IPSIndian Journal of Pharmacology
Home  IPS  Feedback Subscribe Top cited articles Login 
Users Online : 1941 
Small font sizeDefault font sizeIncrease font size
Navigate Here
  Search
 
  
Resource Links
 »  Similar in PUBMED
 »  Search Pubmed for
 »  Search in Google Scholar for
 »Related articles
 »  Article in PDF (501 KB)
 »  Citation Manager
 »  Access Statistics
 »  Reader Comments
 »  Email Alert *
 »  Add to My List *
* Registration required (free)

 
In This Article
 »  Abstract
 » Introduction
 »  Materials and Me...
 » Results
 » Discussion
 » Conclusion
 »  References
 »  Article Figures
 »  Article Tables

 Article Access Statistics
    Viewed2478    
    Printed95    
    Emailed0    
    PDF Downloaded217    
    Comments [Add]    

Recommend this journal

 


 
 Table of Contents    
RESEARCH ARTICLE
Year : 2012  |  Volume : 44  |  Issue : 2  |  Page : 230-233
 

Non-invasive measurement of aortic pressure in patients: Comparing pulse wave analysis and applanation tonometry


Department of Clinical Pharmacology and Therapeutics, Nizam's Institute of Medical Sciences, Hyderabad, India

Date of Submission25-Mar-2011
Date of Decision10-Nov-2011
Date of Acceptance30-Dec-2011
Date of Web Publication16-Mar-2012

Correspondence Address:
M.U.R. Naidu
Department of Clinical Pharmacology and Therapeutics, Nizam's Institute of Medical Sciences, Hyderabad
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0253-7613.93855

Rights and Permissions

 » Abstract 

Objective: The aim of the present study was to validate and compare novel methods to determine aortic blood pressure non-invasively based on Oscillometric Pulse Wave Velocity (PWV) measurement using four limb-cuff pressure waveforms and two lead Electrocardiogram (ECG) with a validated tonometric pulse wave analysis system in patients.
Materials and Methods: After receiving the consent, in 49 patients with hypertension, coronary artery disease, diabetes mellitus, PWV, and central blood pressures were recorded in a randomised manner using both the oscillometric and tonometric devices. All recordings were performed 10 minutes after the patient lying comfortably in a noise-free temperature-controlled room. The test was performed between 09 am and 10 am after overnight fast. A minimum of three measurements were performed by the same skilled and trained operator. From the raw data obtained with two devices, software calculated the final vascular parameters.
Results: A total of 49 patients (8 women and 41 men), of mean age 40.5 years (range: 19-81 years) participated in the present study. After transforming the brachial pressures into aortic pressures, the correlation coefficient between the Aortic Systolic Pressure (ASP) values obtained with two methods was 0.9796 (P<0.0001). The mean difference between ASP with two methods was 0.3 mm Hg. Similarly, Aortic Diastolic Pressure (ADP) values obtained with two methods also correlated significantly with correlation coefficient of 0.9769 (P<0.0001). The mean difference of ADP was 0.2 mm Hg. In case of Aortic Pulse Pressure (APP), the mean difference was 0.1 mm Hg. All parameters of central aortic pressures obtained with two methods correlated significantly.
Conclusion: The new method of transforming the Carotid Femoral PWV (cfPWV) and brachial blood pressure values into aortic blood pressure values seems to be reasonably good. The significant correlation between the values obtained by tonometric device and oscillometric PWV method shows that the latter can be used non-invasively in patients to find the aortic pressure.


Keywords: Aortic pressure, arterial stiffness, non-invasive


How to cite this article:
Naidu M, Reddy C P. Non-invasive measurement of aortic pressure in patients: Comparing pulse wave analysis and applanation tonometry. Indian J Pharmacol 2012;44:230-3

How to cite this URL:
Naidu M, Reddy C P. Non-invasive measurement of aortic pressure in patients: Comparing pulse wave analysis and applanation tonometry. Indian J Pharmacol [serial online] 2012 [cited 2021 Aug 3];44:230-3. Available from: https://www.ijp-online.com/text.asp?2012/44/2/230/93855



 » Introduction Top


Recently, many studies have indicated that arterial stiffness is an independent predictor of increased morbidity and mortality for Cardiovascular Diseases (CVD) such as atherosclerosis [1] in general, and coronary artery disease, [2],[3],[4] peripheral artery disease, [5] chronic kidney disease, [6],[7] hypertension, [8],[9] cerebral stroke, [10] in particular. Being a reliable measure of arterial stiffness, Pulse Wave Velocity (PWV) has been suggested as a better marker of arterial stiffness. [11] With the awareness of arterial stiffness, clinicians have started adding measurement and treatment of underlying arterial stiffness in their clinical practice. [12] International healthcare societies like the European Society of Hypertension (ESH) and European Society of Cardiology (ESC) have included PWV measurement in their 2003 guidelines for management of hypertension. [13],[14]

The pulse pressure wave travels to the peripheral arteries and reflects back from the vasculature. In normal subjects, the reflected pulse pressure wave reaches the origin (aortic root) during the diastole phase of the cardiac cycle. This reflected pressure wave increases the Diastolic Pressure (ADP) gradient at the aortic root, which facilitates the Coronary Artery Blood Flow (CBF). But in the presence of arterial stiffness, the PWV is increased. As a consequence of this increased PWV, the pulse pressure wave is reflected prematurely and much early in a cardiac cycle. This leads to an elevation of the Aortic Systolic Pressure (ASP), decrease in ADP, and a rise in the Aortic Pulse Pressure (APP).

The rise in systolic pulse pressure is called as an augmentation pressure and its ratio to the APP is called as Augmentation Index (AIx). This augmentation of ASP leads to increased afterload and gives rise to the Left Ventricular Hypertrophy (LVH). Studies have shown that AIx correlates with the left ventricular mass in hypertensive patients. [15] Its association with an increased risk of stroke has also been suggested. As the role of increased in ASP and AIx is multifold, its measurement can be used as a surrogate and supplementary measure for arterial stiffness. [16]

Device and method, which can non-invasively measure both the PWV and Central blood pressure, will be of immense help for carrying out large population-based studies on arterial stiffness.

Since the aortic pressure values are deemed to be an outcome of the brachial pressure as well as the PWV, and PeriScope, which has a provision for recording brachial blood pressures and PWV, it is suggested that PeriScope may be capable of finding aortic pressures. In a unpublished pilot study at cardiac catheter laboratories during angiography, the values of invasive aortic pressures found by a fluid-filled catheter method were compared with brachial pressures and cfPWV obtained by PeriScope using multivariate statistical analysis. There was a good correlation in ASP and ADP and the regression equations applied were found to convert the brachial blood pressure and PWV values into equivalent aortic pressures. Thus, the aim of the present study was to validate a novel method determining aortic systolic, diastolic, pulse, augmentation pressures along with AIx based on an oscillometric method using four limb-cuff pressure waveforms and two lead ECG (PeriScope) with a validated tonometric Pulse Wave Analysis System (SphygmoCor, AtCor Medical Pty Ltd, West Ryde, Australia).


 » Materials and Methods Top


Study Population

Patients (with hypertension, CAD, and DM) attending the outpatient department of Nizam's Institute of Medical Sciences, Hyderabad, India, were enrolled in the study. The institutional ethics committee had approved the study protocol and informed consent was obtained before the measurements. Patients with atrial fibrillation or unstable clinical presentation were excluded from the study. A total of 49 patients participated in the present study; [Table 1] presents their demographic data.
Table 1: Demographic characteristics of study participants

Click here to view


In a randomised manner, PWV and central blood pressures were recorded using PeriScope as described earlier [17] and with Sphygmocor as per the procedure described in the instruction manual. The international recommendations for the measurement of arterial stiffness were respected. [18]

Periscope Method in Brief

PeriScope (Genesis Medical Systems, Hyderabad, India) is a validated [17] and tested medical device used to measure Brachial Ankle PWV (baPWV) and derives the Carotid Femoral PWV (cfPWV), which is equivalent to aortic PWV. This device uses four blood pressure cuffs to be tied around four limbs of the subjects. The cuffs are used to determine blood pressure values at the brachium and ankle of the respective limb by the oscillometric method. This method also records arterial pressure waveforms at predetermined cuff pressures. It has two-channel ECG leads to record ECG simultaneously. Based on simultaneous ECG and pressure waveform recording, PeriScope calculates the pulse wave velocities.

This method is devoid of any operator bias since it is fully automated and no operator handling of any probe is involved to record the waveforms. It does not require any special operative skills and can be carried out in any clinical setup just like an ECG recording. In a unpublished pilot study at cardiac catheter laboratories during angiography, the values of invasive aortic pressures found by a fluid-filled catheter method were compared with brachial pressures and cfPWV obtained by PeriScope using multivariate statistical analysis.

There was good correlation (ASP): r=0.9526, P<0.0001; ADP: r=0.9168, P<0.0001). Regression equations applied were found to convert the brachial blood pressure and PWV values into equivalent aortic pressures. These regression equations were introduced into the software of PeriScope to determine the aortic pressure values.

Recordings were taken 10 minutes after the patient lying comfortably in a noise-free temperature-controlled room. All tests were performed after overnight fast between 09 am and 10 am. On each occasion, a minimum of three measurements were taken by the same skilled and well-trained operator. From the raw data obtained by the two devices, the software calculated the final vascular parameters.

Statistics

The regression analysis was carried out to find the correlation between the measurements from the two devices. All values (demographics) are stated as mean and Standard Deviation (SD). Vascular data are also analysed using the methods presented by Bland-Altman. [19] Bland-Altman plots represent the data graphically and analyse the reproducibility of measurements according to different methods and the resulting corrections for SD. For statistical analysis, the GraphPad Instat software (Graphpad Inc, USA) was used.


 » Results Top


A total of 49 patients (8 women and 41 men), with mean age 40.5 years (range: 19-81 years) participated in the present study. Medical treatment was not withheld for the measurements. The mean blood pressure was systolic 134.6 ± 22.4 mm Hg and diastolic 76.3 ± 13.8 mm Hg.

Comparison of ASP, ADP, and APP

In the present study, after transforming the brachial into aortic pressures, the correlation between the ASP values obtained with two methods was highly significant: Correlation coefficient of 0.9796, P<0.0001. The mean difference between ASP with two methods was 0.3 mm Hg with SD of ±4.8 mm Hg [Figure 1]a.
Figure 1: The correlation of AoSysP and AoDiaP between the two methods is extremely significant

Click here to view


The AAMI 1992 standard [20] allows mean difference 5.0 mmHg with an SD of +/−8.0 mmHg between the standard method whereas Grade 'A' BHS protocol for Blood pressure measurements stipulates >60% readings in +/−5 mmHg, > 85% in +/−10 mmHg and >95% +/−15 mmHg. [21]

ADP values obtained by both methods correlated significantly with correlation coefficient of 0.9769 and P<0.0001. The mean difference of ADP was 0.2 mm Hg, with SD of ±2.87 mm Hg [Figure 1]b.

Estimated values of ASP and ADP by the two methods did not differ much and the difference from the mean was within 2 SD. The difference spread for Bland-Altman plots in [Figure 2]a and b for ASP and ADP show a satisfying spread of residues, respectively.
Figure 2: Bland– Altman plots of AoSysP and AoDiaP from both the methods show a good confirmation with each other

Click here to view


Comparison of Augmentation Pressure and AIx

For Aug P, the mean difference was −0.08 mm Hg, with an SD of ±4.9 mm Hg, and for AIx, the mean difference was −0.8% with SD ±11%. With AIx, being a ratio of Augmentation Pressure to pulse pressure multiplied by 100, and also sensitive to small changes, a higher SD is observed. [Figure 3]a and b illustrate the uniform distribution of the residuals.
Figure 3: Bland– Altman plots of AugP and AIx from both the methods show an even spread of residuals

Click here to view



 » Discussion Top


In our earlier study, using a non-invasive PWV measurement with an oscillometric method, we have established the role of arterial stiffness in various CVD. [11] Aortic pressure is a surrogate marker for arterial stiffness. It is important to treat patients with elevated arterial stiffness. Additional estimation of aortic blood pressure with this device will significantly enhance its usage in clinical practice. Since there is a relationship between arterial stiffness, brachial blood pressure, and central pressure, it is logical to explore the possibility of adding central blood pressure parameters to the existing device, which was successfully implemented.

Pulse wave velocity, which is a relevant indicator of arterial stiffness, can be measured non-invasively with a variety of automatic devices. A novel index for estimating arterial stiffness as 'QPV interval' Was determined by means of surface ECG and Doppler ultrasound of the brachial artery simultaneously . [22] This method is complex and requires a skilled operator.

The present method was further validated by comparing it with an established method of Generalized Transfer Function (GTF) using tonometry. The results obtained by the new PeriScope method were compared with that obtained by SphygmoCor, which is a widely used device with tonometry and GTF. Our study showed that the results obtained by these two methods correlated well, with no significant differences. The PeriScope method is able to calculate the central aortic pressure non-invasively which can be applied in routine clinical setting. Being simple and operator-independent, the new device can thus be useful in large population-based studies for identifying patients with a high risk of CVD mortality and morbidity associated with increased arterial stiffness. Since PeriScope is an automated device without any user intervention, the variations are significantly low.

The Bland-Altman analysis shows proper spreading of residues, and therefore no dependence on mean and difference. The analysis showed that the measurements were well within the tolerance band set up by the Association for the Advancement of Medical Instrumentation (AAMI). However, in case of AIx, though the mean difference is low, the SD is high. This could be attributed to the formula for AIx, in which the ratio of Augmentation Pressure to pulse pressure is multiplied by 100.

i.e. Augmentation Index=100*(Augmentation Pressure/Aortic Pulse Pressure), where Augmentation Pressure is the increase in Aortic Systolic pressure due to arterial stiffness. This determination of the AIx gives large scope of variation even with a small change in Augmentation Pressure or APP value.


 » Conclusion Top


With the new method of transforming the cfPWV and brachial blood pressure values into aortic pressure values appears reasonable. The good correlation between the results obtained by tonometric GTF method and oscillometric PWV method shows that the latter can be used non-invasively to find the aortic pressure in patients. However, more studies are warranted in large patient population.

 
 » References Top

1.Van Popele NM, Grobbee DE, Bots ML, Asmar R, Topouchian J, Reneman RS, et al. Association between arterial stiffness and atherosclerosis: The Rotterdam Study. Stroke 2001;32:454-60.  Back to cited text no. 1
[PUBMED]  [FULLTEXT]  
2.Kingwell BA, Waddell TK, Medley TL, Cameron JD, Dart AM. Large artery stiffness predicts ischemic threshold in patients with coronary artery disease. J Am Coll Cardiol 2002;40:773-9.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Weber T, Auer J, O'Rourke MF, Kvas E, Lassnig E, Berent R, et al. Arterial stiffness, wave reflections, and the risk of coronary artery disease. Circulation 2004;109:184-9.  Back to cited text no. 3
[PUBMED]  [FULLTEXT]  
4.Stefanadis C, Dernellis J, Tsiamis E, Stratos C, Diamantopoulos L, Michaelides A, et al. Aortic stiffness as a risk factor for recurrent acute coronary events in patients with ischaemic heart disease. Eur Heart J 2000;21:390-6.  Back to cited text no. 4
[PUBMED]  [FULLTEXT]  
5.Xu Y, Wu Y, Li J, Ma W, Guo X, Luo Y, et al. The predictive value of brachial-ankle pulse wave velocity in coronary atherosclerosis and peripheral artery diseases in urban Chinese patients. Hypertens Res 2008;31:1079-85.  Back to cited text no. 5
[PUBMED]  [FULLTEXT]  
6.Blacher J, Guerin AP, Pannier B, Marchais SJ, Safar ME, London GM. Impact of aortic stiffness on survival in end-stage renal disease. Circulation 1999;99:2434-9.  Back to cited text no. 6
[PUBMED]  [FULLTEXT]  
7.Chue CD, Townend JN, Steeds RP, Ferro CJ. Arterial stiffness in chronic kidney disease: Causes and consequences. Heart 2010;96:817-23.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.Safar ME, Levy BI, Struijker-Boudier H. Current perspectives on arterial stiffness and pulse pressure in hypertension and cardiovascular diseases. Circulation 2003;107:2864-9.  Back to cited text no. 8
[PUBMED]  [FULLTEXT]  
9.Boutouyrie P, Tropeano AI, Asmar R, Gautier I, Benetos A, Lacolley P, et al. Aortic stiffness is an independent predictor of primary coronary events in hypertensive patients: A longitudinal study. Hypertension 2002;39:10-5.  Back to cited text no. 9
[PUBMED]  [FULLTEXT]  
10.Laurent S, Katsahian S, Fassot C, Tropeano AI, Gautier I, Laloux B, et al. Aortic stiffness is an independent predictor of fatal stroke in essential hypertension. Stroke 2003;34:1203-6.  Back to cited text no. 10
[PUBMED]  [FULLTEXT]  
11.Shridhar Y, Naidu MU, Usharani P, Raju YS. Non-invasive evaluation of arterial stiffness in patients with increased risk of cardiovascular morbidity: A cross sectional study. Indian J Pharmacol 2007;39:294-8.  Back to cited text no. 11
    
12.Khoshdel AR, Carney SL, Nair BR, Gillies A. Better management of cardiovascular diseases by pulse wave velocity: Combining clinical practice with clinical research using evidence-based medicine. Clin Med Res 2007;5:45-52.  Back to cited text no. 12
[PUBMED]  [FULLTEXT]  
13.European Society of Hypertension-European Society of Cardiology guidelines for the management of arterial hypertension: Guidelines Committee. J Hypertens 2003;21:1011-53.  Back to cited text no. 13
    
14.2007 Guidelines for the Management of Arterial Hypertension The Task Force for the Management of Arterial Hypertension of the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC). J Hypertens 2007;25:1105-87.  Back to cited text no. 14
    
15.Marchais SJ, Guerin AP, Pannier BM, Levy BI, Safar ME, London GM. Wave reflections and cardiac hypertrophy in chronic uremia. Influence of body size. Hypertension 1993;22:876-83.  Back to cited text no. 15
[PUBMED]  [FULLTEXT]  
16.Laurent S, Cockcroft J, Van Bortel L, Boutouyrie P, Giannattasio C, Hayoz D, et al.; European Network for Non-invasive Investigation of Large Arteries. Expert consensus document on arterial stiffness: Methodological issues and clinical applications. Eur Heart J 2006;27:2588-605.  Back to cited text no. 16
[PUBMED]    
17.Naidu MU, Reddy BM, Yashmaina S, Patnaik AN, Rani PU. Validity and reproducibility of arterial pulse wave velocity measurement using new device with oscillometric technique: A pilot study. Biomed Eng Online 2005;4:49.  Back to cited text no. 17
[PUBMED]  [FULLTEXT]  
18.Van Bortel LM, Duprez D, Starmans-Kool MJ, Safar ME, Giannattasio C, Cockcroft J, et al. Clinical applications of arterial stiffness, task force III: Recommendations for user procedures. Am J Hypertens 2002;15:445-52.  Back to cited text no. 18
[PUBMED]    
19.Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;8:307-10.  Back to cited text no. 19
    
20.White WB, Berson AS, Robbins C, Jamieson MJ, Prisant LM, Roccella E, et al. National standard for measurement of resting and ambulatory blood pressures with automated sphygmomanometers. Hypertension 1993;21:504-9.  Back to cited text no. 20
[PUBMED]  [FULLTEXT]  
21.O'Brien E, Petrie J, Littler W, de Swiet M, Padfield PL, Altman DG, et al. The British Hypertension Society protocol for the evaluation of blood pressure measuring devices. J Hypertens 1993;11 Suppl 2:S43-62.  Back to cited text no. 21
    
22.Lee MY, Chu CS, Lee KT, Wu CM, Su HM, Lin SJ, et al. Validation of a new index for estimating arterial stiffness: Measurement of the QPV interval By Doppler ultrasound. Clin Cardiol 2006;8:345-51.  Back to cited text no. 22
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1]



 

Top
Print this article  Email this article
 

    

Site Map | Home | Contact Us | Feedback | Copyright and Disclaimer
Online since 20th July '04
Published by Wolters Kluwer - Medknow