This keyword refers to the phenomenon of distal pulse amplification. When blood pressure is measured arterially from multiple sites simultaneously, the morphology of the signal changes dependent upon changing characteristics of the vascular tree. As the waveform is measured further from the aorta, the systolic peak becomes higher, the end-diastolic pressure becomes lower, and thus the pulse pressure becomes wider. The systolic upstroke also gets steeper, and the dicrotic notch appears later. The MAP however, remains only slightly higher at the aorta than in peripheral arterial sites. Morphology may vary of course by other underlying cardiovascular disease processes. The main mechanism for the amplification of SBP and pulse pressure is thought to be pressure wave reflection. The pressure wave from aorta to periphery through large vessels, travels relatively unhindered by resistance until it meets the arteriolar level. Here a drastic increase in resistance is met. Following Ohm’s Law, pressure distally in the arterioles is much less. However the resistance arteriolar bed also creates reflected pressure waves proximally, which by constructive interference augment the upstream arterial pressure pulse. The reflected wave coming back from the resistance bed adds to the incident wave coming from the aorta causing an increase in the amplitude of the measured signal (pulse pressure). Thus the phenomenon is more prominent the closer the signal is measured to the arteriolar bed (i.e. peripherally).
S S Franklin, M A Weber Measuring hypertensive cardiovascular risk: the vascular overload concept. Am. Heart J.: 1994, 128(4);793-803 [PubMed:7942450]