Effect of age and gender on ventricular-arterial coupling estimated using a non-invasive technique

Abstract Background Left ventricular-arterial coupling is assessed as the ratio of left ventricular end-systolic elastance (Ees) to arterial elastance (Ea). Previous studies have introduced non-invasive estimations of Ees/Ea. It requires only four variables, namely pre-ejection period, ejection time, end-systolic pressure and diastolic pressure. The aims of the present study were to clarify the reference values of Ees/Ea estimated using the noninvasive technique, and to investigate the effects of age and gender on Ees/Ea in healthy subjects. Methods This retrospective study utilized data from healthy, 30-79-year-old subjects. We recorded electrocardiogram, phonocardiogram, and brachial arterial pulse waves simultaneously using the vascular screening system, and used the observed variables to calculate Ees/Ea. We separated subjects into five groups according to their age and compared Ees/Ea among the different age groups. Results The study included 2114 males and 2292 females. Ees/Ea ranged from 1.87 to 2.04 in males, and 1.98 to 2.32 in females. We observed no age-related differences in Ees/Ea in males (p = 0.10), and significant differences in females (p < 0.001). Ees/Ea in males was not different compared to those in females in 60-69-year-old group (p = 0.92). Whereas Ees/Ea was higher in females compared to those in males in the other age groups. The differences between medians of Ees/Ea in males and those in females were 0.45 (p < 0.001), 0.24 (p < 0.001), 0.13 (p = 0.01), and 0.13 (p = 0.03) in 30–39, 40–49, 50–59, and 70-79-year-old age groups, respectively. Conclusions We clarified the reference values of Ees/Ea in healthy subjects. The effect of age on Ees/Ea is different in males and females, although Ees/Ea is maintained within a relatively narrow range in all subjects

Pilot Study: Estimation of Stroke Volume and Cardiac Output from Pulse Wave Velocity.

Transesophageal echocardiography (TEE) is increasingly replacing thermodilution pulmonary artery catheters to assess hemodynamics in patients at high risk for cardiovascular morbidity. However, one of the drawbacks of TEE compared to pulmonary artery catheters is the inability to measure real time stroke volume (SV) and cardiac output (CO) continuously. The aim of the present proof of concept study was to validate a novel method of SV estimation, based on pulse wave velocity (PWV) in patients undergoing cardiac surgery.This is a retrospective observational study. We measured pulse transit time by superimposing the radial arterial waveform onto the continuous wave Doppler waveform of the left ventricular outflow tract, and calculated SV (SVPWV) using the transformed Bramwell-Hill equation. The SV measured by TEE (SVTEE) was used as a reference.A total of 190 paired SV were measured from 28 patients. A strong correlation was observed between SVPWV and SVTEE with the coefficient of determination (R2) of 0.71. A mean difference between the two (bias) was 3.70 ml with the limits of agreement ranging from -20.33 to 27.73 ml and a percentage error of 27.4% based on a Bland-Altman analysis. The concordance rate of two methods was 85.0% based on a four-quadrant plot. The angular concordance rate was 85.9% with radial limits of agreement (the radial sector that contained 95% of the data points) of ± 41.5 degrees based on a polar plot.PWV based SV estimation yields reasonable agreement with SV measured by TEE. Further studies are required to assess its utility in different clinical situations

The Effects of Hemodynamic Changes on Pulse Wave Velocity in Cardiothoracic Surgical Patients

The effect of blood pressure on pulse wave velocity (PWV) is well established. However, PWV variability with acute hemodynamic changes has not been examined in the clinical setting. The aim of the present study is to investigate the effect of hemodynamic changes on PWV in patients who undergo cardiothoracic surgery. Using data from 25 patients, we determined blood pressure (BP), heart rate (HR), and the left ventricular outflow tract (LVOT) velocity-time integral. By superimposing the radial arterial waveform on the continuous wave Doppler waveform of the LVOT, obtained by transesophageal echo, we were able to determine pulse transit time and to calculate PWV, stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR). Increases in BP, HR, and SVR were associated with higher values for PWV. In contrast increases in SV were associated with decreases in PWV. Changes in CO were not significantly associated with PWV

Difference between ejection times measured at two different peripheral locations as a novel marker of vascular stiffness

<div><p>Pulse wave velocity (PWV) has been recommended as an arterial damage assessment tool and a surrogate of arterial stiffness. However, the current technology does not allow to measure PWV both continuously and in real-time. We reported previously that peripherally measured ejection time (ET) overestimates ET measured centrally. This difference in ET is associated with the inherent vascular properties of the vessel. In the current study we examined ETs derived from plethysmography simultaneously at different peripheral locations and examined the influence of the underlying arterial properties on ET prolongation by changing the subject’s position. We calculated the ET difference between two peripheral locations (ΔET) and its corresponding PWV for the same heartbeat. The ΔET increased with a corresponding decrease in PWV. The difference between ΔET in the supine and standing (which we call ET index) was higher in young subjects with low mean arterial pressure and low PWV. These results suggest that the difference in ET between two peripheral locations in the supine vs standing positions represents the underlying vascular properties. We propose ΔET in the supine position as a potential novel real-time continuous and non-invasive parameter of vascular properties, and the ET index as a potential non-invasive parameter of vascular reactivity.</p></div

A Pulse Wave Velocity Based Method to Assess the Mean Arterial Blood Pressure Limits of Autoregulation in Peripheral Arteries

Background: Constant blood flow despite changes in blood pressure, a phenomenon called autoregulation, has been demonstrated for various organ systems. We hypothesized that by changing hydrostatic pressures in peripheral arteries, we can establish these limits of autoregulation in peripheral arteries based on local pulse wave velocity (PWV).Methods: Electrocardiogram and plethysmograph waveforms were recorded at the left and right index fingers in 18 healthy volunteers. Each subject changed their left arm position, keeping the right arm stationary. Pulse arrival times (PAT) at both fingers were measured and used to calculate PWV. We calculated ΔPAT (ΔPWV), the differences between the left and right PATs (PWVs), and compared them to the respective calculated blood pressure at the left index fingertip to derive the limits of autoregulation.Results: ΔPAT decreased and ΔPWV increased exponentially at low blood pressures in the fingertip up to a blood pressure of 70 mmHg, after which changes in ΔPAT and ΔPWV were minimal. The empirically chosen 20 mmHg window (75–95 mmHg) was confirmed to be within the autoregulatory limit (slope = 0.097, p = 0.56). ΔPAT and ΔPWV within a 20 mmHg moving window were not significantly different from the respective data points within the control 75–95 mmHg window when the pressure at the fingertip was between 56 and 110 mmHg for ΔPAT and between 57 and 112 mmHg for ΔPWV.Conclusions: Changes in hydrostatic pressure due to changes in arm position significantly affect peripheral arterial stiffness as assessed by ΔPAT and ΔPWV, allowing us to estimate peripheral autoregulation limits based on PWV

GLM analysis.

<p>GLM analysis.</p

Mean±SD of RR interval, ET, ΔET, ΔPAT, ΔDAT and PWV in 3 positions.

<p>Mean±SD of RR interval, ET, ΔET, ΔPAT, ΔDAT and PWV in 3 positions.</p

Effect of position and peripheral location on the measured ET.

<p>Each plot indicates the mean ET calculated from each individual subject. (A) ETs measured at the ear. (B) ETs measured at the finger. (C) ETs measured at the toe. (D) ETs measured in the standing position. (E) ETs measured in the sitting position. (F) ETs measured in the supine position. ET: ejection time, ns: not significant, *: P < 0.05, ***: P < 0.001.</p

Bland-Altman plots of the difference between ETs measured at two peripheral locations.

<p>Bland Altman plots showing the difference between ET at the finger and ET at the ear (A)(D)(G), between ET at the toe and ET at the finger (B)(E)(H), and between ET at the toe and ET at the ear (C)(F)(I). Each ET was measured in the standing (A)(B)(C), sitting (D)(E)(F), and supine (G)(H)(I) position. The solid line indicates the mean of difference, and the dashed line indicates the 95% limits of agreement. The difference of ETs between each pair of locations are also shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187781#pone.0187781.t002" target="_blank">Table 2</a> (ΔET). ET: ejection time; SD: standard deviation.</p

Relationship between ΔET_Toe-Finger, ΔPAT_Toe-Finger and ΔDAT_Toe-Finger in an individual subject.

<p>(A), (B), and (C) Measurements derived from a 23 year old female with the most compliant vasculature as evident by the lowest PWV_{ΔPAT Toe-Finger} in the supine position. (D), (E), and (F) Measurements derived from a 36 year old female with the least compliant vasculature as evident by highest PWV_{ΔPAT Toe-Finger} in the supine position. Each dot on the graph was derived from a single heartbeat in the standing (black circles) and supine (white squares) positions. (A) and (D) Scatter plot of ΔET_Toe-Finger and ΔPAT_Toe-Finger. (B) and (E) Scatter plot of ΔET_Toe-Finger and ΔDAT_Toe-Finger. (C) and (F) Scatter plot of ΔDAT_Toe-Finger and ΔPAT_Toe-Finger. ET: ejection time; PAT: pulse arrival time; DAT: dicrotic notch arrival time, PWV: pulse wave velocity.</p