Doppler Ultrasound in the Measurement of Pulse Wave Velocity
Doppler Ultrasound in the Measurement of Pulse Wave Velocity
Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84–0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for the measurement of aortic PWV.
Large arteries are not simple tube conduction structures. They moderate systolic pressure increases and maintain sufficient diastolic level to guarantee myocardial perfusion. With the identification of new diseases and risk factors, it has been seen that these arteries lose their natural elasticity leading to high systolic and low diastolic blood pressure levels, which determine high pulse pressure.
Based on these premises, arterial stiffness is now considered an increasingly important biomarker in the evaluation of cardiovascular risk and the detection of incipient vascular disease. Several studies have shown that this parameter is an independent predictor of cardiovascular mortality in the elderly, hypertensive, diabetics, and patients with chronic renal failure as well as in the general population. The guidelines of the European Societies of Hypertension and Cardiology (2007-2009) have postulated arterial stiffness assessment, measurement of the carotid plaque and ankle/brachial index as markers of vascular status. Any alteration of these measurements may define a state of vasculopathy that significantly increases the evaluation of risk.
Among the different methods of evaluating arterial stiffness, the most widely used in the literature is aortic pulse wave (PWV), specifically in the area running from the aortic arch or common carotid artery to the common femoral artery. Typically, the pulse wave is detected by pressure transducers or arterial tonometry.
The measurement of carotid-femoral PWV (Figure 1) is made by dividing the distance (from the carotid point to the femoral point) by the so-called transit time (the time of travel of the foot of the wave over the distance). Hence, PWV = D (meters)/Dt (seconds).
(Enlarge Image)
Figure 1.
Pulse wave velocity determination. Transit time is estimated by the foot-to-foot method. The foot of the wave is defined at the end of diastole, when the steep rise of the waveform begins. The transit time is the time of travel of the foot of the wave over a known distance.
Whereas the distance is a fixed parameter, the transit time has a certain variability, depending on factors such as cardiac conduction and rhythm. Given this situation, most methods take the average of several measurements.
These methods are highly reliable but have the disadvantages of requiring specific devices and software and of sometimes being impossible to perform accurately due to the difficulty in recording good pulse waves. Furthermore, the time required for the exploration is not negligible.
These disadvantages are overcome if we take the carotid-femoral PWV measurement by ultrasound, making the assumption that real pulse wave corresponds to the flow wave of spectral Doppler. In fact, this method has been used in population-based studies such as the ABC study. On this basis, we designed a comparative study to assess whether PWV measured by mechanical pressure and PWV estimated by ultrasound are similar, and reliable in the measurement of arterial stiffness.
Abstract and Introduction
Abstract
Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84–0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for the measurement of aortic PWV.
Introduction
Large arteries are not simple tube conduction structures. They moderate systolic pressure increases and maintain sufficient diastolic level to guarantee myocardial perfusion. With the identification of new diseases and risk factors, it has been seen that these arteries lose their natural elasticity leading to high systolic and low diastolic blood pressure levels, which determine high pulse pressure.
Based on these premises, arterial stiffness is now considered an increasingly important biomarker in the evaluation of cardiovascular risk and the detection of incipient vascular disease. Several studies have shown that this parameter is an independent predictor of cardiovascular mortality in the elderly, hypertensive, diabetics, and patients with chronic renal failure as well as in the general population. The guidelines of the European Societies of Hypertension and Cardiology (2007-2009) have postulated arterial stiffness assessment, measurement of the carotid plaque and ankle/brachial index as markers of vascular status. Any alteration of these measurements may define a state of vasculopathy that significantly increases the evaluation of risk.
Among the different methods of evaluating arterial stiffness, the most widely used in the literature is aortic pulse wave (PWV), specifically in the area running from the aortic arch or common carotid artery to the common femoral artery. Typically, the pulse wave is detected by pressure transducers or arterial tonometry.
The measurement of carotid-femoral PWV (Figure 1) is made by dividing the distance (from the carotid point to the femoral point) by the so-called transit time (the time of travel of the foot of the wave over the distance). Hence, PWV = D (meters)/Dt (seconds).
(Enlarge Image)
Figure 1.
Pulse wave velocity determination. Transit time is estimated by the foot-to-foot method. The foot of the wave is defined at the end of diastole, when the steep rise of the waveform begins. The transit time is the time of travel of the foot of the wave over a known distance.
Whereas the distance is a fixed parameter, the transit time has a certain variability, depending on factors such as cardiac conduction and rhythm. Given this situation, most methods take the average of several measurements.
These methods are highly reliable but have the disadvantages of requiring specific devices and software and of sometimes being impossible to perform accurately due to the difficulty in recording good pulse waves. Furthermore, the time required for the exploration is not negligible.
These disadvantages are overcome if we take the carotid-femoral PWV measurement by ultrasound, making the assumption that real pulse wave corresponds to the flow wave of spectral Doppler. In fact, this method has been used in population-based studies such as the ABC study. On this basis, we designed a comparative study to assess whether PWV measured by mechanical pressure and PWV estimated by ultrasound are similar, and reliable in the measurement of arterial stiffness.
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