Forward and Backward Pressure Waveform Morphology in Hypertension

Area of Science:

• Cardiovascular Physiology
• Hemodynamics
• Vascular Biology

Background:

• Pulse pressure increases with age and is a risk factor for cardiovascular disease.
• Pulse wave reflection is a key determinant of central aortic pressure and pulse pressure.
• The role of pulse wave reflection and backward waveform morphology in hypertension remains debated.

Purpose of the Study:

• To test the hypothesis that increased pulse wave reflection and altered backward waveform morphology contribute to increased pulse pressure.
• To examine the relationship between backward and forward wave morphology in subjects with varying pulse pressure and during administration of vasoactive drugs.

Main Methods:

• Carotid tonometry and Doppler sonography were used to estimate aortic pressure and flow in 158 subjects.
• Subjects were divided into three groups based on central pulse pressure.
• Vasoactive drugs (dobutamine, norepinephrine, phentolamine, nitroglycerin) were administered to healthy normotensive subjects.

Main Results:

• Morphology of the backward wave relative to the forward wave was similar across different pulse pressure groups.
• Inotropic, vasopressor, and vasodilator drugs (except nitroglycerin) showed similar backward to forward wave ratios.
• Nitroglycerin significantly reduced the backward wave amplitude relative to the forward wave (0.26 to 0.19, P<0.01).

Conclusions:

• Pulse wave reflection is approximately constant and minimally contributes to increased pulse pressure in hypertension.
• Dilation of peripheral muscular conduit arteries can modify wave reflection but has little effect on elevated pulse pressure.
• Altered backward waveform morphology is not a primary driver of increased pulse pressure in hypertension.