded, the pulsus bisferiens with equal, and well defined, percussion and tidal waves is found.*The derivation of " bisferiens" is from bis-ferio (= beat twice) and not, as is often thought, from bis-fero (= bear twice).