Pulse Wave Velocity Variability Research Articles

Evaluation of Carotid-Femoral Pulse Wave Velocity

Carotid-femoral pulse wave velocity (PWV), a measure of arterial stiffness, is determined from the time taken for the arterial pulse to propagate from the carotid to the femoral artery. Propagation time is measured variously from the foot of the waveform or point of maximum upslope. We investigated whether these methods give comparable values of PWV at rest, during beta-adrenergic stimulation, and pacing-induced tachycardia. In subjects at rest (n=43), values obtained using the foot-to-foot method (SphygmoCor system) were 1.7+/-0.75 m/s (mean+/-SD) greater than those obtained using the maximum slope (Complior system) at a mean value of 12 m/s. Isoprotenerol (0.5 to 1.5 microg/min; n=10), and pacing (in subjects with permanent pacemakers; n=11) increased heart rate but had differential effects on systolic blood pressure and pulse pressure. The increase in heart rate produced by isoprotenerol (18+/-3 bpm) and pacing (40 bpm) was associated with an increase in PWV measured using both systems (increases of 0.7+/-0.2 m/s and 0.9+/-0.2 m/s for SphygmoCor and Complior, respectively, during isoprotenerol and increases of 2.1+/-0.5 m/s and 1.1+/-0.2 m/s for SphygmoCor and Complior, respectively, during pacing, each P<0.001). Reanalysis of waveforms recorded from the Complior system using the foot-to-foot method produced similar values of PWV to those obtained with the SphygmoCor, confirming that the difference between these systems was attributable to the timing algorithm rather than other aspects of signal acquisition. Carotid-femoral PWV is critically dependent on the method used to determine propagation time, but this does not account for variation of PWV with heart rate.

Relation between Pulse Wave Velocity, Left Ventricular Diastolic Function, and Circadian Variation of Blood Pressure in Patients with Never Treated Essential Hypertension

Background and Objectives:An increased pulse wave velocity (PWV) and a non-dipping pattern in hypertensive patients have been shown to be associated with an excess of target organ damage. The relationship between the PWV and circadian variation of blood pressure (BP) (dipper or nondipper) were sought, and also the LV diastolic function between dipper and nondipper patients compared. Subjects and Methods:44 hypertensive subjects, who had never been treated, were enrolled (mean age: 48±12 yrs, men: 29). The following procedures were undertaken. 1) 24 hour ambulatory BP monitoring; 2) echocardiography for LV geometry, LV mass index (LVMI), LV systolic and diastolic functions, including tissue Doppler and aortic PWV. The patients were divided into two groups with respect to their ambulatory BP profiles, i.e., dipper and nondipper. The PWV, LV geometry and diastolic functions were compared between dipper and nondipper patients, and the relationship between the PWV and diastolic function analyzed in all patients. Results:Twenty (45%) were nondipper patients. There were no significant differences in the LV geometry, LVMI and PWV between dipper and nondipper patients (PWV; 8.8±3.1 vs. 8.6±3.3 m/sec, p>0.05). In all patients, the PWV was related to the deceleration time (r=0.34, p=0.03) and the mitral E/A (r=-0.31, p=0.02) and mitral Em/Am ratios obtained by the tissue Doppler echocardiography (r=-0.31, p=0.03). The proportion with diastolic dysfunction was higher in the nondipper than the dipper patients (21 vs. 50%, p<0.01). There was a significant relation between the PWV and Em (r=-0.45, p=0.047) in the nondipper, but not in the dipper. Conclusion:Prolonged exposure to high BP (nondipper) was not related with increased aortic stiffness in never treated hypertensive patients. The PWV was closely related with LV diastolic dysfunction in nondipper patients. (Korean Circulation J 2004;34(11):1099-1106)

Simultaneous non-invasive assessment of arterial stiffness and haemodynamics - a validation study.

The purpose of the study was to estimate the reliability of whole-body impedance cardiography (ICGWB)-derived pulse wave velocity (PWV) and stroke volume index to pulse pressure (SI/PP) measurements. The repeatability and reproducibility of ICGWB parameters were also determined. Agreement between the impedance and Doppler ultrasound-based PWV measurements was estimated in 25 healthy subjects in two consecutive measurements. Impedance-derived SI/PP (SIICG/PP) estimates were compared with simultaneously measured SI/PP based on thermodilution (SITD/PP) and direct Fick (SIFICK/PP) methods in 30 surgical patients. PWV measured between the aortic arch and popliteal artery using the impedance technique with selective electrode configuration (PWVIS) agreed well with the Doppler ultrasound method (PWVDOPP), the bias (PWVDOPP - PWVIS) and precision (+/- SD of differences) being 0.00 and 0.79 m s-1, respectively. PWV derived from the whole-body and popliteal impedance plethysmograms (PWVICG) overestimated slightly PWVDOPP values. The repeatability value for PWVIS was excellent, being 0.54 m s-1. The reproducibility values for PWVDOPP and PWVIS were very similar (2.17 and 2.42 m s-1, respectively). Changes in PWVIS correlated strongly with changes in PWVDOPP (r=0.74; P<0.0001), indicating that both methods reflected the true physiological variation in PWV. The agreement between SIICG/PP and SITD/PP or SIFICK was almost identical to the agreement between the SITD/PP and SIFICK/PP. In conclusion,whole-body impedance cardiography provides handy and reliable means of evaluating arterial stiffness on the basis of PWV and SI/PP simultaneously with conventional haemodynamic parameters. The method is highly repeatable and reproducible.

Heart rate: an important confounder of pulse wave velocity assessment.

Arterial stiffness is a strong determinant of cardiovascular risk. Pulse wave velocity (PWV) is an index of arterial stiffness, and its prognostic value has been repeatedly emphasized. The purpose of the present study was to assess the effect of heart rate (HR) on PWV. Twenty-two subjects with a mean age of 77.8+/-8.4 (SD) years and permanent cardiac pacing were studied. In each subject, PWV was measured at 5 different pacing frequencies in the same session (60, 70, 80, 90, 100 bpm), the order of the various frequencies being randomly determined. Furthermore, to test the reproducibility, a repeat measurement of PWV was obtained in one randomly selected frequency. Blood pressure (BP) was measured by conventional means at each pacing frequency. PWV appeared fairly reproducible because no significant difference was disclosed between the 2 measurements obtained at the same HR level (P=0.5) and both measurements were strongly correlated (r=0.87, P<0.001). No significant BP variation was observed during pacing. There was a highly significant effect of HR on PWV estimated by a one-way, within-subjects analysis of variance (P=0.01). This study demonstrates that HR is an important factor in the intraindividual variation of PWV in elderly subjects. This raises methodological concern about the measurement of this parameter. Standardizing PWV for HR level seems mandatory if one wants to interpret PWV changes in clinical trials or in the follow-up of patients.

Determinants of Arterial Stiffness in Greek and French Hypertensive Men

The aim of the present study was to assess the main determinants of arterial stiffness in Greek and French middle-aged, hypertensive men, by using pulse wave velocity (PWV) measurements, which is an established method of quantification of arterial stiffness. The study was performed in 83 consecutive Greek and 79 consecutive French untreated male hypertensive outpatients aged 45-65 years. French subjects were examined in Paris at the "Centre d'Investigations Préventives et Cliniques" (the IPC Center). Greek patients were examined in Athens at the hypertension outpatient clinic in Sotiria Hospital (University of Athens). In both Greek and French hypertensive subjects, aortic stiffness was determined by the same parameters: age, blood pressure and heart rate (HR) explained approximately 40% of the aortic PWV variations, whereas lipids, triglycerides and tobacco smoking were not significant associated with aortic stiffness. After multivariate adjustments, Greek hypertensives had higher aortic stiffness as compared to the French patients by 1.2 m/s (approximately 10%); p < 0.001. Greek hypertensive subjects had also a higher body weight, waist, HR and prevalence of smoking. However, among all these factors only HR had a significant effect on PWV. Also after adjustment for HR, the difference in PWV between the two populations persisted. In conclusion, in two different populations, stiffness seems to be regulated by the same major factors. The higher aortic stiffness found in Greek hypertensives may be explained by the presence of other non-evaluated risk factors and/or patient selection differences

Aortic pulse wave velocity as a marker of cardiovascular disease in subjects over 70 years old.

Aortic pulse wave velocity (PWV) is a significant and independent predictor of cardiovascular diseases (CVD) in hypertensive subjects and in patients with end-stage renal disease, but its contribution to cardiovascular risk in subjects between 70 and 100 years old has never been tested. A cohort of 124 subjects (mean age: 87 +/- 7 years) was studied in two geriatric departments in a Paris suburb. Together with sphygmomanometric blood pressure measurements, aortic PWV was measured using a validated automatic device. Blood pressure, heart rate and body mass index, but not age, explained 48% of the PWV variability in this cohort. Furthermore, PWV was the major factor predicting the presence of CVD. The adjusted odds ratio was 17.44 (95% confidence intervals: 2.52-120.55). Antihypertensive drug therapy and low plasma albumin level had only an additive role. Blood pressure, particularly pulse pressure, had no predictive value. In 70-100-year-old subjects, aortic PWV is a strong independent marker of CVD, a finding that remains to be to confirmed by long-term longitudinal studies.

Role of pulse wave velocity for assessing autonomic nervous system activities in reference to heart rate variability

Pulse wave velocity (PWV) is related to arterial wall elasticity, which in part is regulated by sympathetic nervous system activity. The present study investigated the potential for the simultaneous use of PWV and heart rate variability using noninvasive recordings in order to provide a quantitative evaluation of the sympathovagal interaction modulating cardiovascular functions. We obtained 10 indices from the PWV and heart rate (HR) time series of 92 healthy subjects (control group) and compared the results with those of 135 patients with diabetes mellitus or vertigo. Five indices were obtained from a PWV series, that is, the mean, the coefficient of variation (CV) during supine rest, those immediately after standing up unaided, and the change of the mean PWVs before and after standing. The rest of the indices were also obtained from the instantaneous HR series. Statistical analyses revealed significant differences in the change of the mean PWVs after standing, the mean and CV of resting HR, the mean and CV of standing HR, and the change of mean HRs in patients with diabetic neuropathy as compared with healthy subjects (p < 0.01). The change of the mean PWV immediately after standing allows for the assessment of peripheral vascular sympathetic functions, provided one uses HR variability indices simultaneously.

Interaction of aortic and carotid sinus baroreceptors: effect of activation times.

Changes in pulse-wave velocity were simulated by changing the relative timing between aortic and carotid sinus barorecptor activity in anesthetized rabbits and dogs. In the rabbit, electrical stimulation was used to vary the timing; in the dog, it was also varied by perfusing the carotid sinuses with externally generated pressure pulses that could be triggered in any portion of the cardiac cycle. Changing the relative delay between aortic and carotid sinsus nerve stimulation did not result in variations of blood pressure or heart rate in the rabbit. Varing the time of electrical stimulation of the carotid sinus nerve caused at most 5 mmHg change of blood pressure in the dog. Delay-related heart-rate changes could be usually observed only when the stimulus consisted of short, high-intensity bursts. When the carotid sinus was externally perfused with pulses of pressure, only one out of five dogs showed delay-related variations in blood pressure (3mmHg) and heart rate (6 beats/min). It is concluded that variations in pulse-wave velocity are unlikely to play a significant role in acute cardiovascular control.

Immediate variations in pulse wave velocity caused by adrenalin in short, uniform parts of the arterial tree.

Pulse wave velocity measurements confined to a 6–9-cm segment of the femoral artery in eight anesthetized dogs gave an average value of 7.8 m/sec. The velocity varies with the diastolic blood pressure. This was particularly noticeable in one dog which showed marked spontaneous variations of diastolic blood pressure from beat to beat. The response to Adrenalin was diphasic showing first an increase in pulse wave velocity and then a marked decrease without a corresponding decrease in diastolic blood pressure. This observation suggests a physical change in the artery compatible with relaxation of the smooth muscle, rather than contraction.