Pathophysiology
P-I-21. Physiological arterial pulse wave and changes with aging
生理的動脈脈波とその加齢変化
The Physiological Arterial Pulse Wave
- The arterial pulse wave is the pressure wave generated by the left ventricle during ejection, travelling through the arterial system
- As it travels it is reflected at several points:
- Branching points (mainly in the lower limb)
- Resistance vessels
- The detected wave is a superposition of the forward (ejection) wave and the reflected wave → the reflected pressure is added to the ejected pressure (augmentation = pressure increase)
Pulse Wave Amplification
- As the wave travels from the aortic root to the peripheral arteries its morphology changes:
- Becomes narrower
- Amplitude rises, without significant change in mean pressure
- Causes:
- Peripheral arteries are more rigid → distort the pressure wave
- The pressure wave travels faster in stiffer peripheral arteries
Changes with Aging
- Vascular aging → increased arterial stiffness
- Consequences of aortic wall stiffening:
- Pressure increases more during ejection
- The pulse wave travels faster towards the periphery
- The reflected wave returns sooner → increased systolic pressure
- Impact on the pressure wave:
- Pulse wave amplification decreases, then disappears
- Pulse pressure increases (especially centrally: systolic ↑, diastolic ↓)
- Augmentation pressure and augmentation index increase
- These parameters (measured by pulse wave analysis) are good markers of vascular aging and are associated with increased cardiovascular risk (mainly stroke and myocardial infarction)
Options to Detect Pulse Waves
- Photoplethysmography — emits light into skin/tissue; some absorbed by RBCs, some reflected → reduced light intensity at the detector
- Doppler ultrasound
一問一答
▶What is the physiological arterial pulse wave a superposition of?
The forward (ejection) wave and the reflected wave; the reflected pressure adds to the ejected pressure (augmentation).
▶What is pulse wave amplification?
As the wave travels from the aortic root to peripheral arteries it becomes narrower and its amplitude rises, without significant change in mean pressure.
▶What causes pulse wave amplification toward the periphery?
Peripheral arteries are more rigid (distorting the wave), and the pressure wave travels faster in stiffer arteries.
▶How does aortic wall stiffening with aging affect ejection pressure?
Pressure increases more during ejection because the stiff aorta cannot buffer the stroke volume.
▶With aging, why does the reflected wave return sooner?
Increased arterial stiffness makes the pulse wave travel faster, so the reflected wave returns earlier (during systole).
▶What is the consequence of the reflected wave returning during systole?
It boosts systolic pressure (increased systolic pressure).
▶What happens to pulse wave amplification with aging?
It decreases and then disappears.
▶How does central pulse pressure change with aging?
Pulse pressure increases (especially centrally: systolic rises and diastolic falls).
▶What happens to augmentation pressure and augmentation index with aging?
Both increase.
▶Which cardiovascular events are particularly associated with increased arterial stiffness markers?
Stroke and myocardial infarction.
▶What technique uses light absorption/reflection by red blood cells to detect pulse waves?
Photoplethysmography — light is emitted into skin/tissue, partly absorbed by RBCs and partly reflected, reducing light intensity at the detector.
▶Besides photoplethysmography, what method can detect pulse waves?
Doppler ultrasound.
▶Why does diastolic pressure fall centrally with aging while systolic rises?
Stiff arteries lose the Windkessel buffering that maintains diastolic pressure, so systolic rises and diastolic drops (widening pulse pressure).
▶Why are pulse wave analysis parameters good markers of vascular aging?
They quantify increased arterial stiffness and reflected-wave effects, which rise with age and correlate with cardiovascular risk.
▶What is the augmentation index conceptually?
The proportion of central pulse pressure contributed by the reflected wave — higher with stiffer arteries.
▶Why does increased central systolic pressure burden the heart?
It raises left-ventricular afterload, promoting LV hypertrophy and increasing myocardial oxygen demand.
▶How does loss of pulse wave amplification relate to central pressure?
When amplification disappears, peripheral and central pressures converge, so central systolic pressure (the harmful one) is higher.
▶Why is the lower limb a major source of wave reflection?
Its branching points and resistance vessels reflect a large portion of the forward pressure wave.
▶What generates the arterial pulse wave?
Left ventricular ejection during systole creates the pressure wave that propagates through the arteries.
▶Why is central (aortic) pressure more clinically relevant than brachial pressure in aging?
Central pressure determines the load on the heart, brain, and kidneys, and rises with stiffening even when brachial readings change less.