Pulse Pressure Amplification, Arterial Stiffness, and Peripheral Wave Reflection Determine Pulsatile Flow Waveform of the Femoral Artery

Abstract

Abstract-Aortic stiffness, peripheral wave reflection, and aorta-to-peripheral pulse pressure amplification all predict cardiovascular risk. However, the pathophysiological mechanism behind it is unknown. Tonometric pressure waveforms were recorded on the radial, carotid, and femoral arteries in 138 hypertensive patients (age: 56Ϯ13 years) to estimate aorta-to-peripheral amplifications, aortic augmentation index, and aortic (carotid-femoral) pulse wave velocity. The femoral Doppler velocity waveform was recorded to calculate the reverse/forward flow index and diastolic/systolic forward flow ratio. The aorta-to-femoral and aorta-to-radial amplifications correlated inversely with the aortic augmentation index and pulse wave velocity. The femoral flow waveform was triphasic, composed of systolic forward, subsequent reverse, and diastolic forward phases in 129 patients, whereas it was biphasic and lacked a diastolic forward flow in 9 patients. Both the femoral reverse index (30Ϯ10%) and diastolic forward ratio (12Ϯ4%) correlated positively with the aorta-to-femoral amplification and inversely with the aortic augmentation index and pulse wave velocity; these correlations were independent of age, sex, diastolic pressure, and femoral artery diameter. Patients with biphasic (versus triphasic) flow were older, shorter, included more diabetics, had smaller femoral diameters, and showed greater aortic pulse wave velocity even when adjusted for all of these covariates. In conclusion, because of the inverse (peripheral-to-aortic) pressure gradient, pulse pressure amplification normally produces a substantial reversal of the femoral flow, the degree of which is determined by the aortic distensibility and peripheral wave reflection. Arteriosclerosis (increased stiffness, increased augmentation, and reduced amplification) decreases both the reverse and diastolic forward flows, potentially causing circulatory disturbance of truncal organs and lower extremities. Key Words: blood pressure Ⅲ blood flow Ⅲ arteriosclerosis Ⅲ aorta Ⅲ physiology Ⅲ femoral Ⅲ wave reflection T he arterial pulse provides important information on the cardiovascular prognosis. There is substantial evidence that the aortic pulse wave velocity (PWV) and augmentation index (AIx) predict cardiovascular morbidity and mortality in a variety of populations, as confirmed by recent meta-analysis studies. 1,2 Similar prognostic significance has been also demonstrated for pulse pressure amplification from the central aorta to peripheral medium-sized muscular arteries. [3][4][5] These pulse indices (PWV, AIx, and pulse amplification) depend on the structural and functional properties of the central elastic and peripheral muscular arteries, which interact closely through pressure wave transmission and reflection. 6 -9 Potential mechanisms mediating these pulse abnormalities and cardiovascular disease progression include elevated central pressure leading to an increase in cardiac afterload 10,11 and widened pulsatile pressure causing circumferential tensile stress that...

Central Hemodynamics and Target Organ Damage in Hypertension

“…This hypothesis is consistent with actual observations, although additional effects of arterial distensibility (reservoir function) and blood inertia must also be taken into account. Of particular note in this study is that, as the pulse pressure amplification decreases with aortic stiffening, the reverse flow also decreases proportionally (Hashimoto and Ito 2010). Bogren et al previously speculated that the reverse flow in the lower body may supply diastolic flow into internal abdominal organs such as the kidney (Bogren and Buonocore 1994).…”

“…Due to this amplification, the blood pressure during late systole and early diastole is much higher in the peripheral than central arteries when measured simultaneously (Rowell et al 1968). The amplification ratio was reported to be approximately 130% between the central aorta and femoral artery in a hypertensive population (Hashimoto and Ito 2010).…”

“…A recent investigation has revealed that the aorta-tofemoral pulse pressure amplification is positively correlated with the reverse flow in the femoral artery (Hashimoto and Ito 2010). This finding can be explained by the hypothetical mechanism that the aorta-to-femoral pressure difference is primarily responsible for the bidirectional (triphasic) Refer to the text for more details.…”

Aortic Stiffness Determines Diastolic Blood Flow Reversal in the Descending Thoracic Aorta

“…23,24 In brief, after the brachial blood pressure measurement, pulsatile pressure signals were recorded with applanation tonometry from the radial, carotid, and femoral arteries. These pulse waveforms were used to determine various pressure and stiffness parameters, including the aortic systolic and pulse pressures, incident pressure wave height (P 1h ), augmented pressure, augmentation index (AIx, corrected for heart rate of 75 bpm), the aorta-to-radial and aorta-to-femoral pulse pressure amplifications, and the carotidfemoral and carotid-radial pulse wave velocities (PWV C-F and PWV C-R ).…”

“…Therefore, we sought to comprehensively assess the descending aortic and cerebral (carotid) flow pulse waveforms in patients with hypertension, using a noninvasive and quantitative method. 23,24 Our primary objectives were as follows: (1) to clarify the physiological determinants of the aortic flow reversal (with a particular focus on aortic stiffness and pressure), and (2) to investigate the potential association between aortic reverse flow and carotid antegrade flow. We hypothesized that aortic flow reversal would increase with aortic stiffening and consequently strengthen the pathological (hemodynamic) link between thoracic aorta and cerebral macrovasculature.…”