Objective. Local pulse wave velocity (PWV) plays a crucial role in assessing the regional arterial elasticity. Accurate estimation of local PWV is beneficial for the risk assessment and early diagnosis of cardiovascular diseases. In this study, a method involving incident waves based on coherent plane wave compounding ultrasound (IWCU) is proposed to suppress reflected waves in pulse waves (PW) and improve the performance of transit time (TT)-based local PWV estimation.Approach. The ultrasonic radio frequency echo signals are collected and coherently compounded, and the PWs and central blood flow velocities at 128 beam positions are calculated, from which the incident waves (IWs) are estimated based on the Kelvin-Voigt model. Then, the time delays (TDs) of the IWs propagating are calculated, and the local PWV is finally estimated. The mean and standard deviations (MSD) of the normalized root mean squared errors NRMSEs between the presupposed and estimated TDs and PWVs were calculated for quantitatively evaluating the performance of the proposed IWCU method, and compared with those of the PWs based on coherent plane wave compounding ultrasound and the regional upstroke tracking methods in simulation experiments. The relative errors, Bland-Altman analysis and coefficient of variation (CV) were measured to further assess the accuracy, reproducibility and variability of IWCU method inin vitroandin vivoexperiments.Main results. The IWCU method yields higher accuracy, reproducibility and lower variability for local PWV estimation. The MSD of the NRMSEs for TDs and local PWVs are 11.78 ± 0.52% and 4.10 ± 2.25%. Additionally, the mean relative error and CV are 6.10% and 12.56%, respectively.Significance. The IWCU method provides improved TT-based local PWV estimation, and has the potential to support future clinical diagnoses of arterial stiffness.

Pulse wave velocity (PWV) is the most important index for quantifying the elasticity of an artery. The accurate estimation of the local PWV is of great relevance to the early diagnosis and effective prevention of arterial stiffness. In ultrasonic transit time-based local PWV estimation, the locations of time fiduciary point (TFP) in the upstrokes of the propagating pulse waves (PWs) are inconsistent because of the reflected waves and ultrasonic noise. In this study, a regional upstroke tracking (RUT) approach that involved identifying the most similar TFP-centered region in the upstrokes is proposed to detect the time delay for improving the local PWV estimation. Five RUT algorithms with different tracking points are assessed via simulation and clinical experiments. To quantitatively evaluate the RUT algorithms, the normalized root-mean-squared errors and standard deviations of the estimated PWVs are calculated using an ultrasound simulation model. The reproducibility of the five RUT algorithms based on 30 human subjects is also evaluated using the Bland-Altman analysis and coefficient of variation (CV). The obtained results show that the RUT algorithms with only three tracking points provide greater accuracy, precision, and reproducibility for the local PWV estimation than the TFP methods. Compared with the TFP methods, the RUT algorithms reduce the mean errors from 12.23% ± 3.10% to 7.13% ± 2.31%, as well as the CVs from 21.76% to 13.39%. In conclusion, the proposed RUT algorithms are superior to the TFP methods for local carotid PWV estimation.

In experiments on narcotized rats, the electrical potential and impedance of isolated segment of the right femoral and/or carotid artery were simultaneously recorded in situ via two extracellular nonpolarizable Ag/AgCl electrodes mounted along the arteries at the interelectrode distance of 4 mm. The active, passive, and intermediate pulsing modes of arterial segment were determined according to the phase relations between its electrical impedance and BP, which was simultaneously measured in the symmetrical part of the respective left artery and used to assess pressure in the examined segment. The study assessed the effect of amplitude (0.2-2.0 mA) of alternating probe current (100 kHz), which was used to measure the electrical impedance of arterial segment, on its pulsing mode. The pulsing mode determined at the initial minimal probe current of 0.2 mA was passive with out-of-phase pulsatile oscillations of electrical impedance and BP. After elevation of the probe current amplitude to maximal level of 2 mA, these oscillations became in-phase indicating transition of the arterial segment to active pulsing mode. This transition was accompanied by appearance of arterial voltage impulses synchronized with BP upstrokes and an 11-fold median increase in the peak-to-peak value of electrical impedance oscillations with the interdecile range of 7-15 (N=28). Under moderate amplitude of probe current (0.3-0.5 mA), the intermediate mode of arterial pulsing was observed featured by a delayed, weak, and short active constriction during BP front, which was insufficient to resist and counterbalance the dilating effect of rising BP. In this case, the pulsatile oscillations of electrical impedance were smaller than those observed in active or passive pulsing modes indicating a possibility to stabilize the arterial diameter during pulsatile oscillations of BP. The effect of alternating electric current on the mode of arterial pulsation is explained with electrical model of smooth muscle cell membrane reflecting the rectifying features of potassium channels and predicting membrane hyperpolarization in response to external alternating current passing across the cell. The visibilities of therapeutic neurotropic and angiotropic stimulation with alternating electric current are discussed.

A 22-year-old man with typical angina was seeking medical attention at primary health clinics for a couple of months. Owing to his young age and the absence of coronary artery disease risk factors, he was assured of no serious problem. Proper examination at a referral centre revealed weak peripheral pulses with diminished and delayed carotid upstroke. A normal S1 with a soft S2 were audible. A 3/6 late peaking systolic murmur was best heard in the aortic area radiating to the neck. Symptomatic bicuspid aortic valve disease was suspected. Diagnosis of unicuspid aortic valve was established by transoesophageal and three-dimensional echocardiography. The valve was successfully replaced with a mechanical prosthesis. The patient remains asymptomatic at 1 year follow-up.

Pulse wave velocity (PWV), the speed of propagation of arterial pressure waves through the arterial tree, is related to arterial stiffness and is an important prognostic marker for cardiovascular events. In clinical practice PWV is commonly determined by arterial tonometry, with a noninvasive pressure sensor applied sequentially over carotid and femoral arteries. The electrocardiogram (ECG) is used as a timing reference to determine the time delay or "transit time" between the upstroke of carotid and femoral pulse waveforms. Commercially available vascular ultrasound scanners provide a pulsed wave (PW) Doppler velocity signal, which should allow determination of carotid-femoral transit time and hence PWV. We compared carotid-femoral PWV measured by tonometry and by PW Doppler ultrasound (Seimens, Apsen scanner with 7 MHz linear transducer) in asymptomatic subjects (n = 62, 26 male, aged 21 to 72 y). To test for intra-subject and inter-observer variation, ten subjects were scanned by one observer on two occasions 2 wk apart and by two observers on same day. PWV by tonometry ranged from 5.3 to 15.0 m/s. There was no significant difference between mean values of PWV obtained by the two techniques (mean difference: 0.3 m/s, standard deviation of difference: 1.5 m/s), which were closely correlated (r = 0.83). The coefficient of variation for repeated measures on the same subject by the same observer was 10.1% and the inter-observer coefficient of variation was 5.8%. These results suggest a commercial ultrasound scanner can be used to measure PWV, giving results that are reproducible and closely correlated with those obtained by arterial tonometry. (E-mail: ben_yu.jiang@kcl.ac.uk).

The first and second carotid arterial sounds (CaS1 and CaS2) were recorded simultaneously with the aortic valve echocardiogram, carotid pulse wave contour, heart sounds, and electrocardiogram in 27 healthy, normal subjects. The mean intervals between the onset of the QRS complex and the onsets of the first and second major components of the carotid arterial sounds were Q-CaS1 = 131 +/- 15 ms and Q-CaS2 = 412 +/- 36 ms, respectively. The mean delay of CaS1 after aortic valve opening was 43 +/- 6 ms, while the delay of CaS2 after aortic valve closure was 43 +/- 7 ms. The onset of CaS1 and CaS2 are exactly coincident with the upstroke and with the dicrotic notch of the carotid pulse wave contour. The recording of the carotid arterial sounds, heart sounds, and ECG has enabled us to measure systolic time intervals including the pre-ejection period, left ventricular ejection time, and pulse transmission time more easily than using the conventional method involving the carotid arterial pulse wave contour. The new approach provides accuracy and precision comparable to that of the previous methods.

The genesis and clinical significance of the aortic ejection sound with a low-frequency predominance and delayed appearance were studied. This is recorded on the phonocardiogram in some patients with left ventricular dysfunction. Subjects studied consisted of 10 patients with a low-pitched ejection sound and seven patients with an ordinary high-pitched aortic ejection sound. No patients had echocardiographic findings suggestive of organic lesions of the aortic valve. Time relationships among the ejection sounds, aortic valve echograms and carotid artery pulses, and then movements of the aortic valve cusps and non-invasively estimated left ventricular systolic function were compared between the two groups. Results were as follows: 1. The low-pitched ejection sound: 1) The beginning of the sound was nearly coincident with the onset of the upstroke of the carotid artery pulse and the initial full opening of the aortic valve cusps. 2) The beginning of the ejection systolic murmur followed immediately after the ejection sound. 3) The amplitude of the sound was closely related to the height of the carotid artery pulse in a case of atrial fibrillation. 2. The low-pitched ejection sound vs the high-pitched ejection sound: 1) The onset of the low-pitched ejection sound was significantly delayed. 2) The amplitude and the velocity of the initial opening of the aortic valve cusps were significantly decreased. 3) The preejection period (PEP) was significantly prolonged; the ejection time (ET) was significantly shortened; and the PEP/ET ratio was significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)

The transmission delays of the upstroke and incisura of the arterial pulse were measured in 128 normal subjects, divided in three groups of increasing age, by comparing the timing of the indirect aortic arch pulse (recorded at the suprasternal notch) (SSN) and the indirect, right carotid tracing (CAR). In the total group, the mean delay of the upstroke was 24.4 msec while the mean delay of the incisura was 19 msec (P less than 0.005). This difference was maximal in the oldest age group and became non significant in the group of children under 12. At slow heart rate, this difference was greater than at a more rapid heart rate. The left ventricular ejection times (LVET), measured on the two pulses, showed a very close correlation (r = 0.96) but the LVET was significantly longer in the SSN tracing, especially in the older subjects. These data reveal that the incisura of the arterial pulse travels more rapidly than the upstroke, especially in older patients and at lower heart rates. The most likely explanation of this fact resides in the frequency-dependent influence of vascular reflections, which is more important with increasing age and slower heart rate. Thus, the transmission velocity along the arterial wall is higher for the higher harmonics of the pulse wave (incisura) than for the lower harmonics (upstroke).

Systolic time intervals (STI) were measured in 469 normal children, aged 5.0 to 16.9 years, using simultaneous recordings of the electrocardiogram, phonocardiogram and an external carotid pulse tracing. The data were analyzed to define the influence of sex, age, cardiac cycle length, body weight (BW), body length (BL), and body surface area (BSA) on the left ventricular STI. Regression, equations were evaluated for the calculation of normal standards for the following STI: electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP) systolic quotient (PEP/LVET), isovolumic contraction time (IVCT), electroacustical delay (QS1), and additionally for the so-called tension time (TT), upstroke time (UT), and the ascending index (UT/LVET) of the carotid pulse wave. Heart rate was found to influence all of the STI but the ratio UT/LVET, which revealed to be independent of any variable. Besides heart rate, BSA proved to be a second relevant independent variable for QS2 and LVET, respectively BL for PEP, PEP/LVET and QS1. These findings are in accordance to the results of comparable echocardiographic studies but disagree previous mechanocardiographic studies in smaller groups of children in whom age and not the above-mentioned parameters of the individual development seemed to influence the STI. A second set of equations was evaluated for the calculation of 95%-prediction intervals for the particular STI permitting to define abnormalities of the STI in individual children.