Lan Gao

Impact of cuff positioning on blood pressure measurement accuracy: May a specially designed cuff make a difference?

During blood pressure (BP) measurement, the recommended positioning of the cuff bladder center is directly above the brachial artery. We investigated the relevance of incorrect cuff positioning during (1) auscultatory measurement with an appropriate or improperly small cuff and (2) oscillometric measurement with a wide-range cuff designed to guarantee accurate measurements regardless of position. In subjects with wide BP and arm circumference ranges, (1) auscultatory BP was repeatedly measured with a properly positioned cuff (reference) and, simultaneously, with an identical cuff placed on the other arm in either a correct or an incorrect position (test). The measurements were performed with a properly sized (N=57) or an improperly small cuff (N=33). (2) Auscultatory measurements obtained with a properly positioned and sized cuff were compared with oscillometric measurements obtained with a specially designed wide-range cuff (Omron IntelliWrap) placed on the contralateral arm either in a correct or an incorrect position. Auscultatory BP measures were unaffected by incorrect positioning of a properly sized cuff, whereas with undercuffing, BP was overestimated with the cuff displaced by 90° laterally (systolic/diastolic BP differences: 4.9±4.6/4.0±4.6 mm Hg, P<0.01) or by 180° (3.9±5.4/4.2±5.1 mm Hg, P<0.01) in relation to the correct position. Incorrect placement of the oscillometric cuff had no significant effect on the accuracy of the measurements (difference with correct position <1.5 mm Hg). Incorrect cuff positioning introduces a systematic overestimation of auscultatory BP when the cuff is too small in relation to arm circumference but not when it is correctly sized. No systematic error was observed with oscillometric measurements obtained with a specially designed wide-range cuff.

Short-Term Repeatability of Noninvasive Aortic Pulse Wave Velocity Assessment: Comparison between Methods and Devices

BACKGROUND Aortic pulse wave velocity (PWV) is an indirect index of arterial stiffness and an independent cardiovascular risk factor. Consistency of PWV assessment over time is thus an essential feature for its clinical application. However, studies providing a comparative estimate of the reproducibility of PWV across different noninvasive devices are lacking, especially in the elderly and in individuals at high cardiovascular risk. METHODS Aimed at filling this gap, short-term repeatability of PWV, estimated with 6 different devices (Complior Analyse, PulsePen-ETT, PulsePen-ET, SphygmoCor Px/Vx, BPLab, and Mobil-O-Graph), was evaluated in 102 high cardiovascular risk patients hospitalized for suspected coronary artery disease (72 males, 65 ± 13 years). PWV was measured in a single session twice, at 15-minute interval, and its reproducibility was assessed though coefficient of variation (CV), coefficient of repeatability, and intraclass correlation coefficient. RESULTS The CV of PWV, measured with any of these devices, was <10%. Repeatability was higher with cuff-based methods (BPLab: CV = 5.5% and Mobil-O-Graph: CV = 3.4%) than with devices measuring carotid-femoral PWV (Complior: CV = 8.2%; PulsePen-TT: CV = 8.0%; PulsePen-ETT: CV = 5.8%; and SphygmoCor: CV = 9.5%). In the latter group, PWV repeatability was lower in subjects with higher carotid-femoral PWV. The differences in PWV between repeated measurements, except for the Mobil-O-Graph, did not depend on short-term variations of mean blood pressure or heart rate. CONCLUSIONS Our study shows that the short-term repeatability of PWV measures is good but not homogenous across different devices and at different PWV values. These findings, obtained in patients at high cardiovascular risk, may be relevant when evaluating the prognostic importance of PWV.

Systolic time intervals assessed from analysis of the carotid pressure waveform

OBJECTIVE The timing of mechanical cardiac events is usually evaluated by conventional echocardiography as an index of cardiac systolic function and predictor of cardiovascular outcomes. We aimed to measure the systolic time intervals, namely the isovolumetric contraction time (ICT) and pre-ejection period (PEP), by arterial tonometry. APPROACH Sixty-two healthy volunteers (age 47  ±  17 years) and 42 patients with heart failure and reduced ejection fraction were enrolled (age 66  ±  14 years). Pulse waves were recorded at the carotid artery by arterial tonometry together with simultaneous aortic transvalvular flow by Doppler-echocardiography, synchronized by electrocardiographic gating. The ICT was determined from the time delay between the electrical R wave and the carotid pressure waveform, after adjustment for the pulse transit time from the aortic valve to the carotid artery site, estimated by an algorithm based on the carotid-femoral pulse wave velocity. The PEP was evaluated by adding the electrical QR duration to the ICT. MAIN RESULTS The ICT derived from carotid pulse wave analysis was closely related to that measured by echocardiography (r  =  0.90, p  <  0.0001), with homogeneous distribution in Bland-Altman analysis (mean difference and 95% confidence interval  =  0.2 from  -14.2 to 14.5 ms). ICT and PEP were higher in cardiac patients than in healthy volunteers (p  <  0.0001). The ratio between PEP and left ventricular ejection time was related to the ejection fraction measured with echocardiography (r  =  0.555, p  <  0.0001). SIGNIFICANCE The timing of electro-mechanical cardiac events can be reliably obtained from the carotid pulse waveform and carotid-femoral PWV, evaluated using arterial tonometry. Systolic time intervals assessed with this approach showed good agreement with measurements performed with conventional echocardiography and may represent a promising additional application of arterial tonometry.

NON-INVASIVE MEASUREMENT OF AORTIC PULSE WAVE VELOCITY: A COMPARATIVE EVALUATION OF EIGHT DEVICES

Objective: Several non-invasive devices purport to measure aortic pulse wave velocity (PWV), by applying different approaches and sensors, with the aim of evaluating cardiovascular risk. Purpose of this study is to compare the PWV measured by eight commercially available devices in patients with cardiovascular disease. Design and method: In this study, 102 patients (70% males, mean age 65 ± 13 years) were enrolled among those who were going to undertake an elective cardiac catheterization study. For each patient, the following device was used to non-invasively evaluate aortic PWV, in a random order: BPLab, Complior Analyse, Mobil-O-Graph, pOpmètre, PulsePen-ET, PulsePen-ETT and SphygmoCor. Data were analyzed by computing the coefficient of the correlation (r) and determination (r2) between measured values and with age of patients. Results: The mean blood pressure, heart rate and PWV measured in the population were: 102 ± 16 mmHg, 65 ± 12 s-1 and 11.2 ± 3.6 m/s. Comparative data are shown in Table 1. Devices evaluating carotid-femoral PWV (Complior Analyse, PulsePen-ET, PulsePen-ETT, SphygmoCor) presented a very strong agreement between each other (r > 0.80) and moderate correlation with the PWV measured by the Mobil-O-Graph (r 0.45 to 0.65), while a weak correlation was found between carotid-femoral PWV measurements and the BPLab or the pOpmètre (r < 0.30). A moderate-strong relationship was found between age and cf-PWV (r2 0.20 to 0.38), whereas PWV measured by pOpmètre and BPLab showed a weak correlation with age (r2 0.05 and 0.06 respectively). On the contrary, a very strong relationship was found between Mobil-O-Graph and age (r2 = 0.90). Conclusions: Devices measuring carotid-femoral PWV, considered the gold-standard measure for aortic PWV, present a very good agreement between each other, in our population of patients with cardiovascular disease. The Mobil-O-Graph, which estimates aortic PWV from age and blood pressure values, also present a good correlation with measures of carotid-femoral PWV. The two other measuring devices (BPLab, pOpmètre) does not provide a PWV measure in agreement with carotid-femoral PWV. Our results support the use of devices measuring carotid-femoral PWV for a proper and consistent evaluation of aortic PWV.

COMPARISON BETWEEN AORTIC PULSE WAVE VELOCITY MEASURED INVASIVELY AND NON-INVASIVELY BY EIGHT DIFFERENT DEVICES

Objective: Aortic pulse wave velocity (PWV) is the best indicator of aortic viscoelastic properties. Aim of this study is to investigate if invasively measured aortic PWV is accurately estimated by non-invasive methods which purport to assess it. Design and method: One-hundred and two patients (30% female, mean age 65 ± 13 years) planned to undertake a cardiac catheterization were enrolled in the study. Different non-invasive methods were evaluated for each subject by randomly alternating the following devices: BPLab, Complior Analyse, Mobil-O-Graph, pOpmètre, PulsePen-ET, PulsePen-ETT and SphygmoCor. Immediately after, aortic PWV was evaluated by aortic catheterization and simultaneous measurement of pressure wave above the aortic valve and at the aortic bifurcation (FS-Stiffcath). Invasive data were analyzed by proprietary software and compared with non-invasive PWV values by Bland-Altman analysis and paired parametric tests (for the whole population) and non-parametric tests (for quartiles of population according to PWV). Results: Devices evaluating carotid-femoral PWV (Complior Analyse, PulsePen-ET, PulsePen-ETT, SphygmoCor) and the Mobil-O-Graph presented a strong agreement with aortic invasive PWV (respectively, Pearson R = 0.64, 0.78, 0.71, 0.70, 0.66), while a moderate agreement was present for the BPLab and the pOpmètre (R = 0.23, 0.23). In the whole population, a significant underestimation of invasive PWV was present for Complior Analyse (−0.73 m/s, p = 0.016), SphygmoCor (−0.61 m/s, p = 0.024), Mobil-O-Graph (−1.01 m/s, p < 0.001) and pOpmètre (−1.55 m/s, p = 0.003). A tendency toward the overestimation of aortic PWV for lower PWV values and the underestimation of PWV for higher values was present for all devices, and was significant for the PulsePen-ET and the BPLab in the lowest quartile (PWV < 8.5 m/s, p < 0.05) and for Complior Analyse, SphygmoCor, BPLab and Mobil-O-Graph for the highest quartile (PWV > 13 m/s, p < 0.05). Conclusions: Devices measuring carotid-femoral PWV and the Mobil-O-Graph, which estimates aortic PWV from age and blood pressure values, present a good correlation with invasive aortic PWV in a large population with cardiovascular disease, while a less good agreement was found for other measuring devices (BPLab, pOpmètre). The underestimation of high PWV values may lead to erroneous estimation of cardiovascular risk by non-invasive devices.

Impaired central pulsatile hemodynamics in children and adolescents with Marfan syndrome

Background Marfan syndrome is characterized by aortic root dilation, beginning in childhood. Data about aortic pulsatile hemodynamics and stiffness in pediatric age are currently lacking. Methods and Results In 51 young patients with Marfan syndrome (12.0±3.3 years), carotid tonometry was performed for the measurement of central pulse pressure, pulse pressure amplification, and aortic stiffness (carotid‐femoral pulse wave velocity). Patients underwent an echocardiogram at baseline and at 1 year follow‐up and a genetic evaluation. Pathogenetic fibrillin‐1 mutations were classified between “dominant negative” and “haploinsufficient.” The hemodynamic parameters of patients were compared with those of 80 sex, age, blood pressure, and heart‐rate matched controls. Central pulse pressure was significantly higher (38.3±12.3 versus 33.6±7.8 mm Hg; P=0.009), and pulse pressure amplification was significantly reduced in Marfan than controls (17.9±15.3% versus 32.3±17.4%; P<0.0001). Pulse wave velocity was not significantly different between Marfan and controls (4.98±1.00 versus 4.75±0.67 m/s). In the Marfan group, central pulse pressure and pulse pressure amplification were independently associated with aortic diameter at the sinuses of Valsalva (respectively, β=0.371, P=0.010; β=−0.271, P=0.026). No significant difference in hemodynamic parameters was found according to fibrillin‐1 genotype. Patients who increased aortic Z‐scores at 1‐year follow‐up presented a higher central pulse pressure than the remaining (42.7±14.2 versus 32.3±5.9 mm Hg; P=0.004). Conclusions Central pulse pressure and pulse pressure amplification were impaired in pediatric Marfan syndrome, and associated with aortic root diameters, whereas aortic pulse wave velocity was similar to that of a general pediatric population. An increased central pulse pressure was present among patients whose aortic dilatation worsened at 1‐year follow‐up.

[PP.09.25] DEVICES FOR THE NON-INVASIVE ASSESSMENT OF AORTIC PULSE WAVE VELOCITY: EVALUATION OF SHORT-TERM REPEATABILITY

Objective: Aortic pulse wave velocity (PWV) is a validated indicator of central arterial stiffness and cardiovascular risk. We aimed to compare the repeatability of PWV measures obtained with non-invasive devices. Design and method: We evaluated the repeatibility of non-invasive measures of PWV, obtained with 4 devices measuring two-points carotid-femoral PWV (Complior, PulsePen ETT, PulsePen ET, SphygmoCor), and with 2 devices estimating PWV from the oscillometric cuff-derived brachial pulsewave (BPLab, Mobil-O-Graph). 102 patients planned to undertake a cardiac catheterization (age 65 ± 13 years, 70.6% males) were enrolled. Repeated measures of PWV were obtained with all devices in a single session, 15 minutes apart. Duplicate PWV and carotid-femoral PTT measurements were compared using different indices. Coefficients of variation (CV%) and their confidence intervals (CI) are reported. Results: Devices evaluating carotid-femoral PWV showed a good repeatability (CV%[CI] for Complior: 8.8[7.3–10.1]; PulsePen ETT: 8.0[6.2–9.5]; PulsePen ET: 5.8[4.9–6.6]; SphygmoCor: 9.5[7.7–11.0]), whereas the repeatability of PWV estimated by cuff-based devices was slightly higher (BPLab: 5.5[4.2–6.6], Mobil-O-Graph: 3.4[2.9–3.8]). A lower repeatability of carotid-femoral PWV was present for greater arterial stiffness values (CV%[CI] for PWV<10 m/s vs PWV>=10 m/s: Complior 7.0[5.4–8.3] vs 10.5[8.0–12.5], PulsePen ETT 6.3[3.6–8.1] vs 9.2[6.5–11.3], PulsePen ET 4.9[3.5–6.0] vs 6.5[5.3–7.6], Sphygmocor 8.5[5.7–10.6] vs 10.3[7.7–12.3]. No such difference was observed with cuff-based devices (BPLab 6.0[3.6–7.7] vs 5.1[3.5–6.4], Mobil-O-Graph 3.5[2.8–4.1] vs 3.2[2.6–3.7]). Differences between repeated PWV measurements were not correlated with concomitant blood pressure (R2: 0.005) or heart rate differences (R2: 0.013). Conclusions: Short-term repeatability of PWV measures was good but not homogenous among different devices. A greater repeatability was observed with cuff-based devices, compared to devices measuring carotid-femoral PWV. This is probably due for Mobil-O-Graph to the algorithm for PWV assessment, which considers age and mean blood pressure, and for BPLab to the automated editing procedure which eliminates highly variable PWV values. Repeatability of PWV is not influenced by blood pressure or heart rate concomitant changes. For carotid-femoral PWV, the repeatability of measures is lower for higher PWV values. These results could be usefully considered when assessing PWV in a clinical setting.

[OP.7C.05] AORTIC STIFFNESS AND PULSE WAVE ANALYSIS IN CHILDREN AND ADOLESCENTS WITH MARFAN SYNDROME.

Objective: Marfan syndrome (MFS) is an autosomal dominant genetic disorder characterized by aortic root dilation beginning in childhood. Aortic stiffness is increased in patients with MFS but data in pediatric age are lacking. Aim of this study was to evaluate aortic stiffness and pulse wave analysis in children and adolescents with MFS, compared to general pediatric population, and its association with aortic root diameters. Design and method: Fifty-two children with MFS (age: 12.0 ± 3.3, 5.6–17.5 years), identified according to 2010 Revised Ghent Criteria and without history of cardiovascular surgery were enrolled. Patients underwent a clinical evaluation and an echocardiography. Viscoelastic aortic properties were studied assessing carotid-femoral pulse wave velocity (PWV) and analysing central blood pressure waveform with carotid tonometry. Hemodynamic parameters of MFS patients were compared with those of 73 age, sex, mean blood pressure and heart rate matched controls. Results: Central pulse pressure (CPP) was significantly higher (38.2 ± 12.2 vs 33.6 ± 8.0 mmHg, p = 0.01) and pulse pressure amplification (PPA) was significantly reduced in MFS patients than controls (18.0 ± 15.1% vs 31.8 ± 20.3%, p < 0.0001). PWV was not significantly different between MFS and controls (4.98 ± 1.00 vs 4.79 ± 0.68 m/s). In MFS cohort, after correction for age, sex, mean arterial pressure and heart rate both CPP and PPA were significantly associated with aortic root diameter at the sinuses of Valsalva (CPP R = 0.393 p = 0.008; PPA R = −0.306 p = 0.041). Conclusions: CPP and PPA are increased in children with MFS and are related to aortic root diameter. PWV is similar to general pediatric population. Pulse wave analysis variables are able to predict aortic abnormalities better than PWV in children and adolescents with MFS.

[PP.LB02.03] IMPACT OF CUFF POSITIONING ON BLOOD PRESSURE MEASUREMENT ACCURACY. MAY A SPECIALLY DESIGNED CUFF MAKE A DIFFERENCE?

Objective: It is recommended that during blood pressure measurement cuff bladder should be placed with its centre above brachial artery. This study investigated the size of error related to incorrect cuff positioning using auscultatory and oscillometric devices, the latter coupled with specially designed IntelliWrap cuff. Design and method: In 57 subjects with a wide range of blood pressures and arm circumferences blood pressure was measured repeatedly with correctly placed mercury device (reference) and with test devices (auscultatory and oscillometric) with the cuff placed on the other arm in one of the following positions: correct, rotated by 90° medially (auscultatory only), by 90° laterally or by 180°. Additionally the different cuff positions of auscultatory device were tested using cuffs inappropriately small in relation to arm circumference (undercuffing; N = 33). Results: Systolic and diastolic blood pressures were unaffected by incorrect cuff position when using auscultatory cuff of appropriate size. Conversely, with undercuffing, blood pressure was overestimated when the auscultatory device cuff was displaced by 90° laterally (systolic/diastolic blood pressure differences: 4.9 ± 4.6/4.0 ± 4.6 mmHg, p < 0.01) or by 180° (3.9 ± 5.4/4.2 ± 5.1 mmHg, p < 0.01, see figure). Incorrect placement of the IntelliWrap cuff had no effect on the accuracy of the oscillometric measurements vs. correctly positioned cuff (difference <1.5 mmHg, NS). Figure. Bland-Altman and correlation plot for SBP with auscultatory measurement in correct position versus incorrect (180°) position. Data obtained with properly sized cuff (upper panel) and with too small cuff (lower panel) are shown. Figure. No caption available. Conclusions: Incorrect cuff positioning may introduce a systematic overestimation of auscultatory blood pressure values, in particular when the cuff is too small in relation to arm circumference. No such overestimation is present when using a specifically designed cuff, also able to ensure a complete arm coverage over a wide range of circumferences.

2D.02: ACCURACY OF ISOVOLUMETRIC CONTRACTION TIME OBTAINED BY CAROTID ARTERIAL TONOMETRY IN PATIENTS WITH CHRONIC LEFT VENTRICULAR FAILURE.

Objective: The Buckberg index (SEVR: subendocardial viability ratio) is considered a useful parameter for a non-invasive assessment of the relationship between subendocardial oxygen supply and demand. However, his classic calculation does not include the pre-ejection isovolumic contraction time in stroke work evaluation. The aim of our study was to evaluate the accuracy of the isovolumic contraction time obtained through the carotid pulse wave analysis, to be included in SEVR assessment. Design and method: In 35 patients (mean age ± SD = 66 ± 13 yrs) followed-up for chronic left ventricular systolic failure (EF = 32 ± 8%) with no significant valvular disease, the pressure curve in the common carotid artery by tonometer (PulsePen) and the aortic transvalvular flow by EchocardioDoppler (Philips-EnVisor C-HD) were acquired simultaneously. The synchronization of data acquisition was verified by comparison of the RR intervals in the ECG signals recorded simultaneously to the two methods. The isovolumic contraction time was separately calculated by considering both the delay between the beginning of the aortic flow wave obtained by EchocardioDoppler and the R wave of the corresponding ECG, and the delay between the foot of the pressure wave recorded in the carotid artery by tonometry compared with the R wave of the corresponding ECG. The latter was corrected by considering the delay between ascending aorta and carotid pulses, computed as a function of the carotid-femoral pulse wave speed and of the distance between the point of carotid pulse acquisition and the sternal notch. Results: The isovolumic contraction time computed by tonometry (68.8 ± 20.2 ms) was closely related to that measured with the EchocardioDoppler approach (68.8 ± 20.5 ms): y = 0.93x + 4.94; r2 = 0.93; p < 0.0001, with homogeneous distribution in Bland-Altman analysis (mean difference -0.1 ± 7.57 ms). The ratios between isovolumic contraction time and systolic ejection time separately obtained with the two methods (24.8 ± 8.3% and 22.2 ± 8.5%, respectively) were closely related: y = 0.93x + 1.67; r2 = 0.90 (mean difference -0.1 ± 2.7%). Conclusions: Thus, carotid arterial tonometry allows an accurate and simple assessment of the isovolumic contraction time, which can be employed to improve the assessment of SEVR by also considering the isovolumic contraction time in the stroke work evaluation.