michigan hypertension core curriculum - State of Michigan

Figure 1. Arterial Waveform
These reflected waves “sum up” with the pressure generated from ejected blood into arterial
system and are therefore the major determinants of systolic BP; thus, the arterial waveform (at any
location) consists of both forward traveling and reflected waveforms. Normally, because of the reflected
waves, SBP and pulse pressure (PP) are amplified or increase by ~ 10 – 14 mm Hg when moving from
the aorta to the brachial artery. However, DBP and mean arterial pressure (MAP) change very little
(figure 2).
Figure 2. Change in contours in pressure and flow waves
After the systolic ejection phase, the fall in DBP is dampened as the elastic recoil of the large
capacitance vessels propels forward the blood volume that was stored during systole. The reflected
waveforms largely emanate from the peripheral resistance arterioles and timing wise, arrive back in the
aorta during diastole thereby augmenting coronary perfusion pressure.
The difference between SBP, peak BP during the cardiac cycle, and DBP, the lowest BP during
the cardiac cycle, is the pulse pressure (PP). Pulse pressure is predominantly influenced by the amount
of blood ejected during systole (SV) and the magnitude of the change in pressure inside the arterial
vasculature for a given change in arterial volume (arterial compliance). Arterial compliance will be
discussed in more detail later.
A. Physical Factors: Blood volume (BV) and arterial compliance are important physical factors that
determine BP levels. Blood volume is distributed unevenly between the arterial and venous (capacitance
vessels) sides of the vascular system. Approximately two-thirds to three-quarters of the BV is contained
within the venous capacitance vessels; the remaining one-quarter to one-third is contained in the arterial
NKFM & MDCH 25