Journal of Human Hypertension (2007) 21, 141–148 & 2007 Nature Publishing Group All rights reserved 0950-9240/07 $30.00 www.nature.com/jhh ORIGINAL ARTICLE Relationship between blood pressure parameters and pulse wave velocity in normotensive and hypertensive subjects: invasive study EJ Kim1, CG Park1, JS Park1, SY Suh1, CU Choi1, JW Kim1, SH Kim2, HE Lim1, SW Rha1, HS Seo1 and DJ Oh1 1Division of Cardiology, Department of Internal Medicine, Korea University Guro Hospital, Guro-gu, Seoul, Republic of Korea and 2Division of Cardiology, Department of Internal Medicine, Hallym University Medical Center, Youngdeungpo-dong, Seoul, Republic of Korea Blood pressure (BP) is one of the most important (MAP) showed significant association with PWV. To contributing factors to pulse wave velocity (PWV), a avoid multiple colinearity among SBP, PP and MAP, we classic measure of arterial stiffness. Although there performed multiple regression analysis predicting PWV have been many non-invasive studies to show the thrice. Age, DM and each BP were significantly and relation between arterial stiffness and BP, the results consistently correlated to PWV. In the first and third are controversial. The aim of this study is to evaluate modules, compared to age, SBP and MAP were less the role of BP as an influencing factor on PWV using strong predictors, respectively. However, PP was the invasive method. We observed 174 normotensive stronger predictor than age and DM in the second and untreated hypertensive subjects using coronary module. Lastly, we simultaneously forced MAP and PP angiography. Arterial stiffness was assessed through with other variables in the fourth multivariate analysis. aorto-femoral PWV by foot-to-foot velocity method Age, DM and PP remained significantly correlated with using fluid-filled system. And BP was measured by PWV, but the significance of MAP was lost. This is pressure wave at the right common femoral artery. From the first invasive study to suggest that PP has the univariate analysis, age, diabetes mellitus (DM), hyper- strongest correlation with PWV among a variety of BP tension, waist, waist-to-hip ratio, total cholesterol-to- parameters. high-density lipoprotein cholesterol ratio, systolic BP Journal of Human Hypertension (2007) 21, 141–148. (SBP), pulse pressure (PP) and mean arterial pressure doi:10.1038/sj.jhh.1002120; published online 30 November 2006 Keywords: pulse wave velocity; pulse pressure; large artery stiffness Introduction quantify stiffness, none of them is a gold standard, 16,17 1 but approximations. It is believed that the most Arterial stiffening increases with age and is asso- reliable (and still probably the best) measure of ciated with generalized atherosclerotic vascular 16 2–4 arterial stiffness is pulse wave velocity (PWV). disease. In population-based studies, aortic stiff- PWV is known to be associated with age, gender, ness is an independent predictor of cardiovascular blood pressure (BP), heart rate, salt intake, genetic outcomes after adjustment for traditional cardio- factors and others. Although BP is one of the vascular risk factors.4–7 Arterial stiffness has been 8–11 strongest factors influencing PWV, varying correla- shown to predict coronary artery disease and tion coefficients have been reported between the cardiovascular mortality in patients with essential 12 13,14 various PWV (aorta-leg-arm) and BP (systolic, hypertension, end-stage renal disease and diastolic, mean, pulse) using non-invasive meth- impaired glucose tolerance and diabetes mellitus 5,18–24 15 ods. This variation may be attributable, at least (DM). Although there are many measures to in part, to the inherent variability of both PWV and BP within and across individual subjects and also to Correspondence: Professor Dr CG Park, Division of Cardiology, the method of BP25 and PWV measurements. Department of Internal Medicine, Korea University Guro Hospital, The aim of this study is to elucidate the relation- 80 Guro-dong, Guro-gu, Seoul 152-703, Korea. ship between the various BP and aortic PWV E-mail: [email protected] Received 29 May 2006; revised 9 October 2006; accepted 11 through direct measurement of BP wave in the October 2006; published online 30 November 2006 artery using invasive method. Pulse wave velocity and pulse pressure EJ Kim et al 142 Materials and methods Measurement of haemodynamic variables Haemodynamic measurements were obtained from Study subjects patients in supine position. PWV was measured Investigations were carried out in the cardiology along the descending thoraco-abdominal aorta using department at the Korea University Guro Hospital, the foot-to-foot velocity method. Briefly, waveforms Seoul, Korea, between March 2002 and July 2003. To were obtained using a fluid-filled system (5Fr right obtain BP and aortic PWV through a direct pressure Judkin’s catheter) at the descending aorta, just below wave in the artery using invasive method, we the origin of left subclavian artery and the right selected the study population from those who common femoral artery (Figure 1). At each site, the underwent coronary angiography owing to chest pressure waves were simultaneously recorded with symptoms or preoperative evaluation. Of the 435 the electrocardiography using polygraph at the subjects who gave written informed consents for speed of 100 mm/s. We defined T1 as the time PWV measurement, 227 were receiving antihyper- interval from the starting point of QRS complex to tensive drug therapy and 17 were not clear of their the foot of pressure wave in the descending aorta medical history and, therefore, were excluded from and T2 as the time interval from the starting point of the study. Additional 17 patients were excluded QRS complex to the foot of pressure wave in the owing to one or more of the exclusion criteria; acute right common femoral artery. We measured T1 and myocardial infarction, cardiomyopathy, more than T2 from three different QRS complexes and pressure mild valvular disease, post-cardiac surgery, atrial waves, and computed the mean value to minimize fibrillation, aortic dissection and chronic renal the error. The time delay (T) was calculated as failure. Thus, 174 normotensive and untreated T2ÀT1 and the distance (D) was obtained by the hypertensive subjects (101 women; 73 men) were length of the catheter between the two recording observed. Their median age was 59.0712.03 years 7 sites. PWV was calculated by PWV ¼ D (m)/T (s). ( 1s.d.). The study was approved by the local ethics We measured SBP, DBP and pulse pressure (PP) by committee. pressure tracing method in the right common Hypertension was characterized with repeated femoral artery. Mean arterial pressure (MAP) was X measurements of 140 mm Hg systolic BP (SBP) obtained by the formula MAP ¼ DBP þ PP/3. or X90 mm Hg diastolic BP (DBP). DM was defined as a fasting blood glucose concentration X126 mg/dl or antihyperglycaemic drug treatment. Current Statistical analysis smoking was defined as having smoked the last Values were expressed as mean7one standard cigarette less than 1 month before coronary angio- deviation (s.d.). Differences in the mean value of graphy. PWV between the two groups were compared using Figure 1 The measurement of PWV. Catheter was located on the descending aorta just distal to left subclavian artery (upper left panel), and surface ECG and arterial pressure wave were recorded on a paper with speed 100 mm/s and T1 transit time was measured (upper right panel). Introducing sheath was located on the right common femoral artery (lower left panel) and T2 transit time was measured (lower right panel). Journal of Human Hypertension Pulse wave velocity and pulse pressure EJ Kim et al 143 a Student’s t-test for a parametric statistical test and three modules also included SBP, PP and MAP, Mann–Whitney’s test for a non-parametric analysis. separately. The results indicated that age and DM A Po0.05 was considered significant. Correlations were significantly and consistently correlated to between each of the measured variables and PWV PWV. And within each analysis, SBP, PP and MAP were assessed by Pearson’s correlation coefficient. also showed significant association with PWV. The The effects of traditional cardiovascular risk factors first and third module showed that age was the and haemodynamic variables on PWV were ana- strongest predictor among 3 significant correlating lysed by multivariate regression analysis. With the factors (age, DM, SBP or MAP). In the second variables selected from univariate analyses, we module, on the other hand, PP was the stronger performed the analysis thrice to avoid multiple predictor than age or DM (for age, b ¼ 0.233, colinearity among SBP, PP and MAP. Variables P ¼ 0.001; for DM, b ¼ 0.201, P ¼ 0.005; for PP, included in the first module were common ones, b ¼ 0.255, Po0.001). When we used age as an index such as age, DM, waist-to-hip ratio, total cholesterol- variable for comparison, this result indirectly de- to-high-density lipoprotein cholesterol (HDL-C) monstrated that PP was the only stronger predictor ratio and SBP. The second and third modules for PWV compared to age among BP parameters. included common variables along with PP and That is, PP showed the most potent correlation with MAP. We also performed the fourth multiple regres- PWV over a variety of BP parameters. sion analysis including the same non-haemo- Lastly, we included both MAP and PP with dynamic variables, PP and MAP with a test of other common independent variables in the fourth variance influence factor. Statistical analyses were multiple regression model (Table 4). Considering performed using the SPSS 10.0 software package continuous characteristic of MAP and pulsatile (SPSS Inc., Chicago, IL, USA). characteristic of PP, we tried to determine whether Results Table 1 Baseline clinical characteristics of study subjects The baseline clinical characteristics of the study population are presented in Table 1.