IJCA-17871; No of Pages 3 International Journal of Cardiology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the Editor
Arterial function can be obtained by noninvasive finger pressure waveform Luciano Bernardi a,c,⁎,1, Daniel Gordin a,b,1, Milla Rosengård-Bärlund a,b, Ville-Petteri Mäkinen a, Roberto Mereu c, Alessandro DiToro c, Per-Henrik Groop a,b,d, on behalf of the FinnDiane Study Group a
Folkhälsan Institute of Genetics, Folkhälsan Research Center, Biomedicum Helsinki, Finland Division of Nephrology, Department of Medicine, Helsinki University Central Hospital, Finland Department of Internal Medicine, University of Pavia, IRCCS Policlinico S. Matteo, Pavia, Italy d The Baker IDI Heart and Diabetes Institute, Melbourne, Australia b c
a r t i c l e
i n f o
Article history: Received 13 February 2014 Accepted 29 March 2014 Available online xxxx Keywords: Augmentation index Blood pressure Pulse wave velocity Arterial function
Arterial function, expressed as augmentation index (AIx) and pulse wave velocity (PWV), predicts cardiovascular disease [1–4] and can be assessed by specific validated devices that subsequently record peripheral (carotid, radial, femoral) arterial waveforms. It could have practical implications to obtain the same information from easily applicable finger blood pressure monitors, which are commonly used to test autonomic function. Methods to obtain PWV from finger photoplethysmogram (PPG, [5]), or AIx from finger blood pressure [6] have been proposed. We tested whether reliable AIx and PWV data could be obtained from 5-minute recordings of noninvasive finger blood pressure (Finapres® 2300, Ohmeda, USA), and compared them with data simultaneously obtained from applanation tonometry (SphygmoCor®, Atcor, Australia). The protocol was approved by Helsinki University Ethical Committee, and written consent was obtained from each subject.
Abbreviations: AIx, Augmentation index; AIx-at, Augmentation index by applanation tonometry; AIx-f, Augmentation index by finger blood pressure (transfer function); AIxfbpc, Augmentation index by direct finger blood pressure contour; BMI, body mass index; DBP, diastolic blood pressure; DeltaTDVP, time interval between systolic and diastolic peaks of pulse waveform; PPG, finger photoplethysmogram; PWV, pulse wave velocity; PWV-at, pulse wave velocity by applanation tonometry; PWV-f, pulse wave velocity by finger blood pressure; SBP, systolic blood pressure; TF, Transfer function. ⁎ Corresponding author at: Folkhälsan Research Center, Biomedicum Helsinki, Haartmaninkatu 8, POB 63, FIN-00014 University of Helsinki, Finland. Tel.: +39 0382 502979, fax: +39 0382 529196. E-mail address: [email protected] (L. Bernardi). 1 Equal contribution.
To compare the two methods over a wide range of values we studied 46 consecutive unselected subjects of different ages (31 male, age 44 ± 16 yr, range 24–90, SBP: 129 ± 21 mm Hg, DBP: 74 ± 16 mm Hg, BMI: 24.8 ± 4.5 kg/m2), in supine position, under spontaneous breathing at rest. Two reliable measurements were obtained from 29 (AIx) and 31 (PWV) participants by applanation tonometry (AIx-at, PWV-at), and one measurement in the remaining subjects. When two values were obtained their average was used for comparison. Measurement of AIx by transfer function of finger blood pressure (AIx-f). In theory, the best method to derive noninvasive AIx is through simultaneous recording of peripheral noninvasive and central intra-arterial blood pressure, with subsequent evaluation of the mathematical relationship (transfer function, TF) linking these two signals together (TF1). The TF1 can then be used to reconstruct the central blood pressure profile and obtain the AIx [2–4,6,7]. This rather complex approach requires expensive high-fidelity micro-tip arterial catheters [7], but now this procedure can be simplified since our tonometer provided both the radial artery and the reconstructed central pressure waveforms (hence also TF1). Since the recordings of the radial artery and finger blood pressures were simultaneous, it was possible to obtain the TF that links the finger pressure to the central pressure (TF2) with the same degree of precision as for TF1. By using TF2, the AIx-f can then be calculated (on-line supplement). The obtained TF1 was almost identical in all subjects, confirming that a single TF1 was used by the Sphygmocor® to link the central and radial pressures [7] (Fig. 1). Measurement of AIx by direct analysis of finger blood pressure contour (AIx-fbpc). From the previous considerations it follows that the blood pressure profile alone provides all the necessary information to directly derive AIx. To verify this we normalised the averaged amplitude of the finger blood pressure pulses (first systolic peak = 100, lowest point = 0) and determined the location of the dicrotic notch. Then we calculated the normalised amplitude at 21 equally-spaced points from the first systolic peak to the dicrotic notch (on-line supplement). Each of the amplitudes was compared with the AIx-at by regression analysis. The regression equation linking the PWV-at with the point showing the best correlation was used to an AIx estimate: AIx-fbpc. Pulse wave velocity from the finger blood pressure. Millasseau [5] described and validated a simple technique to estimate the PWV from the PPG without the need of two separate recordings at two different
http://dx.doi.org/10.1016/j.ijcard.2014.03.179 0167-5273/© 2014 Published by Elsevier Ireland Ltd.
Please cite this article as: Bernardi L, et al, Arterial function can be obtained by noninvasive finger pressure waveform, Int J Cardiol (2014), http:// dx.doi.org/10.1016/j.ijcard.2014.03.179
2
L. Bernardi et al. / International Journal of Cardiology xxx (2014) xxx–xxx
sites. They measured the time interval (DeltaTDVP) between the systolic and diastolic peaks of the PPG waveform, which is caused by the delay between the direct (systolic) and the reflected (diastolic) waves, amd related to the PWV in the aorta (Millasseau-index = subject's height/DeltaTDVP). We used the same approach for the averaged finger pressure waveform (on-line supplement), and the regression equation linking the PWV-at with Millasseau-index was used to obtain a “finger-derived” PWV (PWV-f). Data are expressed as mean ± standard deviation (SD). Linear regression analysis between AIx-at and AIx-f or between AIx-at and AIxf-bpc, and then between PWV-at and PWV-f, was used to assess relationship between the established and new measurements. The agreement between the two methods (tonometry- and finger blood pressure-derived variables) was assessed by the Bland–Altman technique [8]. We reasoned that if the agreement (defined as SD of differences) between the two methods would be similar or better than the agreement of two subsequent measures of the validated tonometric method (both obtained at rest, within the same period of recordings), then the two methods would be equivalent. Measurements obtained by applanation tonometry (AIx-at) and finger blood pressure (AIx-f) were similar and highly correlated (r = 0.928, p b 0.0001). The correlation between AIx-at and AIx-fbpc was r = 0.909, p b 0.0001 (best correlation obtained at point 11, Fig. 2, Table 1 and Fig. 2 on-line supplement), and between PVWat and PWV-f was r = 0.726, p b 0.0001, slightly better than in [5]. The SD of the differences between AIx-at and AIx-f (+1.12 ± 6.14), AIx-at and AIx-fbpc (+1.30 ± 4.24) and PWV-at and PWV-f (+0.01 ± 1.09) were similar to the corresponding SD of differences between two subsequent AIx-at (+0.01 ± 6.89) or PWV-at measures (−0.05 ± 1.23) (p = ns, paired t test). Notably, these values were similar to previous tests of reproducibility/agreement [9,10]. Thus, indices of arterial function (AIx or PWV) can be reliably obtained from finger blood pressure profiles. AIx-f (calculated by TF) and AIxfbpc (by direct analysis of the systolic finger waveform) performed equally well. Since we did not compare noninvasive with invasive data, we could not assess whether the tonometric was “better” than
the “finger-derived” approach, but the latter might provide practical advantages. It is easier to obtain and allows continuous monitoring, which is essential for studying acute interventions (e.g. vascular adjustments during postural changes). Conversely, our tonometer limited the analysis to sequences of 6–8 good-quality beats, hence requiring some skill, with no guarantee that a given number of measurements could be obtained in a given time. This potential problem is further amplified when both aortic PWV and radial AIx need to be obtained, as three recording sites need to be examined one after the other. Finally, the finger blood pressure signal can be used to calculate other important markers of cardiovascular risk like baroreflex sensitivity, at no extra cost and with considerable time saving. Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.ijcard.2014.03.179. Conflict of interest PH Groop has gained lecture fees from Eli Lilly, Boehringer Ingelheim, Novartis, Genzyme, MSD, and Novo Nordisk, and he is an advisory board member of Boehringer Ingelheim (global), Novartis (global), Abbott (local), and Cebix (global). He has received grants from Eli Lilly, and Roche. The other authors declare that there is no duality of interest associated with this manuscript. Acknowledgments The skilled assistance of Anna Sandelin is gratefully acknowledged. The study was supported by the Folkhälsan Research Foundation, Helsinki University Central Hospital Research Funds (EVO), the Wilhelm and Else Stockmann Foundation, the Waldemar von Frenckell Foundation, the Liv och Hälsa Foundation, the Signe and Ane Gyllenberg Foundation, the Finnish Medical Society (Finska Läkaresällskapet), the Novo Nordisk Foundation and the Academy of Finland. LB. researched data, performed statistical analyses, wrote part of the analysis software and wrote the manuscript. D.G. researched data, performed statistical analyses, contributed to discussion, and reviewed and
Fig. 1. Average (±SD) transfer functions during simultaneous recordings of Finapres® and SphygmoCor®: central aortic pressure vs. radial artery pressure (SphygmoCor®), central pressure vs. finger pressure (Finapres®), and radial artery pressure (SphygmoCor®) vs. finger pressure (Finapres®). Note that the variability due to the different subjects is minimal, indicating that the transfer function linking each pair of the 3 waveforms is essentially the same. Individual differences are likely due to signal noise and different numbers of heart beats recorded (6– 9 for SphygmoCor® vs 250–450 for Finapres®).
Please cite this article as: Bernardi L, et al, Arterial function can be obtained by noninvasive finger pressure waveform, Int J Cardiol (2014), http:// dx.doi.org/10.1016/j.ijcard.2014.03.179
L. Bernardi et al. / International Journal of Cardiology xxx (2014) xxx–xxx
3
edited the manuscript. V-P.M. performed statistical analyses, wrote part of the analysis software, contributed to discussion, and reviewed and edited the manuscript. RM and AdT researched data, contributed to discussion, and reviewed and edited the manuscript. M.R-B. and P.-H.G. contributed to discussion and reviewed and edited the manuscript. P.-H.G. is the guarantor of the study.
References
Fig. 2. Correlations and regression equations between applanation tonometry- and finger pressure-derived AIx and PWV. P11: normalised amplitude of finger blood pressure contour at point 11 (where we found the highest correlation with AIx-at, see also Fig. 2, on-line supplement).
[1] Vlachopoulos C, Aznaouridis K, O'Rourke MF, Safar ME, Baou K, Stefanadis C. Prediction of cardiovascular events and all-cause mortality with central haemodynamics: a systematic review and meta-analysis. Eur Heart J 2010;31:1865–71. [2] Chirinos JA, Zambrano JP, Chakko S, et al. Aortic pressure augmentation predicts adverse cardiovascular events in patients with established coronary artery disease. Hypertension 2005;45:980–5. [3] Gordin D, Wadén J, Forsblom C, et al. Arterial stiffness and vascular complications in patients with type 1 diabetes: the Finnish Diabetic Nephropathy (FinnDiane) Study. Ann Med 2012;44:196–204. [4] Prince CT, Secrest AM, Mackey RH, Arena VC, Kingsley LA, Orchard TJ. Cardiovascular autonomic neuropathy, HDL cholesterol, and smoking correlate with arterial stiffness markers determined 18 years later in type 1 diabetes. Diabetes Care 2010;33:652–7. [5] Millasseau SC, Kelly RP, Ritter JM, Chowienczyk PJ. Determination of age-related increases in large artery stiffness by digital pulse contour analysis. Clin Sci 2002;103:371–7. [6] Karamanoglu M, Feneley MP. On-line synthesis of the human ascending aortic pressure pulse from the finger pulse. Hypertension 1997;30:1416–24. [7] Chen CH, Nevo E, Fetics B, et al. Estimation of central aortic pressure waveform by mathematical transformation of radial tonometry pressure. Validation of generalized transfer function. Circulation 1997;95:1827–36. [8] Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307–10. [9] Wilkinson IB, Fuchs SA, Jansen IM, et al. Reproducibility of pulse wave velocity and augmentation index measured by pulse wave analysis. J Hypertens 1998;16:2079–84. [10] Frimodt-Møller M, Nielsen AH, Kamper AL, Strandgaard S. Reproducibility of pulsewave analysis and pulse-wave velocity determination in chronic kidney disease. Nephrol Dial Transplant 2008;23:594–600.
Please cite this article as: Bernardi L, et al, Arterial function can be obtained by noninvasive finger pressure waveform, Int J Cardiol (2014), http:// dx.doi.org/10.1016/j.ijcard.2014.03.179
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the Editor
Arterial function can be obtained by noninvasive finger pressure waveform Luciano Bernardi a,c,⁎,1, Daniel Gordin a,b,1, Milla Rosengård-Bärlund a,b, Ville-Petteri Mäkinen a, Roberto Mereu c, Alessandro DiToro c, Per-Henrik Groop a,b,d, on behalf of the FinnDiane Study Group a
Folkhälsan Institute of Genetics, Folkhälsan Research Center, Biomedicum Helsinki, Finland Division of Nephrology, Department of Medicine, Helsinki University Central Hospital, Finland Department of Internal Medicine, University of Pavia, IRCCS Policlinico S. Matteo, Pavia, Italy d The Baker IDI Heart and Diabetes Institute, Melbourne, Australia b c
a r t i c l e
i n f o
Article history: Received 13 February 2014 Accepted 29 March 2014 Available online xxxx Keywords: Augmentation index Blood pressure Pulse wave velocity Arterial function
Arterial function, expressed as augmentation index (AIx) and pulse wave velocity (PWV), predicts cardiovascular disease [1–4] and can be assessed by specific validated devices that subsequently record peripheral (carotid, radial, femoral) arterial waveforms. It could have practical implications to obtain the same information from easily applicable finger blood pressure monitors, which are commonly used to test autonomic function. Methods to obtain PWV from finger photoplethysmogram (PPG, [5]), or AIx from finger blood pressure [6] have been proposed. We tested whether reliable AIx and PWV data could be obtained from 5-minute recordings of noninvasive finger blood pressure (Finapres® 2300, Ohmeda, USA), and compared them with data simultaneously obtained from applanation tonometry (SphygmoCor®, Atcor, Australia). The protocol was approved by Helsinki University Ethical Committee, and written consent was obtained from each subject.
Abbreviations: AIx, Augmentation index; AIx-at, Augmentation index by applanation tonometry; AIx-f, Augmentation index by finger blood pressure (transfer function); AIxfbpc, Augmentation index by direct finger blood pressure contour; BMI, body mass index; DBP, diastolic blood pressure; DeltaTDVP, time interval between systolic and diastolic peaks of pulse waveform; PPG, finger photoplethysmogram; PWV, pulse wave velocity; PWV-at, pulse wave velocity by applanation tonometry; PWV-f, pulse wave velocity by finger blood pressure; SBP, systolic blood pressure; TF, Transfer function. ⁎ Corresponding author at: Folkhälsan Research Center, Biomedicum Helsinki, Haartmaninkatu 8, POB 63, FIN-00014 University of Helsinki, Finland. Tel.: +39 0382 502979, fax: +39 0382 529196. E-mail address: [email protected] (L. Bernardi). 1 Equal contribution.
To compare the two methods over a wide range of values we studied 46 consecutive unselected subjects of different ages (31 male, age 44 ± 16 yr, range 24–90, SBP: 129 ± 21 mm Hg, DBP: 74 ± 16 mm Hg, BMI: 24.8 ± 4.5 kg/m2), in supine position, under spontaneous breathing at rest. Two reliable measurements were obtained from 29 (AIx) and 31 (PWV) participants by applanation tonometry (AIx-at, PWV-at), and one measurement in the remaining subjects. When two values were obtained their average was used for comparison. Measurement of AIx by transfer function of finger blood pressure (AIx-f). In theory, the best method to derive noninvasive AIx is through simultaneous recording of peripheral noninvasive and central intra-arterial blood pressure, with subsequent evaluation of the mathematical relationship (transfer function, TF) linking these two signals together (TF1). The TF1 can then be used to reconstruct the central blood pressure profile and obtain the AIx [2–4,6,7]. This rather complex approach requires expensive high-fidelity micro-tip arterial catheters [7], but now this procedure can be simplified since our tonometer provided both the radial artery and the reconstructed central pressure waveforms (hence also TF1). Since the recordings of the radial artery and finger blood pressures were simultaneous, it was possible to obtain the TF that links the finger pressure to the central pressure (TF2) with the same degree of precision as for TF1. By using TF2, the AIx-f can then be calculated (on-line supplement). The obtained TF1 was almost identical in all subjects, confirming that a single TF1 was used by the Sphygmocor® to link the central and radial pressures [7] (Fig. 1). Measurement of AIx by direct analysis of finger blood pressure contour (AIx-fbpc). From the previous considerations it follows that the blood pressure profile alone provides all the necessary information to directly derive AIx. To verify this we normalised the averaged amplitude of the finger blood pressure pulses (first systolic peak = 100, lowest point = 0) and determined the location of the dicrotic notch. Then we calculated the normalised amplitude at 21 equally-spaced points from the first systolic peak to the dicrotic notch (on-line supplement). Each of the amplitudes was compared with the AIx-at by regression analysis. The regression equation linking the PWV-at with the point showing the best correlation was used to an AIx estimate: AIx-fbpc. Pulse wave velocity from the finger blood pressure. Millasseau [5] described and validated a simple technique to estimate the PWV from the PPG without the need of two separate recordings at two different
http://dx.doi.org/10.1016/j.ijcard.2014.03.179 0167-5273/© 2014 Published by Elsevier Ireland Ltd.
Please cite this article as: Bernardi L, et al, Arterial function can be obtained by noninvasive finger pressure waveform, Int J Cardiol (2014), http:// dx.doi.org/10.1016/j.ijcard.2014.03.179
2
L. Bernardi et al. / International Journal of Cardiology xxx (2014) xxx–xxx
sites. They measured the time interval (DeltaTDVP) between the systolic and diastolic peaks of the PPG waveform, which is caused by the delay between the direct (systolic) and the reflected (diastolic) waves, amd related to the PWV in the aorta (Millasseau-index = subject's height/DeltaTDVP). We used the same approach for the averaged finger pressure waveform (on-line supplement), and the regression equation linking the PWV-at with Millasseau-index was used to obtain a “finger-derived” PWV (PWV-f). Data are expressed as mean ± standard deviation (SD). Linear regression analysis between AIx-at and AIx-f or between AIx-at and AIxf-bpc, and then between PWV-at and PWV-f, was used to assess relationship between the established and new measurements. The agreement between the two methods (tonometry- and finger blood pressure-derived variables) was assessed by the Bland–Altman technique [8]. We reasoned that if the agreement (defined as SD of differences) between the two methods would be similar or better than the agreement of two subsequent measures of the validated tonometric method (both obtained at rest, within the same period of recordings), then the two methods would be equivalent. Measurements obtained by applanation tonometry (AIx-at) and finger blood pressure (AIx-f) were similar and highly correlated (r = 0.928, p b 0.0001). The correlation between AIx-at and AIx-fbpc was r = 0.909, p b 0.0001 (best correlation obtained at point 11, Fig. 2, Table 1 and Fig. 2 on-line supplement), and between PVWat and PWV-f was r = 0.726, p b 0.0001, slightly better than in [5]. The SD of the differences between AIx-at and AIx-f (+1.12 ± 6.14), AIx-at and AIx-fbpc (+1.30 ± 4.24) and PWV-at and PWV-f (+0.01 ± 1.09) were similar to the corresponding SD of differences between two subsequent AIx-at (+0.01 ± 6.89) or PWV-at measures (−0.05 ± 1.23) (p = ns, paired t test). Notably, these values were similar to previous tests of reproducibility/agreement [9,10]. Thus, indices of arterial function (AIx or PWV) can be reliably obtained from finger blood pressure profiles. AIx-f (calculated by TF) and AIxfbpc (by direct analysis of the systolic finger waveform) performed equally well. Since we did not compare noninvasive with invasive data, we could not assess whether the tonometric was “better” than
the “finger-derived” approach, but the latter might provide practical advantages. It is easier to obtain and allows continuous monitoring, which is essential for studying acute interventions (e.g. vascular adjustments during postural changes). Conversely, our tonometer limited the analysis to sequences of 6–8 good-quality beats, hence requiring some skill, with no guarantee that a given number of measurements could be obtained in a given time. This potential problem is further amplified when both aortic PWV and radial AIx need to be obtained, as three recording sites need to be examined one after the other. Finally, the finger blood pressure signal can be used to calculate other important markers of cardiovascular risk like baroreflex sensitivity, at no extra cost and with considerable time saving. Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.ijcard.2014.03.179. Conflict of interest PH Groop has gained lecture fees from Eli Lilly, Boehringer Ingelheim, Novartis, Genzyme, MSD, and Novo Nordisk, and he is an advisory board member of Boehringer Ingelheim (global), Novartis (global), Abbott (local), and Cebix (global). He has received grants from Eli Lilly, and Roche. The other authors declare that there is no duality of interest associated with this manuscript. Acknowledgments The skilled assistance of Anna Sandelin is gratefully acknowledged. The study was supported by the Folkhälsan Research Foundation, Helsinki University Central Hospital Research Funds (EVO), the Wilhelm and Else Stockmann Foundation, the Waldemar von Frenckell Foundation, the Liv och Hälsa Foundation, the Signe and Ane Gyllenberg Foundation, the Finnish Medical Society (Finska Läkaresällskapet), the Novo Nordisk Foundation and the Academy of Finland. LB. researched data, performed statistical analyses, wrote part of the analysis software and wrote the manuscript. D.G. researched data, performed statistical analyses, contributed to discussion, and reviewed and
Fig. 1. Average (±SD) transfer functions during simultaneous recordings of Finapres® and SphygmoCor®: central aortic pressure vs. radial artery pressure (SphygmoCor®), central pressure vs. finger pressure (Finapres®), and radial artery pressure (SphygmoCor®) vs. finger pressure (Finapres®). Note that the variability due to the different subjects is minimal, indicating that the transfer function linking each pair of the 3 waveforms is essentially the same. Individual differences are likely due to signal noise and different numbers of heart beats recorded (6– 9 for SphygmoCor® vs 250–450 for Finapres®).
Please cite this article as: Bernardi L, et al, Arterial function can be obtained by noninvasive finger pressure waveform, Int J Cardiol (2014), http:// dx.doi.org/10.1016/j.ijcard.2014.03.179
L. Bernardi et al. / International Journal of Cardiology xxx (2014) xxx–xxx
3
edited the manuscript. V-P.M. performed statistical analyses, wrote part of the analysis software, contributed to discussion, and reviewed and edited the manuscript. RM and AdT researched data, contributed to discussion, and reviewed and edited the manuscript. M.R-B. and P.-H.G. contributed to discussion and reviewed and edited the manuscript. P.-H.G. is the guarantor of the study.
References
Fig. 2. Correlations and regression equations between applanation tonometry- and finger pressure-derived AIx and PWV. P11: normalised amplitude of finger blood pressure contour at point 11 (where we found the highest correlation with AIx-at, see also Fig. 2, on-line supplement).
[1] Vlachopoulos C, Aznaouridis K, O'Rourke MF, Safar ME, Baou K, Stefanadis C. Prediction of cardiovascular events and all-cause mortality with central haemodynamics: a systematic review and meta-analysis. Eur Heart J 2010;31:1865–71. [2] Chirinos JA, Zambrano JP, Chakko S, et al. Aortic pressure augmentation predicts adverse cardiovascular events in patients with established coronary artery disease. Hypertension 2005;45:980–5. [3] Gordin D, Wadén J, Forsblom C, et al. Arterial stiffness and vascular complications in patients with type 1 diabetes: the Finnish Diabetic Nephropathy (FinnDiane) Study. Ann Med 2012;44:196–204. [4] Prince CT, Secrest AM, Mackey RH, Arena VC, Kingsley LA, Orchard TJ. Cardiovascular autonomic neuropathy, HDL cholesterol, and smoking correlate with arterial stiffness markers determined 18 years later in type 1 diabetes. Diabetes Care 2010;33:652–7. [5] Millasseau SC, Kelly RP, Ritter JM, Chowienczyk PJ. Determination of age-related increases in large artery stiffness by digital pulse contour analysis. Clin Sci 2002;103:371–7. [6] Karamanoglu M, Feneley MP. On-line synthesis of the human ascending aortic pressure pulse from the finger pulse. Hypertension 1997;30:1416–24. [7] Chen CH, Nevo E, Fetics B, et al. Estimation of central aortic pressure waveform by mathematical transformation of radial tonometry pressure. Validation of generalized transfer function. Circulation 1997;95:1827–36. [8] Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1:307–10. [9] Wilkinson IB, Fuchs SA, Jansen IM, et al. Reproducibility of pulse wave velocity and augmentation index measured by pulse wave analysis. J Hypertens 1998;16:2079–84. [10] Frimodt-Møller M, Nielsen AH, Kamper AL, Strandgaard S. Reproducibility of pulsewave analysis and pulse-wave velocity determination in chronic kidney disease. Nephrol Dial Transplant 2008;23:594–600.
Please cite this article as: Bernardi L, et al, Arterial function can be obtained by noninvasive finger pressure waveform, Int J Cardiol (2014), http:// dx.doi.org/10.1016/j.ijcard.2014.03.179
