Journal of Hypertension 2006, 24: Received 27 September 2005 Revised 23 February 2006 Accepted 27 February 2006

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1 Original article 1319 Systolic and diastolic hypertension impair endothelial vasodilatory function in different types of vessels in the elderly: the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study Lars Lind Background Endothelium-dependent vasodilation (EDV) is known to be impaired in middle-aged hypertensive individuals, but less is known regarding hypertension in the elderly. Objective In the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS) study, different techniques to evaluate EDV in resistance and conduit arteries were applied in elderly subjects and were related to the type of hypertension. Design and methods In this population-based study, 1016 subjects aged 70 years were evaluated by the invasive forearm technique with acetylcholine (EDV), brachial artery ultrasound to assess flow-mediated dilatation (FMD) and pulse wave analysis with a beta-2 receptor agonist challenge, terbutaline. Those without antihypertensive treatment were divided into three groups: normotensive individuals (n U 256), and those with isolated systolic hypertension (n U 309) or combined systolic/diastolic hypertension (n U 79). Results Compared with normotensive individuals, EDV was reduced in those with combined systolic/diastolic hypertension only (P U ), whereas FMD was mainly reduced in those with isolated systolic hypertension (P U 0.013). Furthermore, in regression analysis, EDV was related to diastolic blood pressure only (r US0.10, P U 0.017), whereas FMD was mainly related to systolic blood pressure (r U S0.13, P U ). The pulse wave-based method to analyse vasoreactivity was not consistently affected by hypertension. Conclusions In elderly subjects, systolic hypertension mainly impairs conduit artery endothelial vasodilatory function, whereas diastolic hypertension mainly induces dysfunction in resistance arteries. J Hypertens 24: Q 2006 Lippincott Williams & Wilkins. Journal of Hypertension 2006, 24: Keywords: blood pressure, endothelium, hypertension, ultrasound, vasodilation Department of Medicine, Uppsala University Hospital, Uppsala and AstraZeneca R&D, Mölndal, Sweden Correspondence and requests for reprints to Lars Lind, MD, Department of Medicine, University Hospital, Uppsala, Sweden Tel: ; lars.lind@medsci.uu.se Received 27 September 2005 Revised 23 February 2006 Accepted 27 February 2006 Introduction Hypertension is one of the major cardiovascular risk factors increasing the risk of myocardial infarction and stroke [1,2]. During the past two decades much attention has also been paid to the function of the endothelium, as endothelial dysfunction early was shown to induce atherosclerosis in animal models [3], and later was shown to predict cardiovascular events in human patient populations [4,5]. Two different methods to assess peripheral artery endothelium-dependent vasodilation (EDV) are now widely used in clinical research: the invasive forearm model using acetylcholine infusion in the brachial artery, which mainly evaluates vasodilation in resistance arteries, and the brachial artery ultrasound technique using hyperemia to induce flow-mediated dilatation (FMD) in a conduit artery. Both of these techniques have been reported to be related to the major cardiovascular risk factors [6 15], but the techniques in themselves do not seem to be closely related at the individual level [16,17]. A third non-invasive technique based on pulse wave analysis and vasodilation with a beta-2 agonist have recently been validated by different groups [18 21]. This technique mainly induces vasodilation in resistance vessels. Impaired EDV evaluated with this technique has been described in patients with coronary heart disease, hypercholesterolemia or diabetes [18 20]. A number of studies using both EDV and FMD have shown impairment in EDV in subjects with essential hypertension [6,7,22 34], although some investigators could not show any impairment [35 37]. The majority of these investigations have been performed in middleaged hypertensive individuals and only a few studies have addressed endothelial function in the elderly, an age group in which isolated systolic hypertension is the most common form of hypertension. Furthermore, ß 2006 Lippincott Williams & Wilkins

2 1320 Journal of Hypertension 2006, Vol 24 No 7 although it has been reported that EDV and FMD are not related and might therefore contain different information on endothelial function [16,17], few studies have used more than one technique to assess EDV in the same study. The Prospective Investigation of the Vasculature in Uppsala Seniors (the PIVUS study) was initiated with the primary aim of evaluating the predictive power of three different tests of EDV described above to predict future cardiovascular events in more than 1000 subjects aged 70 years living in the community of Uppsala, Sweden. As this primary aim will demand a long followup period, we here report a secondary aim of the study. We divided subjects with increased blood pressure without any antihypertensive treatment into three groups: normotensive individuals, and those with isolated systolic hypertension, or combined systolic/diastolic hypertension, and evaluated the three methods of EDV in these groups. The hypothesis was that isolated systolic hypertension and combined systolic/diastolic hypertension might affect EDV in resistance vessels and in a conduit artery differently. Materials Subjects All individuals aged 70 years living in the community of Uppsala, Sweden were eligible. The individuals were chosen from the register of community living and were invited in a randomized order from the start of the study in April 2001 to the last included individual in June The individuals received an invitation by letter within 1 month of their 70th birthday in order to standardize for age. Of the 2025 individuals invited, 1016 subjects were investigated, giving a participation rate of 50.1%. The study was approved by the Ethics Committee of the University of Uppsala, and the participants gave informed consent. Baseline investigation The participants were asked to answer a questionnaire about their medical history, smoking habits and regular medication. All subjects were investigated in the morning after an overnight fast. No medication or smoking was allowed after midnight. After recordings of height, weight, abdominal and hip circumference, an arterial cannula was inserted in the brachial artery for blood sampling and later regional infusions of vasodilators. During the investigation, the subjects were supine in a quiet room maintained at a constant temperature. Blood pressure was measured by a calibrated mercury sphygmomanometer in the non-cannulated arm to the nearest mmhg after at least 30 min of rest and the Table 1 Basic characteristics, major cardiovascular risk factors and measures of endothelium-dependent vasodilation in the total sample Total sample n 1016 Women (%) 50.2 Height (cm) Weight (kg) Waist circumferernce (cm) BMI (kg/m 2 ) Waist/hip ratio SBP (mmhg) DBP (mmhg) Heart rate (beats/min) Serum cholesterol (mmol/l) LDL-cholesterol (mmol/l) HDL-cholesterol (mmol/l) Serum triglycerides (mmol/l) Fasting blood glucose (mmol/l) Current smoking (%) 11 EDV (%) 459 ( ) EIDV (%) 328 ( ) FMD (%) 4.4 ( ) Change in RI (%) Change in AIx (%) AIx, Augmentation index; BMI, body mass index; DBP, diastolic blood pressure; EDV, endothelium-dependent vasodilation (invasive forearm technique); EIDV, endothelium-independent vasodilation (invasive forearm technique); FMD, flowmediated dilatation; HDL, high-density lipoprotein; LDL, low-density lipoprotein; RI, reflectance index; SBP, systolic blood pressure. Means are given SD or as median and 10th and 90th percentiles in parenthesis. average of three recordings was used. Lipid variables and fasting blood glucose were measured by standard laboratory techniques. Characteristics of the sample are given in Tables 1 and 2. Table 2 Self-reported history of cardiovascular disorders and regular drug intake given in percentage in the investigated sample and in 100 non-attendees Total investigated sample Not attending n Myocardial infarction Stroke Angina pectoris CABG/PTCA Congestive heart failure Diabetes Any regular drug Any cardiovascular drug Any antihypertensive medication Beta-blockers Calcium antagonists Diuretics ACE inhibitors Angiotensin II blockers Nitroglycerine Digoxin Statins Other antihyperlipidemic drugs Insulin Oral antidiabetic drugs Warfarin Aspirin/clopidogrel Other antiarrythmic drugs ACE, Angiotensin-converting enzyme; CABG, coronary artery bypass grafting; PTCA, percutaneous transluminal coronary angioplasty.

3 Endothelial function and blood pressure Lind 1321 As the participation rate in this cohort was only 50%, we carried out an evaluation of cardiovascular disorders and medications in 100 consecutive individuals who were invited to the study, but denied participation. The prevalences of cardiovascular drug intake, a history of myocardial infarction, coronary revascularization, antihypertensive medication, statin use and insulin treatment were similar to those in the investigated sample, whereas the prevalences of diabetes, congestive heart failure and stroke tended to be higher among the non-participants (see Table 2). Methods The invasive forearm technique Forearm blood flow (FBF) was measured by venous occlusion plethysmography (Elektromedicin, Kullavik, Sweden). A mercury in-silastic strain-gauge was placed at the upper third of the forearm, which rested comfortably slightly above the level of the heart. The straingauge was connected to a calibrated plethysmograph. Venous occlusion was achieved by a blood pressure cuff applied proximal to the elbow and inflated to 50 mmhg by a rapid cuff inflator. Evaluations of FBF were made by calculations of the mean of at least five consecutive recordings. An arterial cannula was placed in the brachial artery. No more than one attempt to insert the cannula in each arm was allowed. Resting FBF was measured 30 min after cannula insertion. After evaluation of resting FBF, local intra-arterial drug infusions were given during 5 min for each dose, with a 20 min washout period between the drugs. The infused dosages were 25 and 50 mg/min for acetylcholine (Clin-Alpha, Switzerland) to evaluate EDV and 5 and 10 mg/min for sodium nitroprusside (SNP; Nitropress; Abbot, UK) to evaluate endothelium-independent vasodilation (EIDV). The dosages of these drugs were chosen to result in FBF on the steep part of the dose response curve without giving systemic effects. The drugs were given in a random order at a maximal rate of 1 ml/min. In the present study, only data from the highest doses of acetylcholine and SNP were used. EDV was defined as FBF during infusion of 50 mg/min of acetylcholine minus resting FBF divided by resting FBF. EIDV was defined as FBF during the infusion of 10 mg/min of SNP minus resting FBF divided by resting FBF. We did not use any distal cuff to exclude hand circulation during measurements of EDV to avoid discomfort and increase sympathetic drive caused by this procedure [38]. We have previously shown that almost identical results are obtained when FBF is measured with or without a hand cuff in the resting state, or during the infusion of SNP or another muscarinic receptor agonist, methacholine [38]. Our own pilot studies showed that this is also valid during acetylcholine-mediated vasodilation, in which no difference in FBF was seen and the correlation coefficient between cuff versus no cuff measurements was EDV and EIDV could successfully be evaluated in 87% of the participants of the study. Cannulation of the artery was not performed in the 3% of subjects who were on regular treatment with warfarin, and in another 10% cannulation failed. We have previously shown the reproducibility (coefficient of variation; CV) for EDV and EIDV to be 8 10% [38]. The brachial artery ultrasound technique The brachial artery was assessed by external B-mode ultrasound imaging 2 3 cm above the elbow (Acuson XP128 with a 10 MHz linear transducer; Acuson Mountain View, California, USA), according to the recommendations of the International Brachial Artery Task Force [39]. Depths and gains settings were optimized to identify the lumen to vessel wall interface. The subject rested in the supine position for at least 30 min before the first scan and remained supine during the evaluation. Blood flow increase was induced by the inflation of a pneumatic cuff placed around the forearm to a pressure at least 50 mmhg above systolic blood pressure (SBP). When the cuff was rapidly deflated 5 min later, the artery was scanned continuously for 90 s and recorded on a super-vhs videotape for later analysis of the diameter in end-diastole. FMD was defined as the maximal brachial artery diameter recorded between 30 and 90 s after cuff release minus diameter at rest divided by the diameter at rest. FMD was successfully evaluated in 97% of the participants. In the remaining 3%, only suboptimal images were obtained, not allowing proper analysis. We have previously shown the reproducibility (CV) to be 3% for baseline brachial artery diameter and 29% for FMD [16]. Pulse wave analysis A micromanometer-tipped probe (Sphygmocor; Pulse Wave Medical Ltd., Sydney, Australia) was applied to the surface of the skin overlying the radial artery, and the peripheral radial pulse wave was continuously recorded. The mean values of approximately 10 pulse waves were used for analyses. Recordings were regarded as satisfactory if the variations in the systolic peak and the diastolic peak were 5% or below. Only three attempts to achieve a satisfactory recording were allowed. The maximal systolic peak and the reflected waves were identified by the calculations of the first and second derivative of the pulse curve. After a baseline recording, terbutaline was subcutaneously administered (0.25 mg in the upper part of the arm) and a re-evaluation of the pulse wave was performed

4 1322 Journal of Hypertension 2006, Vol 24 No 7 after 15 and 20 min. We had previously found that the maximal alterations in the pulse waveform occurred after 15 min in young healthy subjects [21], but we also performed a measurement after 20 min in this sample of elderly subjects. The maximal change occurring at either 15 or 20 min was thus used for calculations. In previous studies, the augmentation index (AIx) derived from the first reflected wave in systole was used [18,19]. We and others have previously validated change in the relative height of the first diastolic reflected wave (the reflection index; RI) [20,21], and found this index to be closely related to the change in AIx after terbutaline. Here, we report the changes in RI and AIx as relative changes from baseline after terbutaline. A large reduction of the pulse wave indices thus indicates a good response. The changes in the RI and AIx could successfully be evaluated in 86% of the sample. In 5% of the subjects, the pulse waves showed too high variability as a result of atrial fibrillation or frequent ectopic beats, and in 9% of the subjects the reflected waves could not be detected in a reproducible way. We have previously shown the reproducibility (CV) for the changes in RI and AIx to be 9.4 and 16%, respectively [21]. The three different techniques to evaluate EDV were performed in the order described above. Three technicians were employed at the laboratory, but each vasodilatory technique was performed and evaluated by one unique technician throughout the study, who was not aware of the results of the other techniques or any clinical data. Statistics Non-normally distributed variables, such as EDV and FMD, were log-transformed in order to achieve a normal distribution. Differences between groups regarding continuous variables were evaluated by means of factorial analysis of variance. Linear regression analysis was applied to evaluate relationships between pairs of variables. Two-tailed significance values were given with P < 0.05 regarded as significant. The statistical programme StatView (SAS Inc., Cary, North Carolina, USA) was used for calculations. Results Of the total sample, 32% of the subjects were on regular antihypertensive treatment (median duration of hypertension 10 years, range years) and another 38% showed blood pressure greater than 139/89 mmhg. Seventy per cent of the sample was thus considered to be hypertensive. As could be seen in Fig. 1 and Table 3, FMD, but not the other measures of EDV, was reduced in hypertensive Fig FMD (%) Normotensives Hypertensives Flow-mediated vasodilation (FMD) in hypertensive and normotensive individuals given in median, 10th, 25th, 75th and 90th percentiles. P ¼ for difference between groups. subjects in the total sample (P ¼ ). This difference between the groups for FMD was still significant after adjustment for the other major cardiovascular risk factors: smoking, diabetes, obesity and hypercholesterolemia (P ¼ ). No interaction was seen between sex and hypertension regarding FMD (P ¼ 0.56). Within the hypertensive group, EDV and the change in RI were significantly lower in those on hypertensive treatment when compared with those without (EDV median 420% in those with antihypertensive treatment compared with 480% in those without, P ¼ , change in RI Table 3 Basic characteristics, major cardiovascular risk factors and measures of endothelium-dependent vasodilation in the total sample split into hypertenive and normotensive individuals Hypertensives Normotensives P value n SBP (mmhg) DBP (mmhg) Heart rate (beats/min) Pulse pressure (mmhg) Diabetes (%) Obesity (%) Smoking (%) Hypercholesterolemia (%) Change in RI (%) Change in AIx (%) EDV (%) 454 ( ) 476 ( ) 0.13 EIDV (%) 323 ( ) 347 ( ) 0.39 AIx, Augmentation index; DBP, diastolic blood pressure; EDV, endotheliumdependent vasodilation (invasive forearm technique); EIDV, endothelium-independent vasodilation (invasive forearm technique); RI, reflectance index by pulse wave analysis; SBP, systolic blood pressure. See text for definitions of diabetes, obesity and hypercholesterolemia. Means are given SD or as median and 10th and 90th percentiles in parenthesis.

5 Endothelial function and blood pressure Lind 1323 Fig. 2 Fig. 3 ln FMD SBP (mmhg) ln EDV DBP (mmhg) Relationship between systolic blood pressure (SBP) and flow-mediated vasodilation (ln FMD, ln-transformed, r ¼ 0.13, P ¼ ) in subjects free from antihypertensive medication. mean 28 14% in those with antihypertensive treatment compared with 32 13% in those without, P ¼ ), whereas no difference was seen for FMD (median 3.9% in those with antihypertensive treatment compared with 4.3% in those without, P ¼ 0.78). When only subjects not treated with antihypertensive drugs were analysed (n ¼ 647), it was found that FMD, but not EDV and the change in RI, was inversely related to SBP (r ¼ 0.13, P ¼ , Fig. 2). On the contrary, EDV and the change in RI, but not FMD, were related to diastolic blood pressure (DBP; r ¼ 0.10, P ¼ and r ¼ 0.17, P < , respectively, Fig. 3, see Table 4 for details). The relationship between FMD and SBP was still significant after adjustment for baseline brachial artery diameter and AIx in multiple regression analysis (P ¼ ). This was also the case for the relationship between EDV and DBP (P ¼ 0.021). EIDV was not significantly related to SBP or DBP (r ¼ and r ¼ 0.02, respectively). Neither was the change in AIx induced by terbutaline significantly related to SBP or DBP (r ¼ 0.01 and r ¼ 0.07, respectively). In a further analysis of the subjects without antihypertensive treatment, three different groups were created; those with blood pressure below 140/90 mmhg (n ¼ 256), those with SBP greater than 139 and DBP less than 90 mmhg (isolated systolic hypertension, n ¼ 309) and those with both SBP greater than 139 and DBP greater than 89 mmhg (combined systolic and diastolic hypertension, n ¼ 73, please see Table 5 for the basic characteristics in these groups). It was then found that EDV was only reduced in the group with combined hypertension (P ¼ compared with Change in RI DBP (mmhg) Relationship between diastolic blood pressure (DBP) and endotheliumdependent vasodilation (ln EDV) evaluated using the invasive forearm technique (relative increase in FBF at the highest dose of acetylcholine, top panel, ln-transformed, r ¼ 0.10, P ¼ 0.017) and by pulse wave analysis (change in reflectance index, RI, lower panel, r ¼ 0.17, P < ) in subjects free from antihypertensive medication. normotensive individuals), whereas FMD was reduced to a similar extent in both hypertensive groups (although only the isolated systolic hypertensive group reached significance compared with normotensive individuals, P ¼ 0.013, see Fig. 4). These differences between groups for EDV and FMD were still significant after adjustment Table 4 Relationships between blood pressure and different measures of endothelium-dependent vasodilation given as Pearson s correlation coefficient with P value in parenthesis if less than 0.05 SBP DBP EDV (0.017) EIDV FMD 0.13 (0.0023) Change in RI (0.0001) Change in AIx AIx, Augmentation index; DBP, diastolic blood pressure; EDV, endotheliumdependent vasodilation (invasive forearm technique); EIDV, endothelium-independent vasodilation (invasive forearm technique); FMD, flow-mediated dilatation; RI, reflectance index at pulse wave analysis; SBP, systolic blood pressure.

6 1324 Journal of Hypertension 2006, Vol 24 No 7 Table 5 Basic characteristics, major cardiovascular risk factors and measures of endothelium-dependent vasodilation in the sample free from antihypertensive medication split into normotensive individuals, and those with isolated systolic hypertension and combined systolic/ diastolic hypertension Normotensives Isolated systolic hypertension Combined hypertension P value n SBP (mmhg) DBP (mmhg) Heart rate (beats/min) Pulse pressure (mmhg) Diabetes (%) Obesity (%) Current smoking (%) Hypercholesterolemia (%) DBP, Diastolic blood pressure; SBP, systolic blood pressure. See text for definitions of diabetes, obesity and hypercholesterolemia. Means are given SD or prevalence in percentage. Fig EDV (%) FMD (%) NT ISHT HT for the other major cardiovascular risk factors: smoking, diabetes, obesity and hypercholesterolemia (P ¼ and P ¼ 0.020, respectively). Neither the change in RI nor EIDV were significantly different between the groups. Only three subjects showed isolated diastolic hypertension (SBP < 140 and DBP > 89 mmhg), making this group not suitable for statistical evaluation. No significant correlation between FMD and EDV was found in the total sample of subjects without antihypertensive treatment (r ¼ 0.03, r ¼ 0.47). Neither could any relationship be found when the three groups (normotensive individuals, isolated systolic hypertension or combined systolic and diastolic hypertension) were analysed separately (r ¼ 0.03, r ¼ 0.59 for normotensive individuals, r ¼ 0.02, r ¼ 0.79 in isolated systolic hypertension and r ¼ 0.01, r ¼ 0.89 in combined systolic and diastolic hypertension) NT ISHT HT Endothelium-dependent vasodilation (EDV) evaluated using the invasive forearm technique (top panel) and by flow-mediated dilatation (FMD; lower panel) in subjects without antihypertensive medication split into normotensive individuals (NT), and those with isolated systolic hypertension (ISHT) and combined systolic/diastolic hypertension (HT) given in median, 10th, 25th, 75th and 90th percentiles. P ¼ for difference between NT and HT for EDV and P ¼ for difference between NT and ISHT for FMD. Discussion The present study showed that EDV evaluated using the invasive forearm technique was mainly impaired in subjects with a high DBP, as in combined hypertension, whereas FMD was mainly impaired by systolic hypertension. Systolic and diastolic hypertension thus seem to impair endothelial function in different types of vessels in the elderly. The invasive forearm technique The first two studies to evaluate EDV in hypertensive individuals in 1990 used EDV [6,7]. They both found a profound dysfunction in EDV in middle-aged hypertensive subjects, who in general had combined systolic/ diastolic hypertension. In the following years, most [22 34], but not all [35 37], other investigators using EDV could reproduce the original findings. A study of normotensive and hypertensive individuals at different ages showed a linear reduction in EDV by age, with the regression line being shifted downwards in the hypertensive individuals [25].

7 Endothelial function and blood pressure Lind 1325 In studies that were unable to find a relationship between blood pressure and EDV, only a low dose of acetylcholine was used [36]. The dose used in the present study was three time higher and in the same order as that used in the other studies demonstrating a reduced EDV in hypertensive patients [6,7]. It should, however, be pointed out that a limitation of the present study is that we did not evaluate a full dose response curve for acetylcholine. The impairment in EDV seen in hypertensive individuals has been attributed to either a cyclooxygenasederived constricting factor [23,25] or to the increased generation of free radicals inactivating the vasodilatory properties of nitric oxide [24]. This is the first study to evaluate EDV in a large number of elderly subjects with increased blood pressure. It clearly shows that EDV is only impaired in diastolic hypertension, such as seen in subjects with combined systolic/diastolic hypertension. Furthermore, in correlation analysis, EDV was related to DBP, but not SBP. Therefore, as EDV mainly reflects EDV in resistance arteries, this type of artery seems to be mainly affected by high DBP. This seems logical as an increased DBP is mainly caused by increased total peripheral resistance in resistance vessels. Park et al. [40] dissected resistance arteries from subcutaneous fat and found the vasodilatory properties of resistance vessels to be impaired when challenged with acetylcholine in vitro in patients with combined systolic/ diastolic hypertension. However, the authors found the response in resistance arteries from subcutaneous fat to be related to the response in the brachial artery (FMD), in contrast to what was found in the present study in which no relationship between FMD and EDV could be found. Differences in age, lack of hypertensive treatment in the present group, or differences between resistance arteries from subcutaneous fat measured in vitro and the invasive forearm technique in vivo are all factors that might explain this difference between studies. EDV was not impaired when untreated and treated hypertensive individuals were combined in the total sample. This was probably because DBP was almost normalized in the treated group. A positive effect of antihypertensive treatment might be another reason for this finding, as several studies have reported that EDV is affected by antihypertensive therapy [41 48]. EIDV, evaluated by the invasive forearm technique, was not significantly related to hypertension, in accordance with most other investigations [6,7,23 25,27,30]. Flow-mediated vasodilation In the present study, FMD was related mainly to systolic hypertension. This is in accordance with previous findings that FMD was mainly associated with SBP, rather than DBP, both when blood pressure was measured in the office [49] and as a 24-h ambulatory measurement [50]. Systolic hypertension is mainly caused by vascular stiffening in conduit arteries and FMD is measured in a conduit artery. In the present study, FMD was only significantly reduced in the isolated systolic hypertensive group when compared with the normotensive group, despite being numerically even lower in the combined hypertensive group. This was possibly because the latter group was considerably smaller not having the power to detect such a difference. Pulse wave analysis In the present study, the change in RI, but not AIx, after terbutaline was related to DBP, but not SBP. This is in line with previous findings that the change in RI is related to EDV [17]. Why only the change in RI was related to DBP is not known, because the response of the two different wave reflections to beta-2 receptor stimulation are inter-related. It might be that AIx is more related to arterial stiffness, whereas the RI is more related to peripheral vascular resistance. It could also be that the change in RI has a better reproducibility than AIx. This is the first study reporting an association between EDV assessed by pulse wave analysis and DBP, although the data are not as consistent as for EDV and FMD, because no significant difference between the groups among untreated individuals was seen. Ageing and endothelium-dependent vasodilation As previously shown by Taddei and co-workers [25], aging impairs EDV in both normotensive and hypertensive individuals. However, the relationship between age and EDV is shifted downwards in hypertensive individuals, so that EDV of a young hypertensive patient is similar to that found in a middle-aged normotensive individual. In the present elderly population, EDV and FMD were reduced even in healthy individuals when compared with young individuals [51]. Therefore, the difference between EDV for normotensive and hypertensive values of blood pressure would be reduced in this elderly cohort. This might explain why the correlations found between blood pressure and the measures of EDV were rather low compared with those reported in middle-aged hypertensive samples. Although the impact of EDV on hypertensive development might be reduced in the elderly compared with younger individuals, it is striking that EDV in a conduit artery (FMD) is related mainly to increased systolic hypertension, a condition thought to originate from an

8 1326 Journal of Hypertension 2006, Vol 24 No 7 increased stiffening of conduit arteries, whereas EDV in resistance vessels is related to increased diastolic pressure, a condition thought to originate from increased resistance in smaller arteries. However, only future prospective studies in the elderly could determine the clinical importance of the impairments in EDV described above in relation to the development of hypertension and hypertensive-related organ damage. Limitation of the study The present sample is limited to Caucasians aged 70 years. So, caution should be exercised when drawing conclusions in other ethnic and age groups. The present study had a moderate participation rate. However, an analysis of non-participants showed the present sample to be fairly representative of the total population regarding most cardiovascular disorders and drug intake. EIDV was only assessed by one of the methods for practical and ethical reasons not to prolong the investigation procedure, as we would have had to give nitroglycerine before terbutaline, and would have had to wait for the withdrawal of the nitroglycerine effect. Furthermore, we have previously shown that EIDV evaluated by SNP infusion in the brachial artery and nitroglycerineprovoked change in the brachial artery diameter are closely related [16], so additional measurements of EIDV would probably not add substantial information to the study. Another limitation is that we used only one measurement of blood pressure on one occasion to define hypertension in those not treated with antihypertensive drugs. In the clinical setting the diagnosis of hypertension usually requires repeated measurements, but in large-scale epidemiological research this is usually not performed. Some misclassification might thus have occurred in the present study, but as EDV could change rapidly with blood pressure [52,53], repeated measurements of blood pressure on occasions when EDV was not evaluated could also induce errors. Conclusion Systolic hypertension mainly impairs conduit artery endothelial function, whereas diastolic hypertension mainly induces endothelial dysfunction in resistance arteries in elderly subjects. References 1 Wilson PWF, D Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB. Prediction of coronary heart disease using risk factor categories. Circulation 1998; 97: Wolf PA, D Agostino RB, Belanger AJ, Kannel WB. Probability of stroke: a risk profile from the Framingham Study. Stroke 1991; 22: Zeiher AM, Drexler H, Wollschlager H, Just H. Modulation of coronary vasomotor tone in humans. Progressive endothelial dysfunction with different early stages of coronary atherosclerosis. Circulation 1991; 83: Schachinger V, Britten MB, Zeiher AM. 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